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Sample records for astrometric observations influence

  1. Astrometric observations of triton

    NASA Astrophysics Data System (ADS)

    Qiao, R. C.; Yan, Y. R.; Shen, K. X.; Dourneau, G.; Xi, X. J.; Cheng, X.; Wang, S. H.; Tang, Z. H.; Liu, J. R.

    2007-04-01

    Astrometric positions of the Neptunian Satellite Triton are given for the opposition of Neptune for the years 1996, 2003, 2005 and 2006. The 943 observed positions were obtained at the Cassegrain focus of a 156-cm reflector. In our reduction, the up-to-date catalogue of stars UCAC2 was chosen to ensure a proper astrometric calibration. Our observed positions are compared to theoretical positions provided from JPL and IMCCE ephemerides. The observed minus calculated residuals have s.d. values of the order of 0.04 arcsec. The data are available in electronic form as Supplementary Material to the online version of the paper on Blackwell Synergy, at the CDS via anonymous FTP to http://cdsarc.u-strasbg.fr or via http://cdsweb.u-strasbg.fr/Abstract.html. E-mail: rcqiao@ntsc.ac.cn

  2. Interannaul variations of the vertical and their possible influence on the star catalogs derived from ground-based astrometric observations

    NASA Astrophysics Data System (ADS)

    Li, Z. X.

    The efforts at Shanghai Observatory since 1991, in response to the Resolution of IAU Comm.19: "Applications of optical astrometry time and latitude programs", is described in the paper, especially the studies concerned with the interannual variations of the vertical and their influence on the astronomical studies. It is clear now that there is a component of the order 0.01 - 0.02" on an interannual time scale in latitude residuals which is correlated with geophysical phenomena on the Earth. A recent study has confirmed that the component discovered is actually the variation of the vertical, related to ground-based observation in astronomy. So, it should be emphasized now that the variation of the vertical is significant enough to be considered in astronomy from now on. Its influence on the past studies, including the star catalogs already published and the ERP before 1980 when optical astrometry observations were still used, should be studied in the future. In comparing the HIPPARCOS catalog with those derived by the past observations, we should keep in mind the existence of this error in an astrometric observation and its influence on the star catalogs and other results derived from ground-based astrometric observations.

  3. Phobos and Deimos astrometric observations from Viking

    NASA Technical Reports Server (NTRS)

    Duxbury, T. C.; Callahan, J. D.

    1988-01-01

    This article describes the reduced astrometric observations of Phobos and Deimos derived from Viking Orbiter 1 and 2 imaging data. This data set spans four years from 1976 to 1980, contains 275 sets of spacecraft-centered, right ascension and declination observations, and has a limiting accuracy of a few km (1 sigma). The details of observation formulation and use for ephemeris improvement are given.

  4. CCD astrometric observations of Amalthea and Thebe

    NASA Astrophysics Data System (ADS)

    Veiga, C. H.; Vieira Martins, R.

    2005-07-01

    This paper presents the results of observations of Jupiter's satellites Amalthea and Thebe made in 1995, 1996 and 2001 at the Laboratório Nacional de Astrofísica (LNA), Brazil. The observations were made in visible light wavelengths with a 1.6 m reflector telescope and the light of Jupiter was covered by a mask placed near the CCD surface. The already published positions for 1995, whose astrometric reduction used the Galilean satellites, are now reduced using the stars in the CCD fields like the new positions of 1996 and 2001. The 2001 data are much better than those obtained in 1995, and that those from 1996 show large residuals. Considering the 310 frames observed, the mean residual is about 0.01 arcsec and the standard deviation is about 0.15 arcsec.

  5. Astrometric analysis of Europa-Io occultations observed in 1991

    NASA Astrophysics Data System (ADS)

    Descamps, P.

    1994-11-01

    Astrometric results from an analysis of 36 lightcurves of Io's occultations by Europa, observed during 1991 in the visible bands, are presented. They are issued from the adjustment of a theoretical astrometric-photometric model to observations using Hapke's law. These observations are of importance because they give high quality astrometric information useful to the determination of the location of Io's hotspots. In fact, accurate positioning of hotspots on Io is made possible from infrared observations only if the occultation timing is well-known.

  6. Phobos and Deimos astrometric observations from the Phobos mission

    NASA Technical Reports Server (NTRS)

    Koliuka, IU.; Tikhonov, V.; Ivanov, N.; Poliakov, V.; Avanesov, G.

    1991-01-01

    This article describes the reduced astrometric observations of Phobos and Deimos as derived from the Phobos Mission imaging data. These astrometric data span 2 months in 1989, contain 37 sets of spacecraft-centered, right ascension and declination observations of Phobos and 8 sets of Deimos. The phobos observations have an orbital position accuracy of about 2 km while the Deimos observations have an accuracy of about 10 km. The details of observation formulation and use for ephemeris improvement are given.

  7. Astrometric observations after 1988.0

    NASA Astrophysics Data System (ADS)

    Li, Zhengxin

    After the closing of the BIH, optical astrometric instruments over the world were still operated in the past four years. A brief presentation of the situation since 1988.0 is described, including the number of instruments operated, the number of measurements made, average precision of a group measurement and ERP obtained.

  8. Combination of space- and ground-based astrometric observations to create astrometric catalogs

    NASA Astrophysics Data System (ADS)

    Vondrák, J.; Štefka, V.

    2008-09-01

    Modern space-based astrometric observations made by Hipparcos satellite yielded two principal catalogs in optical wavelength: Hipparcos and Tycho. These catalogs, that recently celebrated ten years of existence, contain star positions with unprecedented accuracy. However, their proper motions are, due to a relatively short interval of Hipparcos mission, quite often not as good as their formal standard errors indicate. This deficiency is especially significant for about twenty per cent of double or multiple stars contained in these catalogs. The combination with ground-based astrometric observations that have much longer history is therefore very important for improving the Hipparcos proper motions. Significant improvement in this respect was achieved during the past years by creating combined catalogs, such as Tycho-2, FK6, GC+HIP, TYC2+HIP, or ARIHIP. Yet a large and important group of astrometric observations of latitude/universal time variations, made in the programs of monitoring Earth orientation, stood apart from these activities. Recently we started to use these observations, covering almost the whole 20th century, to create astrometric catalogs EOC-1, EOC-2, EOC-3 and most recently EOC-4. To construct them, we used the Earth orientation observations in combination with the above mentioned catalogs. The latter two, EOC-3 and EOC-4, contain not only the ``classical'' linear proper motions, but also periodic changes due to orbital motions, for a substantial portion of the observed stars.

  9. A new method for astrometric observations of asteroids

    NASA Technical Reports Server (NTRS)

    Pauwels, Thierry

    1992-01-01

    In this paper we propose a new method for photographic astrometric observations of asteroids. We discuss its advantages and disadvantages and compare them to the advantages and disadvantages of the classical photographic methods. The new method is best suited for observations on a spot where no CCD cameras, blink or stereo comparators are available and when a fast detection of unknown objects is required.

  10. On the astrometric observations, 1962.0 - 1991.0.

    NASA Astrophysics Data System (ADS)

    Li, Zheng-Xin; Chen, You-Fen; Qian, Chang-Xia

    The astrometric observations, which have been obtained by the 155 optical instruments since the beginning of 1962, are stored in the database of the Shanghai Observatory. A brief presentation of the astrometric data during the period of 1962.0 - 1991.0 is given. The relations among the precision of the 5-day ERP results, the algorithm used in the reduction, the number or the weight of measurements made in a year, and the time of the measurement in a year, are discussed.

  11. Phobos and Deimos astrometric observations from Mariner 9

    NASA Technical Reports Server (NTRS)

    Duxbury, T. C.; Callahan, J. D.

    1989-01-01

    This article describes the reduced astrometric observations of Phobos and Deimos derived from Mariner 9 imaging data. This data set spans 11 months from 1971 and 1972, contains 82 sets of spacecraft-centered right ascension and declination observations, and has an accuracy of 3 to 10 km (1-sigma) in orbital position. The details of the observation formulation and its use for ephemeris improvement are given.

  12. The NSDB database of astrometric observations of the natural planetary satellites and the Gaia astrometric reference catalogue

    NASA Astrophysics Data System (ADS)

    Arlot, Jean-Eudes; Lainey, Valery; Robert, Vincent

    2015-08-01

    The study of the dynamics of the Natural Planetary Satellites needs a large sample of observational astrometric data to determinate orbital and physical parameters. More, some small effects may be detected through precise astrometric observations such as tidal effects which modify slightly the orbits of the satellites. For that goal, databases gather observations from the XIXth to the XXIth centuries starting with old photographic observations until today observations from space probes.Unfortunately, the old data have a poor astrometric accuracy due to the unprecise refernce star catalogues available at the time of the observations. Since phtographic plates are still available, it is possible to remake the astrometric reduction of the plates using today catalogues. The problem of the proper motion of the stars which prevents to reduce data older than 40 years will now be solved by the future Gaia reference star catalogues the astrometric accuracy being equal to one mas on more than one century.A search for the most interesting old plates and tests of digitization and reduction of these plates have been made using UCAC reference satr catalogues and the results are more than promissing, allowing to increase of one order of magnitude the accuracy of the observations. Using such data, cumulative small effects on the dynamics of the natural planetary satellites could now be detected as soon as the Gaia reference star catalogue will be available.

  13. Astrometric observations of Nereid in 2006-2007

    NASA Astrophysics Data System (ADS)

    Qiao, R. C.; Cheng, X.; Shen, K. X.; Dourneau, G.; Wang, S. H.; Hu, X. Y.; Tang, Z. H.; Xi, X. J.

    2008-12-01

    In this paper, we present 112 new CCD astrometric positions of Nereid, the second and faint satellite of Neptune (mv ~= 19). We observed this small satellite in the 2006-2007 period with the 1 and 2.16-m telescopes of Xinglong Station near Beijing, both equipped with large CCD detectors of 1340 × 1300 and 2080 × 2048 pixels, respectively. The high density and highly accurate star catalogue UCAC2 was used in the reduction so that a classical astrometric calibration method was applied. We have shown that our observations of Nereid appear to be of equal or higher precision (σ ~= 0.2 arcsec) than most of the recent CCD ones. The data are available in electronic form as Supplementary Material to the online version of the paper on Blackwell Synergy, at the CDS via Anonymous FTP to http://cdsarc.u-stasbg.fr or via http://cdsweb.u-strasbg.fr/Abstract.html. E-mail: rcqiao@ntsc.ac.cn

  14. New astrometric observations of Triton in 2007-2009

    NASA Astrophysics Data System (ADS)

    Qiao, R. C.; Zhang, H. Y.; Dourneau, G.; Yu, Y.; Yan, D.; Shen, K. X.; Cheng, X.; Xi, X. J.; Hu, X. Y.; Wang, S. H.

    2014-06-01

    Astrometric positions of the Neptunian satellite Triton with a visual magnitude of 13.5 were obtained during three successive oppositions in 2007, 2008 and 2009. A total of 1095 new observed positions of Triton were collected during 46 nights of observations, involving eight missions and three telescopes. We compared our observations to the best ephemerides of Triton available now. This comparison has shown that our observations present a high level of accuracy as they provide standard deviations of residuals hardly higher than 50 mas and mean residuals lower than 30 mas, corresponding to about only 500 km in the position of the very distant satellite Triton. Moreover, we have compared most of the different planetary ephemerides of Neptune available now as well as two recent orbit models of Triton. These new comparisons have clearly shown the differences between all of these ephemerides which can be significant and that are presented in this work.

  15. ASTROMETRIC MASSES OF 26 ASTEROIDS AND OBSERVATIONS ON ASTEROID POROSITY

    SciTech Connect

    Baer, James; Chesley, Steven R.; Matson, Robert D. E-mail: steve.chesley@jpl.nasa.gov

    2011-05-15

    As an application of our recent observational error model, we present the astrometric masses of 26 main-belt asteroids. We also present an integrated ephemeris of 300 large asteroids, which was used in the mass determination algorithm to model significant perturbations from the rest of the main belt. After combining our mass estimates with those of other authors, we study the bulk porosities of over 50 main-belt asteroids and observe that asteroids as large as 300 km in diameter may be loose aggregates. This finding may place specific constraints on models of main-belt collisional evolution. Additionally, we observe that C-group asteroids tend to have significantly higher macroporosity than S-group asteroids.

  16. Astrometric Observations of Comets and Asteroids and Subsequent Orbital Investigations

    NASA Technical Reports Server (NTRS)

    Marsden, Brian G.; McCrosky, Richard E.

    1997-01-01

    An earlier series of photographic observations was made with the 1.5-m reflector from 1972 to 1989. The start of the series to which this report refers occurred shortly before the conversion from photographic to CCD operation in August 1989, at which point there was a dramatic increase in the productivity of the program. This is evident gives a month-by-month summary of the observations; the earlier data refer to the measurement or remeasurement of photographic plates previously taken with the same telescope. The total number of observations made was 24,423, of which 1338 were of comets. Of the 23,085 observations of asteroids, 21,529 referred to asteroids that were unnumbered when the observations were made. Since an important emphasis of the program was to improve knowledge of the orbits to the point where asteroids can be numbered, the fact that only 4262 of the observations refer to asteroids that are still unnumbered is a measure of the program's success, with 30-35 percent of all the new numberings being habitually made solely because of the recent data from the Oak Ridge program, which even at the time of McCrosky's retirement was still the fourth largest comet-asteroid astrometric program in the world.

  17. Improving the Planetary Ephemeris with Astrometric Observations of Cassini

    NASA Astrophysics Data System (ADS)

    Jones, Dayton L.; Fomalont, E.; Dhawan, V.; Romney, J.; Lanyi, G.; Border, J.; Folkner, B.; Jacobson, B.

    2009-05-01

    During the past three years we have carried out a series of astrometric VLBA observations of the Cassini spacecraft. At each epoch, we used phase referencing to obtain high precision relative positions between Cassini and an angularly nearby calibration source. The calibration sources were separately tied to nearby defining sources of the International Celestial Reference Frame (ICRF) through additional phase-referenced VLBA experiments. By combining our position measurements of Cassini with a model of Cassini's orbit around Saturn (from Doppler measurements by the Deep Space Network), we are able to determine the ICRF position of Saturn at each epoch to about 0.3 mas. This is about 2 km at the average distance of Saturn. These results will improve the Saturn ephemeris, particularly in ecliptic latitude (the plane of Saturn's orbit). The error in latitude decreases dramatically as the total time span of VLBA data approaches 1/4 of Saturn's orbital period in 2011-2012. Saturn is the first outer planet whose ephemeris can be improved and more closely tied to the ICRF and the inner solar system through long-term observations of an orbiter. The planned Juno mission to Jupiter will allow this technique to be applied there also. The planetary ephemeris is an essential tool for studies of solar system dynamics, interplanetary spacecraft navigation, and test of general relativity. It requires continuous maintenance and improvement. This research has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, and has relied on observations by the Very Long Baseline Array, a facility of the National Science Foundation operated by the National Radio Astronomy Observatory under a cooperative agreement with Associated Universities, Inc.

  18. Astrometric observations and comparison with theory of Saturn's satellites from Bordeaux Observatory, 1984

    NASA Astrophysics Data System (ADS)

    Dourneau, G.; Le Campion, J. F.; Dulou, M. R.

    1989-08-01

    The astrometric observations of Saturn's satellites reported in this paper have been reduced from the SAO catalog. Observed positions of the satellites are given both in absolute topocentric astrometric coordinates and in differential coordinates by using a reference satellite. Residuals derived from comparison between observed and computed positions of the satellites are also reported. A discussion shows that Iapetus, which presents the highest residuals, needs, more than all other observed satellites, an improvement of its theory of motion.

  19. The astrometric Gaia-FUN-SSO observation campaign of 99942 Apophis

    NASA Astrophysics Data System (ADS)

    Thuillot, W.; Bancelin, D.; Ivantsov, A.; Desmars, J.; Assafin, M.; Eggl, S.; Hestroffer, D.; Rocher, P.; Carry, B.; David, P.; Abe, L.; Andreev, M.; Arlot, J.-E.; Asami, A.; Ayvasian, V.; Baransky, A.; Belcheva, M.; Bendjoya, Ph.; Bikmaev, I.; Burkhonov, O. A.; Camci, U.; Carbognani, A.; Colas, F.; Devyatkin, A. V.; Ehgamberdiev, Sh. A.; Enikova, P.; Eyer, L.; Galeev, A.; Gerlach, E.; Godunova, V.; Golubaev, A. V.; Gorshanov, D. L.; Gumerov, R.; Hashimoto, N.; Helvaci, M.; Ibryamov, S.; Inasaridze, R. Ya.; Khamitov, I.; Kostov, A.; Kozhukhov, A. M.; Kozyryev, Y.; Krugly, Yu N.; Kryuchkovskiy, V.; Kulichenko, N.; Maigurova, N.; Manilla-Robles, A.; Martyusheva, A. A.; Molotov, I. E.; Nikolov, G.; Nikolov, P.; Nishiyama, K.; Okumura, S.; Palaversa, L.; Parmonov, O.; Peng, Q. Y.; Petrova, S. N.; Pinigin, G. I.; Pomazan, A.; Rivet, J.-P.; Sakamoto, T.; Sakhibullin, N.; Sergeev, O.; Sergeyev, A. V.; Shulga, O. V.; Suarez, O.; Sybiryakova, Y.; Takahashi, N.; Tarady, V.; Todd, M.; Urakawa, S.; Uysal, O.; Vaduvescu, O.; Vovk, V.; Zhang, X.-L.

    2015-11-01

    Aims: Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99 942) Apophis was conducted during the asteroid's latest period of visibility, from 12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO . Methods: The 2732 high quality astrometric observations acquired during the Gaia-FUN-SSO campaign were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric reduction process and the precision of the newly obtained measurements are discussed. We compare the residuals of astrometric observations that we obtained using this reduction process to data sets that were individually reduced by observers and accepted by the Minor Planet Center. Results: We obtained 2103 previously unpublished astrometric positions and provide these to the scientific community. Using these data we show that our reduction of this astrometric campaign with a reliable stellar catalog substantially improves the quality of the astrometric results. We present evidence that the new data will help to reduce the orbit uncertainty of Apophis during its close approach in 2029. We show that uncertainties due to geolocations of observing stations, as well as rounding of astrometric data can introduce an unnecessary degradation in the quality of the resulting astrometric positions. Finally, we discuss the impact of our campaign reduction on the recovery process of newly discovered asteroids. Full Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/583/A59

  20. Astrometric observations of the faint satellites of Jupiter during the 1975 - 1976 opposition

    NASA Technical Reports Server (NTRS)

    Mulholland, J. D.; Shelus, P. J.; Benedict, G. F.

    1979-01-01

    The series of astrometric observations of the satellites of the trans-martian planets re-established at the McDonald Observatory in 1972 is continued. The positions deduced from photographic observations of the jovian system obtained during the 1975-76 opposition are presented together with the discovery positions of four asteroids found on these plates.

  1. Astrometric observations of comets and asteroids and subsequent orbital investigations

    NASA Technical Reports Server (NTRS)

    Mccroskey, Richard E.; Marsden, Brian G.

    1988-01-01

    The 155-cm reflector was used for observations of comets and minor planets on 28 nights during April-October. Twenty-two of the observations refer to comets, 62 to numbered minor planets (numbered, that is, by the end of the semester: only nine of them refer to minor planets already numbered at the time of the last report), and the remainer to unnumbered minor planets. Observations were made of four new comets discovered during the semester and a fifth discovered in January. Observations of Wilson (19861), P/Tempel 2 and two other returning short-period comets are also continuing. Among the odd numbered minor planets observed were the earth-approaching objects (1685) Toro and (1980) Tezcatlipoca. The Earth approacher 1980 PA was numbered (3908).

  2. Astrometrical positions of NEO inferred from CCD observations at Bucharest

    NASA Astrophysics Data System (ADS)

    Popescu, R.; Popescu, P.; Nedelcu, A.

    2005-09-01

    We show up the capability of the old Prin-Merz astrograph, completely renewed, to perform narrow-field astrometry. A highly accurate metrological system has been conceived in order to monitor, focus, and track the reference stars. Besides, a high quantum efficiency CCD camera based on a back illuminated chip, allows this instrument to "observe" celestial objects up to 18 magnitudes, in less than 30 seconds of exposure. Due to the small FOV of the instrument we use the most dense star catalogue available - USNO B1.0 which can provide us reference stars enough to compute an accurate plate solution. 2 NEO have been observed during the testing phase (3908) Nyx and (85640) 1998 OX4 and the results are presented in this paper. All the data have been submitted to the MPC.

  3. Strong tidal dissipation in Io and Jupiter from astrometric observations.

    PubMed

    Lainey, Valéry; Arlot, Jean-Eudes; Karatekin, Ozgür; Van Hoolst, Tim

    2009-06-18

    Io is the volcanically most active body in the Solar System and has a large surface heat flux. The geological activity is thought to be the result of tides raised by Jupiter, but it is not known whether the current tidal heat production is sufficiently high to generate the observed surface heat flow. Io's tidal heat comes from the orbital energy of the Io-Jupiter system (resulting in orbital acceleration), whereas dissipation of energy in Jupiter causes Io's orbital motion to decelerate. Here we report a determination of the tidal dissipation in Io and Jupiter through its effect on the orbital motions of the Galilean moons. Our results show that the rate of internal energy dissipation in Io (k(2)/Q = 0.015 +/- 0.003, where k(2) is the Love number and Q is the quality factor) is in good agreement with the observed surface heat flow, and suggest that Io is close to thermal equilibrium. Dissipation in Jupiter (k(2)/Q = (1.102 +/- 0.203) x 10(-5)) is close to the upper bound of its average value expected from the long-term evolution of the system, and dissipation in extrasolar planets may be higher than presently assumed. The measured secular accelerations indicate that Io is evolving inwards, towards Jupiter, and that the three innermost Galilean moons (Io, Europa and Ganymede) are evolving out of the exact Laplace resonance.

  4. Comparison of earth rotation as inferred from radio interferometric, laser ranging and astrometric observations

    NASA Technical Reports Server (NTRS)

    Robertson, D. S.; Carter, W. E.; Eanes, R. J.; Schutz, B. E.; Tapley, B. D.; King, R. W.; Langley, R. B.; Morgan, P. J.; Shapiro, I. I.

    1983-01-01

    Results of measurements of the earth's rotation vector for a 400-day period from late September 1980 to December 1981, for which date from VLBI, satellite laser ranging (SLR), and lunar laser ranging (LLR) were available, are compared. The acquisition of the data and their evaluation are described. VLBI, SLR, and classical astrometric determinations of the X-parameter required to describe the location of the rotation pole on the earth's surface are shown, and VLBI, LLR, and classical astrometric determinations of the angle of rotation about this pole (UT1) are presented. The results indicate that VLBI and SLR, at their present stages of development, yield standard errors under 20 cm in the determinations of X, about twofold smaller than obtained from classical measurements, and that VLBI and LLR yield determination of UT1 with standard errors less than 40 cm, somewhat smaller than that of the corresponding determinations from classical observations. Methods for improving these types of intercomparisons are suggested.

  5. VizieR Online Data Catalog: Astrometric observations of Phobos (Pasewaldt+, 2015)

    NASA Astrophysics Data System (ADS)

    Pasewaldt, A.; Oberst, J.; Willner, K.; Beisembin, B.; Hoffmann, H.; Matz, K. D.; Roatsch, T.; Michael, G.; Cardesin-Moinelo, A.; Zubarev, A. E.

    2015-04-01

    The data is given in the form of two tables. Each table contains the same set of observations: Data in tablea1.dat has been reduced using MEX navigation orbits and predicted attitude by the European Space Operations Centre (ESOC). tablea2.dat data has been derived using MEX accurate orbits by the Royal Observatory of Belgium (ROB) and measured attitude by the European Space Astronomy Centre (ESAC). >From 158 astrometric observations 103 were determined by means of both methods, 27 using only control point measurements, and 28 performing only limb fit observations. Hence, each data table contains 261 entries, namely 130 control point measurements and 131 limb fit observations. (2 data files).

  6. Astrometric observations of planets, minor planets, and satellites - 1976-1980

    NASA Astrophysics Data System (ADS)

    Klemola, A. R.

    1981-07-01

    Equatorial coordinates for Uranus, Neptune, several minor planets, and the Jovian satellites were measured between 1976 and 1980. All observations were made with the yellow lens of the 0.51 m Carnegie double astrograph for the purpose of refining the predictions of stellar occultations. After 1977 the astrometric reduction program for equatorial coordinates included the option for precorrection of measurements for higher order terms, and other than Jupiter II, positions of Jovian satellites for 1980 December 09.56840 and 12.56285 were made by means of manual and automatic machine measurements.

  7. VERY LONG BASELINE ARRAY ASTROMETRIC OBSERVATIONS OF THE CASSINI SPACECRAFT AT SATURN

    SciTech Connect

    Jones, Dayton L.; Folkner, William M.; Lanyi, Gabor; Border, James; Jacobson, Robert A.; Fomalont, Ed; Dhawan, Vivek; Romney, Jon

    2011-02-15

    The planetary ephemeris is an essential tool for interplanetary spacecraft navigation, studies of solar system dynamics (including, for example, barycenter corrections for pulsar timing ephemerides), the prediction of occultations, and tests of general relativity. We are carrying out a series of astrometric very long baseline interferometry observations of the Cassini spacecraft currently in orbit around Saturn, using the Very Long Baseline Array (VLBA). These observations provide positions for the center of mass of Saturn in the International Celestial Reference Frame (ICRF) with accuracies {approx}0.3 mas (1.5 nrad) or about 2 km at the average distance of Saturn. This paper reports results from eight observing epochs between 2006 October and 2009 April. These data are combined with two VLBA observations by other investigators in 2004 and a Cassini-based gravitational deflection measurement by Fomalont et al. in 2009 to constrain a new ephemeris (DE 422). The DE 422 post-fit residuals for Saturn with respect to the VLBA data are generally 0.2 mas, but additional observations are needed to improve the positions of all of our phase reference sources to this level. Over time we expect to be able to improve the accuracy of all three coordinates in the Saturn ephemeris (latitude, longitude, and range) by a factor of at least three. This will represent a significant improvement not just in the Saturn ephemeris but also in the link between the inner and outer solar system ephemerides and in the link to the inertial ICRF.

  8. Astrometric positions for 18 irregular satellites of giant planets from 23 years of observations

    NASA Astrophysics Data System (ADS)

    Gomes-Júnior, A. R.; Assafin, M.; Vieira-Martins, R.; Arlot, J.-E.; Camargo, J. I. B.; Braga-Ribas, F.; da Silva Neto, D. N.; Andrei, A. H.; Dias-Oliveira, A.; Morgado, B. E.; Benedetti-Rossi, G.; Duchemin, Y.; Desmars, J.; Lainey, V.; Thuillot, W.

    2015-08-01

    Context. The irregular satellites of the giant planets are believed to have been captured during the evolution of the solar system. Knowing their physical parameters, such as size, density, and albedo is important for constraining where they came from and how they were captured. The best way to obtain these parameters are observations in situ by spacecrafts or from stellar occultations by the objects. Both techniques demand that the orbits are well known. Aims: We aimed to obtain good astrometric positions of irregular satellites to improve their orbits and ephemeris. Methods: We identified and reduced observations of several irregular satellites from three databases containing more than 8000 images obtained between 1992 and 2014 at three sites (Observatório do Pico dos Dias, Observatoire de Haute-Provence, and European Southern Observatory - La Silla). We used the software Platform for Reduction of Astronomical Images Automatically (PRAIA) to make the astrometric reduction of the CCD frames. The UCAC4 catalog represented the International Celestial Reference System in the reductions. Identification of the satellites in the frames was done through their ephemerides as determined from the SPICE/NAIF kernels. Some procedures were followed to overcome missing or incomplete information (coordinates, date), mostly for the older images. Results: We managed to obtain more than 6000 positions for 18 irregular satellites: 12 of Jupiter, 4 of Saturn, 1 of Uranus (Sycorax), and 1 of Neptune (Nereid). For some satellites the number of obtained positions is more than 50% of what was used in earlier orbital numerical integrations. Conclusions: Comparison of our positions with recent JPL ephemeris suggests there are systematic errors in the orbits for some of the irregular satellites. The most evident case was an error in the inclination of Carme. Position tables are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http

  9. Astrometric observations of the faint outer satellites of Jupiter during the 1993 opposition

    NASA Technical Reports Server (NTRS)

    Shelus, Peter J.; Whipple, Arthur L.; Benedict, G. F.

    1993-01-01

    Astrometric positions for the faint outer Jovian satellites VI-XIII during the 1993 opposition have been obtained from the measurement of plates taken with the 2.1 m Otto Struve reflector at McDonald Observatory.

  10. Astrometric observations of the faint outer satellites of Jupiter during the 1993 opposition

    NASA Astrophysics Data System (ADS)

    Shelus, Peter J.; Whipple, Arthur L.; Benedict, G. F.

    1993-12-01

    Astrometric positions for the faint outer Jovian satellites VI-XIII during the 1993 opposition have been obtained from the measurement of plates taken with the 2.1 m Otto Struve reflector at McDonald Observatory.

  11. Astrometric Observations of the Faint Outer Satellites of Jupiter During the 1994 and 1995 Oppositions

    NASA Astrophysics Data System (ADS)

    Whipple, Arthur L.; Shelus, Peter J.; Whited, Randy W.; Cochran, Anita L.; MacQueen, Phillip J.; Benedict, George F.

    1996-07-01

    We present astrometric positions for the faint outer satellites of Jupiter VI-XIII during the 1994 and 1995 oppositions. These positions have been obtained from measurements of photographic plates taken with the 2.1 m Otto Struve reflector and from wide field CCD frames taken with the 0.76 m reflector. Both telescopes are located at McDonald Observatory. The new CCD-based instrumentation and astrometric reduction system is described.

  12. Speckle observations with PISCO in Merate (Italy) - XII. Astrometric measurements of visual binaries in 2011

    NASA Astrophysics Data System (ADS)

    Scardia, M.; Prieur, J.-L.; Pansecchi, L.; Argyle, R. W.; Spanò, P.; Riva, M.; Landoni, M.

    2013-10-01

    We present relative astrometric measurements of visual binaries, made in 2011 with the Pupil Interferometry Speckle camera and COronagraph (PISCO) at the 102-cm Zeiss telescope of the Brera Astronomical Observatory in Merate (Italy). Our observing list contains orbital couples as well as binaries whose motion is still uncertain. We obtained new measurements of 469 objects, with angular separations in the range 0.14-8.1 arcsec, and an average accuracy of 0.02 arcsec. The mean error on the position angles is 0 .^{circ}7. Most of the position angles were determined without the usual 180° ambiguity with the application of triple-correlation techniques and/or by inspection of the long integration files. Thanks to a new low-magnification option included in PISCO, we have been able to observe fainter stars than previously. The limiting magnitude of our instrumentation on the Zeiss telescope is now close to mV = 10-12, which permits the observation of some red dwarfs. Finally, we present new revised orbits for ADS 8739, 9182 Aa,Ab, 9626 Ba,Bb, 12880 and 14412, partly derived from those observations. The corresponding estimated values for the masses of those systems are compatible with the spectral types.

  13. The Time Transfer Functions: an efficient tool to compute range, Doppler and astrometric observables

    NASA Astrophysics Data System (ADS)

    Hees, A.; Bertone, S.; Le Poncin-Lafitte, C.; Teyssandier, P.

    2015-12-01

    Determining range, Doppler and astrometric observables is of crucial interest for modelling and analyzing space observations. We recall how these observables can be computed when the travel time of a light ray is known as a function of the positions of the emitter and the receiver for a given instant of reception (or emission). For a long time, such a function--called a reception (or emission) time transfer function--has been almost exclusively calculated by integrating the null geodesic equations describing the light rays. However, other methods avoiding such an integration have been considerably developped in the last twelve years. We give a survey of the analytical results obtained with these new methods up to the third order in the gravitational constant G for a mass monopole. We briefly discuss the case of quasi-conjunctions, where higher-order enhanced terms must be taken into account for correctly calculating the effects. We summarize the results obtained at the first order in G when the multipole structure and the motion of an axisymmetric body is taken into account. We present some applications to on-going or future missions like Gaia and Juno. We give a short review of the recent works devoted to the numerical estimates of the time transfer functions and their derivatives.

  14. The ESPRI project: astrometric exoplanet search with PRIMA. I. Instrument description and performance of first light observations

    NASA Astrophysics Data System (ADS)

    Sahlmann, J.; Henning, T.; Queloz, D.; Quirrenbach, A.; Elias, N. M.; Launhardt, R.; Pepe, F.; Reffert, S.; Ségransan, D.; Setiawan, J.; Abuter, R.; Andolfato, L.; Bizenberger, P.; Baumeister, H.; Chazelas, B.; Delplancke, F.; Dérie, F.; Di Lieto, N.; Duc, T. P.; Fleury, M.; Graser, U.; Kaminski, A.; Köhler, R.; Lévêque, S.; Maire, C.; Mégevand, D.; Mérand, A.; Michellod, Y.; Moresmau, J.-M.; Mohler, M.; Müller, A.; Müllhaupt, P.; Naranjo, V.; Sache, L.; Salvade, Y.; Schmid, C.; Schuhler, N.; Schulze-Hartung, T.; Sosnowska, D.; Tubbs, B.; van Belle, G. T.; Wagner, K.; Weber, L.; Zago, L.; Zimmerman, N.

    2013-03-01

    Context. The ESPRI project relies on the astrometric capabilities offered by the PRIMA facility of the Very Large Telescope Interferometer for discovering and studying planetary systems. Our survey consists of obtaining high-precision astrometry for a large sample of stars over several years to detect their barycentric motions due to orbiting planets. We present the operation's principle, the instrument's implementation, and the results of a first series of test observations. Aims: We give a comprehensive overview of the instrument infrastructure and present the observation strategy for dual-field relative astrometry in the infrared K-band. We describe the differential delay lines, a key component of the PRIMA facility that was delivered by the ESPRI consortium, and discuss their performance within the facility. This paper serves as reference for future ESPRI publications and for the users of the PRIMA facility. Methods: Observations of bright visual binaries were used to test the observation procedures and to establish the instrument's astrometric precision and accuracy. The data reduction strategy for the astrometry and the necessary corrections to the raw data are presented. Adaptive optics observations with NACO were used as an independent verification of PRIMA astrometric observations. Results: The PRIMA facility was used to carry out tests of astrometric observations. The astrometric performance in terms of precision is limited by the atmospheric turbulence at a level close to the theoretical expectations and a precision of 30 μas was achieved. In contrast, the astrometric accuracy is insufficient for the goals of the ESPRI project and is currently limited by systematic errors that originate in the part of the interferometer beamtrain that is not monitored by the internal metrology system. Conclusions: Our observations led to defining corrective actions required to make the facility ready for carrying out the ESPRI search for extrasolar planets. Part of this

  15. Astrometric observations of Phobos and Deimos during the 1971 opposition of Mars

    NASA Astrophysics Data System (ADS)

    Robert, V.; Lainey, V.; Pascu, D.; Arlot, J.-E.; De Cuyper, J.-P.; Dehant, V.; Thuillot, W.

    2014-12-01

    Context. Accurate positional measurements of planets and satellites are used to improve our knowledge of their dynamics and to infer the accuracy of planet and satellite ephemerides. Aims: In the framework of the FP7 ESPaCE project, we provide the positions of Mars, Phobos, and Deimos taken with the U.S. Naval Observatory 26-inch refractor during the 1971 opposition of the planet. Methods: These plates were measured with the digitizer of the Royal Observatory of Belgium and reduced through an optimal process that includes image, instrumental, and spherical corrections to provide the most accurate data. Results: We compared the observed positions of the planet Mars and its satellites with the theoretical positions from INPOP10 and DE430 planetary ephemerides, and from NOE and MAR097 satellite ephemerides. The rms residuals in RA and Dec of one position is less than 60 mas, or about 20 km at Mars. This accuracy is comparable to the most recent CCD observations. Moreover, it shows that astrometric data derived from photographic plates can compete with those of old spacecraft (Mariner 9, Viking 1 and 2). Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A104

  16. Astrometric observations of satellites of Uranus using a 26-inch refractor in 2007-2011

    NASA Astrophysics Data System (ADS)

    Roshchina, E. A.; Izmailov, I. S.; Kiseleva, T. P.

    2015-05-01

    This paper reports CCD observations of Uranus and its main satellites using a 26-inch refractor at the Pulkovo Observatory in 2007-2011. These are 2450 CCD frames with images of Uranus and its four main satellites, i.e., Ariel, Umbriel, Titania, and Oberon. The field of view of the FLI Proline 9000 CCD camera is 12' × 12', which allows us to obtain stars and perform astrometric reduction by Turner's method to determine the satellites' equatorial coordinates. UCAC2 is used as a reference catalogue. The equatorial coordinates are compared with the GUST 06 theory. The average accuracy of normal places is 0.030″-0.040″ in right ascension and declination. The positions of the satellites and their theoretical uranocentric coordinates by GUST 06 are used to calculate the equatorial coordinates of Uranus. The positions of Uranus are compared with the INPOP10 planetary theory. The paper also presents the satellites' differential coordinates relative to one another.

  17. Astrometric observations of visual binaries using 26-inch refractor during 2007-2014 at Pulkovo

    NASA Astrophysics Data System (ADS)

    Izmailov, I. S.; Roshchina, E. A.

    2016-04-01

    We present the results of 15184 astrometric observations of 322 visual binaries carried out in 2007-2014 at Pulkovo observatory. In 2007, the 26-inch refractor ( F = 10413 mm, D = 65 cm) was equipped with the CCD camera FLI ProLine 09000 (FOV 12' × 12', 3056 × 3056 pixels, 0.238 arcsec pixel-1). Telescope automation and weather monitoring system installation allowed us to increase the number of observations significantly. Visual binary and multiple systems with an angular distance in the interval 1."1-78."6 with 7."3 on average were included in the observing program. The results were studied in detail for systematic errors using calibration star pairs. There was no detected dependence of errors on temperature, pressure, and hour angle. The dependence of the 26-inch refractor's scale on temperature was taken into account in calculations. The accuracy of measurement of a single CCD image is in the range of 0."0005 to 0."289, 0."021 on average along both coordinates. Mean errors in annual average values of angular distance and position angle are equal to 0."005 and 0.°04 respectively. The results are available here http://izmccd.puldb.ru/vds.htmand in the Strasbourg Astronomical Data Center (CDS). In the catalog, the separations and position angles per night of observation and annual average as well as errors for all the values and standard deviations of a single observation are presented. We present the results of comparison of 50 pairs of stars with known orbital solutions with ephemerides.

  18. Cassini ISS astrometric observations of the inner jovian satellites, Amalthea and Thebe

    NASA Astrophysics Data System (ADS)

    Cooper, N. J.; Murray, C. D.; Porco, C. C.; Spitale, J. N.

    2006-03-01

    We present a total of 289 new astrometric observations of the inner jovian satellites, Amalthea and Thebe, obtained using the Cassini ISS narrow angle camera. Observations were made using image sequences from 2000 December 11-12 (inbound) and 2001 January 15-16 (outbound), at phase angles of approximately 2° and 122°, respectively. Target distances were of order 284 RJ, giving a maximum resolution of approximately 100 km/pixel. Centroided line and sample values for 239 observations of Amalthea and 50 of Thebe are provided, together with estimated camera pointing information for each image. Orbit fitting using a uniformly precessing Keplerian ellipse model, taking into account the oblateness of Jupiter up to terms in J6, gave RMS fit residuals of 0.364 and 0.443 pixel for Amalthea and Thebe, respectively (equivalent to 0.450 and 0.547 arcsec). RMS residuals relative to the JPL JUP230 ephemeris were 0.306 and 0.604 pixel (equivalent to 0.378 and 0.746 arcsec), for Amalthea and Thebe. The fitted orbital parameters confirm the relatively high inclinations of these satellites ( 0.374°±0.002° and 1.076°±0.003°, respectively), equivalent to maximum vertical displacements above Jupiter's equatorial plane of 1188±6 and 4240±12 km, respectively, consistent with current estimates of the half-thicknesses of the Amalthea and Thebe gossamer rings [Ockert-Bell, M.E., Burns, J.A., Dauber, I.J., Thomas, P.C., Veverka, J., Belton, M.J.S., Klaasen, K.P., 1999. Icarus 138, 188-213].

  19. Modified asteroid observations from homogenization of catalogs to be used for astrometric purposes

    NASA Astrophysics Data System (ADS)

    Martínez Usó, M. J.; López Ortí, J. A.; Marco Castillo, F. J.

    2002-11-01

    Along the last decades we have lived a quick evolution in the field of the Celestial Reference Systems. The new scientific and technological means have allowed us to improve the definitions of the reference systems and the compilation of new and better materializations for their associated reference frames. So, in a few years, the FK5 has substituted the old FK4 as the fundamental catalog while the Hipparcos catalogue plays nowadays this paper in substitution of the FK5 in visual wavelengths. This evolution has caused the old observations of asteroids obtained from catalogs referred to old reference systems to be now obsolete. In some cases, the observations may be recomputed in the new massive catalogs recently compiled, but in other worse cases this computation is not possible possibly due to the loss of fundamental data. In these last cases, the data are lost for astrometrical effects. In our paper, we propose two main objectives. In the first place, we try to obtain a method to homogenize different catalogues referred to the same reference system. This aim will be arranged by means of the minimization of the residual function, which will be previously represented by means of a development in a set of suitable functions. This method will be similar to the one developed by (Bien, R. et al. 1978) and (Schwan, H. 1977). In the second place, we shall propose a practical application of the last process arranging the homogenization of several catalogs and, afterwards, we shall compare minor planets positions corrected by means of the previously obtained catalog corrections with the positions obtained taking the Hipparcos as the reference frame.

  20. Astrometric observations of the satellites of Saturn during 1975-1976

    NASA Technical Reports Server (NTRS)

    Mulholland, J. D.; Shelus, P. J.

    1980-01-01

    Absolute astrometric positions of satellites I-IX of Saturn have been obtained from plates taken with the 2.1-m Otto Struve reflector of the McDonald Observatory during 1975 and 1976. The positions are presented both in absolute celestial coordinates and in intersatellitary relative coordinates.

  1. Astrometric observations of the satellites of Saturn during 1975-1976

    NASA Astrophysics Data System (ADS)

    Mulholland, J. D.; Shelus, P. J.

    1980-08-01

    Absolute astrometric positions of satellites I-IX of Saturn have been obtained from plates taken with the 2.1-m Otto Struve reflector of the McDonald Observatory during 1975 and 1976. The positions are presented both in absolute celestial coordinates and in intersatellitary relative coordinates.

  2. Astrometric observations of the faint outer satellites of Jupiter during the 1989-1990 opposition

    NASA Astrophysics Data System (ADS)

    Whipple, Arthur L.; Shelus, Peter J.; Benedict, G. F.

    1992-02-01

    The 2.1 m Otto Struve reflector at the McDonald Observatory has been used to determine the astrometric positions of faint outer Jovian satellites VI-XIII during the 1989-1990 opposition. The plates were measured to furnish 65 single-image positions of the satellites; of these, six positions are normal points of two images, and one position of satellite VI is a normal point of three images.

  3. Development of a radio-astrometric catalog by means of very long baseline interferometry observations

    NASA Technical Reports Server (NTRS)

    Fanselow, J. L.; Sovers, O. J.; Thomas, J. B.; Bletzacker, F. R.; Kearns, T. J.; Cohen, E. J.; Purcell, G. H., Jr.; Rogstad, D. H.; Skjerve, L. J.; Young, L. E.

    1981-01-01

    The Jet Propulsion Laboratory has been developing a radio-astrometric catalogue for use in the application of radio interferometry to interplanetary navigation and geodesy. The catalogue consists of approximately 100 compact extragalactic radio sources whose relative positions have formal uncertainties of the order of 0.01 arcsec. The sources cover nearly all of the celestial sphere above -40 deg declination. By using the optical counterparts of many of these radio sources, this radio reference frame has been tied to the FK4 optical system with a global accuracy of approximately 0.1 arcsec. This paper describes the status of this work.

  4. Astrometric CCD observations of the third and the fourth moons of Uranus with the normal astrograph at the Pulkovo observatory

    NASA Astrophysics Data System (ADS)

    Dement'eva, A. A.

    2015-09-01

    The results of astrometric CCD observations of two major moons of Uranus (Oberon and Titania) with the Normal Astrograph ( D/F = 0.33 m/3.5 m; CCD S2C with a FOV of 18' × 16') at the Pulkovo Observatory are presented. The observations were conducted in 2008-2011. The CCD image reduction is based on the Turner method with a reference to the UCAC3 catalogue system. The (O-C) values are calculated with the use of the MULTI-SAT server for the ephemerides of planetary moons. The obtained equatorial coordinates are compared to two modern theories of planetary motion: INPOP10 + Lainey (2008) and DE421/LE421 + Lainey (2008). The observations agree well with both theories.

  5. Astrometric observations of PHOBOS and Deimos during the 1988 opposition of Mars

    NASA Astrophysics Data System (ADS)

    Colas, F.

    1992-12-01

    813 intersatellite observations of Phobos and Deimos have been made during the 1988 opposition of Mars with the 1-meter telescope at Pic-du-Midi Observatory. These data represent one third of all the Earth-based observations; what is more, the accuracy is similar to that of the best photographic measurements (Colas & Arlot 1991). In this paper we describe the acquisition, the methods of reduction, and the entire data set. A special effort has been made to estimate the errors for each night. For this purpose, we use numerical simulations to study the influence of the read-out noise and of the sky-background on the measurement of a star-like object on a CCD array. These observations with a good error estimation represent an important set of data for anyone who wants to build a new theory of the motion of the Martian satellites. In addition, we give a method for the estimation of the weight of an observation suitable for any dynamical theory.

  6. Astrometric education in China†

    NASA Astrophysics Data System (ADS)

    Jin, W. J.; Zhu, Z.

    2008-07-01

    With measuring precision on the order of milli-arcseconds for ground-based survey facilities or even micro-arcseconds for space astrometric satellites, the importance of astrometric education continues to be important. The content of astrometric courses in China during the past fifteen years is reviewed and the current astrometric courses for undergraduate and graduate students at universities and observatories in China are presented. Finally the improvements of astrometric education in content and teaching methods are suggested.

  7. Astrometric observations of Phobos with the SRC on Mars Express. New data and comparison of different measurement techniques

    NASA Astrophysics Data System (ADS)

    Pasewaldt, A.; Oberst, J.; Willner, K.; Beisembin, B.; Hoffmann, H.; Matz, K. D.; Roatsch, T.; Michael, G.; Cardesín-Moinelo, A.; Zubarev, A. E.

    2015-08-01

    Aims: From April 2008 to August 2011 Mars Express carried out 74 Phobos flybys at distances between 669 and 5579 km. Images taken with the Super Resolution Channel (SRC) were used to determine the spacecraft-centered right ascension and declination of this Martian moon. Methods: Image positions of Phobos were measured using the limb-fit and control-point measurement techniques. Camera pointing and pointing drift were controlled by means of background star observations that were compared to corresponding positions from reference catalogs. Blurred and noisy images were restored by applying an image-based point spread function in a Richardson-Lucy deconvolution. Results: Here, we report on a set of 158 Phobos astrometric observations with estimated accuracies between 0.224 and 3.405 km circular w.r.t. the line of sight to the satellite. Control point measurements yield slightly more accurate results than the limb fit ones. Our observations are in good agreement with the current Phobos ephemerides by the Jet Propulsion Laboratory (JPL) and the Royal Observatory of Belgium (ROB) with mean offsets of up to 335 m. Our data can be used for the maintenance and update of these models. Tables A.1 and A.2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A28

  8. Astrometric CCD observations of the inner Jovian satellites in 1999-2000

    NASA Astrophysics Data System (ADS)

    Kulyk, I.; Jockers, K.; Karpov, N.; Sergeev, A.

    2002-02-01

    This paper presents the results of observations of the inner Jovian satellites Thebe, Amalthea, Adrastea and Metis made in October-November 1999 and in November 2000. We provide Delta alpha and Delta delta of Thebe and Amalthea with respect to the Galilean satellites, while the positions of Adrastea and Metis are referred to either the Galilean moons or to Thebe or to Amalthea. All observed positions are compared with theoretical ones. Residual statistics show an inner accuracy of our observations in the range from about 0.1 to 0.9 arcsec. The dependence of the differences of the observed and calculated positions on the orbital longitude is presented for our observations of Adrastea and Metis.

  9. Astrometrical observations of Pluto-Charon system with the automated telescopes of Pulkovo observatory

    NASA Astrophysics Data System (ADS)

    Slesarenko, V. Yu.; Bashakova, E. A.; Devyatkin, A. V.

    2016-03-01

    The space probe "New Horizons" was launched on 19th of January 2006 in order to study Pluto and its moons. Spacecraft performed close fly-by to Pluto on 14th of July 2015 and obtained the most detailed images of Pluto and its moon until this moment. At the same time, observation obtained by the ground-based telescopes may also be helpful for the research of such distant system. Thereby, the Laboratory of observational astrometry of Pulkovo Observatory of RAS made a decision to reprocess observations obtained during last decade. More than 350 positional observations of Pluto-Charon system were carried out with the mirror astrograph ZA-320M at Pulkovo and Maksutov telescope MTM-500M near Kislovodsk. These observations were processed by means of software system APEX-II developed in Pulkovo observatory and numerical simulations were performed to calculate the differences between positions of photocenter and barycenter of Pluto-Charon system.

  10. Lunar occultation of Saturn. IV - Astrometric results from observations of the satellites

    NASA Technical Reports Server (NTRS)

    Dunham, D. W.; Elliot, J. L.

    1978-01-01

    The method of determining local lunar limb slopes, and the consequent time scale needed for diameter studies, from accurate occultation timings at two nearby telescopes is described. Results for photoelectric observations made at Mauna Kea Observatory during the occultation of Saturn's satellites on March 30, 1974, are discussed. Analysis of all observations of occultations of Saturn's satellites during 1974 indicates possible errors in the ephemerides of Saturn and its satellites.

  11. Tests of general relativity using astrometric and radiometric observations of the planets

    NASA Technical Reports Server (NTRS)

    Anderson, J. D.; Keesey, M. S. W.; Lau, E. L.; Standish, E. M., Jr.; Newhall, X. X.

    1976-01-01

    Current least squares fits to solar system data, including transit circle observations of the terrestrial and giant planets, radar observations of the terrestrial planets, Mariner 9 range fixes to Mars, and Pioneer 10/11 range fixes to Jupiter, have yielded some new results of interest to experimental relativity. Solutions have been obtained for the parameterized post-Newtonian (PPN) parameters beta and gamma, the solar gravitational quadrupole moment J2, a time variation in the gravitational constant G, and four Nordtvedt parameters.

  12. Astrometric observations of Hevelius and derived values of ΔT (dynamical time - universal time).

    NASA Astrophysics Data System (ADS)

    Wünsch, J.

    About 1500 meridian altitudes of the Sun observed by Johannes Hevelius (1611 - 1687) at Danzig in the years 1652 - 1679 and about 1160 distances of fixed stars from the lunar limb obtained in 1658 - 1679 as well as 48 occultations of stars by the Moon were analyzed with the aim to obtain a value of the time difference ΔT = ET - UT between ephemeris time and universal time for the period of Hevelius' observations. This time difference is a measure of the "clock error" of the rotation of the Earth, caused mainly by secular deceleration due to tidal friction.

  13. Results of 194 Double Stars Measurements from Astrometric CCD Observations at the Nikolaev Observatory (Ukraine)

    NASA Astrophysics Data System (ADS)

    Bodryagin, Daniil; Bondarchuk, Larisa; Maigurova, Nadiia

    2016-04-01

    This paper presents the results of double stars measurements from CCD observations at the 50-cm telescope of the Nikolaev Observatory. The accurate positions at current epoch and proper motions were obtained for 194 WDS pairs. The position angles and separations were measured using REDUC software. The measures standard errors were 0.05" for separations and 0.2° for position angles.

  14. Relativistic theory of astrometric observations. III. Radio interferometry of remote sources

    SciTech Connect

    Pavlov, N.V.

    1985-01-01

    A relativistic VLBI equation and relativistic expressions for the delay time and the interference frequency are derived in the post-Newtonian approximation of the GTR. In the equations obtained all the relativistic corrections due to the solar gravitational field and the motion of the terrestrial observer are taken into account within the limits of the adopted calculation accuracy.

  15. Astrometric observations of the faint satellites of Jupiter and minor planets, 1974-1977

    NASA Technical Reports Server (NTRS)

    Benedict, G. R.; Shelus, P. J.; Mulholland, J. D.

    1978-01-01

    Precise positions of the faint satellites VI-XII of Jupiter during the 1974 opposition, and for Jupiter XIII during the 1976-1977 and 1977-1978 oppositions, have been obtained from plates taken with the 2.1-m Otto Struve reflector of the McDonald Observatory by the use of a new quasi-automatic plate measurement and reduction procedure on a PDS microdensitometer. Observations of selected asteroids, including two of 1977 UB (Chiron) are given also.

  16. A Comparison of the Astrometric Precision and Accuracy of Double Star Observations with Two Telescopes

    NASA Astrophysics Data System (ADS)

    Alvarez, Pablo; Fishbein, Amos E.; Hyland, Michael W.; Kight, Cheyne L.; Lopez, Hairold; Navarro, Tanya; Rosas, Carlos A.; Schachter, Aubrey E.; Summers, Molly A.; Weise, Eric D.; Hoffman, Megan A.; Mires, Robert C.; Johnson, Jolyon M.; Genet, Russell M.; White, Robin

    2009-01-01

    Using a manual Meade 6" Newtonian telescope and a computerized Meade 10" Schmidt-Cassegrain telescope, students from Arroyo Grande High School measured the well-known separation and position angle of the bright visual double star Albireo. The precision and accuracy of the observations from the two telescopes were compared to each other and to published values of Albireo taken as the standard. It was hypothesized that the larger, computerized telescope would be both more precise and more accurate.

  17. A new astrometric measurement and reduction of USNO photographic observations of Phobos and Deimos: 1967-1997

    NASA Astrophysics Data System (ADS)

    Robert, V.; Lainey, V.; Pascu, D.; Pasewaldt, A.; Arlot, J.-E.; De Cuyper, J.-P.; Dehant, V.; Thuillot, W.

    2015-10-01

    Context. Accurate positional measurements of planets and satellites are used to improve our knowledge of both their orbits and their dynamics and to infer the accuracy of the planet and satellite ephemerides. Aims: In the framework of the European FP7 ESPaCE program, we provide the positions of Mars, Phobos, and Deimos taken with the US Naval Observatory 61-inch astrometric reflector and 26-inch refractor from 1967 to 1997. Methods: Four hundred twenty five astrophotographic plates were measured with the digitizer of the Royal Observatory of Belgium and reduced through an optimal process that includes image, instrumental, and spherical corrections using the UCAC4 catalog to provide the most accurate equatorial (RA, Dec) positions. Results: We compared the observed positions of the planet Mars and its satellites with the theoretical positions from INPOP13c and DE430 planetary ephemerides and from NOE MarsSatV10 and MAR097 satellite ephemerides. The rms residuals in RA and Dec of one position are less than 62 mas or about 20 km at the opposition of Mars. The rms intersatellite residuals in RA and Dec of one position are less than 40 mas or about 13 km at Mars. This accuracy is comparable to the most recent CCD observations. We also fitted the NOE model to the new computed positions and compared the orbital evolution of Phobos and Deimos with those derived from the same model, but only fitted to spacecraft data. Our results show that astrophotographic plate data can now compete with those of old spacecraft. Full Table 2 and Tables of the XY positions of the satellites and their references are available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/582/A36, and at the Natural Satellites Data Center service of IMCCE via http://www.imcce.fr/nsdc/

  18. Astrometric observations of Saturn's satellites from McDonald Observatory, 1972. [using reference stars

    NASA Technical Reports Server (NTRS)

    Abbot, R. I.; Mulholland, J. D.; Shelus, P. J.

    1974-01-01

    Observations of Saturn's satellites were reduced by means of secondary reference stars obtained by reduction of Palomar Sky Survey (PSS) plates. This involved the use of 39 SAO stars and plate overlap technique to determine the coordinates of 59 fainter stars in the satellite field. Fourteen plate constants were determined for each of the two PSS plates. Comparison of two plate measurement and reduction techniques on the satellite measurements demonstrate the existence of a serious background gradient effect and the utility of microdensitometry to eliminate this error source in positional determinations of close satellites.

  19. Astrometric Star Catalogues as Combination of Hipparcos/Tycho Catalogues with Ground-Based Observations

    NASA Astrophysics Data System (ADS)

    Vondrak, J.

    The successful ESA mission Hipparcos provided very precise parallaxes, positions and proper motions of many stars in optical wavelength. Therefore, it is a primary representation of International Celestial Reference System in this wavelength. However, the shortness of the mission (less than four years) causes some problems with proper motions of the stars that are double or multiple. Therefore, a combination of the positions measured by Hipparcos satellite with ground-based observations with much longer history provides a better reference frame that is more stable in time. Several examples of such combinations are presented (ACT, TYCHO-2, FK6, GC+HIP, TYC2+HIP, ARIHIP) and briefly described. The stress is put on the most recent Earth Orientation Catalogue (EOC) that uses about 4.4 million optical observations of latitude/universal time variations (made during the twentieth century at 33 observatories in Earth orientation programmes), in combination with some of the above mentioned combined catalogues. The second version of the new catalogue EOC-2 contains 4418 objects, and the precision of their proper motions is far better than that of Hipparcos Catalogue.

  20. Astrometric follow-up observations of directly imaged sub-stellar companions to young stars and brown dwarfs

    NASA Astrophysics Data System (ADS)

    Ginski, C.; Schmidt, T. O. B.; Mugrauer, M.; Neuhäuser, R.; Vogt, N.; Errmann, R.; Berndt, A.

    2014-11-01

    The formation of massive planetary or brown dwarf companions at large projected separations from their host star is not yet well understood. In order to put constraints on formation scenarios, we search for signatures in the orbit dynamics of the systems. We are specifically interested in the eccentricities and inclinations since those parameters might tell us about the dynamic history of the systems and where to look for additional low-mass sub-stellar companions. For this purpose, we utilized VLT/NACO to take several well-calibrated high-resolution images of six target systems and analyse them together with available literature data points of those systems as well as Hubble Space Telescope archival data. We used a statistical least-squares Monte Carlo approach to constrain the orbit elements of all systems that showed significant differential motion of the primary star and companion. We show for the first time that the GQ Lup system shows significant change in both separation and position angle. Our analysis yields best-fitting orbits for this system, which are eccentric (e between 0.21 and 0.69), but cannot rule out circular orbits at high inclinations. Given our astrometry, we discuss formation scenarios of the GQ Lup system. In addition, we detected an even fainter new companion candidate to GQ Lup, which is most likely a background object. We also updated the orbit constraints of the PZ Tel system, confirming that the companion is on a highly eccentric orbit with e > 0.62. Finally, we show with a high significance, that there is no orbital motion observed in the cases of the DH Tau, HD 203030 and 1RXS J160929.1-210524 systems, and give the most precise relative astrometric measurement of the UScoCTIO 108 system to date.

  1. BINARY ASTROMETRIC MICROLENSING WITH GAIA

    SciTech Connect

    Sajadian, Sedighe

    2015-04-15

    We investigate whether or not Gaia can specify the binary fractions of massive stellar populations in the Galactic disk through astrometric microlensing. Furthermore, we study whether or not some information about their mass distributions can be inferred via this method. In this regard, we simulate the binary astrometric microlensing events due to massive stellar populations according to the Gaia observing strategy by considering (i) stellar-mass black holes, (ii) neutron stars, (iii) white dwarfs, and (iv) main-sequence stars as microlenses. The Gaia efficiency for detecting the binary signatures in binary astrometric microlensing events is ∼10%–20%. By calculating the optical depth due to the mentioned stellar populations, the numbers of the binary astrometric microlensing events being observed with Gaia with detectable binary signatures, for the binary fraction of about 0.1, are estimated to be 6, 11, 77, and 1316, respectively. Consequently, Gaia can potentially specify the binary fractions of these massive stellar populations. However, the binary fraction of black holes measured with this method has a large uncertainty owing to a low number of the estimated events. Knowing the binary fractions in massive stellar populations helps with studying the gravitational waves. Moreover, we investigate the number of massive microlenses for which Gaia specifies masses through astrometric microlensing of single lenses toward the Galactic bulge. The resulting efficiencies of measuring the mass of mentioned populations are 9.8%, 2.9%, 1.2%, and 0.8%, respectively. The numbers of their astrometric microlensing events being observed in the Gaia era in which the lens mass can be inferred with the relative error less than 0.5 toward the Galactic bulge are estimated as 45, 34, 76, and 786, respectively. Hence, Gaia potentially gives us some information about the mass distribution of these massive stellar populations.

  2. The PHEMU09 catalogue and astrometric results of the observations of the mutual occultations and eclipses of the Galilean satellites of Jupiter made in 2009

    NASA Astrophysics Data System (ADS)

    Arlot, J.-E.; Emelyanov, N.; Varfolomeev, M. I.; Amossé, A.; Arena, C.; Assafin, M.; Barbieri, L.; Bolzoni, S.; Bragas-Ribas, F.; Camargo, J. I. B.; Casarramona, F.; Casas, R.; Christou, A.; Colas, F.; Collard, A.; Combe, S.; Constantinescu, M.; Dangl, G.; De Cat, P.; Degenhardt, S.; Delcroix, M.; Dias-Oliveira, A.; Dourneau, G.; Douvris, A.; Druon, C.; Ellington, C. K.; Estraviz, G.; Farissier, P.; Farmakopoulos, A.; Garlitz, J.; Gault, D.; George, T.; Gorda, S. Yu.; Grismore, J.; Guo, D. F.; Herald, D.; Ida, M.; Ishida, M.; Ivanov, A. V.; Klemt, B.; Koshkin, N.; Le Campion, J. F.; Liakos, A.; Liao, S. L.; Li, S. N.; Loader, B.; Lopresti, C.; Lo Savio, E.; Marchini, A.; Marino, G.; Masi, G.; Massallé, A.; Maulella, R.; McFarland, J.; Miyashita, K.; Napoli, C.; Noyelles, B.; Pauwels, T.; Pavlov, H.; Peng, Q. Y.; Perelló, C.; Priban, V.; Prost, J.; Razemon, S.; Rousselle, J. P.; Rovira, J.; Ruisi, R.; Ruocco, N.; Salvaggio, F.; Sbarufatti, G.; Shakun, L.; Scheck, A.; Sciuto, C.; da Silva Neto, D. N.; Sinyaeva, N. V.; Sofia, A.; Sonka, A.; Talbot, J.; Tang, Z. H.; Tejfel, V. G.; Thuillot, W.; Tigani, K.; Timerson, B.; Tontodonati, E.; Tsamis, V.; Unwin, M.; Venable, R.; Vieira-Martins, R.; Vilar, J.; Vingerhoets, P.; Watanabe, H.; Yin, H. X.; Yu, Y.; Zambelli, R.

    2014-12-01

    Context. In 2009, the Sun and the Earth passed through the equatorial plane of Jupiter and therefore the orbital planes of its main satellites. It was the equinox on Jupiter. This occurrence made mutual occultations and eclipses between the satellites possible. Experience has shown that the observations of such events provide accurate astrometric data able to bring new information on the dynamics of the Galilean satellites. Observations are made under the form of photometric measurements, but need to be made through the organization of a worldwide observation campaign maximizing the number and the quality of the data obtained. Aims: This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Galilean satellites of Jupiter made during the international campaign in 2009. The final goal is to derive new accurate astrometric data. Methods: We used an accurate photometric model of mutual events adequate with the accuracy of the observation. Our original method was applied to derive astrometric data from photometric observations of mutual occultations and eclipses of the Galilean satellites of Jupiter. Results: We processed the 457 lightcurves obtained during the international campaign of photometric observations of the Galilean satellites of Jupiter in 2009. Compared with the theory, for successful observations, the r.m.s. of O-C residuals are equal to 45.8 mas and 81.1 mas in right ascension and declination, respectively; the mean O-C residuals are equal to -2 mas and -9 mas in right ascension and declination, respectively, for mutual occultations; and -6 mas and +1 mas in right ascension and declination, respectively, for mutual eclipses.

  3. Astrometric and spectroscopic confirmation of a brown dwarf companion to GSC 08047-00232. VLT/NACO deep imaging and spectroscopic observations

    NASA Astrophysics Data System (ADS)

    Chauvin, G.; Lagrange, A.-M.; Lacombe, F.; Dumas, C.; Mouillet, D.; Zuckerman, B.; Gendron, E.; Song, I.; Beuzit, J.-L.; Lowrance, P.; Fusco, T.

    2005-02-01

    We report VLT/NACO imaging observations of the stars GSC 08047-00232 and HIP 6856, probable members of the large Tucana-Horologium association. During our previous ADONIS/SHARPII deep imaging survey, a substellar candidate companion was discovered around each star. Based on VLT/NACO astrometric measurements, we find that GSC 08047-00232 and the faint candidate companion near to it share the same proper motion with a significance of 3.1 σ. On the contrary, the candidate companion to HIP 6856 is probably a background object with a significance of 4.3 σ. We also detect a new fainter and closer candidate companion to HIP 6856, but which is likely a background object too with a significance of 4 σ. Recent VLT/NACO spectroscopic measurements of GSC 08047-00232 finally confirm the substellar nature of this young brown dwarf with a derived spectral type M 9.5±1. GSC 08047-00232 B, with an estimated mass of 25±10 MJup and an effective temperature of 2100±200 K, is presently the third substellar companion identified among young, nearby associations. Based on observations obtained at the VLT in ESO with programs 70.C-0677 and 072.C-0644.

  4. NEAT: a microarcsec astrometric telescope

    NASA Astrophysics Data System (ADS)

    Shao, M.; Nemati, B.; Zhai, C.; Goullioud, R.; Malbet, F.; Leger, A.

    2011-10-01

    NEAT, Nearby Exo-Earth Astrometric Telescope is a medium-small telescope ~ 1m in diameter that is designed to make ultra precise < 1 uas (microarcsec) astrometric measurements of nearby stars in a ~ 1hr observation. Four major error sources prevent normal space telescopes from obtaining accuracies close to 1 uas. Even with a small 1m telescope, photon noise is usually not a problem for the bright nearby target stars. But in general, the reference stars are much fainter. Typically a field of view of ~0.5 deg dia is needed to obtain enough bright reference stars. The NEAT concept uses a very simple but unusual design to avoid optically induced astrometric errors. The third source of error is the accuracy and stability of the focal plane. A 1uas error over a ~2000 arcsec field of view implies the focal plane is accurate or at least stable to 5 parts in 1010 over the lifetime of the mission (~5yrs). The 4th class of error has to do with our knowledge of the PSF and how that PSF is sampled by an imperfect detector. A Nyquist sampled focal plane would have > 2 pixels per λ/D, and centroiding to 1uas means centroiding to 10-5 pixels. This paper describes the mission concept, and an overview of the technology needed to perform 1uas astrometry with a small telescope, and how we overcome problems 1 and 2. A companion paper will describe the technical progress we've made in solving problems 3 and 4.

  5. The SIM Lite Astrometric Observatory

    NASA Astrophysics Data System (ADS)

    Unwin, Stephen C.

    2009-05-01

    SIM Lite is an observatory mission dedicated to precision astrometry. With a single measurement accuracy of 1 microarcsecond (µas) and a noise floor below 0.035 µas it will have the capability to do an extensive search for Earth-mass planets in the `habitable zone’ around several dozen of the nearest stars. SIM Lite maintains its wide-angle accuracy of 4 µas for all targets down to V = 19, limited only by observing time. This opens up a wide array of astrophysical problems. As a flexibly pointed instrument, it is a natural complement to sky surveys such as JMAPS and Gaia, and will tackle questions that don't require the acquisition of statistics on a large number of targets. It will provide accurate masses for the first time for a variety of exotic star types, including X-ray binaries; it will study the structure and evolution of our Galaxy through tidal streams from dwarf spheroidals and the trajectories of halo stars and galaxies. Its faint-target capability will enable the use of astrometric and photometric variability as a probe of the disk accretion and jet formation processes in blazars. SIM Lite will have an extensive GO (General Observer) program, open to all categories of astrometric science. The project successfully completed a series of technology milestones in 2005, and is currently under study by by NASA as a flight mission. The research described in this talk was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  6. Detailed Astrometric Analysis of Pluto

    NASA Astrophysics Data System (ADS)

    ROSSI, GUSTAVO B.; Vieira-Martins, R.; Camargo, J. I.; Assafin, M.

    2013-05-01

    Abstract (2,250 Maximum Characters): Pluto is the main representant of the transneptunian objects (TNO's), presenting some peculiarities such as an atmosphere and a satellite system with 5 known moons: Charon, discovered in 1978, Nix and Hydra, in 2006, P4 in 2011 and P5 in 2012. Until the arrival of the New Horizons spacecraft to this system (july 2015), stellar occultations are the most efficient method, from the ground, to know physical and dinamical properties of this system. In 2010, it was evident a drift in declinations (about 20 mas/year) comparing to the ephemerides. This fact motivated us to remake the reductions and analysis of a great set of our observations at OPD/LNA, in a total of 15 years. The ephemerides and occultations results was then compared with the astrometric and photometric reductions of CCD images of Pluto (around 6500 images). Two corrections were used for a refinement of the data set: diferential chromatic refraction and photocenter. The first is due to the mean color of background stars beeing redder than the color of Pluto, resulting in a slightly different path of light through the atmosphere (that may cause a difference in position of 0.1”). It became more evident because Pluto is crossing the region of the galactic plane. The photocenter correction is based on two gaussians curves overlapped, with different hights and non-coincident centers, corresponding to Pluto and Charon (since they have less than 1” of angular separation). The objective is to separate these two gaussian curves from the observed one and find the right position of Pluto. The method is strongly dependent of the hight of each of the gaussian curves, related to the respective albedos of charon and Pluto. A detailed analysis of the astrometric results, as well a comparison with occultation results was made. Since Pluto has an orbital period of 248,9 years and our interval of observation is about 15 years, we have around 12% of its observed orbit and also, our

  7. Astrometric solar system anomalies

    SciTech Connect

    Nieto, Michael Martin; Anderson, John D

    2009-01-01

    There are at least four unexplained anomalies connected with astrometric data. perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it often experiences a change in total orbital energy per unit mass. next, a secular change in the astronomical unit AU is definitely a concern. It is increasing by about 15 cm yr{sup -1}. The other two anomalies are perhaps less disturbing because of known sources of nongravitational acceleration. The first is an apparent slowing of the two Pioneer spacecraft as they exit the solar system in opposite directions. Some astronomers and physicists are convinced this effect is of concern, but many others are convinced it is produced by a nearly identical thermal emission from both spacecraft, in a direction away from the Sun, thereby producing acceleration toward the Sun. The fourth anomaly is a measured increase in the eccentricity of the Moon's orbit. Here again, an increase is expected from tidal friction in both the Earth and Moon. However, there is a reported unexplained increase that is significant at the three-sigma level. It is produent to suspect that all four anomalies have mundane explanations, or that one or more anomalies are a result of systematic error. Yet they might eventually be explained by new physics. For example, a slightly modified theory of gravitation is not ruled out, perhaps analogous to Einstein's 1916 explanation for the excess precession of Mercury's perihelion.

  8. Astrometric reference stars: from UCAC to URAT

    NASA Astrophysics Data System (ADS)

    Zacharias, N.

    2004-10-01

    Currently available astrometric catalogs will be reviewed, and instrumentation and observational issues discussed, particularly systematic errors and their control. The U.S. Naval Observatory (USNO) CCD Astrograph Catalog (UCAC) is an all-sky astrometric survey to 16th magnitude. It was observed with a semi-automated telescope on a low budget. The second data release (July 2003) contains positions, proper motions, and photometry for over 48 million stars; the final release is expected in 2006. Design studies have been performed for a new 0.9-meter aperture USNO Robotic Astrometric Telescope (URAT) with a single chip (≥ 100 Mpixel), 3 degree FOV and circular symmetric pupil. Its operation is envisioned to be fully automatic, generating stellar positions on the 5 to 10 mas level to at least 18th magnitude with a limiting magnitude of about 20 to 21. These reference stars, being on an inertial system (linked to quasars), will be very beneficial for LSST, PanSTARRS and other projects. With a few years of observing, absolute trigonometric parallaxes (5-20 mas, depending on magnitude) could be obtained for all stars accessible by URAT from an initially southern hemisphere location.

  9. Improved astrometric analysis of Pluto

    NASA Astrophysics Data System (ADS)

    Benedetti-Rossi, G.; Vieira-Martins, R.; Camargo, J.; Assafin, M.; Braga-Ribas, F.

    2014-07-01

    Pluto is the main representantive body of the transneptunian objects (TNOs). It presents an atmosphere and a satellite system with 5 known moons (three of them discovered less than 10 years ago). To learn about the physical and dynamical properties of this system, the most efficient method from the ground --- in spite of its rarity --- are stellar occultations, which showed an evident drift of about 20 milli-arcsecond (mas) in the declination when comparing to the ephemerides [1]. This fact was a great motivation to repeat the reductions and analyses for a large set of our observations. Around 6500 CCD images of Pluto were obtained over 174 nights using 3 telescopes at Pico dos Dias Observatory (OPD/LNA) in Brazil, covering a time span from 1995 to 2013, and another 12 nights in 2007 and 2009 using the ESO/MPG 2.2-m telescope equipped with the Wide Field Imager (WFI). The astrometric positions were reduced using PRAIA (Platform for Reduction of Astronomical Images Automatically) [2] using UCAC4 as the reference catalog. Also, they were corrected for differential chromatic refraction and later the (x,y) center of Pluto was determined from corrections to the measured photocenter, contaminated by Charon. Both corrections were obtained with the original procedures. The final astrometric positions were then compared to the planetary ephemerides (DE421+plu021) and occultation results. We obtained the mean values of 7 mas and 36 mas for the right ascension and declination, respectively, and the standard deviations of σ_α = 45 mas and σ_δ = 49 mas for the offsets in the sense of ''observed minus ephemerides position''. Moreover, we obtained the same behavior for the declination as obtained from stellar occultations, with a drift of around 100 mas since 2005. With the imminent arrival of the New Horizons spacecraft to this system (scheduled for July 2015), new ephemerides may be corrected so that they do not present systematic drifts near the time interval that contains

  10. Progress of astrometric research in Nikolaev Observatory

    NASA Astrophysics Data System (ADS)

    Ivantsov, Anatoliy; Maigurova, Nadia; Martynov, Maxim; Pinigin, Gennadiy

    2012-08-01

    A catalog of astrometric positions and proper motions of 140237 stars in fields of ecliptical zone and high proper motion stars was derived from CCD - observations made at AMC telescope (Nikolaev) in 2008 - 2009. The UCAC2 catalog was used as a reference one for astrometric reductions. The standard error for a single position is 20 - 65 mas in right ascension and 30 - 70 mas in declination. Cross - identification of the obtained data with modern astrometric catalogs such as TYCHO2, 2MASS, CMC14, PPMX, XPM, USNO - A2.0 and XPM - 1.0 was made for investigation systematical errors and calculation of the proper motions [1]. The final catalog contains star positions, proper motions as well as photometric data (B, V, r ´, J, H, K) taken from other catalogs. For analysis of perturbed motion of selected asteroids, there was made astrometric reduction for three thousands of positions of 68 selected asteroids observed at the Russian - Turkish telescope RTT150 in 2008 - 2011 [2]. The research is conducted within the International Joint Project between IMCCE (France), NAO (Ukraine), KFU (Russia), and TUG (Turkey). The reduction was made with the UCAC2 and UCAC3 catalogs. The standard error of a single position is 0.15 arcsec in right ascension and 0.13 arcsec in declination. Also, the first results of astrometric reduction are presented for the observations of selected asteroids made at the AZT8 (Evpatoriya ) and Mobitel (Nikolaev) telescopes. The obtained positions are expected to be used for derivation masses of asteroids by dynamical method. This work is supported by State Agency on Science, Innovation and Information of Ukraine, Russian Foundation for Basic Research. 1. Jin, W., Pinigin, G., Tang, Zh., Shulga, A. (2011). The collaboration between ShAO and NAO: Celebration of the 1 90th anniversary of NAO. Proc. Int. Conf. “Astronomical Research: from near - Earth Space to the Galaxy”, Nikolaev (pp. 92 - 104). 2 . Ivantsov, A., Gumerov, R., Khamitov, I., Aslan, Z

  11. Gaia astrometric data reduction one year into science operations

    NASA Astrophysics Data System (ADS)

    Lammers, Uwe Rainer; Lindegren, Lennart; Hernandez, Jose; Hobbs, David; Bastian, Ulrich; Michalik, Daniel; Klioner, Sergei

    2015-08-01

    The European Space Agency's astrometry satellite Gaia was launched in December 2013 and started its scientific operations in July 2014 after an extended payload commissioning period.We report on the status of the core astrometric data reduction, using the Astrometric Global Iterative Solution (AGIS) and observational data from the first ten months of Gaia science operations. AGIS is a global, simultaneous least-squares estimation of all relevant satellite attitude, payload calibration, and astrometric parameters of selected, well-behaved single stars.After years of testing and validating AGIS with simulation data we now present preliminary results from trial runs with real mission data. These tests give astrometric post-fit residuals at a level commensurate with overall expectations, considering that at this stage of the mission our understanding of the relevant instrumental effects and the behaviour of the very complex payload is still limited.The positive results also indicate that a target date of summer 2016 for a first public release of a Gaia-only astrometric catalogue is feasible. In addition we report on experiments with joint Gaia and Tycho data that allow a useful astrometric solution with less than 1 year of Gaia data.

  12. Astrometric Exoplanet Detection with Gaia

    NASA Astrophysics Data System (ADS)

    Perryman, Michael; Hartman, Joel; Bakos, Gáspár Á.; Lindegren, Lennart

    2014-12-01

    We provide a revised assessment of the number of exoplanets that should be discovered by Gaia astrometry, extending previous studies to a broader range of spectral types, distances, and magnitudes. Our assessment is based on a large representative sample of host stars from the TRILEGAL Galaxy population synthesis model, recent estimates of the exoplanet frequency distributions as a function of stellar type, and detailed simulation of the Gaia observations using the updated instrument performance and scanning law. We use two approaches to estimate detectable planetary systems: one based on the signal-to-noise ratio of the astrometric signature per field crossing, easily reproducible and allowing comparisons with previous estimates, and a new and more robust metric based on orbit fitting to the simulated satellite data. With some plausible assumptions on planet occurrences, we find that some 21,000 (±6000) high-mass (~1-15M J) long-period planets should be discovered out to distances of ~500 pc for the nominal 5 yr mission (including at least 1000-1500 around M dwarfs out to 100 pc), rising to some 70,000 (±20, 000) for a 10 yr mission. We indicate some of the expected features of this exoplanet population, amongst them ~25-50 intermediate-period (P ~ 2-3 yr) transiting systems.

  13. Astrometric exoplanet detection with Gaia

    SciTech Connect

    Perryman, Michael; Hartman, Joel; Bakos, Gáspár Á.; Lindegren, Lennart

    2014-12-10

    We provide a revised assessment of the number of exoplanets that should be discovered by Gaia astrometry, extending previous studies to a broader range of spectral types, distances, and magnitudes. Our assessment is based on a large representative sample of host stars from the TRILEGAL Galaxy population synthesis model, recent estimates of the exoplanet frequency distributions as a function of stellar type, and detailed simulation of the Gaia observations using the updated instrument performance and scanning law. We use two approaches to estimate detectable planetary systems: one based on the signal-to-noise ratio of the astrometric signature per field crossing, easily reproducible and allowing comparisons with previous estimates, and a new and more robust metric based on orbit fitting to the simulated satellite data. With some plausible assumptions on planet occurrences, we find that some 21,000 (±6000) high-mass (∼1-15M {sub J}) long-period planets should be discovered out to distances of ∼500 pc for the nominal 5 yr mission (including at least 1000-1500 around M dwarfs out to 100 pc), rising to some 70,000 (±20, 000) for a 10 yr mission. We indicate some of the expected features of this exoplanet population, amongst them ∼25-50 intermediate-period (P ∼ 2-3 yr) transiting systems.

  14. PACMAN: PRIMA astrometric instrument software

    NASA Astrophysics Data System (ADS)

    Abuter, Roberto; Sahlmann, Johannes; Pozna, Eszter

    2010-07-01

    The dual feed astrometric instrument software of PRIMA (PACMAN) that is currently being integrated at the VLTI will use two spatially modulated fringe sensor units and a laser metrology system to carry out differential astrometry. Its software and hardware compromises a distributed system involving many real time computers and workstations operating in a synchronized manner. Its architecture has been designed to allow the construction of efficient and flexible calibration and observation procedures. In parallel, a novel scheme of integrating M-code (MATLAB/OCTAVE) with standard VLT (Very Large Telescope) control software applications had to be devised in order to support numerically intensive operations and to have the capacity of adapting to fast varying strategies and algorithms. This paper presents the instrument software, including the current operational sequences for the laboratory calibration and sky calibration. Finally, a detailed description of the algorithms with their implementation, both under M and C code, are shown together with a comparative analysis of their performance and maintainability.

  15. The ESPRI project: astrometric exoplanet search with PRIMA

    NASA Astrophysics Data System (ADS)

    Launhardt, R.; Queloz, D.; Henning, Th.; Quirrenbach, A.; Delplancke, F.; Andolfato, L.; Baumeister, H.; Bizenberger, P.; Bleuler, H.; Chazelas, B.; Dérie, F.; Di Lieto, L.; Duc, T. P.; Duvanel, O.; Elias, N. M., II; Fluery, M.; Geisler, R.; Gillet, D.; Graser, U.; Koch, F.; Köhler, R.; Maire, C.; Mégevand, D.; Michellod, Y.; Moresmau, J.-M.; Müller, A.; Müllhaupt, P.; Naranjo, V.; Pepe, F.; Reffert, S.; Sache, L.; Ségransan, D.; Salvadé, Y.; Schulze-Hartung, T.; Setiawan, J.; Simond, G.; Sosnowska, D.; Stilz, I.; Tubbs, B.; Wagner, K.; Weber, L.; Weise, P.; Zago, L.

    2008-07-01

    PRIMA, the instrument for Phase-Referenced Imaging and Micro-arcsecond Astrometry at the VLTI, is currently being developed at ESO. PRIMA will implement the dual-feed capability, at first for two UTs or ATs, to enable simultaneous interferometric observations of two objects that are separated by up to 1 arcmin. PRIMA is designed to perform narrow-angle astrometry in K-band with two ATs as well as phase-referenced aperture synthesis imaging with instruments like Amber and Midi. In order to speed up the full implementation of the 10 microarcsec astrometric capability of the VLTI and to carry out a large astrometric planet search program, a consortium lead by the Observatoire de Genève, Max Planck Institute for Astronomy, and Landessternwarte Heidelberg, has built Differential Delay Lines for PRIMA and is developing the astrometric observation preparation and data reduction software. When the facility becomes fully operational in 2009, we will use PRIMA to carry out a systematic astrometric Exoplanet Search program, called ESPRI. In this paper, we describe the narrow-angle astrometry measurement principle, give an overview of the ongoing hardand software developments, and outline our anticipated astrometric exoplanet search program.

  16. Gamma astrometric measurement experiment -science and implementation

    NASA Astrophysics Data System (ADS)

    Gai, Mario; Vecchiato, Alberto; Lattanzi, Mario G.; Ligori, Sebastiano; Loreggia, Davide; Fineschi, Silvano

    GAME (Gamma Astrometric Measurement Experiment) is a mission concept taking advantage of astronomical techniques for high precision measurements of interest to Fundamental Physics, and in particular the γ parameter of the Parameterized Post-Newtonian formulation of gravi-tation theories modifying the General Relativity. A space based telescope, looking close to the Solar limb thanks to coronagraphic techniques, may implement astrometric measurements sim-ilar to those performed in the solar eclipse of 1919, when Dyson, Eddington and collaborators measured for the first time the gravitational bending of light. Simulations show that the final accuracy of GAME can reach the 10-7 level. GAME will be a decisive experiment for the understanding of gravity physics, cosmology and the Universe evolution. The observations leading to Dark Matter (e.g. galaxy rotation curves) and Dark Energy (accelerated expansion of the Universe) might be explained with a modified version of General Relativity, e.g. in which the curvature invariant R is no longer constant as in Einstein's equations, i.e. the f (R) gravity theories. A 10-7 level determination of γ will provide stringent constraints on acceptable theories. Also, high precision astrometry makes accessible other appealing measurements, e.g. the light deflection induced by the quadrupole moment of giant planets, like Jupiter or Saturn, and, by high precision determination of the orbits of Mercury and high elongation asteroids, the PPN parameter β. GAME may also carry out measurements on selected astrophysical targets, e.g. nearby, bright stars known to host companions with minimum masses in the planetary/brown dwarf regime, and orbital radii in the 3-7 AU range, which are observed by no other present or planned campaigns. GAME, also thanks to high-cadence, high-precision photometry on transit-ing exoplanet systems, will thus improve on our understanding of the actual mass distribution and multiplicity of sub-stellar companions

  17. Astrometrically registered simultaneous observations of the 22 GHz H{sub 2}O and 43 GHz SiO masers toward R Leonis Minoris using KVN and source/frequency phase referencing

    SciTech Connect

    Dodson, Richard; Rioja, María J.; Jung, Tae-Hyun; Sohn, Bong-Won; Byun, Do-Young; Cho, Se-Hyung; Lee, Sang-Sung; Kim, Jongsoo; Kim, Kee-Tae; Oh, Chung-Sik; Han, Seog-Tae; Je, Do-Heung; Chung, Moon-Hee; Wi, Seog-Oh; Kang, Jiman; Lee, Jung-Won; Chung, Hyunsoo; Kim, Hyo-Ryoung; Kim, Hyun-Goo; Lee, Chang-Hoon; and others

    2014-11-01

    Oxygen-rich asymptotic giant branch (AGB) stars can be intense emitters of SiO (v = 1 and 2, J = 1 → 0) and H{sub 2}O maser lines at 43 and 22 GHz, respectively. Very long baseline interferometry (VLBI) observations of the maser emission provide a unique tool to probe the innermost layers of the circumstellar envelopes in AGB stars. Nevertheless, the difficulties in achieving astrometrically aligned H{sub 2}O and v = 1 and v = 2 SiO maser maps have traditionally limited the physical constraints that can be placed on the SiO maser pumping mechanism. We present phase-referenced simultaneous spectral-line VLBI images for the SiO v = 1 and v = 2, J = 1 → 0, and H{sub 2}O maser emission around the AGB star R LMi, obtained from the Korean VLBI Network (KVN). The simultaneous multi-channel receivers of the KVN offer great possibilities for astrometry in the frequency domain. With this facility, we have produced images with bona fide absolute astrometric registration between high-frequency maser transitions of different species to provide the positions of the H{sub 2}O maser emission and the center of the SiO maser emission, hence reducing the uncertainty in the proper motions for R LMi by an order of magnitude over that from Hipparcos. This is the first successful demonstration of source frequency phase referencing for millimeter VLBI spectral-line observations and also where the ratio between the frequencies is not an integer.

  18. Forthcoming Occultations of Astrometric Radio Sources by Planets

    NASA Technical Reports Server (NTRS)

    L'vov, Victor; Malkin, Zinovy; Tsekmeister, Svetlana

    2010-01-01

    Astrometric observations of radio source occultations by solar system bodies may be of large interest for testing gravity theories, dynamical astronomy, and planetary physics. In this paper, we present an updated list of the occultations of astrometric radio sources by planets expected in the coming years. Such events, like solar eclipses, generally speaking can only be observed in a limited region. A map of the shadow path is provided for the events that will occurr in regions with several VLBI stations and hence will be the most interesting for radio astronomy experiments.

  19. ON THE SOURCE OF ASTROMETRIC ANOMALOUS REFRACTION

    SciTech Connect

    Taylor, M. Suzanne; McGraw, John T.; Zimmer, Peter C.; Pier, Jeffrey R.

    2013-03-15

    More than a century ago, astronomers using transit telescopes to determine precise stellar positions were hampered by an unexplained periodic shifting of the stars they were observing. With the advent of CCD transit telescopes in the past three decades, this unexplained motion, termed 'anomalous refraction' by these early astronomers, is again being observed. Anomalous refraction is described as a low-frequency, large angular scale ({approx}2 Degree-Sign ) motion of the entire image plane with respect to the celestial coordinate system as observed and defined by astrometric catalogs. These motions, of typically several tenths of an arcsecond amplitude with timescales on the order of 10 minutes, are ubiquitous to ground-based drift-scan astrometric measurements regardless of location or telescopes used and have been attributed to the effect of tilting of equal-density layers of the atmosphere. The cause of this tilting has often been attributed to atmospheric gravity waves, but this cause has never been confirmed. Although theoretical models of atmospheric refraction show that atmospheric gravity waves are a plausible cause of anomalous refraction, an observational campaign specifically directed at defining this relationship provides clear evidence that anomalous refraction is not consistent with the passage of atmospheric gravity waves. The source of anomalous refraction is found to be meter-scale, slowly evolving quasi-coherent dynamical structures in the boundary layer below 60 m above ground level.

  20. Fundamental Physics with Gaia: A Generic Globals Update Block for Gaia's Astrometric Iterative Solution

    NASA Astrophysics Data System (ADS)

    Lammers, U.; Klioner, S.

    2012-09-01

    Gaia is ESA's ambitious space astrometry mission with a foreseen launch date around mid-2013. Its main objective is to perform a stellar census of the 1000 million brightest objects in our galaxy from which an astrometric catalogue of micro-arcsec level accuracy will be constructed. The Astrometric Global Iterative Solution (AGIS) is the mathematical and numerical framework for creating the astrometric core solution for this catalogue. At past ADASS meetings we have presented the basic working principles of AGIS and the development status of its main constituents. This year we discuss plans for another key step to mature AGIS into an operational system: Global (G) parameters are those influenced by all observations of Gaia in a global sense (e.g. the fundamental parameters of the Parametrized Post-Newtonian (PPN) formalism). We outline a scheme that will allow us to define in a very flexible way at run time the list of G-parameters to solve for. The scheme resembles the Generic Calibration concept that is implemented in AGIS since a while already.

  1. Astrometric Results of NEOs from the Characterization and Astrometric Follow-up Program at Adler Planetarium

    NASA Astrophysics Data System (ADS)

    Nault, Kristie A.; Brucker, Melissa J.; Hammergren, Mark; Gyuk, Geza; Solontoi, Mike R.

    2015-11-01

    We present astrometric results of near-Earth objects (NEOs) targeted in fourth quarter 2014 and in 2015. This is part of Adler Planetarium’s NEO characterization and astrometric follow-up program, which uses the Astrophysical Research Consortium (ARC) 3.5-m telescope at Apache Point Observatory (APO). The program utilizes a 17% share of telescope time, amounting to a total of 500 hours per year. This time is divided up into two hour observing runs approximately every other night for astrometry and frequent half-night runs approximately several times a month for spectroscopy (see poster by M. Hammergren et. al.) and light curve studies (see poster by M. J. Brucker et. al.).Observations were made using Seaver Prototype Imaging Camera (SPIcam), a visible-wavelength, direct imaging CCD camera with 2048 x 2048 pixels and a field of view of 4.78’ x 4.78’. Observations were made using 2 x 2 binning.Special emphasis has been made to focus on the smallest NEOs, particularly around 140m in diameter. Targets were selected based on absolute magnitude (prioritizing for those with H > 25 mag to select small objects) and a 3σ uncertainty less than 400” to ensure that the target is in the FOV. Targets were drawn from the Minor Planet Center (MPC) NEA Observing Planning Aid, the JPL What’s Observable tool, and the Spaceguard priority list and faint NEO list.As of August 2015, we have detected 670 NEOs for astrometric follow-up, on point with our goal of providing astrometry on a thousand NEOs per year. Astrometric calculations were done using the interactive software tool Astrometrica, which is used for data reduction focusing on the minor bodies of the solar system. The program includes automatic reference star identification from new-generation star catalogs, access to the complete MPC database of orbital elements, and automatic moving object detection and identification.This work is based on observations done using the 3.5-m telescope at Apache Point Observatory

  2. Deep Astrometric Standards and Galactic Structure

    NASA Astrophysics Data System (ADS)

    Platais, Imants; Wyse, Rosemary F. G.; Zacharias, Norbert

    2006-01-01

    The advent of next-generation imaging telescopes, such as the Large Synoptic Survey Telescope (LSST) and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), has revitalized the need for deep and precise reference frames. The proposed weak-lensing observations with these facilities put the highest demands on image quality over wide angles on the sky. It is particularly difficult to achieve a subarcsecond point-spread function on stacked images, where precise astrometry plays a key role. Current astrometric standards are insufficient to achieve the science goals of these facilities. We thus propose the establishment of a few selected deep (V=25) astrometric standards (DAS). These will enable a reliable geometric calibration of solid-state mosaic detectors in the focal plane of large ground-based telescopes, and will make a substantial contribution to our understanding of stellar populations in the Milky Way. In this paper we examine the need for such standards and discuss the strategy for selecting them and their acquisition and reduction techniques. The feasibility of DAS is demonstrated by a pilot study around the open cluster NGC 188, using the Kitt Peak National Observatory 4 m CCD Mosaic camera, and by Subaru Suprime-Cam observations. The goal of reaching an accuracy of 5-10 mas in positions and obtaining absolute proper motions good to 2 mas yr-1 over a several square-degree area is challenging, but reachable with the NOAO 4 m telescopes and CCD mosaic imagers, or a similar setup. Our proposed DAS aims to establish four fields near the Galactic plane, at widely separated coordinates. In addition to their utilitarian purpose for DAS, the data we will obtain in these fields will enable fundamental Galactic science in their own right. The positions, proper motions, and VI photometry of faint stars will address outstanding questions of Galactic disk formation and evolution, stellar buildup, and mass assembly via merger events.

  3. Newcomb Astrometric Satellite: Preliminary Design

    NASA Astrophysics Data System (ADS)

    Cobb, Michael L.; Johnston, Kenneth J.; Reasenberg, Robert D.; Phillips, James D.; Simon, Richard S.

    1993-12-01

    Newcomb is conceived as a low cost astrometric satellite able to yield 100 micro arcseconds positional accuracy for about 1000 stars. Using a set of three (or four) fixed-angle stellar interferometers, each with a 30 cm baseline, Newcomb's 27 month mission life should produce a POINTS-like lock-up of the coordinate system with as few as 180 stars. The three interferometers are constructed of Ultra Low Expansion (ULE) glass, and are thermally controlled to 0.01 K. Selection of a Sun-synchronous orbit with a fixed Earth profile will help shield the payload from strong thermal excursions. Because the payload is small, several launch possibilities exist including Space Test Program (STP) and NASA. Several design tradeoffs remain and will be briefly discussed.

  4. The astrometric data-reduction software for exoplanet detection with PRIMA

    NASA Astrophysics Data System (ADS)

    Elias, Nicholas M., II; Köhler, Rainer; Stilz, Ingo; Reffert, Sabine; Geisler, Ronny; Quirrenbach, Andreas; de Jong, Jeroen; Delplancke, Françoise; Tubbs, Robert N.; Launhardt, Ralf; Henning, Thomas; Mégevand, Denis; Queloz, Didier

    2008-07-01

    PRIMA/PACMAN is scheduled for commissioning on Paranal in late 2008 as part of the VLTI. In this paper, we discuss the important aspects of its astrometric data-reduction software. For example, the top-level requirements, interfaces to existing ESO software, data types, data levels, and data flow among the recipes dictate the overall design of any software package. In addition, the complexity of the PACMAN instrument, the long-term nature of astrometric observations, and the need to improve algorithms as the understanding of the hardware improves, impose additional requirements on the astrometric data-reduction software.

  5. Effects of disc asymmetries on astrometric measurements. Can they mimic planets?

    NASA Astrophysics Data System (ADS)

    Kral, Q.; Schneider, J.; Kennedy, G.; Souami, D.

    2016-07-01

    Astrometry covers a parameter space that cannot be reached by RV or transit methods to detect terrestrial planets on wide orbits. In addition, high accuracy astrometric measurements are necessary to measure the inclination of the planet's orbits. Here we investigate the principles of an artefact of the astrometric approach, namely the displacement of the photo-centre owing to inhomogeneities in a dust disc around the parent star. Indeed, theory and observations show that circumstellar discs can present strong asymmetries. We model the pseudo-astrometric signal caused by these inhomogeneities, asking whether a dust clump in a disc can mimic the astrometric signal of an Earth-like planet. We show that these inhomogeneities cannot be neglected when using astrometry to find terrestrial planets. We provide the parameter space for which these inhomogeneities can affect the astrometric signals but still not be detected by mid-IR observations. We find that a small cross section of dust corresponding to a cometary mass object is enough to mimic the astrometric signal of an Earth-like planet. Astrometric observations of protoplanetary discs to search for planets can also be affected by the presence of inhomogeneities. Some further tests are given to confirm whether an observation is a real astrometric signal from a planet or an impostor. Eventually, we also study the case where the cross-section of dust is high enough to provide a detectable IR-excess and to have a measurable photometric displacement by actual instruments such as Gaia, IRAC, or GRAVITY. We suggest a new method, which consists of using astrometry to quantify asymmetries (clumpiness) in inner debris discs that cannot be otherwise resolved.

  6. Astrometric solar-system anomalies

    NASA Astrophysics Data System (ADS)

    Anderson, John D.; Nieto, Michael Martin

    2010-01-01

    There are at least four unexplained anomalies connected with astrometric data. Perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it often experiences a change in total orbital energy per unit mass. Next, a secular change in the astronomical unit AU is definitely a concern. It is reportedly increasing by about 15 cm yr-1. The other two anomalies are perhaps less disturbing because of known sources of nongravitational acceleration. The first is an apparent slowing of the two Pioneer spacecraft as they exit the solar system in opposite directions. Some astronomers and physicists, including us, are convinced this effect is of concern, but many others are convinced it is produced by a nearly identical thermal emission from both spacecraft, in a direction away from the Sun, thereby producing acceleration toward the Sun. The fourth anomaly is a measured increase in the eccentricity of the Moon's orbit. Here again, an increase is expected from tidal friction in both the Earth and Moon. However, there is a reported unexplained increase that is significant at the three-sigma level. It is prudent to suspect that all four anomalies have mundane explanations, or that one or more anomalies are a result of systematic error. Yet they might eventually be explained by new physics. For example, a slightly modified theory of gravitation is not ruled out, perhaps analogous to Einstein's 1916 explanation for the excess precession of Mercury's perihelion.

  7. Determining PPN gamma with Gaia's Astrometric Core Solution

    NASA Astrophysics Data System (ADS)

    Hobbs, David; Holl, B.; Lindegren, L.; Raison, F.; Klioner, S.; Butkevich, A.

    2009-05-01

    Gaia is the ESA space astrometry mission due for launch in December 2011. Its objective is to map a large part of our Galaxy and its surroundings by simultaneous positional, photometric and spectroscopic measurements. In addition to its huge output of fundamental astrometric and astrophysical data, it will provide stringent new tests of general relativity. One of the largest relativistic effects observed via Gaia's measurements is the gravitational light bending due to the Sun and major planets. This opens the possibility of accurately measuring the parameter γ of the Parameterized Post-Newtonian (PPN) formulation, which is of key importance to fundamental physics. By analyzing the astrometric residuals, which compare the observations to predictions based on general relativity, a constraint on PPN γ could be obtained which is significantly better than today's best estimate from the Cassini mission of 2x10-5. The effects of introducing global unknowns into Gaia's Astrometric Global Iterative Solution (AGIS) are not well understood and the convergence properties of the solution may be affected in undesirable ways. For this reason we have implemented the algorithm to determine PPN γ within our simulation software, known as AGISLab. This light-weight and scalable simulation tool allows to investigate the convergence properties of the solution when PPN γ is included together with the astrometric and attitude updates. In particular we have considered the statistical correlation between PPN γ and the stellar parallaxes which slows the convergence of the iterative solution. By introducing a further global pseudo parameter, equivalent to a common parallax shift but constrained to zero, this correlation is eliminated resulting in an improved convergence and a better estimate of the standard error of PPN γ. Preliminary results are presented based on simulated data, which include only the deflection of light by the Sun.

  8. Reduction of the Gaia astrometric data

    NASA Astrophysics Data System (ADS)

    Fabricius, C.; Torra, J.; Portell, J.; Castañeda, J.

    2011-11-01

    In two years, the European Space Agency (ESA) will launch the Gaia mission.Gaia will observe all point-like sources in the sky between magnitude 6 and20, a total of more than a thousand million stars and planets. For thebrightest sources we will obtain parallaxes and yearly proper motions witha precision of 10 microarcseconds, while the precision will degrade to300 microarcseconds for thefaintest stars. The reduction of the astrometric data is a very complex andextensive task, which only can be undertaken in a collaboration betweenmany groups within the ESA member states.We describe the role of Spain and of the national supercomputing centre(CNS-BSC) in this work, and describe some of the most critical points inmodelling the instrument and in the observations.We describe the initial data treatment which must be carried out dailyduring the mission, and the process of repeated improvement of theintermediate data which is carried out several times, before reaching thefinal values. The fulfilment of these tasks, especially the latter, is atechnological challenge for the mission.

  9. Astrometric Solar-System Anomalies

    NASA Astrophysics Data System (ADS)

    Anderson, John D.

    2009-05-01

    There are four unexplained anomalies connected with astrometric data. Perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it experiences a gain in total orbital energy per unit mass (Anderson et al., Phys. Rev. Lett. 100, 091102). This amounts to a net velocity increase of 13.5 mm/s for the NEAR spacecraft at a closest approach of 539 km, 3.9 mm/s for the Galileo spacecraft at 960 km, and 1.8 mm/s for the Rosetta spacecraft at 1956 km. Next, I suggest the change in the astronomical unit AU is definitely a concern. It is increasing by about 15 cm/yr (Krasinsky and Brumberg, Celes. Mech. & Dynam. Astron. 90, 267). The other two anomalies are perhaps less disturbing because of known sources of nongravitational acceleration. The first is an apparent slowing of the two Pioneer spacecraft as they exit the solar system in opposite directions (Anderson et al., Phys. Rev. D 65, 082004). Some, including me, are convinced this effect is of concern, but many are convinced it is produced by a nearly identical thermal emission from both spacecraft, in a direction away from the Sun, thereby producing acceleration toward the Sun. The fourth anomaly is a measured increase in the eccentricity of the Moon's orbit. Here again, an increase is expected from tidal friction in both the Earth and Moon. However, there is a reported increase that is about three times larger than expected (J. G. Williams, DDA/AAS Brouwer Award Lecture, Halifax, Nova Scotia 2006). We suspect that all four anomalies have mundane explanations. However, the possibility that they will be explained by a new theory of gravitation is not ruled out, perhaps analogous to Einstein's 1916 explanation of the excess precession of Mercury's perihelion.

  10. Astrometric Calibration of the Gemini NICI Planet-Finding Campaign

    NASA Astrophysics Data System (ADS)

    Hayward, Thomas L.; Biller, Beth A.; Liu, Michael C.; Nielsen, Eric L.; Wahhaj, Zahed; Chun, Mark; Ftaclas, Christ; Hartung, Markus; Toomey, Douglas W.

    2014-12-01

    We describe the astrometric calibration of the Gemini NICI Planet-Finding Campaign. The Campaign requires a relative astrometric accuracy of ≈20 mas across multiyear timescales in order to distinguish true companions from background stars by verifying common proper motion and parallax with their parent stars. The calibration consists of a correction for instrumental optical image distortion, plus on-sky imaging of astrometric fields to determine the pixel scale and image orientation. We achieve an accuracy of lsim7 mas between the center and edge of the 18'' NICI field, meeting the 20 mas requirement. Most of the Campaign data in the Gemini Science Archive are accurate to this level but we identify a number of anomalies and present methods to correct the errors. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

  11. Astrometric orbits of SB^9 stars

    NASA Astrophysics Data System (ADS)

    Jancart, S.; Jorissen, A.; Babusiaux, C.; Pourbaix, D.

    2005-10-01

    Hipparcos Intermediate Astrometric Data (IAD) have been used to derive astrometric orbital elements for spectroscopic binaries from the newly released Ninth Catalogue of Spectroscopic Binary Orbits (SB^9). This endeavour is justified by the fact that (i) the astrometric orbital motion is often difficult to detect without the prior knowledge of the spectroscopic orbital elements, and (ii) such knowledge was not available at the time of the construction of the Hipparcos Catalogue for the spectroscopic binaries which were recently added to the SB^9 catalogue. Among the 1374 binaries from SB^9 which have an HIP entry (excluding binaries with visual companions, or DMSA/C in the Double and Multiple Stars Annex), 282 have detectable orbital astrometric motion (at the 5% significance level). Among those, only 70 have astrometric orbital elements that are reliably determined (according to specific statistical tests), and for the first time for 20 systems. This represents a 8.5% increase of the number of astrometric systems with known orbital elements (The Double and Multiple Systems Annex contains 235 of those DMSA/O systems). The detection of the astrometric orbital motion when the Hipparcos IAD are supplemented by the spectroscopic orbital elements is close to 100% for binaries with only one visible component, provided that the period is in the 50-1000 d range and the parallax is >5 mas. This result is an interesting testbed to guide the choice of algorithms and statistical tests to be used in the search for astrometric binaries during the forthcoming ESA Gaia mission. Finally, orbital inclinations provided by the present analysis have been used to derive several astrophysical quantities. For instance, 29 among the 70 systems with reliable astrometric orbital elements involve main sequence stars for which the companion mass could be derived. Some interesting conclusions may be drawn from this new set of stellar masses, like the enigmatic nature of the companion to the

  12. The Full-sky Astrometric Mapping Explorer Concept Study

    NASA Astrophysics Data System (ADS)

    Horner, S. D.; Germain, M. E.; Greene, T. P.; Harris, F. H.; Johnson, M. S.; Johnston, K. J.; Monet, D. G.; Murison, M. A.; Phillips, J. D.; Reasenberg, R. D.; Seidelmann, P. K.; Talabac, S. J.; Urban, S. E.; van Buren, D.; Vassar, R. H.

    1999-05-01

    NASA has selected the Full-sky Astrometric Mapping Explorer (FAME) to be one of five MIDEX missions to be funded for a concept study. This concept study will be submitted to NASA on 18 June, with final selection, scheduled for September, of two of these missions for flight in 2003 or 2004. FAME is designed to perform an all-sky, astrometric survey with unprecedented accuracy. It will create a rigid astrometric catalog of 40,000,000 stars with visual band magnitudes 5 < V < 15. For bright stars, 5 < V < 9, FAME will determine positions and parallaxes accurate to < 50 microarcseconds, with proper motion errors < 50 microarcseconds/year. For fainter stars, 9 < V < 15, FAME will determine positions and parallaxes accurate to < 300 microarcseconds, with proper motion errors < 300 microarcseconds/year. FAME will also collect photometric data on these 40,000,000 stars in four Sloan DSS colors. During the concept study, the team has worked to optimize the scientific return from FAME while minimizing cost and risk. The optical design was modified for improved accuracy of individual observations and improved mechanical design. The optical, mechanical, and thermal design of the instrument have been improved. Tests using CCDs in TDI mode are being conducted to confirm the accuracy obtainable from individual observations as well as determine the optimal clocking scheme for astrometric devices operated in TDI mode. The use of solar radiation pressure for spacecraft precession has undergone further feasibility study, as have the mechanisms for deploying the solar shield. Numerous other trade studies have been conducted, including orbit/communications, on board processing, and the use of neutral density filters for astrometry of bright stars versus other options. A detailed error budget has been formulated and the mission requirements have been defined. We look forward to selection for launch and a successful FAME mission that will redefine the extragalactic distance scale and

  13. The Full-sky Astrometric Mapping Explorer - An optical, astrometric survey mission

    NASA Astrophysics Data System (ADS)

    Horner, S. D.; Germain, M. E.; Greene, T. P.; Harris, F. H.; Harris, H. C.; Johnson, M. S.; Johnston, K. J.; Monet, D. G.; Murison, M. A.; Phillips, J. D.; Reasenberg, R. D.; Seidelmann, P. K.; Urban, S. E.; Vassar, R. H.

    1999-12-01

    The Full-sky Astrometric Mapping Explorer (FAME) is a NASA MIDEX mission scheduled for launch in 2004. It will perform an all sky, astrometric survey with unprecedented accuracy. FAME will determine the positions, parallaxes, proper motions, and photometry of 40,000,000 stars with visual band magnitudes 5 < V < 15. For bright stars, 5 < V < 9, FAME will determine positions and parallaxes accurate to < 50 microarcseconds, with proper motion errors < 50 microarcseconds/year. For fainter stars, 9 < V < 15, FAME will determine positions and parallaxes accurate to < 500 microarcseconds, with proper motion errors < 500 microarcseconds/year. FAME will also collect photometric data on these 40,000,000 stars in four Sloan DSS colors. FAME will enable a wide range of scientific investigations using its large, rich database of information on stellar properties. It will: * Calibrate the zero point of the extragalactic distance scale to 1% * Determine absolute luminosities of a wide range of spectral types * Detect a meaningful statistical sample of companion stars, brown dwarfs, and giant planets * Enable studies of the kinematics of our galaxy, including the effect of dark matter in the disk * Characterize stellar variability of a large sample of stars at the 0.1% level * Define a rigid optical reference frame for future scientific endeavors FAME is evolved from design concepts from the Hipparcos mission, using current CCD technology to observe more and fainter stars. Like Hipparcos, FAME has a compound mirror consisting of two flats angled relative to each other. The compound mirror feeds the two fields of view separated by the ``basic angle'' into a common telescope. The two fields of view are used to control the growth of stochastic errors in determining the relative separations of stars. FAME is a joint development effort of the U.S. Naval Observatory, the Naval Research Laboratory, Lockheed Martin Missiles and Space Advanced Technology Center, and the Smithsonian

  14. Astronomical VLBI: Comparison and Contrast with Geodetic/Astrometric VLBI

    NASA Astrophysics Data System (ADS)

    Walker, R. Craig

    2000-05-01

    The VLBI technique can be used for both high precision geometric measurements in geodetic and astrometric observations, and to study astronomical sources with high resolution. The equipment required for both types of observations is essentially the same and many telescopes and correlators are used for both. This synergy gives both the geodesy and astronomy communities access to more resources than either could support alone. The IVS membership is familiar with geodetic/astrometric VLBI, but perhaps less so with astronomical VLBI. Therefore, this presentation will begin with an introduction to the existing astronomical VLBI instruments. That will be followed by a number of examples of astronomical VLBI results to give a flavor for the science. Then some direct comparisons between geodetic and astronomical VLBI will be made with emphasis on observing modes and on the importance of various aspects of the data. Finally, the interaction between the groups will be discussed, both in terms of how they are interdependent and how differences in style have created some complications.

  15. Statistical analysis of the astrometric errors for the most productive asteroid surveys

    NASA Astrophysics Data System (ADS)

    Vereš, Peter; Farnocchia, Davide; Chesley, Steven R.; Chamberlin, Alan

    2016-10-01

    Accurate orbits of minor planets allow reliable predictions of an object's location in time and space. High fidelity ephemerides are crucial for the space missions targeting asteroids and comets, mitigation of Earth impact hazard, study of non-gravitational effects on small bodies and mass determination of encountering objects through mutual perturbations. The length of the observation arc as well as high quality astrometry play an essential role in achieving accurate orbits. In particular, accurate astrometry can allow the recovery of small near-Earth objects that could otherwise be lost. The vast majority of the 715,000 known asteroids have been discovered and observed by major dedicated optical CCD surveys. However, uncertainties of individual astrometric positions are not directly provided by observers yet and so orbit determination traditionally relies on conservative estimates of astrometric errors. We present a statistical study of astrometric residuals of optical CCD astrometry for the nine most prolific past and current asteroid surveys: Pan-STARRS1 (F51), Mt. Lemmon (G96), Catalina (703), LINEAR (704), Spacewatch (691), LONEOS (699), NEAT (644), NEOWISE (C51) and SST (G45). The study was limited to multiple apparition asteroids, which have well-constrained orbits, after correcting for the star catalog position and proper motion biases (Farnocchia et al., 2015). Therefore, the resulting astrometric residuals can be largely attributed to astrometric and timing errors in the reported astrometry. We analyze the behavior of residuals in right ascension, declination, along-track and cross-track, as well as timing errors. Astrometric residuals generally depend on reported magnitude by a quadratic function with astrometric quality degradation near the limiting magnitude and the saturation limit for bright objects. We found no systematic timing errors exceeding one second for the tested surveys. The presented analysis provides useful information to improve the

  16. An astrometric facility for planetary detection on the space station

    NASA Technical Reports Server (NTRS)

    Nishioka, Kenji; Scargle, Jeffrey D.; Givens, John J.

    1987-01-01

    An Astrometric Telescope Facility (ATF) for planetary detection is being studied as a potential space station initial operating capability payload. The primary science objective of this mission is the detection and study of planetary systems around other stars. In addition, the facility will be capable of other astrometric measurements such as stellar motions of other galaxies and highly precise direct measurement of stellar distance within the Milky Way Galaxy. The results of a recently completed ATF preliminary systems definition study are summarized. Results of this study indicate that the preliminary concept for the facility is fully capable of meeting the science objective without the development of any new technologies. A simple straightforward operations approach was developed for the ATF. A real-time facility control is not normally required, but does maintain a near real-time ground monitoring capability for the facility and science data stream on a full-time basis. Facility observational sequences are normally loaded once a week. In addition, the preliminary system is designed to be fail-safe and single-fault tolerant. Routine interactions by the space station crew with the ATF will not be necessary, but onboard controls are provided for crew override as required for emergencies and maintenance.

  17. Analysis of an astrometric Fizeau interferometer for GAIA

    NASA Technical Reports Server (NTRS)

    Loiseau, Sacha; Shaklan, Stuart

    1995-01-01

    The concepts related to the operation and design of the global astrometric interferometer for astrophysics (GAIA) bring together solutions chosen for the astrometry satellite and interferometric techniques. Like the Hipparcos satellite, GAIA is a continuously scanning instrument for which the integration time on any observed object is limited by the field of view of the detector. If a final astrometric accuracy of 10 microarcsec is aimed at, a field of 1 deg in diameter is needed. A design is presented for the proposed 2.6 m baseline Fizeau interferometer with two 40 cm apertures and overall dimensions compatible with the size of the Ariane 5 payload shroud. It has a 0.9 deg diffraction limited field of view. The response of the optical system to small perturbations on each optical element is given in terms of the fringe visibility, which is shown to be dependent on the sub-aperture spot separation. The robustness of the design to thermal, mechanical and manufacturing errors is discussed. The unavoidable distortion present in wide field optical systems is analyzed in terms of displacement of the interference fringes.

  18. Astrometric Search for Planets Encircling Nearby Stars (ASPENS)

    NASA Astrophysics Data System (ADS)

    Koerner, D. W.; Henry, T. J.; Fuhrman, L. A.; Parker, C. C.; Kaplan, I. J.; Jao, Wei-Chun; Subasavage, J.

    2003-12-01

    The Astrometric Search for Planets Encircling Nearby Stars (ASPENS) expands on CTIOPI, an existing parallax survey, to measure changes in apparent stellar positions with milli-arcsecond precision. NAU and GSU participation in the SMARTS consortium provides observing time on the CTIO 0.9m telescope to study a large sample of nearby stars visible from the southern hemisphere. The survey is sensitive to Jupiter-mass (MJ) companions orbiting at 5 AU from late M Dwarfs 8 pc away and 13-MJ companions (deuterium-burning mass limit) 5 AU from late K dwarfs at a distance of 20 pc. This economic probe of the substellar companion mass regime forms a natural complement to future high-precision efforts with interferometry, since the latter are less suitable to large-scale long-duration surveys. ASPENS data are housed in a relational database that facilitates easy retrieval and analysis. This tool is designed to incorporate astrometric measurements from other surveys and to yield limits on companions for incorporation into NStars Database.

  19. A Search For Stellar-mass Black Holes Via Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Lu, J. R.; Sinukoff, E.; Ofek, E. O.; Udalski, A.; Kozlowski, S.

    2016-10-01

    While dozens of stellar-mass black holes (BHs) have been discovered in binary systems, isolated BHs have eluded detection. Their presence can be inferred when they lens light from a background star. We attempt to detect the astrometric lensing signatures of three photometrically identified microlensing events, OGLE-2011-BLG-0022, OGLE-2011-BLG-0125, and OGLE-2012-BLG-0169 (OB110022, OB110125, and OB120169), located toward the Galactic Bulge. These events were selected because of their long durations, which statistically favors more massive lenses. Astrometric measurements were made over one to two years using laser-guided adaptive optics observations from the W. M. Keck Observatory. Lens model parameters were first constrained by the photometric light curves. The OB120169 light curve is well fit by a single-lens model, while both OB110022 and OB110125 light curves favor binary lens models. Using the photometric fits as prior information, no significant astrometric lensing signal was detected and all targets were consistent with linear motion. The significant lack of astrometric signal constrains the lens mass of OB110022 to 0.05–1.79 M ⊙ in a 99.7% confidence interval, which disfavors a BH lens. Fits to OB110125 yielded a reduced Einstein crossing time and insufficient observations during the peak, so no mass limits were obtained. Two degenerate solutions exist for OB120169, which have a lens mass between 0.2–38.8 M ⊙ and 0.4–39.8 M ⊙ for a 99.7% confidence interval. Follow-up observations of OB120169 will further constrain the lens mass. Based on our experience, we use simulations to design optimal astrometric observing strategies and show that with more typical observing conditions the detection of BHs is feasible.

  20. Astrophysical and Technical Aspects of Astrometric Methods on Hubble

    NASA Astrophysics Data System (ADS)

    Currie, D. G.

    2005-10-01

    The astrometric analysis of eta Carinae, the associated homunculus, the surrounding ejected debris field and the inner core region with its more recent ejecta has provided both a wide variety of astrophysical results and a study on the use, methods and accuracy of astrometric procedures, both for the "plane of the sky" and for radial velocity or 3D astrometry, on extended or diffuse objects. From an astrophysical point of view, it has revealed the origin, history and 3D structure of the homunculus that was ejected in the Great Eruption of 1842. Additional information on the structure of the homunculus has been provided by the use of the Fabry-Perot with ADONIS on the European Southern Observatory's 3.6 meter telescope at La Silla, Chile. The analysis of the surrounding ejected debris has yielded information on the history of previous eruptions and may yield information as to the physical nature of these earlier eruptions. The interaction of the debris from various eruptions addresses the current state of the circumstellar media. Finally, recent analysis of the inner core region, using both the UVES spectrograph on the ESO's VLT at Paranal, Chile and the WFPC and the HRC/ACS on HST has yielded a definitive determination of the date of the origin of the Weigelt blobs. It should also yield definitive information on the motion of the inner disk. In general, it has yielded a large body of new information and, in addition, it has also greatly constrained theories and conjectures as to the history, structure, origin and evolution of eta Carinae and its ejecta. On the other hand, eta CAR has also been a very interesting object for the technical development of astrometric methods for use on diffuse objects. It is bright enough to allow multiple observations to understand the reproducibility of the results without a large penalty for telescope time. It is also bright enough to provide sufficient photons in an acceptable exposure time to obtain a very good signal

  1. Gaia: Astrometric Performance and Current Status of the Project

    NASA Astrophysics Data System (ADS)

    Lindegren, Lennart

    2009-05-01

    The ESA Gaia mission is an all-sky astrometric and spectrophotometric survey of all point-like objects between 6th and 20th magnitude. Some 1 billion stars, a few million galaxies, half a million quasars, and a few hundred thousand asteroids will be observed over 5-6 years with typically 80 field-of-view transits per object. Expected accuracies for stellar parallaxes, annual proper motions and mean epoch positions are 7-25 microarcsec down to 15th magnitude and 100-300 microarcsec at 20th magnitude. The astrometric data are complemented by low-resolution spectrophotometric data in the 330-1000 nm wavelength range and, for the brighter stars, radial velocity measurements. The primary scientific objective of Gaia is to study galactic structure and evolution by correlating the spatial distributions and kinematics of stars with their astrophysical properties. However, a much wider range of topics in stellar astrophysics, solar system and exoplanet science, cosmology and fundamental physics will benefit from the mission data. A very accurate, dense and faint non-rotating optical reference frame will be established through direct observations of quasars. The project is in its advanced implementation phase, on schedule for a targeted launch in late 2011. Critical payload elements such as SiC telescope mirrors and optical bench, CCDs and electronic units, have been or are in the process of being manufactured. In parallel, preparations for the scientific data processing are well under way within the Gaia Data Processing and Analysis Consortium. Final mission results are expected around 2021, but early releases of preliminary data are expected. This review summarizes the main science goals and overall organisation of the project, then focuses on the expected performance and certain key issues of the measurement principle and its technical implementation.

  2. Star Confusion Effect on SIM PlanetQuest Astrometric Performance

    NASA Technical Reports Server (NTRS)

    Zhai, C.; Yu, M.; Milman, M.; Fathpour, N.; Morales, M.; Nemati, B.; Regehr, M.; Heflin, M.; Sievers, L.

    2007-01-01

    SIM PlanetQuest will measure star positions to an accuracy of a few microarcseconds using precise white light fringe measurements. One challenge for SIM observation scenario is "star confusion," where multiple stars are present in the instrument field of view. This is especially relevant for observing dim science targets because the density of number of stars increases rapidly with star magnitude. We study the effect of star confusion on the SIM astrometric performance due to systematic fringe errors caused by the extra photons from the confusion star(s}. Since star confusion from multiple stars may be analyzed as a linear superposition of the effect from single star confusion, we quantify the astrometric errors due to single star confusion surveying over many spectral types, including AOV, FOV, K5III, and MOV, and for various visual magnitude differences. To the leading order, the star confusion effect is characterized by the magnitude difference, spectral difference, and the angular separation between the target and confusion stars.Strategies for dealing with star confusion are presented. For example, since the presence of additional sources in the field of view leads to inconsistent delay estimates from different channels, with sufficient signal to noise ratio, the star confusion can be detected using chi-square statistics of fringe measurements from multiple spectral channels. An interesting result is that the star confusion can be detected even though the interferometer cannot resolve the separation between the target and confusion stars when their spectra are sufficiently different. Other strategies for mitigating the star confusion effect are also discussed.

  3. Near-Earth Object Astrometric Interferometry

    NASA Technical Reports Server (NTRS)

    Werner, Martin R.

    2005-01-01

    Using astrometric interferometry on near-Earth objects (NEOs) poses many interesting and difficult challenges. Poor reflectance properties and potentially no significant active emissions lead to NEOs having intrinsically low visual magnitudes. Using worst case estimates for signal reflection properties leads to NEOs having visual magnitudes of 27 and higher. Today the most sensitive interferometers in operation have limiting magnitudes of 20 or less. The main reason for this limit is due to the atmosphere, where turbulence affects the light coming from the target, limiting the sensitivity of the interferometer. In this analysis, the interferometer designs assume no atmosphere, meaning they would be placed at a location somewhere in space. Interferometer configurations and operational uncertainties are looked at in order to parameterize the requirements necessary to achieve measurements of low visual magnitude NEOs. This analysis provides a preliminary estimate of what will be required in order to take high resolution measurements of these objects using interferometry techniques.

  4. Astrometric properties of the Tautenburg Plate Scanner

    NASA Astrophysics Data System (ADS)

    Brunzendorf, Jens; Meusinger, Helmut

    The Tautenburg Plate Scanner (TPS) is an advanced plate-measuring machine run by the Thüringer Landessternwarte Tautenburg (Karl Schwarzschild Observatory), where the machine is housed. It is capable of digitising photographic plates up to 30 cm × 30 cm in size. In our poster, we reported on tests and preliminary results of its astrometric properties. The essential components of the TPS consist of an x-y table movable between an illumination system and a direct imaging system. A telecentric lens images the light transmitted through the photographic emulsion onto a CCD line of 6000 pixels of 10 µm square size each. All components are mounted on a massive air-bearing table. Scanning is performed in lanes of up to 55 mm width by moving the x-y table in a continuous drift-scan mode perpendicular to the CCD line. The analogue output from the CCD is digitised to 12 bit with a total signal/noise ratio of 1000 : 1, corresponding to a photographic density range of three. The pixel map is produced as a series of optionally overlapping lane scans. The pixel data are stored onto CD-ROM or DAT. A Tautenburg Schmidt plate 24 cm × 24 cm in size is digitised within 2.5 hours resulting in 1.3 GB of data. Subsequent high-level data processing is performed off-line on other computers. During the scanning process, the geometry of the optical components is kept fixed. The optimal focussing of the optics is performed prior to the scan. Due to the telecentric lens refocussing is not required. Therefore, the main source of astrometric errors (beside the emulsion itself) are mechanical imperfections in the drive system, which have to be divided into random and systematic ones. The r.m.s. repeatability over the whole plate as measured by repeated scans of the same plate is about 0.5 µm for each axis. The mean plate-to-plate accuracy of the object positions on two plates with the same epoch and the same plate centre has been determined to be about 1 µm. This accuracy is comparable to

  5. Optical design of an astrometric space telescope

    NASA Astrophysics Data System (ADS)

    Richardson, E. H.; Morbey, C. L.

    1986-01-01

    A three-mirror telescope derived from the Paul corrector is described. It differs from the original Paul design in several respects. (1) The third mirror is located behind the primary mirror instead of in front of it. (2) The telescope is made off-axis so that there is no central obstruction, thus avoiding the extension and asymmetry of the diffraction pattern caused by the spiders holding an on-axis secondary mirror. (3) Baffling is not a problem as it is with the usual Paul design. The focal surface is flat where a moving ronchi grating is located. This is the first element in the astrometric analyzer. A real image of the pupil is produced behind the focus. This is helpful in the design of relay optics (not described) which reimage the grating onto a CCD.

  6. Nearby Exo-Earth Astrometric Telescope (NEAT)

    NASA Technical Reports Server (NTRS)

    Shao, M.; Nemati, B.; Zhai, C.; Goullioud, R.

    2011-01-01

    NEAT (Nearby Exo ]Earths Astrometric Telescope) is a modest sized (1m diameter telescope) It will be capable of searching approx 100 nearby stars down to 1 Mearth planets in the habitable zone, and 200 @ 5 Mearth, 1AU. The concept addresses the major issues for ultra -precise astrometry: (1) Photon noise (0.5 deg dia field of view) (2) Optical errors (beam walk) with long focal length telescope (3) Focal plane errors , with laser metrology of the focal plane (4) PSF centroiding errors with measurement of the "True" PSF instead of using a "guess " of the true PSF, and correction for intra pixel QE non-uniformities. Technology "close" to complete. Focal plane geometry to 2e-5 pixels and centroiding to approx 4e -5 pixels.

  7. Astrometric studies in the region of Algol

    NASA Astrophysics Data System (ADS)

    Gatewood, George; de Jonge, Joost Kiewiet; Heintz, Wulff D.

    1995-01-01

    The distance and masses of the components of the triple star Algol (Beta Persei) are derived from photographic and electronic data collected with the two 0.76 m objectives of the Thaw Refractor at the University of Pittsburgh's Allegheny Observatory and with the 0.61 m visual refractor at Swarthmore College's Sproul Observatory. These datasets constitute the major narrow-field astrometric collections of this star. The newly derived weighted mean trigonometric parallax of Algol is now +0.0343 +/- 0.00085 corresponding to a distance modulus of 2.32 +/- 0.054 mag. The total mass of the Algol system is estimated at 6.05 +/- 0.45 solar mass. The photocentric semimajor axis of the AB/C orbit is determined in the blue, yellow, and red bandpasses of the three independent astrometric systems. The total mass for the A and B component stars is found to be 4.63 +/- 0.35 solar mass and the mass of the C component is determined to be 1.42 +/- 0.13 solar mass. Residuals to this solution showed no meaningful correlation to the orbital motion of A/B. Thus it is probable that the photocenter is located near the center of mass of the A/B subsystem. There is no evidence of a previously suggested 32 yr orbital motion and no significant acceleration is evident in the 60 yr photographic series. It is therefore unlikely that the system has a fourth stellar mass component. It is noted that the visual band interferometric studies of the Algol system have the AB and C components interchanged.

  8. Full-sky Astrometric Mapping Explorer (FAME)

    NASA Astrophysics Data System (ADS)

    Johnston, K.; Gaume, R.; Harris, F.; Monet, D.; Murison, M.; Seidelmann, P. K.; Urban, S.; Johnson, M.; Horner, S.; Vassar, R.

    2000-12-01

    The FAME project began Phase B development in September 2000. FAME is a MIDEX class NASA Explorer mission that will perform an all-sky, astrometric survey with unprecedented accuracy. FAME will produce an astrometric catalog of 40 million stars between 5th and 15th magnitude. For the bright stars (5th to 9th magnitude) FAME will determine positions and parallaxes accurate to better than 50 microarcseconds, with proper motion errors less than 50 microarcseconds per year. For the fainter stars (between 9th and 15th magnitude) FAME will determine positions and parallaxes accurate to better than 500 microarcseconds, with proper motion errors less than 500 microarcseconds per year. FAME will also collect photometric data on these 40 million stars in four Sloan DSS colors. The FAME science, instrument, and spacecraft requirements and error budgets are being refined to establish the basis for the improved design of the instrument and spacecraft. The Attitude Control System (ACS) based on solar radiation pressure is being studied, including the limitations on the solar angle between the Sun and the rotation angle. The data processing plans are being developed. The CCD procurement contract is in place and design and fabrication of the CCDs is in progress. CCD tests for operations in various Time Delay Integration (TDI) situations are underway and described in another poster. It appears that the current FAME launch schedule will be delayed somewhat due to recent NASA budget restrictions. The FAME project is funded by the NASA Explorer program administered by Goddard Space Flight Center for the Office of Space Science under contract number S-13610-Y.

  9. Verification of the astrometric performance of the Korean VLBI network, using comparative SFPR studies with the VLBA AT 14/7 mm

    SciTech Connect

    Rioja, María J.; Dodson, Richard; Jung, TaeHyun; Sohn, Bong Won; Byun, Do-Young; Cho, Se-Hyung; Lee, Sang-Sung; Kim, Jongsoo; Kim, Kee-Tae; Oh, Chung Sik; Han, Seog-Tae; Je, Do-Heung; Chung, Moon-Hee; Wi, Seog-Oh; Kang, Jiman; Lee, Jung-Won; Chung, Hyunsoo; Kim, Hyo Ryoung; Kim, Hyun-Goo; Agudo, Iván; and others

    2014-11-01

    The Korean VLBI Network (KVN) is a new millimeter VLBI dedicated array with the capability to simultaneously observe at multiple frequencies, up to 129 GHz. The innovative multi-channel receivers present significant benefits for astrometric measurements in the frequency domain. The aim of this work is to verify the astrometric performance of the KVN using a comparative study with the VLBA, a well-established instrument. For that purpose, we carried out nearly contemporaneous observations with the KVN and the VLBA, at 14/7 mm, in 2013 April. The KVN observations consisted of simultaneous dual frequency observations, while the VLBA used fast frequency switching observations. We used the Source Frequency Phase Referencing technique for the observational and analysis strategy. We find that having simultaneous observations results in superior compensation for all atmospheric terms in the observables, in addition to offering other significant benefits for astrometric analysis. We have compared the KVN astrometry measurements to those from the VLBA. We find that the structure blending effects introduce dominant systematic astrometric shifts, and these need to be taken into account. We have tested multiple analytical routes to characterize the impact of the low-resolution effects for extended sources in the astrometric measurements. The results from the analysis of the KVN and full VLBA data sets agree within 2σ of the thermal error estimate. We interpret the discrepancy as arising from the different resolutions. We find that the KVN provides astrometric results with excellent agreement, within 1σ, when compared to a VLBA configuration that has a similar resolution. Therefore, this comparative study verifies the astrometric performance of the KVN using SFPR at 14/7 mm, and validates the KVN as an astrometric instrument.

  10. POINTS: high astrometric capacity at modest cost via focused design

    NASA Astrophysics Data System (ADS)

    Reasenberg, Robert D.; Babcock, Robert W.; Murison, Marc A.; Noecker, Martin C.; Phillips, James D.; Schumaker, Bonny L.; Ulvestad, James S.; McKinley, William G.; Zielinski, Robert J.; Lillie, Charles F.

    1996-10-01

    POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometric measurements from space, yielding submicroarcsecond astrometric results from the mission. It comprises a pair of independent Michelson stellar interferometers and a laser metrology system that measures both the critical starlight paths and the angle between the baselines. The instrument has two baselines of 2 m, each with two subapertures of 35 cm; by articulating the angle between the baselines, it observes targets separated by 87 to 93 deg. POINTS does global astrometry, i.e., it measures widely separated targets, which yields closure calibration, numerous bright reference stars, and absolute parallax. Simplicity, stability, and the mitigation of systematic error are the central design themes. The instrument has only three moving-part mechanisms, and only one of these must move with sub-milliradian precision; and other two can tolerate a precision of several tenths of a degree. Optical surfaces preceding the beamsplitter or its fold flat are interferometrically critical; on each side of the interferometer, there are only three such. Thus, light loss and wavefront distortion are minimized. POINTS represents a minimalistic design developed ab initio for space. Since it is intended for astrometry, and therefore does not require the u-v-plane coverage of an imaging instrument, each interferometer need have only two subapertures. The design relies on articulation of the angle between the interferometers and body pointing to select targets; the observations are restricted to the `instrument plane.' That plane, which is fixed in the pointed instrument, is defined by the sensitive direction for the two interferometers. Thus, there is no need for siderostats and moving delay lines, which would have added many precision mechanisms with rolling and sliding parts that would be required to function throughout the mission. Further, there is no need for a third interferometer, as

  11. Astrometric Telescope Facility isolation and pointing study

    NASA Technical Reports Server (NTRS)

    Hibble, William; Allen, Terry; Jackson, Louis; Medbery, James; Self, Richard

    1988-01-01

    The Astrometric Telescope Facility (ATF), an optical telescope designed to detect extrasolar planetary systems, is scheduled to be a major user of the Space Station's Payload Pointing System (PPS). However, because the ATF has such a stringent pointing stability specification and requires + or - 180 deg roll about its line of sight, mechanisms to enhance the basic PPS capability are required. The ATF pointing performance achievable by the addition of a magnetic isolation and pointing system (MIPS) between the PPS upper gimbal and the ATF, and separately, by the addition of a passive isolation system between the Space Station and the PPS base was investigated. The candidate MIPS can meet the ATF requirements in the presence of a 0.01 g disturbance. It fits within the available annular region between the PPS and the ATF while meeting power and weight limitations and providing the required roll motion, payload data and power services. By contrast, the passive base isolator system must have an unrealistically low isolation bandwidth on all axes to meet ATF pointing requirements and does not provide roll about the line of sight.

  12. Limits of Astrometric and Photometric Precision on KBOs

    NASA Astrophysics Data System (ADS)

    Dunham, Emilie; Kosiarek, Molly; Markatou, Evangelia Anna; Wang, Amanda

    2014-09-01

    We present photometric and astrometric measurements of the Kuiper Belt Objects (KBO) Haumea and Makemake obtained between 2013 June 5 and 2013 July 31 with the 14-inch Wallace Astrophysical Observatory (WAO) telescopes. Using photometry, we determined that Haumea and Makemake have R magnitudes 17.225 ± 0.347 and 16.850 ± 0.107, respectively. We obtained rotational light curves for Haumea and Makemake over eight separate nights. Astrometry yielded mean residuals with respect to the JPL ephemeris of -0.0095 ± 0.027'' with an rms residual of 0.480'' in R.A. and 0.261 ± 0.019'' with an rms residual of 0.335 in decl. for Makemake, and 0.219 ± 0.090'' in R.A. with an rms residual of 0.748'', and 0.223 ± 0.068'' in decl. with an rms residual of 0.571'' for Haumea. Additionally, we calculated that observing Haumea with two 14-inch telescopes and Makemake with four 14-inch telescopes could resolve their periodicity. With improved observing techniques and modern CCD cameras, it is possible to utilize small telescopes in universities around the world to observe large KBOs.

  13. Reprocessing the Hipparcos Intermediate Astrometric Data of spectroscopic binaries. II. Systems with a giant component

    NASA Astrophysics Data System (ADS)

    Pourbaix, D.; Boffin, H. M. J.

    2003-02-01

    By reanalyzing the Hipparcos Intermediate Astrometric Data of a large sample of spectroscopic binaries containing a giant, we obtain a sample of 29 systems fulfilling a carefully derived set of constraints and hence for which we can derive an accurate orbital solution. Of these, one is a double-lined spectroscopic binary and six were not listed in the DMSA/O section of the catalogue. Using our solutions, we derive the masses of the components in these systems and statistically analyze them. We also briefly discuss each system individually. Based on observations from the Hipparcos astrometric satellite operated by the European Space Agency (ESA 1997) and on data collected with the Simbad database.

  14. Astrometric Detection of Extrasolar Planets: Results of a Feasibility Study with the Palomar 5 Meter Telescope

    NASA Technical Reports Server (NTRS)

    Pravdo, Steven H.; Shaklan, Stuart B.

    1996-01-01

    The detection of extrasolar planets around stars like the Sun remains an important goal of astronomy. We present results from Palomar 5 m observations of the open cluster NGC 2420 in which we measure some of the sources of noise that will be present in an astrometric search for extrasolar planets. This is the first time that such a large aperture has been used for high-precision astrometry. We find that the atmospheric noise is 150 micro-arcsec hr(exp 1/2) across a 90 sec field of view and that differential chromatic refraction (DCR) can be calibrated to 128 micro-arcsec for observations within 1 hr of the meridian and 45 deg of zenith. These results confirm that a model for astrometric measurements can be extrapolated to large apertures. We demonstrate, based upon these results, that a large telescope achieves the sensitivity required to perform a statistically significant search for extra solar planets. We describe an astrometric technique to detect planets, the astrometric signals expected, the role of reference stars, and the sources of measurement noise: photometric noise, atmospheric motion between stars, sky background, instrumental noise, and DCR. For the latter, we discuss a method to reduce the noise further to 66 micro-arcsecond for observations within 1 hr of the meridian and 45 deg of zenith. We discuss optimal lists of target stars taken from the latest Gliese & Jahreiss catalog of nearby stars with the largest potential astrometric signals, declination limits for both telescope accessibility and reduced DCR, and galactic latitude limits for a sufficiant number of reference stars. Two samples are described from which one can perform statistically significant searches for gas giant planets around nearby stars. One sample contains 100 "solar class" stars with an average stellar mass of 0.82 solar mass; the other maximizes the number of stars, 574, by searching mainly low-mass M stars. We perform Monte Carlo simulations of the statistical significance of

  15. A new reduction of Astrometric Photographic Plates using the DAMIAN Digitizer

    NASA Astrophysics Data System (ADS)

    Robert, Vincent; De Cuyper, J.; Arlot, J.; Lainey, V.; Pascu, D.

    2010-05-01

    A new astrometric reduction of old photographic plates that benefits from modern technologies can provide a better knowledge of the orbital motion of planetary satellites. In that respect, an international collaboration has been set up between the USNO, the OBSPM and the ROB to digitize USNO plates with the new generation scanning machine. The procedure can be applied to various photographic plates and it is assumed that the astrometric results will be the most precise. Here we consider a set of a few hundred photographic plates of the Galilean satellites, taken at the USNO, and covering the years 1967-1998. A specific procedure was developed to obtain a high accuracy in the position of each moon. So far, 30 plates were digitized at the Paris Observatory with the MAMA machine (2006 and 2007) and the complete series is now being digitized at the Brussels Observatory with the new DAMIAN machine. The first results suggest an accuracy better than 50 mas in (RA,Dec) positions of each moon. Since the position of Jupiter may also be deduced from the observed Ra and Dec positions of the satellites, using the Galilean satellite ephemerides, we can also assess the accuracy of Jupiter's ephemeris. First astrometric results will be presented.

  16. Astrometric exoplanet surveys in practice: challenges, opportunities, and results

    NASA Astrophysics Data System (ADS)

    Sahlmann, Johannes

    2015-08-01

    Conversely to the transit photometry and radial velocity methods, the astrometric discovery of exoplanets is still limited by the sensitivity of available instruments. Furthermore, the signature of a planet (described by 7 free parameters) is orders of magnitude smaller than the standard motion of a star (5 free parameters), which has to be solved for first. This has important implications in the design and implementation of astrometric planet search surveys and the large parameter space to be explored calls for efficient fitting algorithms. I will present results of the so-far most precise astrometric planet search from the ground, targeting 20 very low-mass stars and brown dwarfs with an accuracy of 100 micro-arcseconds, which include the discovery of binaries with components in the planetary mass regime and several planet candidates with Neptune-to-Jupiter masses. The employed genetic and MCMC algorithms were shown to be efficient in constraining all astrometric parameters, which makes them important tools for the exploitation of the data currently collected by the Gaia satellite. Gaia is expected to astrometrically discover thousands of giant exoplanets and I will report on several ongoing projects in preparation of this unique harvest, including the expected yield of circumbinary planets.

  17. Astrometric Support for the Lunar-based Ultraviolet Telescope

    NASA Astrophysics Data System (ADS)

    Qi, Zhaoxiang; Yu, Yong; Cao, Li; Cai, Hongbo; Qiu, Yunlei; Wei, Jianyan; Tang, Zhenghong; Wang, Jing; Deng, Jinsong; Liao, Shilong; Guo, Sufen

    2015-11-01

    The Lunar-based Ultraviolet Telescope (LUT) is an astronomical instrument aboard Chang'e 3, the lunar probe of China's Lunar Exploration Program that successfully landed on the northern part of the Moon's Mare Imbrium (340.4884E, 44.1214N) in late 2013. LUT is charting an ultraviolet map of the plane of the Milky Way and is also providing long-term light variability monitoring for a sample of RR Lyrae stars. However, the principal goal of the computer-controlled landing of the probe was a safe descent to a stable resting-place, and therefore, the precise orientation of LUT was never a priority. For this reason, at least theoretically, touch-down could have occurred anywhere and, for LUT, at any attitude, which would make the pointing and tracking of the wanted celestial objects practically impossible. Moreover, to reduce the data transmission load, the whole frame of every exposure could not be downloaded: only the image data containing the objects can make it to the ground; also, in order to save on electricity, the telescope does not usually track objects, which means that targets' accurate positions and velocities (within the focal plane CCD) are both needed. This paper presents the astrometric solution devised to solve these problems: feasibility is first shown with experiments done from Earth, and then confirmed with actual LUT observations from the Moon's surface.

  18. The Astrometric Calibration of the Gemini Planet Imager

    NASA Astrophysics Data System (ADS)

    Tran, Debby; Konopacky, Quinn; GPIES Collaboration

    2016-06-01

    The Gemini Planet Imager (GPI), housed on the 8-meter Gemini South telescope in Chile, is an instrument designed to detect Jupiter-like extrasolar planets by direct imaging. It relies on adaptive optics to correct the effects of atmospheric turbulence, along with an advanced coronagraph and calibration system. One of the scientific goals of GPI is to measure the orbital properties of the planets it discovers. Because these orbits have long periods, precise measurements of the relative position between the star and the planet (relative astrometry) are required. In this poster, I will present the astrometric calibration of GPI. We constrain the plate scale and orientation of the camera by observing different binary star systems with both GPI and another well-calibrated instrument, NIRC2, at the Keck telescope in Hawaii. We measure their separations with both instruments and use that information to calibrate the plate scale. By taking these calibration measurements over the course of one year, we have measured the plate scale to 0.05% and shown that it is stable across multiple epochs. I will also discuss our effort to correct for optical distortion using pinhole masks in the laboratory.

  19. Surveys, Astrometric Follow-Up, and Population Statistics

    NASA Astrophysics Data System (ADS)

    Jedicke, R.; Granvik, M.; Micheli, M.; Ryan, E.; Spahr, T.; Yeomans, D. K.

    Asteroid surveys are the backbone of asteroid science, and with this in mind we begin with a broad review of the impact of asteroid surveys on our field. We then provide a brief history of asteroid discoveries so as to place contemporary and future surveys in perspective. Surveys in the United States (U.S.) have discovered the vast majority of the asteroids, and this dominance has been consolidated since the publication of Asteroids III. Our descriptions of the asteroid surveys that have been operational since that time are focused on those that have contributed the vast majority of asteroid observations and discoveries. We also provide some insight into upcoming next-generation surveys that are sure to alter our understanding of the small bodies in the inner solar system and provide evidence to untangle their complicated dynamical and physical histories. The Minor Planet Center, the nerve center of the asteroid discovery effort, has improved its operations significantly in the past decade so that it can manage the increasing discovery rate, and ensure that it is well-placed to handle the data rates expected in the next decade. We also consider the difficulties associated with astrometric follow-up of newly identified objects. It seems clear that both of these efforts must operate in new modes in order to keep pace with expected discovery rates of next-generation ground- and spacebased surveys.

  20. BAM: A metrology device for a high precision astrometric mission

    NASA Astrophysics Data System (ADS)

    Riva, A.; Gai, M.; Lattanzi, M. G.; Russo, F.; Buzzi, R.

    2014-12-01

    Gaia is ESA next-generation astrometric space mission, that will be launched in December 2013. The main objective of Gaia is to produce an astrometric census of one billion objects down to the 20th magnitude. The level of astrometric precision will be around the 10 microarcseconds. In order to achieve such demanding performances, the complexity of the satellite is huge, and a proper fully automated operation must be adopted. One of the essential parts of the satellite is the BAM instrument, an interferometric device with the task of monitoring the variation of the Basic Angle between the two telescope that compose the payload. In this paper we describe the main features of this sub-instrument and its performances.

  1. The research of the accuracy of asteroid orbit fitting using both radar and astrometric observations. (Russian Title: Исследование точности решения задачи улучшения орбит астероидов по данным их радарных и угловых наблюдений)

    NASA Astrophysics Data System (ADS)

    Baturin, A. P.; Kinzersky, V. V.

    2014-12-01

    The least-square orbit fitting problem for asteroids using their radar and astrometric observations has been considered. The both types of radar observations have been taken into account: the time delay observations and the Doppler observations. The research of accuracy increase due to the using of radar observations in addition to astrometric ones has been carried out. This research has been done by means of several orbit fittings using different samples of observations of some asteroids. The samples contain all radar observations and different numbers of astrometric ones. The orbit arc of radar observations of chosen asteroids is very short (several days) while the arcs of astrometric observations for all used samples are much longer. It has been demonstrated that the using of radar observations in the orbit fitting may increase the accuracy of obtained solution by 1-3 orders even in the cases of very long astromeric arcs (several years). During the research the convenient windows-interface for the calculating program has been developed. The functions of the program also have been expanded. Particularly, the ability of perturbations calculation from different planet ephemerides and of calculations with different machine precision have been added to the program.

  2. Enabling interferometry technologies for the GAIA astrometric mission

    NASA Astrophysics Data System (ADS)

    Bisi, M.; Bonino, L.; Cecconi, Massimo; Cesare, Stefano; Bertinetto, Fabrizio; Mana, Giovanni; Carollo, D.; Gai, Mario; Lattanzi, Mario G.; Canuto, Enrico; Donati, F.

    1999-08-01

    Within a Technology Research Program funded by the European Space Agency, a team led by Alenia Aerospazio has investigated and started the development of some technologies which are considered fundamental for the achievement of the scientific objectives of the future astrometric mission GAIA. The activities have been focused on the design of a two-aperture optical interferometer and of a system for the active stabilization of its configuration within few picometers. A laboratory prototype of the active stabilization system has been implemented and tested. The results achieved in the laboratory tests proved that the very challenging requirements imposed by the GAIA astrometric goal of 10 micro-arcsec accuracy can be fulfilled.

  3. An Astrometric Search for a Stellar Companion to the Sun

    NASA Astrophysics Data System (ADS)

    Perlmutter, Saul

    A companion star within 0.8 pc of the Sun has been postulated to explain a possible 26 Myr periodicity in mass extinctions of species on the Earth. Such a star would already be catalogued in the Yale Bright Star catalogue unless it is fainter than mv = 6.5; this limits the possible stellar types for an unseen companion to red dwarfs, brown dwarfs, or compact objects. Red dwarfs account for about 75% of these possible stars. We describe here the design and development of an astrometric search for a nearby red dwarf companion with a six-month peak-to-peak parallax of >= 2.5 arcseconds. We are measuring the parallax of 2,770 candidate faint red stars selected from the Dearborn Observatory catalogue. An automated 30-inch telescope and CCD camera system collect digitized images of the candidate stars, along with a 13^'times 16 ^' surrounding field of background stars. Second-epoch images, taken a few months later, are registered to the first epoch images using the background stars as fiducials. An apparent motion, ma, of the candidate stars is found to a precision of sigma_{ma}~0.08 pixel ~0.2 arcseconds for fields with N fiducial>= 10 fiducial stars visible above the background noise. This precision is sufficient to detect the parallactic motion of a star at 0.8 pc with a two month interval between the observation epochs. Images with fewer fiducial stars above background noise are observed with a longer interval between epochs. If a star is found with high parallactic motion, we will confirm its distance with further parallax measurements, photometry, and spectral studies, and will measure radial velocity and proper motion to establish its orbit. We have demonstrated the search procedure with observations of 41 stars, and have shown that none of these is a nearby star.

  4. Properties of planet-induced deviations in the astrometric microlensing centroid shift trajectory

    NASA Astrophysics Data System (ADS)

    Han, Cheongho; Lee, Chunguk

    2002-01-01

    An extrasolar planet can be detected by microlensing because it can distort the smooth lensing light curve created by the primary lens. As a new method to search for and characterize extrasolar planets, Safizadeh, Dalal & Griest proposed to detect the planet-induced distortions in the trajectory of the microlensed source star's centroid motion (astrometric curve), which is observable by using the next generation of high-precision interferometers. In this paper we investigate the properties of the planet-induced deviations in the astrometric curves (excess centroid shifts Δδ) and the correlations of Δδ with the photometric deviations. For this, we construct vector field maps of Δδ, which represent the difference of the centroid shift from that expected in the absence of the planet as a function of source positions. From this investigation, we find that significant astrometric deviations occur not only in the region near the caustics but also in the region close to the planet-primary axis between the caustics. However, owing to the difference in the locations of the caustics between the two types of systems with the planet-primary separations (normalized by the angular Einstein ring radius) up>1.0 and up<1.0, the locations of the major deviation regions of the two systems are different from each other. For systems with up>1.0, the major deviation vectors have orientations, in most cases, pointing towards the planet, while they point away from the planet for systems with up<1.0. The major deviation region is surrounded by the region of moderate deviations, within which the orientation of Δδ is reversed compared with the orientation in the major deviation region. We also find that the astrometric deviation is closely correlated with the photometric one, as discussed by Safizadeh et al. The astrometric deviation increases as the photometric deviation increases, and Δδ is directed towards the planet when the light curve has positive deviation, and vice versa

  5. Revisiting TW Hydrae in light of new astrometric data

    NASA Astrophysics Data System (ADS)

    Teixeira, R.; Ducourant, C.; Galli, P. A. B.; Le Campion, J. F.; Zuckerman, B.; Krone-Martins, A. G. O.; Chauvin, G.; Song, I.

    2014-10-01

    Our efforts in the present work focused mainly on refining and improving the previous description and understanding of the stellar association TW Hydrae (TWA) including a very detailed membership analysis and its dynamical and evolutionary age.To achieve our objectives in a fully reliable way we take advantage of our own astrometric measurements (Ducourant et al. 2013) performed with NTT/EFOSC2 - ESO (La Silla - Chile) spread over three years (2007 - 2010) and of those published in the literature.A very detailed membership analysis based on the convergent point strategy as developed by our team (Galli et al. 2012, 2013) allowed us to define a consistent kinematic group containing 31 stars among the 44 proposed as TWA member in the literature. Assuming that our sample of stars may be contaminated by non-members and to get rid of the particular influence of each star we applied a Jacknife resampling technique generating 2000 random lists of 13 stars taken from our 16 stars and calculated for each the epoch of convergence when the radius is minimum. The mean of the epochs obtained and the dispersion about the mean give a dynamical age of 7.5± 0.7 Myr for the association that is in good agreement with the previous traceback age (De La Reza et al. 2006). We also estimated age for TWA moving group members from pre-main sequence evolutionary models (Siess et al. 2000) and find a mean age of 7.4± 1.2 Myr. These results show that the dynamical age of the association obtained via the traceback technique and the average age derived from theoretical evolutionary models are in good agreement.

  6. Toward astrometric tracking with the infrared spatial interferometer

    NASA Technical Reports Server (NTRS)

    Treuhaft, R. N.; Bester, M.; Danchi, W. C.; Townes, C. H.

    1994-01-01

    Infrared interferometric demonstrations with the University of California, Berkeley's infrared spatial interferometer (ISI) on Mt. Wilson explore the potential of infrared and optical astrometry for deep space tracking, reference frame development, and DSN science. Astrometric data taken and analyzed over the last five years from the ISI have shown that instrumental and atmospheric effects limit current demonstrations. The benefits of sensitivity upgrades, which were performed in 1991 and 1992, have been demonstrated by comparing point-to-point phase fluctuations for the fall 1989 and fall 1992 observing epochs. This comparison showed that point-to-point phase fluctuations due to tropospheric and quantum noise, for optimal integration times of 0.2 sec, are approaching the 0.1-cycle level needed to reliably connect the interferometric phase. The increase in sensitivity, coupled with that arising from very recent hardware upgrades, will greatly enhance phase-connection capabilities necessary for astrometry in the presence of atmospheric refractivity fluctuations. The current data set suggests that atmospheric fluctuations on Mt. Wilson during the best seeing are dominated by a low-lying component, approximately 25 m high, which may be minimized with in situ calibration in the future. During poor seeing conditions that currently prohibit the interferometric phase connection necessary for astrometry, fluctuations seem to be generated by atmospheric inhomogeneities at much higher altitudes above Mt. Wilson. Data taken over the last year suggest that the ISI will soon be able to achieve 50- to 100-nrad astrometry in a single observing session, employing current ground-based laser distance interferometer calibrations to minimize atmospheric effects.

  7. Optical design for the Laser Astrometric Test of Relativity

    NASA Technical Reports Server (NTRS)

    Turyshev, Slava G.; Shao, Michael; Nordtvedt, Kenneth L., Jr.

    2004-01-01

    This paper discusses the Laser Astrometric Test of Relativity (LATOR) mission. LATOR is a Michelson-Morley-type experiment designed to test the pure tensor metric nature of gravitation the fundamental postulate of Einstein's theory of general relativity. With its focus on gravity's action on light propagation it complements other tests which rely on the gravitational dynamics of bodies.

  8. Parallax and Orbital Effects in Astrometric Microlensing with Binary Sources

    NASA Astrophysics Data System (ADS)

    Nucita, A. A.; De Paolis, F.; Ingrosso, G.; Giordano, M.; Manni, L.

    2016-06-01

    In gravitational microlensing, binary systems may act as lenses or sources. Identifying lens binarity is generally easy, in particular in events characterized by caustic crossing since the resulting light curve exhibits strong deviations from a smooth single-lensing light curve. In contrast, light curves with minor deviations from a Paczyński behavior do not allow one to identify the source binarity. A consequence of gravitational microlensing is the shift of the position of the multiple image centroid with respect to the source star location — the so-called astrometric microlensing signal. When the astrometric signal is considered, the presence of a binary source manifests with a path that largely differs from that expected for single source events. Here, we investigate the astrometric signatures of binary sources taking into account their orbital motion and the parallax effect due to the Earth’s motion, which turn out not to be negligible in most cases. We also show that considering the above-mentioned effects is important in the analysis of astrometric data in order to correctly estimate the lens-event parameters.

  9. Astrometric Models of the Phobos Orbiter TV Cameras

    NASA Technical Reports Server (NTRS)

    Duxbury, T. C.

    1993-01-01

    Astrometric models of the 3 Phobos Orbiter TV cameras, their pointing in inertial space, the position of the Phobos Orbiter with respect to Mars, Phobos and Deimos, and transformations from inertial to body-fixed coordinates are needed to transform between the image coordinates of a picture element (.

  10. ESTABLISHING {alpha} Oph AS A PROTOTYPE ROTATOR: IMPROVED ASTROMETRIC ORBIT

    SciTech Connect

    Hinkley, Sasha; Hillenbrand, Lynne; Crepp, Justin R.; Monnier, John D.; Oppenheimer, Ben R.; Brenner, Douglas; Sivaramakrishnan, Anand; Roberts, Lewis C. Jr; Zhao Ming; Vasisht, Gautam; Pueyo, Laurent; Ireland, Michael; Zimmerman, Neil; Parry, Ian R.; Martinache, Frantz; Lai, Olivier; Soummer, Remi; Beichman, Charles; Lloyd, James P.; Bernat, David

    2011-01-10

    The nearby star {alpha} Oph (Ras Alhague) is a rapidly rotating A5IV star spinning at {approx} 89% of its breakup velocity. This system has been imaged extensively by interferometric techniques, giving a precise geometric model of the star's oblateness and the resulting temperature variation on the stellar surface. Fortuitously, {alpha} Oph has a previously known stellar companion, and characterization of the orbit provides an independent, dynamically based check of both the host star and the companion mass. Such measurements are crucial to constrain models of such rapidly rotating stars. In this study, we combine eight years of adaptive optics imaging data from the Palomar, AEOS, and CFHT telescopes to derive an improved, astrometric characterization of the companion orbit. We also use photometry from these observations to derive a model-based estimate of the companion mass. A fit was performed on the photocenter motion of this system to extract a component mass ratio. We find masses of 2.40{sup +0.23}{sub -0.37} M{sub sun} and 0.85{sup +0.06}{sub -0.04} M{sub sun} for {alpha} Oph A and {alpha} Oph B, respectively. Previous orbital studies of this system found a mass too high for this system, inconsistent with stellar evolutionary calculations. Our measurements of the host star mass are more consistent with these evolutionary calculations, but with slightly higher uncertainties. In addition to the dynamically derived masses, we use IJHK photometry to derive a model-based mass for {alpha} Oph B, of 0.77 {+-} 0.05 M{sub sun} marginally consistent with the dynamical masses derived from our orbit. Our model fits predict a periastron passage on 2012 April 19, with the two components having a 50 mas separation from 2012 March to May. A modest amount of interferometric and radial velocity data during this period could provide a mass determination of this star at the few percent level.

  11. HIGH-PRECISION ASTROMETRIC MILLIMETER VERY LONG BASELINE INTERFEROMETRY USING A NEW METHOD FOR ATMOSPHERIC CALIBRATION

    SciTech Connect

    Rioja, M.; Dodson, R.

    2011-04-15

    We describe a new method which achieves high-precision very long baseline interferometry (VLBI) astrometry in observations at millimeter (mm) wavelengths. It combines fast frequency-switching observations, to correct for the dominant non-dispersive tropospheric fluctuations, with slow source-switching observations, for the remaining ionospheric dispersive terms. We call this method source-frequency phase referencing. Provided that the switching cycles match the properties of the propagation media, one can recover the source astrometry. We present an analytic description of the two-step calibration strategy, along with an error analysis to characterize its performance. Also, we provide observational demonstrations of a successful application with observations using the Very Long Baseline Array at 86 GHz of the pairs of sources 3C274 and 3C273 and 1308+326 and 1308+328 under various conditions. We conclude that this method is widely applicable to mm-VLBI observations of many target sources, and unique in providing bona fide astrometrically registered images and high-precision relative astrometric measurements in mm-VLBI using existing and newly built instruments, including space VLBI.

  12. Joint astrometric solution of HIPPARCOS and Gaia. A recipe for the Hundred Thousand Proper Motions project

    NASA Astrophysics Data System (ADS)

    Michalik, Daniel; Lindegren, Lennart; Hobbs, David; Lammers, Uwe

    2014-11-01

    Context. The first release of astrometric data from Gaia is expected in 2016. It will contain the mean stellar positions and magnitudes from the first year of observations. For more than 100 000 stars in common with the Hipparcos Catalogue it will be possible to compute very accurate proper motions due to the time difference of about 24 years between the two missions. This Hundred Thousand Proper Motions (HTPM) project is planned to be part of the first release. Aims: Our aim is to investigate how early Gaia data can be optimally combined with information from the Hipparcos Catalogue in order to provide the most accurate and reliable results for HTPM. Methods: The Astrometric Global Iterative Solution (AGIS) was developed to compute the astrometric core solution based on the Gaia observations and will be used for all releases of astrometric data from Gaia. We adapt AGIS to process Hipparcos data in addition to Gaia observations, and use simulations to verify and study the joint solution method. Results: For the HTPM stars we predict proper motion accuracies between 14 and 134 μas yr-1, depending on stellar magnitude and amount of Gaia data available. Perspective effects will be important for a significant number of HTPM stars, and in order to treat these effects accurately we introduce a formalism called scaled model of kinematics (SMOK). We define a goodness-of-fit statistic which is sensitive to deviations from uniform space motion, caused for example by binaries with periods of 10-50 years. Conclusions: HTPM will significantly improve the proper motions of the Hipparcos Catalogue well before highly accurate Gaia-only results become available. Also, HTPM will allow us to detect long period binary and exoplanetary candidates which would be impossible to detect from Gaia data alone. The full sensitivity will not be reached with the first Gaia release but with subsequent data releases. Therefore HTPM should be repeated when more Gaia data become available

  13. Astrometric and Photometric Follow-Up of Faint Near Earth Objects

    NASA Technical Reports Server (NTRS)

    Spahr, Timothy

    2004-01-01

    During the last year, the Near-Earth Object (NEO) follow-up program at Mt. Hopkins funded by the Near-Earth Object Observations (NEOO) program continued to improve. The Principal Investigator was again granted all the requested observing time. In addition to the requested time on the 4 8 in. telescope, 2 nights were also granted on the MMT for observations of extremely faint main-belt asteroids and NEOs. It is expected that the MMT can easily reach V = 25 over a 24 X 24 arcminute field of view. Improvements in the last year included more tweaks to the automatic astrometric routine for higher-quality astrometric fits. Use of the new USNO-B1.0 reference catalog has allowed the PI to push the average RMS of reference star solutions below 0.2 in.. Shift-and- stack techniques are used to improve the signal-to-noise ratio of the target objects. The 48 in. telescope at Mt. Hopkins is completely automated, and can be run remotely from either the Principal Investigator's office at SAO, or even his study at home. Most observing runs are now done remotely.

  14. An astrometric search for a stellar companion to the sun

    SciTech Connect

    Perlmutter, S.

    1986-11-25

    A companion star within 0.8 pc of the Sun has been postulated to explain a possible 26 Myr periodicity in mass extinctions of species on the Earth. Such a star would already be catalogued in the Yale Bright Star catalogue unless it is fainter than m/sub nu/ = 6.5; this limits the possible stellar types for an unseen companion to red dwarfs, brown dwarfs, or compact objects. Red dwarfs account for about 75% of these possible stars. We describe here the design and development of an astrometric search for a nearby red dwarf companion with a six-month peak-to-peak parallax of greater than or equal to2.5 arcseconds. We are measuring the parallax of 2770 candidate faint red stars selected from the Dearborn Observatory catalogue. An automated 30-inch telescope and CCD camera system collect digitized images of the candidate stars, along with a 13' x 16' surrounding field of background stars. Second-epoch images, taken a few months later, are registered to the first epoch images using the background stars as fiducials. An apparent motion, m/sub a/, of the candidate stars is found to a precision of sigma/sub m//sub a/ approx. = 0.08 pixel approx. = 0.2 arcseconds for fields with N/sub fiducial/ greater than or equal to 10 fiducial stars visible above the background noise. This precision is sufficient to detect the parallactic motion of a star at 0.8 pc with a two month interval between the observation epochs. Images with fewer fiducial stars above background noise are observed with a longer interval between epochs. If a star is found with high parallactic motion, we will confirm its distance with further parallax measurements, photometry, and spectral studies, and will measure radial velocity and proper motion to establish its orbit. We have demonstrated the search procedure with observations of 41 stars, and have shown that none of these is a nearby star. 37 refs., 16 figs., 3 tabs.

  15. Astrometric Image Centroid Displacements due to Gravitational Microlensing by the Ellis Wormhole

    NASA Astrophysics Data System (ADS)

    Toki, Yukiharu; Kitamura, Takao; Asada, Hideki; Abe, Fumio

    2011-10-01

    Continuing work initiated in an earlier publication, we study the gravitational microlensing effects of the Ellis wormhole in the weak-field limit. First, we find a suitable coordinate transformation, such that the lens equation and analytic expressions of the lensed image positions can become much simpler. Second, we prove that two images always appear for the weak-field lens by the Ellis wormhole. By using these analytic results, we discuss astrometric image centroid displacements due to gravitational microlensing by the Ellis wormhole. The astrometric image centroid trajectory by the Ellis wormhole is different from the standard one by a spherical lensing object that is expressed by the Schwarzschild metric. The anomalous shift of the image centroid by the Ellis wormhole lens is smaller than that by the Schwarzschild lens, provided that the impact parameter and the Einstein ring radius are the same. Therefore, the lensed image centroid by the Ellis wormhole moves slower. Such a difference, although it is very small, will be, in principle, applicable for detecting or constraining the Ellis wormhole by using future high-precision astrometry observations. In particular, the image centroid position gives us additional information, so that the parameter degeneracy existing in photometric microlensing can be partially broken. The anomalous shift reaches the order of a few micro arcseconds, if our galaxy hosts a wormhole with throat radius larger than 105 km. When the source moves tangentially to the Einstein ring, for instance, the maximum position shift of the image centroid by the Ellis wormhole is 0.18 normalized by the Einstein ring radius. For the same source trajectory, the maximum difference between the centroid displacement by the Ellis wormhole lens and that by the Schwarzschild one with the same Einstein ring radius is -0.16 in the units of the Einstein radius, where the negative means that the astrometric displacement by the Ellis wormhole lens is smaller

  16. ASTROMETRIC IMAGE CENTROID DISPLACEMENTS DUE TO GRAVITATIONAL MICROLENSING BY THE ELLIS WORMHOLE

    SciTech Connect

    Toki, Yukiharu; Kitamura, Takao; Asada, Hideki; Abe, Fumio

    2011-10-20

    Continuing work initiated in an earlier publication, we study the gravitational microlensing effects of the Ellis wormhole in the weak-field limit. First, we find a suitable coordinate transformation, such that the lens equation and analytic expressions of the lensed image positions can become much simpler. Second, we prove that two images always appear for the weak-field lens by the Ellis wormhole. By using these analytic results, we discuss astrometric image centroid displacements due to gravitational microlensing by the Ellis wormhole. The astrometric image centroid trajectory by the Ellis wormhole is different from the standard one by a spherical lensing object that is expressed by the Schwarzschild metric. The anomalous shift of the image centroid by the Ellis wormhole lens is smaller than that by the Schwarzschild lens, provided that the impact parameter and the Einstein ring radius are the same. Therefore, the lensed image centroid by the Ellis wormhole moves slower. Such a difference, although it is very small, will be, in principle, applicable for detecting or constraining the Ellis wormhole by using future high-precision astrometry observations. In particular, the image centroid position gives us additional information, so that the parameter degeneracy existing in photometric microlensing can be partially broken. The anomalous shift reaches the order of a few micro arcseconds, if our galaxy hosts a wormhole with throat radius larger than 10{sup 5} km. When the source moves tangentially to the Einstein ring, for instance, the maximum position shift of the image centroid by the Ellis wormhole is 0.18 normalized by the Einstein ring radius. For the same source trajectory, the maximum difference between the centroid displacement by the Ellis wormhole lens and that by the Schwarzschild one with the same Einstein ring radius is -0.16 in the units of the Einstein radius, where the negative means that the astrometric displacement by the Ellis wormhole lens is

  17. A study of astrometric distortions due to “tree rings” in CCD sensors using LSST Photon Simulator

    SciTech Connect

    Beamer, Benjamin; Nomerotski, Andrei; Tsybychev, Dmitri

    2015-05-22

    Imperfections in the production process of thick CCDs lead to circularly symmetric dopant concentration variations, which in turn produce electric fields transverse to the surface of the fully depleted CCD that displace the photogenerated charges. We use PhoSim, a Monte Carlo photon simulator, to explore and examine the likely impacts these dopant concentration variations will have on astrometric measurements in LSST. The scale and behavior of both the astrometric shifts imparted to point sources and the intensity variations in flat field images that result from these doping imperfections are similar to those previously observed in Dark Energy Camera CCDs, giving initial confirmation of PhoSim's model for these effects. In addition, the organized shape distortions were observed as a result of the symmetric nature of these dopant variations, causing nominally round sources to be imparted with a measurable ellipticity either aligned with or transverse to the radial direction of this dopant variation pattern.

  18. A study of astrometric distortions due to “tree rings” in CCD sensors using LSST Photon Simulator

    DOE PAGES

    Beamer, Benjamin; Nomerotski, Andrei; Tsybychev, Dmitri

    2015-05-22

    Imperfections in the production process of thick CCDs lead to circularly symmetric dopant concentration variations, which in turn produce electric fields transverse to the surface of the fully depleted CCD that displace the photogenerated charges. We use PhoSim, a Monte Carlo photon simulator, to explore and examine the likely impacts these dopant concentration variations will have on astrometric measurements in LSST. The scale and behavior of both the astrometric shifts imparted to point sources and the intensity variations in flat field images that result from these doping imperfections are similar to those previously observed in Dark Energy Camera CCDs, givingmore » initial confirmation of PhoSim's model for these effects. In addition, the organized shape distortions were observed as a result of the symmetric nature of these dopant variations, causing nominally round sources to be imparted with a measurable ellipticity either aligned with or transverse to the radial direction of this dopant variation pattern.« less

  19. Astrometric Gravitation Probe: a space mission concept for fundamental physics

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Fienga, Agnes; Gai, Mario; Lattanzi, Mario G.; Riva, Alberto; Busonero, Deborah

    2015-08-01

    Modern technological developments have pushed the accuracy of astrometric measurements in the visible band down to the micro-arcsec level. This allows to test theories of gravity in the weak field limit to unprecedented level, with possible consequences spanning from the validity of fundamental physics principles, to tests of theories describing cosmological and galactic dynamics without resorting to Dark Matter and Dark Energy.This is the main goal of Astrometric Gravitation Probe (AGP) mission, which will be achieved by highly accurate astrometric determination of light deflection (as a modern rendition of the Dyson, Eddington, and Robertson eclipse experiment of 1919), aberration, and of the orbits of selected Solar System objects, with specific reference to the excess shift of the pericentre effect.The AGP concept was recently proposed for the recent call for ESA M4 missions as a collaboration among several scientists coming from many different European and US institutions. Its payload is based on a 1.15 m diameter telescope fed through a coronagraphic system by four fields, two set in symmetric positions around the Sun, and two in the opposite direction, all imaged on a CCD detector. Large parts of the instrument are common mode to all fields. The baseline operation mode is the scan of the ±1.13 deg Ecliptic strip, repeated for a minimum of 3 years and up to an optimal duration of 5 years. Operations and calibrations are simultaneous, defined in order to ensure common mode instrumental effects, identified and removed in data reduction. The astrometric and coronagraphic technologies build on the heritage of Gaia and Solar Orbiter.We review the mission concept and its science case, and discuss how this measurement concepts can be scaled to different mission implementations.

  20. The parallax and astrometric orbit of Mu Cassiopeiae

    NASA Technical Reports Server (NTRS)

    Russell, J. L.; Gatewood, G. D.

    1984-01-01

    A total of 371 photographic plates were made of the binary Mu Cassiopeia (Mu Cas) region with a 76 cm refractor. An astrometric orbit of nearly 22.09 yr was calculated, accompanied by an eccentricity of close to 0.58 and a semimajor axis close to 0.19 arcsec. The absolute magnitude was approximately 5.83 and the radial velocity 164 km/sec.

  1. BASE: Bayesian Astrometric and Spectroscopic Exoplanet Detection and Characterization Tool

    NASA Astrophysics Data System (ADS)

    Schulze-Hartung, Tim

    2012-08-01

    BASE is a novel program for the combined or separate Bayesian analysis of astrometric and radial-velocity measurements of potential exoplanet hosts and binary stars. The tool fulfills two major tasks of exoplanet science, namely the detection of exoplanets and the characterization of their orbits. BASE was developed to provide the possibility of an integrated Bayesian analysis of stellar astrometric and Doppler-spectroscopic measurements with respect to their binary or planetary companions’ signals, correctly treating the astrometric measurement uncertainties and allowing to explore the whole parameter space without the need for informative prior constraints. The tool automatically diagnoses convergence of its Markov chain Monte Carlo (MCMC[2]) sampler to the posterior and regularly outputs status information. For orbit characterization, BASE delivers important results such as the probability densities and correlations of model parameters and derived quantities. BASE is a highly configurable command-line tool developed in Fortran 2008 and compiled with GFortran. Options can be used to control the program’s behaviour and supply information such as the stellar mass or prior information. Any option can be supplied in a configuration file and/or on the command line.

  2. Astrometric Monitoring of the HR 8799 Planets: Orbit Constraints from Self-consistent Measurements

    NASA Astrophysics Data System (ADS)

    Konopacky, Q. M.; Marois, C.; Macintosh, B. A.; Galicher, R.; Barman, T. S.; Metchev, S. A.; Zuckerman, B.

    2016-08-01

    We present new astrometric measurements from our ongoing monitoring campaign of the HR 8799 directly imaged planetary system. These new data points were obtained with NIRC2 on the W.M. Keck II 10 m telescope between 2009 and 2014. In addition, we present updated astrometry from previously published observations in 2007 and 2008. All data were reduced using the SOSIE algorithm, which accounts for systematic biases present in previously published observations. This allows us to construct a self-consistent data set derived entirely from NIRC2 data alone. From this data set, we detect acceleration for two of the planets (HR 8799b and e) at >3σ. We also assess possible orbital parameters for each of the four planets independently. We find no statistically significant difference in the allowed inclinations of the planets. Fitting the astrometry while forcing coplanarity also returns χ 2 consistent to within 1σ of the best fit values, suggesting that if inclination offsets of ≲20° are present, they are not detectable with current data. Our orbital fits also favor low eccentricities, consistent with predictions from dynamical modeling. We also find period distributions consistent to within 1σ with a 1:2:4:8 resonance between all planets. This analysis demonstrates the importance of minimizing astrometric systematics when fitting for solutions to highly undersampled orbits.

  3. CATALOG MATCHING WITH ASTROMETRIC CORRECTION AND ITS APPLICATION TO THE HUBBLE LEGACY ARCHIVE

    SciTech Connect

    Budavari, Tamas; Lubow, Stephen H. E-mail: lubow@stsci.edu

    2012-12-20

    Object cross-identification in multiple observations is often complicated by the uncertainties in their astrometric calibration. Due to the lack of standard reference objects, an image with a small field of view can have significantly larger errors in its absolute positioning than the relative precision of the detected sources within. We present a new general solution for the relative astrometry that quickly refines the World Coordinate System of overlapping fields. The efficiency is obtained through the use of infinitesimal three-dimensional rotations on the celestial sphere, which do not involve trigonometric functions. They also enable an analytic solution to an important step in making the astrometric corrections. In cases with many overlapping images, the correct identification of detections that match together across different images is difficult to determine. We describe a new greedy Bayesian approach for selecting the best object matches across a large number of overlapping images. The methods are developed and demonstrated on the Hubble Legacy Archive, one of the most challenging data sets today. We describe a novel catalog compiled from many Hubble Space Telescope observations, where the detections are combined into a searchable collection of matches that link the individual detections. The matches provide descriptions of astronomical objects involving multiple wavelengths and epochs. High relative positional accuracy of objects is achieved across the Hubble images, often sub-pixel precision in the order of just a few milliarcseconds. The result is a reliable set of high-quality associations that are publicly available online.

  4. Early-Type Stars: Most Favorable Targets for Astrometrically Detectable Planets in the Habitable Zone

    NASA Astrophysics Data System (ADS)

    Gould, Andrew; Ford, Eric B.; Fischer, Debra A.

    2003-07-01

    Early-type stars appear to be a difficult place to look for planets astrometrically. First, they are relatively heavy, and for fixed planetary mass the astrometric signal falls inversely as the stellar mass. Second, they are relatively rare (and so tend to be more distant), and for fixed orbital separation the astrometric signal falls inversely as the distance. Nevertheless, because early-type stars are relatively more luminous, their habitable zones are at larger semimajor axis. Since astrometric signal scales directly as orbital size, this gives early-type stars a strong advantage, which more than compensates for the other two factors. Using the Hipparcos Catalog, we show that F and A stars constitute the majority of viable targets for astrometric searches for planets with semimajor axes currently in the habitable zone. Thus, astrometric surveys are complementary to transit searches, which are primarily sensitive to habitable planets around late-type stars.

  5. Astrometric discovery of GJ 802b : in the Brown Dwarf Oasis?

    NASA Technical Reports Server (NTRS)

    Pravdo, Steven H.; Shaklan, Stuart B.; Lloyd, James

    2005-01-01

    The Stellar Planet Survey is an ongoing astrometric search for giant planets and brown dwarfs around a sample of 30 M dwarfs. We have discovered several low-mass companions by measuring the motion of our target stars relative to their reference frames. The lowest mass discovery thus far is GJ 802b, a companion to the M5 dwarf GJ 802A. The orbital period is 3.14 +/-0:03 yr, the system mass is 0:214 +/- 0:045 M(circled dot operator), and the semimajor axis is 1:28+/- 0:10 AU or 81 + 6 mas. Imaging observations indicate that GJ 802b is likely to be a brow with the astrometrically determined mass 0:058 +/- 0:021 M(circled dot operator) (1 (sigma) limits). The remaining uncertainty in the orbit is the eccentricity that is now loosely constrained. We dis the system age limits the mass and the prospects of further narrowing the mass range when e is more precisely determined.

  6. Orbit of an Astrometric Binary System

    NASA Astrophysics Data System (ADS)

    Descamps, Pascal

    2005-08-01

    We present a new method to solve the problem of initial orbit determination of any binary system. This method is mainly based on the material available for an observer, for example relative positions at a given time of the couple in the “plane of sky”, namely the tangent plane to the celestial sphere at the position of the primary component. The problem of orbit determination is solved by splitting in successive stages in order to decorrelate the parameters of each other as much as possible. On one hand, the geometric problem is solved using the first Kepler’s law from a single observing run and, on the other hand, dynamical parameters are then inferred from the fit of the Kepler’s equation. At last, the final stage consists in determining the main physical parameters involved in the secular evolution of the system, that is the spin axis and the J2 parameter of the primary if we assume that it is a quasi-spherical body. As a matter of fact there is no need to make too restrictive initial assumptions (such as circular orbit or zero eccentricity) and initial guesses of parameters required by a non-linear least-squares Levenberg Marquardt algorithm are finally obtained after each stage. Such a protocol is very useful to study systems like binary asteroids for which all of the parameters should be considered a priori as unknowns. As an example of application, we used our method to estimate the set of the Pluto Charon system parameters from observations collected in the literature since 1980.

  7. VizieR Online Data Catalog: Amalthea and Thebe CCD astrometric obs. (Veiga+, 2005)

    NASA Astrophysics Data System (ADS)

    Veiga, C. H.; Vieira Martins, R.

    2005-07-01

    This paper presents the results of observations of Jupiter's satellites Amalthea and Thebe made in 1995, 1996 and 2001 at the Laboratorio Nacional de Astrofisica (LNA), Brazil. The observations were made in visible light wavelengths with a 1.6m reflector telescope and the light of Jupiter was covered by a mask placed near the CCD surface. The already published positions for 1995, whose astrometric reduction used the Galilean satellites, are now reduced using the stars in the CCD fields like the new positions of 1996 and 2001. The 2001 data are much better than those obtained in 1995, and that those from 1996 show large residuals. Considering the 310 frames observed, the mean residual is about 0.01" and the standard deviation is about 0.15". (1 data file).

  8. Bayesian analysis of exoplanet and binary orbits. Demonstrated using astrometric and radial-velocity data of Mizar A

    NASA Astrophysics Data System (ADS)

    Schulze-Hartung, T.; Launhardt, R.; Henning, T.

    2012-09-01

    Aims: We introduce BASE (Bayesian astrometric and spectroscopic exoplanet detection and characterisation tool), a novel program for the combined or separate Bayesian analysis of astrometric and radial-velocity measurements of potential exoplanet hosts and binary stars. The capabilities of BASE are demonstrated using all publicly available data of the binary Mizar A. Methods: With the Bayesian approach to data analysis we can incorporate prior knowledge and draw extensive posterior inferences about model parameters and derived quantities. This was implemented in BASE by Markov chain Monte Carlo (MCMC) sampling, using a combination of the Metropolis-Hastings, hit-and-run, and parallel-tempering algorithms to explore the whole parameter space. Nonconvergence to the posterior was tested by means of the Gelman-Rubin statistic (potential scale reduction). The samples were used directly and transformed into marginal densities by means of kernel density estimation, a "smooth" alternative to histograms. We derived the relevant observable models from Newton's law of gravitation, showing that the motion of Earth and the target can be neglected. Results: With our methods we can provide more detailed information about the parameters than a frequentist analysis does. Still, a comparison with the Mizar A literature shows that both approaches are compatible within the uncertainties. Conclusions: We show that the Bayesian approach to inference has been implemented successfully in BASE, a flexible tool for analysing astrometric and radial-velocity data. BASE, the computer program introduced in this article, can be downloaded at http://www.mpia.de/homes/schulze/base.html.

  9. Competing Processes of Sibling Influence: Observational Learning and Sibling Deidentification

    ERIC Educational Resources Information Center

    Whiteman, Shawn D.; McHale, Susan M.; Crouter, Ann C.

    2007-01-01

    Although commonly cited as explanations for patterns of sibling similarity and difference, observational learning and sibling deidentification processes have rarely been examined directly. Using a person-oriented approach, we identified patterns in adolescents' perceptions of sibling influences and connected these patterns to sibling similarities…

  10. Limits of Astrometric and Photometric Precision on KBOs using Small Telescopes

    NASA Astrophysics Data System (ADS)

    Markatou, Evangelia Anna; Wang, Amanda; Kosiarek, Molly; Dunham, Emilie

    2014-06-01

    We conducted photometric and astrometric measurements on Haumea and Makemake, two Kuiper Belt Objects which are typically observed by 1-meter class telescopes or larger, with the goal of testing the limitations of small telescopes. Here we present our measurements of Haumea and Makemake obtained between June 5th, 2013 and July 31st, 2013 with the 14-inch Wallace Astrophysical Observatory (WAO) telescopes. Using photometry, we determined that Haumea and Makemake have R-band magnitudes of 17.225±0.347 and 16.850±0.107 respectively. These values agree with the previous R-band measurements of 17.240±0.030 (Lacerda et al. 2008) and 16.802±0.041 (Rabinowitz et al. 2007) for Haumea and Makemake respectively. We obtained rotational light curves for Haumea and Makemake over eight separate nights, again by analysing the photometry observations. Astrometry yielded residuals of -0.039±0.025 arcseconds in RA and 0.234±0.017 arcseconds in DEC for Makemake, and 0.295±0.077 arcseconds in RA and 0.184±0.0554 arcseconds in DEC for Haumea. These results, when submitted to the minor planet center, are able to increase the accuracy of the JPL ephemeris. Additionally, we calculated that observing Haumea with two 14-inch telescopes and Makemake with four 14-inch telescopes, in ideal conditions, could resolve their periodicity. We conclude that with improved observing techniques and modern CCD cameras, it is possible to utilize small telescopes in universities around the world to observe large KBOs and obtain accurate photometric and astrometric results.

  11. Vlbi Astrometric Orbit Solutions Of The Triple Systems Algol And Ux Arietis

    NASA Astrophysics Data System (ADS)

    Lucien Mutel, Robert; Peterson, W. M.; Guedel, M.; Goss, M.

    2011-01-01

    Multi-epoch phase-referenced VLBI observations are a powerful technique to make sub-milliarcsecond astrometric measurements. We report on high-accuracy orbit and proper motion determination of the well-known active binaries Algol and UX Arietis, combining multi-epoch HSA and VLBA phase-referenced observations with archival VLBI datasets. We find that both Algol and UX Arietis are triple systems, For Algol, we refine the proper motion and outer orbit solutions, confirming the recent optical result of Zavala et al. (2010) that component C's position angle had been reported in error by 180 deg. For UX Arietis, we find a third component orbital solution that accounts for previous VLBI reports of an acceleration term in the proper motion fit.

  12. Geodetic and Astrometric Measurements with Very-Long-Baseline Interferometry. Ph.D. Thesis - MIT

    NASA Technical Reports Server (NTRS)

    Robertson, D. S.

    1975-01-01

    The use of very-long-baseline interferometry (VLBI) observations for the estimation of geodetic and astrometric parameters is discussed. Analytic models for the dependence of delay and delay rate on these parameters are developed and used for parameter estimation by the method of weighted least squares. Results are presented from approximately 15,000 delay and delay-rate observations, obtained in a series of nineteen VLBI experiments involving a total of five stations on two continents. The closure of baseline triangles is investigated and found to be consistent with the scatter of the various baseline-component results. Estimates are made of the wobble of the earth's pole and of the irregularities in the earth's rotation rate. Estimates are also made of the precession constant and of the vertical Love number, for which a value of 0.55 + or - 0.05 was obtained.

  13. Gamma Astrometric Measurement Experiment (GAME) - Implementation and performance

    NASA Astrophysics Data System (ADS)

    Gai, Mario; Gai, Mario; Vecchiato, Alberto; Lattanzi, Mario G.; Ligori, Sebastiano; Loreggia, Davide

    The GAME mission concept is aimed at test of the General Relativity, through very precise measurement of the gravitational deflection of light by the Sun, by means of an optimised telescope operating in the visible and launched in orbit on a small class satellite. We recall the science motivations, discussed in detail in a separate contribution by Vecchiato et al., and describe the mission requirements derivation, the proposed mission profile, the preliminary payload design and the expected performance. The targeted precision on the "γ" parameter of the Parametrised Post-Newtonian formulation of General Relativity is in the range 10-6 to 10-7 or better, with an improvement of one or two orders of magnitude with respect to the best currently available experimental results. Such precision is suitable to detect possible deviations of γ from the unity value, associated to generalised Einstein models for gravitation, with potentially huge impacts on the cosmological distribution of dark matter and dark energy. The measurement principle is based on the differential astrometric signature on the stellar positions, i.e. on the spatial component of the gravitational effect, rather than the temporal component as in the most recent experiments based on radio link delay timing. Calibration is based on frequent measurement of angular separation of bright sources in stellar fields affected by negligible deflection. The instrument concept is based on a dual field, multiple aperture Fizeau interferometer, observing simultaneously two sky regions close to the Solar limb. A split flat mirror is used to fold the telescope line of sight on two different directions on the sky, separated by a base angle of about 4 degrees, which represents the gauge applied on the sky to measure the desired angular value of deflection. Stability or calibration of the base angle is the key to fulfilling the GAME science goals. An internal laser metrology option is considered for both on ground

  14. Evaluating Observation Influence on Regional Water Budgets in Reanalyses

    NASA Technical Reports Server (NTRS)

    Bosilovich, Michael G.; Chern, Jiun-Dar; Mocko, David; Robertson, Franklin R.; daSilva, Arlindo M.

    2014-01-01

    The assimilation of observations in reanalyses incurs the potential for the physical terms of budgets to be balanced by a term relating the fit of the observations relative to a forecast first guess analysis. This may indicate a limitation in the physical processes of the background model, or perhaps inconsistencies in the observing system and its assimilation. In the MERRA reanalysis, an area of long term moisture flux divergence over land has been identified over the Central United States. Here, we evaluate the water vapor budget in this region, taking advantage of two unique features of the MERRA diagnostic output; 1) a closed water budget that includes the analysis increment and 2) a gridded diagnostic output data set of the assimilated observations and their innovations (e.g. forecast departures). In the Central United States, an anomaly occurs where the analysis adds water to the region, while precipitation decreases and moisture flux divergence increases. This is related more to a change in the observing system than to a deficiency in the model physical processes. MERRAs Gridded Innovations and Observations (GIO) data narrow the observations that influence this feature to the ATOVS and Aqua satellites during the 06Z and 18Z analysis cycles. Observing system experiments further narrow the instruments that affect the anomalous feature to AMSUA (mainly window channels) and AIRS. This effort also shows the complexities of the observing system, and the reactions of the regional water budgets in reanalyses to the assimilated observations.

  15. Astrometric Jitter of the Sun as a Star

    NASA Astrophysics Data System (ADS)

    Makarov, V. V.; Parker, D.; Ulrich, R. K.

    2010-07-01

    The daily variation of the solar photocenter over some 11 yr is derived from the Mount Wilson data reprocessed by Ulrich et al. to closely match the surface distribution of solar irradiance. The standard deviations of astrometric jitter are 0.52 μAU and 0.39 μAU in the equatorial and the axial dimensions, respectively. The overall dispersion is strongly correlated with solar cycle, reaching 0.91 μAU at maximum activity in 2000. The largest short-term deviations from the running average (up to 2.6 μAU) occur when a group of large spots happen to lie on one side with respect to the center of the disk. The amplitude spectrum of the photocenter variations never exceeds 0.033 μAU for the range of periods 0.6-1.4 yr, corresponding to the orbital periods of planets in the habitable zone. Astrometric detection of Earth-like planets around stars as quiet as the Sun is not affected by star spot noise, but the prospects for more active stars may be limited to giant planets.

  16. ASTROMETRY.NET: BLIND ASTROMETRIC CALIBRATION OF ARBITRARY ASTRONOMICAL IMAGES

    SciTech Connect

    Lang, Dustin; Mierle, Keir; Roweis, Sam; Hogg, David W.; Blanton, Michael

    2010-05-15

    We have built a reliable and robust system that takes as input an astronomical image, and returns as output the pointing, scale, and orientation of that image (the astrometric calibration or World Coordinate System information). The system requires no first guess, and works with the information in the image pixels alone; that is, the problem is a generalization of the 'lost in space' problem in which nothing-not even the image scale-is known. After robust source detection is performed in the input image, asterisms (sets of four or five stars) are geometrically hashed and compared to pre-indexed hashes to generate hypotheses about the astrometric calibration. A hypothesis is only accepted as true if it passes a Bayesian decision theory test against a null hypothesis. With indices built from the USNO-B catalog and designed for uniformity of coverage and redundancy, the success rate is >99.9% for contemporary near-ultraviolet and visual imaging survey data, with no false positives. The failure rate is consistent with the incompleteness of the USNO-B catalog; augmentation with indices built from the Two Micron All Sky Survey catalog brings the completeness to 100% with no false positives. We are using this system to generate consistent and standards-compliant meta-data for digital and digitized imaging from plate repositories, automated observatories, individual scientific investigators, and hobbyists. This is the first step in a program of making it possible to trust calibration meta-data for astronomical data of arbitrary provenance.

  17. Astrometry.net: Blind Astrometric Calibration of Arbitrary Astronomical Images

    NASA Astrophysics Data System (ADS)

    Lang, Dustin; Hogg, David W.; Mierle, Keir; Blanton, Michael; Roweis, Sam

    2010-05-01

    We have built a reliable and robust system that takes as input an astronomical image, and returns as output the pointing, scale, and orientation of that image (the astrometric calibration or World Coordinate System information). The system requires no first guess, and works with the information in the image pixels alone; that is, the problem is a generalization of the "lost in space" problem in which nothing—not even the image scale—is known. After robust source detection is performed in the input image, asterisms (sets of four or five stars) are geometrically hashed and compared to pre-indexed hashes to generate hypotheses about the astrometric calibration. A hypothesis is only accepted as true if it passes a Bayesian decision theory test against a null hypothesis. With indices built from the USNO-B catalog and designed for uniformity of coverage and redundancy, the success rate is >99.9% for contemporary near-ultraviolet and visual imaging survey data, with no false positives. The failure rate is consistent with the incompleteness of the USNO-B catalog; augmentation with indices built from the Two Micron All Sky Survey catalog brings the completeness to 100% with no false positives. We are using this system to generate consistent and standards-compliant meta-data for digital and digitized imaging from plate repositories, automated observatories, individual scientific investigators, and hobbyists. This is the first step in a program of making it possible to trust calibration meta-data for astronomical data of arbitrary provenance.

  18. Interstellar Medium, Young Stars, and Astrometric Binaries in Galactic Archaeology Spectroscopic Surveys

    NASA Astrophysics Data System (ADS)

    Zwitter, T.; Kos, J.; Žerjal, M.; Traven, G.

    2016-10-01

    Current ongoing stellar spectroscopic surveys (RAVE, GALAH, Gaia-ESO, LAMOST, APOGEE, Gaia) are mostly devoted to studying Galactic archaeology and the structure of the Galaxy. But they allow also for important auxiliary science: (i) the Galactic interstellar medium can be studied in four dimensions (position in space plus radial velocity) through weak but numerous diffuse interstellar bands and atomic absorptions seen in spectra of background stars, (ii) emission spectra which are quite frequent even in field stars can serve as a good indicator of their youth, pointing e.g. to stars recently ejected from young stellar environments, (iii) an astrometric solution of the photocenter of a binary to be obtained by Gaia can yield accurate masses when joined by spectroscopic information obtained serendipitously during a survey. These points are illustrated by first results from the first three surveys mentioned above. These hint at the near future: spectroscopic studies of the dynamics of the interstellar medium can identify and quantify Galactic fountains which may sustain star formation in the disk by entraining fresh gas from the halo; RAVE already provided a list of ˜ 14,000 field stars with chromospheric emission in Ca II lines, to be supplemented by many more observations by Gaia in the same band, and by GALAH and Gaia-ESO observations of Balmer lines; several millions of astrometric binaries with periods up to a few years which are being observed by Gaia can yield accurate masses when supplemented with measurements from only a few high-quality ground based spectra.

  19. Astrometric plates obtained at the primary focus of large aperture reflectors

    NASA Technical Reports Server (NTRS)

    Markos, A.

    1984-01-01

    Coma, astigmatism, and great differences in stellar magnitudes between photographed object and reference stars constitute the main sources of errors in measuring positional plates. These three sources of error can easily be eliminated by the method used at the Klet Observatory for obtaining precise observations of faint objects. The astrometric plates are taken by the method of two diaphragms. The first diaphragm, with a small central aperture; is located in front of the photographic plate. The second diaphragm is situated in front of the mirror. By a very short (of the order of tens of seconds) exposure a sufficient number of reference stars can be obtained throughout the entire plate. The stars are very well defined to the very edge of the plate and are easy to measure. Moreover, this method makes it possible to use plates of larger dimensions than usual so that it is always possible to find the necessary reference stars.

  20. Astrometric detection of giant planets around nearby M dwarfs: the Gaia potential

    NASA Astrophysics Data System (ADS)

    Sozzetti, A.; Giacobbe, P.; Lattanzi, M. G.; Micela, G.; Morbidelli, R.; Tinetti, G.

    2014-01-01

    Cool M dwarfs within a few tens of parsecs from the Sun are becoming the focus of dedicated observational programs in the realm of exoplanet astrophysics. Gaia, in its all-sky survey of >109 objects, will deliver precision astrometry for a magnitude-limited (V = 20) sample of M dwarfs. We investigate some aspects of the synergy between the Gaia astrometric data on nearby M dwarfs and other ground-based and space-borne programs for planet detection and characterization. We carry out numerical simulations to gauge the Gaia potential for precision astrometry of exoplanets orbiting a sample of known dM stars within ˜30 pc from the Sun. We express Gaia detection thresholds as a function of system parameters and in view of the latest mission profile, including the most up-to-date astrometric error model. Our major findings are as follows: (1) it will be possible to accurately determine orbits and masses for Jupiter-mass planets with orbital periods in the range 0.2 ≲ P ≲ 6.0 yr and with an astrometric signal-to-noise ratio ς/σAL ≳ 10. Given present-day estimates of the planet fraction fp around M dwarfs, ≈102 giant planets could be found by Gaia around the sample. Comprehensive screening by Gaia of the reservoir of ˜4 × 105 M dwarfs within 100 pc could result in ˜2600 detections and as many as ˜500 accurate orbit determinations. The value of fp could then be determined with an accuracy of 2 per cent, an improvement by over an order of magnitude with respect to the most precise values available to-date; (2) in the same period range, inclination angles corresponding to quasi-edge-on configurations will be determined with enough precision (a few per cent) so that it will be possible to identify intermediate-separation planets which are potentially transiting within the errors. Gaia could alert us of the existence of 10 such systems. More than 250 candidates could be identified assuming solutions compatible with transit configurations within 10 per cent

  1. Astrometric accuracy of aperture making interferometry with JWST-NIRISS

    NASA Astrophysics Data System (ADS)

    Thatte, Deepashri; Greenbaum, Alexandra; Martel, André; Sivaramakrishnan, Anand; Artigau, Étienne

    2015-09-01

    JWST/NIRISS has a non-redundant aperture mask (NRM) for use with its F380M, F430M, F480M and F277W filters. In addition to high-resolution imaging with moderate contrast, the NRM provides better astrometric accuracy over a wide field of view than regular imaging. We investigate the accuracy achievable with the NRM by using an image-plane algorithm to analyze the PSFs of a point source that were obtained at a fixed pixel location with sub-pixel dithers during the second Cryo-Vacuum test campaign of the Integrated Science Instrument Module at NASA's Goddard Space Flight Center. Astrometry of brown dwarfs with the NRM will be sensitive to the presence of terrestrial planets and can be used to probe the architecture of planetary systems around these objects.

  2. Determining the Mass of Proxima Centauri through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2014-10-01

    We propose to determine the mass of our nearest neighbor, Proxima Centauri, using the novel technique of astrometric microlensing. Proxima is a dM6e star, with an estimated mass of about 0.12 Msun, lying at a distance of 1.3 pc and having a large proper motion of 3.8 arcsec/yr. In a reprise of the famous 1919 solar eclipse that verified general relativity, Proxima will pass in front of a pair of 18th-magnitude background stars in 2015, affording us two independent opportunities to measure the relativistic deflection. The first passage will occur in May 2015 (impact parameter 1.5 arcsec), and the second in June 2015 (impact parameter 1.4 arcsec). As Proxima passes in front, it will cause a relativistic deflection of the background stars' images by ~0.5 milliarcsec, an amount readily detectable with HST/WFC3.The gravitational deflection angle depends only upon the distances and relative positions of the stars, and the mass of the lens (Proxima). Since the distance to Proxima is well known from accurate parallax measurements, and the relative stellar positions can be determined precisely before the event, the astrometric measurement offers a unique and direct method to measure the mass of a single, isolated star. We anticipate better than 10% accuracy for the mass determination. The mass of Proxima is of special interest because it is the nearest M dwarf, representing the most common type of star in the Galaxy, for which the mass-luminosity relation is still uncertain at present.

  3. Determining the Mass of Proxima Centauri through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2013-10-01

    We propose to determine the mass of our nearest neighbor, Proxima Centauri, using the novel technique of astrometric microlensing. Proxima is a dM6e star, with an estimated mass of about 0.12 Msun, lying at a distance of 1.3 pc and having a large proper motion of 3.8 arcsec/yr. In a reprise of the famous 1919 solar eclipse that verified general relativity, Proxima will pass in front of a pair of 18th-magnitude background stars in 2015, affording us two independent opportunities to measure the relativistic deflection. The first passage will occur in May 2015 {impact parameter 1.5 arcsec}, and the second in June 2015 {impact parameter 1.4 arcsec}. As Proxima passes in front, it will cause a relativistic deflection of the background stars' images by 0.5 milliarcsec, an amount readily detectable with HST/WFC3.The gravitational deflection angle depends only upon the distances and relative positions of the stars, and the mass of the lens {Proxima}. Since the distance to Proxima is well known from accurate parallax measurements, and the relative stellar positions can be determined precisely before the event, the astrometric measurement offers a unique and direct method to measure the mass of a single, isolated star. We anticipate better than 10% accuracy for the mass determination. The mass of Proxima is of special interest because it is the nearest M dwarf, representing the most common type of star in the Galaxy, for which the mass-luminosity relation is still uncertain at present.

  4. Determining the Mass of Proxima Centauri through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2012-10-01

    We propose to determine the mass of our nearest neighbor, Proxima Centauri, using the novel technique of astrometric microlensing. Proxima is a dM6e star, with an estimated mass of about 0.12 Msun, lying at a distance of 1.3 pc and having a large proper motion of 3.8 arcsec/yr. In a reprise of the famous 1919 solar eclipse that verified general relativity, Proxima will pass in front of a pair of 18th-magnitude background stars in 2015, affording us two independent opportunities to measure the relativistic deflection. The first passage will occur in May 2015 {impact parameter 1.5 arcsec}, and the second in June 2015 {impact parameter 1.4 arcsec}. As Proxima passes in front, it will cause a relativistic deflection of the background stars' images by 0.5 milliarcsec, an amount readily detectable with HST/WFC3.The gravitational deflection angle depends only upon the distances and relative positions of the stars, and the mass of the lens {Proxima}. Since the distance to Proxima is well known from accurate parallax measurements, and the relative stellar positions can be determined precisely before the event, the astrometric measurement offers a unique and direct method to measure the mass of a single, isolated star. We anticipate better than 10% accuracy for the mass determination. The mass of Proxima is of special interest because it is the nearest M dwarf, representing the most common type of star in the Galaxy, for which the mass-luminosity relation is still uncertain at present.

  5. Astrometric search for Planets in the closest Brown Dwarf Binary system Luhman 16AB

    NASA Astrophysics Data System (ADS)

    Bedin, Luigi

    2014-10-01

    Located at 2.0 pc, the L8+T1 dwarfs system Luhman16AB is the third closest system known to Earth, making it a key benchmark for detailed investigation of brown dwarf atmospheric properties, thermal evolution, multiplicity and planet-hosting frequency. Indeed, a recent ground-based astrometric campaign suggested this system to host a 5-30 Jupiter masses exoplanet.We propose to use HST in spatial-scanning mode to obtain the most accurate annual parallax of any brown dwarf to date, achieving an unprecedented accuracy of 1 part in 10000 (50 micro-arcsecond) for each of the two components of Luh16, and to constrain their absolute space motions with similar accuracy. Most importantly, we will be able to confirm the giant planet candidate and to search for faint companions co-moving with the targets, either resolved or through astrometric perturbations of the A-B orbital motion, the latter probing down to few Earth-masses.Present-day ground-based direct imaging and AO facilities have fundamental limitations (field of view, PSF stability, differential chromatic effects, visibility) which introduce systematic and seasonal errors that are hard to quantify, and which have already resulted many times in clamorous false alarm in the recent past. This is particularly true for faint and red objects.Luhman 16A and B will be problematic for GAIA (faint, color, crowding, visibility), and the here proposed HST spatial-scanning mode observations will actually be an important complementary validation of the final GAIA catalog itself (expected 2020). Similarly, JWST is not expected to provide any better astrometry than HST because of its broader and irregular PSFs.

  6. High Precision Bright-Star Astrometry with the USNO Astrometric CMOS Hybrid Camera System

    NASA Astrophysics Data System (ADS)

    Secrest, Nathan; Dudik, Rachel; Berghea, Ciprian T.; Hennessy, Greg; Dorland, Bryan

    2015-05-01

    While GAIA will provide excellent positional measurements of hundreds of millions of stars between 5 < mag < 20, an ongoing challenge in the field of high-precision differential astrometry is the positional accuracy of very bright stars (mag < 5), due to the enormous dynamic range between bright stars of interest, such as those in the Hipparcos catalog, and their background field stars, which are especially important for differential astrometry. Over the past few years, we have been testing the USNO Astrometric CMOS Hybrid Camera System (UAHC), which utilizes an H4RG-10 detector in windowing mode, as a possible solution to the NOFS USNO Bright Star Astrometric Database (UBAD). In this work, we discuss the results of an astrometric analysis of single-epoch Hipparcos data taken with the UAHC from the 1.55m Kaj Strand Astrometric Reflector at NOFS from June 27-30, 2014. We discuss the calibration of this data, as well as an astrometric analysis pipeline we developed that will enable multi-epoch differential and absolute astrometry with the UAHC. We find that while the overall differential astrometric stability of data taken with the UAHC is good (5-10 mas single-measurement precision) and comparable to other ground-based astrometric camera systems, bright stars in the detector window suffer from several systematic effects, such as insufficient window geometry and centroiding failures due to read-out artifacts - both of which can be significantly improved with modifications to the electronics, read-out speed and microcode.

  7. Detecting human influence in observed changes in precipitation

    NASA Astrophysics Data System (ADS)

    Polson, Debbie; Hegerl, Gabriele; Bollasina, Massimo; Wilcox, Laura; Zhang, Xuebin; Osborn, Timothy; Balan Sarojini, Beena

    2015-04-01

    Human induced changes to the precipitation could cause some of the most serious impacts of climate change, with potential consequences for water resources, health, agriculture and ecosystems. However, quantifying and understanding the drivers of changes to precipitation is challenging due to its large spatial and temporal variability, the lack of long-term observational records over much of the globe and the counteracting affects of greenhouse gases and aerosols. Nevertheless, detection and attribution studies have shown that human influence has changed both global and regional precipitation over the latter half of the 20th century. Using climates models to derive fingerprints of external forcing, we are able to show that greenhouse gas warming has driven large scale changes in precipitation. Greenhouse gas forcing is detectable in observed changes to zonal mean precipitation over land (Polson et al., 2012a). It has also been shown to have caused the intensification of the water cycle, enhancing existing patterns of the precipitation in the tropics and subtropics, over both land and ocean (Polson et al., 2012b). While at global scales, the influence of greenhouse gases is detectable in observations, separating the response of precipitation to anthropogenic aerosol forcing is more difficult. However, in some regions the influence of aerosols dominate, making it possible to detect aerosol forcing. Observed precipitation in the monsoon regions underwent substantial changes during the second half of the twentieth century, with drying from the 1950s to mid-1980s and increasing precipitation in recent decades. Climate model simulations are used to derive fingerprints of individual climate forcings (i.e., greenhouse gas, anthropogenic aerosol, and natural) and detection and attribution methods applied to determine which, if any, have driven these changes to monsoon precipitation. Even when accounting for internal variability of the climate, a clear signal of anthropogenic

  8. Influence of the lower boundary in lysimeter observations

    NASA Astrophysics Data System (ADS)

    Weller, Ulrich; Richter, Katja; Gubis, Jozef; Vogel, Hans-Jörg

    2014-05-01

    Lysimeters are a valuable tool to study the water household in soils under close to natural conditions. One major drawback is that they are cut off at the lower boundary. This influences strongly the percolation of water. As long as water is leaching down in the soil, it is stagnating at the lower boundary until saturated conditions are reached and the water can percolate through the gravel filter, and under unsaturated conditions there is no flow at all at the lower boundary. In natural soils the water potential at the same depth differs considerably from the regime in a lysimeter. If the depth of the soil or the soil forming substrate is deep enough, the lower boundary is at the potential that allows the percolation of the long term mean of percolation. In other situations, a water table may influence the matric potential in the natural soil, or a less permeable layer may impede free drainage. In all these situations the matric potential at the depth of the lower boundary of the lysimeter will differ substantially in the natural soil. The latest generation of lysimeter therefore has a controlled lower boundary. The matric potential can be actively adjusted to a desired value over a broad range. Most applications connect the suction in the lysimeter to a reference value obtained in the field at the same depth in order to mimic the correct distribution of the soil water. In this presentation we demonstrate the long term influence of the different lower boundary regimes on percolation and evaporation of water based on soil physical models, and we show first field data on the practical implementations with several months of observations.

  9. Attribution of observed surface humidity changes to human influence.

    PubMed

    Willett, Katharine M; Gillett, Nathan P; Jones, Philip D; Thorne, Peter W

    2007-10-11

    Water vapour is the most important contributor to the natural greenhouse effect, and the amount of water vapour in the atmosphere is expected to increase under conditions of greenhouse-gas-induced warming, leading to a significant feedback on anthropogenic climate change. Theoretical and modelling studies predict that relative humidity will remain approximately constant at the global scale as the climate warms, leading to an increase in specific humidity. Although significant increases in surface specific humidity have been identified in several regions, and on the global scale in non-homogenized data, it has not been shown whether these changes are due to natural or human influences on climate. Here we use a new quality-controlled and homogenized gridded observational data set of surface humidity, with output from a coupled climate model, to identify and explore the causes of changes in surface specific humidity over the late twentieth century. We identify a significant global-scale increase in surface specific humidity that is attributable mainly to human influence. Specific humidity is found to have increased in response to rising temperatures, with relative humidity remaining approximately constant. These changes may have important implications, because atmospheric humidity is a key variable in determining the geographical distribution and maximum intensity of precipitation, the potential maximum intensity of tropical cyclones, and human heat stress, and has important effects on the biosphere and surface hydrology.

  10. The science, technology and mission design for the Laser Astrometric test of relativity

    NASA Technical Reports Server (NTRS)

    Turyshev, Slava G.

    2006-01-01

    The Laser Astrometric Test of Relativity (LATOR) is a Michelson-Morley-type experiment designed to test the Einstein's general theory of relativity in the most intense gravitational environment available in the solar system - the close proximity to the Sun.

  11. Comparative feasibility study of two concepts for a space-based astrometric satellite

    NASA Technical Reports Server (NTRS)

    Bamdermann, L.; Bareket, N.; Metheny, W.

    1982-01-01

    A comparative feasibility study of two concepts for an astrometric satellite: a visual imaging telescope with a 16.5 meter focal length and a white light interferometer with a 15 meter baseline separation was conducted.

  12. VizieR Online Data Catalog: Astrometric orbits of SB9 stars (Jancart+, 2005)

    NASA Astrophysics Data System (ADS)

    Jancart, S.; Jorissen, A.; Babusiaux, C.; Pourbaix, D.

    2006-07-01

    Hipparcos Intermediate Astrometric Data (IAD) have been used to derive astrometric orbital elements for spectroscopic binaries from the newly released Ninth Catalogue of Spectroscopic Binary Orbits (SB9). This endeavour is justified by the fact that (i) the astrometric orbital motion is often difficult to detect without the prior knowledge of the spectroscopic orbital elements, and (ii) such knowledge was not available at the time of the construction of the Hipparcos Catalogue for the spectroscopic binaries which were recently added to the SB9 catalogue. Among the 1374 binaries from SB9 which have an HIP entry (excluding binaries with visual companions, or DMSA/C in the Double and Multiple Stars Annex), 282 have detectable orbital astrometric motion (at the 5% significance level). Among those, only 70 have astrometric orbital elements that are reliably determined (according to specific statistical tests), and for the first time for 20 systems. This represents a 8.5% increase of the number of astrometric systems with known orbital elements (The Double and Multiple Systems Annex contains 235 of those DMSA/O systems). (6 data files).

  13. The Astrometric Recognition of the Solar Clementine Gnomon (1702)

    NASA Astrophysics Data System (ADS)

    Sigismondi, Costantino

    The Clementine gnomon has been built in 1702 to measure the Earth's obliquity variation. For this reason the pinhole was located in the walls of Diocletian's times (305 a. D.) in order to remain stable along the centuries, but its original form and position have been modified. We used an astrometric method to recover the original position of the pinhole: reshaping the pinhole to a circle of 1.5 cm of diameter, the positions of the Northern and Southern limbs have been compared with the ephemerides. A sistematic shift of 4.5 mm Southward of the whole solar image shows that the original pinhole was 4.5 mm North of the actual position, as the images in the Bianchini's book (1703) suggest. The oval shape of the actual pinhole is also wrong. Using a circle the larger solar spots are clearly visible. Some reference stars of the catalogue of Philippe de la Hire (1702), used originally for measuring the ecliptic latitude of the Sun, are written next to the meridian line, but after the last restauration (2000), four of them are wrongly located. Finally the deviation from the true North, of the meridian line's azimuth confirms the value recovered in 1750. This, with the local deviations of a true line, will remain as systematic error, like for all these historical instruments.

  14. Gaia astrometry for stars with too few observations. A Bayesian approach

    NASA Astrophysics Data System (ADS)

    Michalik, Daniel; Lindegren, Lennart; Hobbs, David; Butkevich, Alexey G.

    2015-11-01

    Context. The astrometric solution for Gaia aims to determine at least five parameters for each star, representing its position, parallax, and proper motion, together with appropriate estimates of their uncertainties and correlations. This requires at least five distinct observations per star. In the early data reductions the number of observations may be insufficient for a five-parameter solution, and even after the full mission many stars will remain under-observed, including faint stars at the detection limit and transient objects. In such cases it is reasonable to determine only the two position parameters. The formal uncertainties of such a two-parameter solution would however grossly underestimate the actual errors in position, due to the neglected parallax and proper motion. Aims: We aim to develop a recipe to calculate sensible formal uncertainties that can be used in all cases of under-observed stars. Methods: Prior information about the typical ranges of stellar parallaxes and proper motions is incorporated in the astrometric solution by means of Bayes' rule. Numerical simulations based on the Gaia Universe Model Snapshot (GUMS) are used to investigate how the prior influences the actual errors and formal uncertainties when different amounts of Gaia observations are available. We develop a criterion for the optimum choice of priors, apply it to a wide range of cases, and derive a global approximation of the optimum prior as a function of magnitude and galactic coordinates. Results: The feasibility of the Bayesian approach is demonstrated through global astrometric solutions of simulated Gaia observations. With an appropriate prior it is possible to derive sensible positions with realistic error estimates for any number of available observations. Even though this recipe works also for well-observed stars it should not be used where a good five-parameter astrometric solution can be obtained without a prior. Parallaxes and proper motions from a solution using

  15. IRREGULAR SATELLITES OF THE OUTER PLANETS: ORBITAL UNCERTAINTIES AND ASTROMETRIC RECOVERIES IN 2009-2011

    SciTech Connect

    Jacobson, R.; Brozovic, M.; Gladman, B.; Alexandersen, M.; Nicholson, P. D.; Veillet, C.

    2012-11-01

    More than 100 small satellites have been identified orbiting the giant planets in distant, inclined, eccentric orbits. Detailed study of these objects requires that their orbits be known well enough to permit routine observations both from the Earth and from spacecraft. Unfortunately, many of the satellites have very poorly known orbits due to a scarcity of astrometric measurements. We have developed a reliable method to estimate the future on-sky position uncertainties of the satellites and have verified that those uncertainties provide a correct measure of the true on-sky positional uncertainty. Based on the uncertainties, we identified a set of satellites that are effectively 'lost' and another set that would be lost if additional observations were not obtained in the near future. We attempted recoveries of 26 of the latter group using the Hale 5 m and CFHT 3.6 m telescopes and found 23. This validated our method's predictions and led to significant improvements in our knowledge of the orbits of the recovered moons. There remains a handful of irregular moons which are recoverable and whose orbits will benefit from additional observations during the next decade, while 16 moons of Jupiter and Saturn are essentially lost and will require a re-survey to be located again.

  16. Observational Properties of Synthetic Visual Binary Catalog

    NASA Astrophysics Data System (ADS)

    Nurmi, P.

    2004-08-01

    Forthcoming astrometric missions will observe a huge number of new binaries from which a large fraction will be visual binaries. Detailed planning of optimal detection procedures requires pre-launch information about the observational properties of expected visual binaries. Hence, a synthetic binary catalog is created and analyzed for observational properties of visual binary stars. These results help to understand what kind of binaries we expect to find in the final output catalogs of astrometric missions. These results represent `true' binary distributions if all of them would be observed. All real observational projects or astrometric satellites sample only small fractions of these populations depending on the observational capabilities of the missions. In this study we consider only relative numbers with respect to the total number of binary stars assumed to exist in the sky down to the magnitude limit depending on the astrometric mission.

  17. Astrometric confirmation and preliminary orbital parameters of the young exoplanet 51 Eridani b with the Gemini Planet Imager

    SciTech Connect

    De Rosa, Robert J.; Nielsen, Eric L.; Blunt, Sarah C.; Graham, James R.; Konopacky, Quinn M.; Marois, Christian; Pueyo, Laurent; Rameau, Julien; Ryan, Dominic M.; Wang, Jason J.; Bailey, Vanessa; Chontos, Ashley; Fabrycky, Daniel C.; Follette, Katherine B.; Macintosh, Bruce; Marchis, Franck; Ammons, S. Mark; Arriaga, Pauline; Chilcote, Jeffrey K.; Cotten, Tara H.; Doyon, René; Duchêne, Gaspard; Fitzgerald, Michael P.; Gerard, Benjamin; Goodsell, Stephen J.; Greenbaum, Alexandra Z.; Hibon, Pascale; Ingraham, Patrick; Johnson-Groh, Mara; Kalas, Paul G.; Lafrenière, David; Maire, Jerome; Metchev, Stanimir; Millar-Blanchaer, Maxwell A.; Morzinski, Katie M.; Oppenheimer, Rebecca; Patel, Rahul I.; Patience, Jennifer L.; Perrin, Marshall D.; Rajan, Abhijith; Rantakyrö, Fredrik T.; Ruffio, Jean-Baptiste; Schneider, Adam C.; Sivaramakrishnan, Anand; Song, Inseok; Tran, Debby; Vasisht, Gautam; Ward-Duong, Kimberly; Wolff, Schuyler G.

    2015-11-13

    We present new Gemini Planet Imager observations of the young exoplanet 51 Eridani b that provide further evidence that the companion is physically associated with 51 Eridani. Combining this new astrometric measurement with those reported in the literature, we significantly reduce the posterior probability that 51 Eridani b is an unbound foreground or background T-dwarf in a chance alignment with 51 Eridani to 2 × 10–7, an order of magnitude lower than previously reported. If 51 Eridani b is indeed a bound object, then we have detected orbital motion of the planet between the discovery epoch and the latest epoch. By implementing a computationally efficient Monte Carlo technique, preliminary constraints are placed on the orbital parameters of the system. The current set of astrometric measurements suggest an orbital semimajor axis of ${14}_{-3}^{+7}$ AU, corresponding to a period of ${41}_{-12}^{+35}$ years (assuming a mass of 1.75 M⊙ for the central star), and an inclination of ${138}_{-13}^{+15}$ deg. The remaining orbital elements are only marginally constrained by the current measurements. As a result, these preliminary values suggest an orbit that does not share the same inclination as the orbit of the distant M-dwarf binary, GJ 3305, which is a wide physically bound companion to 51 Eridani.

  18. Astrometric confirmation and preliminary orbital parameters of the young exoplanet 51 Eridani b with the Gemini Planet Imager

    DOE PAGES

    De Rosa, Robert J.; Nielsen, Eric L.; Blunt, Sarah C.; Graham, James R.; Konopacky, Quinn M.; Marois, Christian; Pueyo, Laurent; Rameau, Julien; Ryan, Dominic M.; Wang, Jason J.; et al

    2015-11-13

    We present new Gemini Planet Imager observations of the young exoplanet 51 Eridani b that provide further evidence that the companion is physically associated with 51 Eridani. Combining this new astrometric measurement with those reported in the literature, we significantly reduce the posterior probability that 51 Eridani b is an unbound foreground or background T-dwarf in a chance alignment with 51 Eridani to 2 × 10–7, an order of magnitude lower than previously reported. If 51 Eridani b is indeed a bound object, then we have detected orbital motion of the planet between the discovery epoch and the latest epoch. By implementing a computationally efficient Monte Carlo technique, preliminary constraints are placed on the orbital parameters of the system. The current set of astrometric measurements suggest an orbital semimajor axis ofmore » $${14}_{-3}^{+7}$$ AU, corresponding to a period of $${41}_{-12}^{+35}$$ years (assuming a mass of 1.75 M⊙ for the central star), and an inclination of $${138}_{-13}^{+15}$$ deg. The remaining orbital elements are only marginally constrained by the current measurements. As a result, these preliminary values suggest an orbit that does not share the same inclination as the orbit of the distant M-dwarf binary, GJ 3305, which is a wide physically bound companion to 51 Eridani.« less

  19. Astrometric and photometric data fusion for inactive space object mass and area estimation

    NASA Astrophysics Data System (ADS)

    Linares, Richard; Jah, Moriba K.; Crassidis, John L.; Leve, Fred A.; Kelecy, Tom

    2014-06-01

    This paper presents a new method to determine the mass of an inactive space object from the fusion of photometric and astrometric data. Typically, the effect of solar radiation pressure is used to determine area-to-mass ratio for space objects from angles observations. The area-to-mass ratio of a space object can greatly affect its orbital dynamics. As a consequence, angles data are sensitive to this quantity. On the other hand, photometric data is not sensitive to mass but is a strong function of the albedo-area and the rotational dynamics of the space object. The albedo-area can be used to determine the amount of energy reflected from solar radiation. Since these two data types are sensitive to albedo-area and area-to-mass, then through fusion of photometric data with angles data it is possible to determine the area and mass of a space object. This work employs an unscented Kalman filter to estimate rotational and translational states, area and mass of an inactive space object. Mass is not observable with only angles data or only photometric data alone, but it is shown in this work that with the two combined data types mass can be recovered. Recovery of space object characteristics and attitude and orbit trajectories with sufficient accuracy is demonstrated in this paper via simulation.

  20. High Precision Bright-Star Astrometry with the USNO Astrometric CMOS Hybrid Camera System

    NASA Astrophysics Data System (ADS)

    Secrest, Nathan; Dudik, Rachel; Berghea, Ciprian; Hennessy, Greg; Dorland, Bryan

    2015-08-01

    While GAIA will provide excellent positional measurements of hundreds of millions of stars between 5 < mag < 20, an ongoing challenge in the field of high-precision differential astrometry is the positional accuracy of very bright stars (mag < 5), due to the enormous dynamic range between bright stars of interest, such as those in the Hipparcos catalog, and their background field stars, which are especially important for differential astrometry. Over the past few years, we have been testing the USNO Astrometric CMOS Hybrid Camera System (UAHC), which utilizes an H4RG-10 detector in windowing mode, as a possible solution to the NOFS USNO Bright Star Astrometric Database (UBAD). In this work, we discuss the results of an astrometric analysis of single-epoch Hipparcos data taken with the UAHC from the 1.55m Kaj Strand Astrometric Reflector at NOFS from June 27-30, 2014. We discuss the calibration of this data, as well as an astrometric analysis pipeline we developed that will enable multi-epoch differential and absolute astrometry with the UAHC. We find that while the overall differential astrometric stability of data taken with the UAHC is good (5-10 mas single-measurement precision) and comparable to other ground-based astrometric camera systems, bright stars in the detector window suffer from several systematic effects, such as insufficient window geometry and centroiding failures due to read-out artifacts—both of which can be significantly improved with modifications to the electronics, read-out speed and microcode.

  1. The Laser Astrometric Test of Relativity (LATOR) Mission

    NASA Technical Reports Server (NTRS)

    Turyshev, Slava G.; Shao, Michael; Nordtvedt, Kenneth, Jr.

    2003-01-01

    This paper discusses new fundamental physics experiment that will test relativistic gravity at the accuracy better than the effects of the second order in the gravitational field strength, proportional to G(sup 2). The Laser Astrometric Test Of Relativity (LATOR) mission uses laser interferometry between two micro-spacecraft whose lines of sight pass close by the Sun to accurately measure deflection of light in the solar gravity. The key element of the experimental design is a redundant geometry optical truss provided by a long-baseline (100 m) multi-channel stellar optical interferometer placed on the International Space Station (ISS). The spatial interferometer is used for measuring the angles between the two spacecraft and for orbit determination purposes. In Euclidean geometry, determination of a triangle s three sides determines any angle therein; with gravity changing the optical lengths of sides passing close by the Sun and deflecting the light, the Euclidean relationships are overthrown. The geometric redundancy enables LATOR to measure the departure from Euclidean geometry caused by the solar gravity field to a very high accuracy. LATOR will not only improve the value of the parameterized post-Newtonian (PPN) gamma to unprecedented levels of accuracy of 1 part in 10(exp 8), it will also reach ability to measure effects of the next post-Newtonian order (c(sup -4)) of light deflection resulting from gravity s intrinsic non-linearity. The solar quadrupole moment parameter, J(sub 2), will be measured with high precision, as well as a variety of other relativistic effects including Lense-Thirring precession. LATOR will lead to very robust advances in the tests of Fundamental physics: this mission could discover a violation or extension of general relativity, or reveal the presence of an additional long range interaction in the physical law. There are no analogs to the LATOR experiment; it is unique and is a natural culmination of solar system gravity

  2. Covariance study to evaluate the influence of optical follow-up strategies on estimated orbital parameters

    NASA Astrophysics Data System (ADS)

    Cordelli, E.; Vananti, A.; Schildknecht, T.

    2016-05-01

    An in-depth study, using simulations and covariance analysis, is performed to identify the optimal sequence of observations to obtain the most accurate orbit propagation. The accuracy of the results of an orbit determination/improvement process depends on: tracklet length, number of observations, type of orbit, astrometric error, time interval between tracklets and observation geometry. The latter depends on the position of the object along its orbit and the location of the observing station. This covariance analysis aims to optimize the observation strategy taking into account the influence of the orbit shape, of the relative object-observer geometry and the interval between observations.

  3. The Gaia mission: the dawn of Astrometric Cosmology? Status and prospects after 14 months of science operations

    NASA Astrophysics Data System (ADS)

    Spagna, Alessandro; Crosta, Mariateresa; Lattanzi, Mario G.; Re Fiorentin, Paola

    2016-05-01

    The concept of precisely gauging a gravity-dominated Universe like ours through the individual observations of its fundamental constituents, the stars, immediately calls astrometry, the oldest quantitative specialty of astronomy, into play. Today, thanks to the launch of the Gaia satellite, astrometry has reached such levels to become a key player in the field of local cosmology and experimental gravitation. Updates on the status of the mission, orbiting in L2 since January 2014 and in nominal observation mode since July 2014, are presented. We also discuss how the astrometric observations from within the gravitational fields of the Solar System can uniquely probe possible deviations from General Relativity and how accurate absolute kinematics at the scale of the Milky Way can, for the first time in situ, account for the predictions of the CDM model for the formation of the Galactic halo.

  4. THE APPLICATION OF MULTIVIEW METHODS FOR HIGH-PRECISION ASTROMETRIC SPACE VLBI AT LOW FREQUENCIES

    SciTech Connect

    Dodson, R.; Rioja, M.; Imai, H.; Asaki, Y.; Hong, X.-Y.; Shen, Z.

    2013-06-15

    High-precision astrometric space very long baseline interferometry (S-VLBI) at the low end of the conventional frequency range, i.e., 20 cm, is a requirement for a number of high-priority science goals. These are headlined by obtaining trigonometric parallax distances to pulsars in pulsar-black hole pairs and OH masers anywhere in the Milky Way and the Magellanic Clouds. We propose a solution for the most difficult technical problems in S-VLBI by the MultiView approach where multiple sources, separated by several degrees on the sky, are observed simultaneously. We simulated a number of challenging S-VLBI configurations, with orbit errors up to 8 m in size and with ionospheric atmospheres consistent with poor conditions. In these simulations we performed MultiView analysis to achieve the required science goals. This approach removes the need for beam switching requiring a Control Moment Gyro, and the space and ground infrastructure required for high-quality orbit reconstruction of a space-based radio telescope. This will dramatically reduce the complexity of S-VLBI missions which implement the phase-referencing technique.

  5. The Influence of Observation Length on the Dependability of Data

    ERIC Educational Resources Information Center

    David Ferguson, Tyler; Briesch, Amy M.; Volpe, Robert J.; Daniels, Brian

    2012-01-01

    Although direct observation is one of the most frequently used assessment methods by school psychologists, studies have shown that the number of observations needed to obtain a dependable estimate of student behavior may be impractical. Because direct observation may be used to inform important decisions about students, it is crucial that data be…

  6. The Full-sky Astrometric Mapping Explorer - Astrometry for the New Millennium

    NASA Astrophysics Data System (ADS)

    Horner, S. D.; Germain, M. E.; Greene, T. P.; Harris, F. H.; Johnson, M. S.; Johnson, K. J.; Monet, D. G.; Murison, M. A.; Phillips, J. D.; Reasenberg, R. D.; Seidelmann, P. K.; Urban, S. E.; Vassar, R. H.

    FAME is designed to perform an all-sky, astrometric survey with unprecedented accuracy. It will create a rigid astrometric catalog of ~40,000,000 stars with visual band magnitudes 5 < V < 15. For bright stars, 5 < V < 9, FAME will determine positions and parallaxes accurate to < 50 microarcseconds, with proper motion errors < 50 microarcseconds/year. For fainter stars, 9 < V < 15, FAME will determine positions and parallaxes accurate to < 300 microarcseconds, with proper motion errors < 300 microarcseconds/year. It will also collect photometric data on these 40,000,000 stars in four Sloan DSS colors. The FAME data will provide a rigid, accurate, optical, astrometric grid. The proper motion data, combined with Hipparcos and other data should be ideal for use by the Space Interferometry Mission (SIM) to select its astrometric reference grid stars. FAME will also identify stars with nonlinear proper motions as candidates for further study by SIM, Terrestrial Planet Finder, and future ground based interferometers as possible planetary systems. The fundamental astrometric data provided at relatively low cost by FAME will help optimize the scientific return from these future projects. This is in addition to the considerable direct scientific return from FAME. It will redefine the extragalactic distance scale and provide a large, rich database of information on stellar properties that will enable numerous science investigations into stellar structure and evolution, the dynamics of the Milky Way, and stellar companions including brown dwarfs and giant planets. NASA has selected the Full-sky Astrometric Mapping Explorer (FAME) to be one of five MIDEX missions to be funded for a concept study. This concept study will be submitted to NASA on 18 June, with final selection, scheduled for September, of two of these missions for fli ght in 2003 or 2004. FAME is a joint development e ffort of the U.S. Naval Observatory, the Smithsonian Astrophysical Observatory, the Infrared

  7. Influence of ground scattering on satellite auroral observations.

    PubMed

    Hays, P B; Anger, C D

    1978-06-15

    Satellite observations of the optical emission features in the aurora and nighttime airglow are usually contaminated by scattering from clouds and snow. It is shown here that this contamination can easily be removed when the emission layer is viewed against a surface of known albedo. The effect of the earth's curvature, parallax, and varying image angle are found to be significant but can be removed from the observation.

  8. Influence of ground scattering on satellite auroral observations

    NASA Technical Reports Server (NTRS)

    Hays, P. B.; Anger, C. D.

    1978-01-01

    Satellite observations of the optical emission features in the aurora and nighttime airglow are usually contaminated by scattering from clouds and snow. It is shown here that this contamination can easily be removed when the emission layer is viewed against a surface of known albedo. The effect of the earth's curvature, parallax, and varying image angle are found to be significant but can be removed from the observation.

  9. Rotation periods and astrometric motions of the Luhman 16AB brown dwarfs by high-resolution lucky-imaging monitoring

    NASA Astrophysics Data System (ADS)

    Mancini, L.; Giacobbe, P.; Littlefair, S. P.; Southworth, J.; Bozza, V.; Damasso, M.; Dominik, M.; Hundertmark, M.; Jørgensen, U. G.; Juncher, D.; Popovas, A.; Rabus, M.; Rahvar, S.; Schmidt, R. W.; Skottfelt, J.; Snodgrass, C.; Sozzetti, A.; Alsubai, K.; Bramich, D. M.; Calchi Novati, S.; Ciceri, S.; D'Ago, G.; Figuera Jaimes, R.; Galianni, P.; Gu, S.-H.; Harpsøe, K.; Haugbølle, T.; Henning, Th.; Hinse, T. C.; Kains, N.; Korhonen, H.; Scarpetta, G.; Starkey, D.; Surdej, J.; Wang, X.-B.; Wertz, O.

    2015-12-01

    Context. Photometric monitoring of the variability of brown dwarfs can provide useful information about the structure of clouds in their cold atmospheres.The brown-dwarf binary system Luhman 16AB is an interesting target for such a study, because its components stand at the L/T transition and show high levels of variability. Luhman 16AB is also the third closest system to the solar system, which allows precise astrometric investigations with ground-based facilities. Aims: The aim of the work is to estimate the rotation period and study the astrometric motion of both components. Methods: We have monitored Luhman 16AB over a period of two years with the lucky-imaging camera mounted on the Danish 1.54 m telescope at La Silla, through a special i + z long-pass filter, which allowed us to clearly resolve the two brown dwarfs into single objects. An intense monitoring of the target was also performed over 16 nights, in which we observed a peak-to-peak variability of 0.20 ± 0.02 mag and 0.34 ± 0.02 mag for Luhman 16A and 16B, respectively. Results: We used the 16-night time-series data to estimate the rotation period of the two components. We found that Luhman 16B rotates with a period of 5.1 ± 0.1 h, in very good agreement with previous measurements. For Luhman 16A, we report that it rotates more slowly than its companion, and even though we were not able to get a robust determination, our data indicate a rotation period of roughly 8 h. This implies that the rotation axes of the two components are well aligned and suggests a scenario in which the two objects underwent the same accretion process. The 2-year complete data set was used to study the astrometric motion of Luhman 16AB. We predict a motion of the system that is not consistent with a previous estimate based on two months of monitoring, but cannot confirm or refute the presence of additional planetary-mass bodies in the system. Based on data collected by MiNDSTEp with the Danish 1.54 m telescope at the ESO La

  10. Update on Astrometric Follow-Up at Apache Point Observatory by Adler Planetarium

    NASA Astrophysics Data System (ADS)

    Nault, Kristie A.; Brucker, Melissa; Hammergren, Mark

    2016-10-01

    We began our NEO astrometric follow-up and characterization program in 2014 Q4 using about 500 hours of observing time per year with the Astrophysical Research Consortium (ARC) 3.5m telescope at Apache Point Observatory (APO). Our observing is split into 2 hour blocks approximately every other night for astrometry (this poster) and several half-nights per month for spectroscopy (see poster by M. Hammergren et al.) and light curve studies.For astrometry, we use the ARC Telescope Imaging Camera (ARCTIC) with an SDSS r filter, in 2 hour observing blocks centered around midnight. ARCTIC has a magnitude limit of V~23 in 60s, and we target 20 NEOs per session. ARCTIC has a FOV 1.57 times larger and a readout time half as long as the previous imager, SPIcam, which we used from 2014 Q4 through 2015 Q3. Targets are selected primarily from the Minor Planet Center's (MPC) NEO Confirmation Page (NEOCP), and NEA Observation Planning Aid; we also refer to JPL's What's Observable page, the Spaceguard Priority List and Faint NEOs List, and requests from other observers. To quickly adapt to changing weather and seeing conditions, we create faint, midrange, and bright target lists. Detected NEOs are measured with Astrometrica and internal software, and the astrometry is reported to the MPC.As of June 19, 2016, we have targeted 2264 NEOs, 1955 with provisional designations, 1582 of which were detected. We began observing NEOCP asteroids on January 30, 2016, and have targeted 309, 207 of which were detected. In addition, we serendipitously observed 281 moving objects, 201 of which were identified as previously known objects.This work is based on observations obtained with the Apache Point Observatory 3.5m telescope, which is owned and operated by the Astrophysical Research Consortium. We gratefully acknowledge support from NASA NEOO award NNX14AL17G and thank the University of Chicago Department of Astronomy and Astrophysics for observing time in 2014.

  11. Parallax of a Mira variable R Ursae Majoris studied with astrometric VLBI

    NASA Astrophysics Data System (ADS)

    Nakagawa, Akiharu; Kurayama, Tomoharu; Matsui, Makoto; Omodaka, Toshihiro; Honma, Mareki; Shibata, Katsunori M.; Sato, Katsuhisa; Jike, Takaaki

    2016-10-01

    We have measured an annual parallax of the Mira variable R Ursae Majoris (R UMa) with the VLBI Exploration for Radio Astronomy (VERA). From the monitoring VLBI observations over a span of about two years, we detected H2O maser spots in the LSR velocity range from 37 to 42 km s-1. We derived an annual parallax of 1.97 ± 0.05 mas, and this gives a corresponding distance of 508 ± 13 pc. The VLBI maps revealed 72 maser spots distributed in an ˜110 au area around the expected stellar position. Circumstellar kinematics of the maser spots were also revealed by subtracting a systemic motion in the Hipparcos catalog from proper motions of each maser spot derived from our VLBI observations. Infrared photometry was also conducted to measure a K-band apparent magnitude, and we obtained a mean magnitude of mK = 1.19 ± 0.02 mag. Using the trigonometric distance, mK is converted to a K-band absolute magnitude of MK = -7.34 ± 0.06 mag. This result gives a much more accurate absolute magnitude for R UMa than previously provided. We solved a zero-point of the MK-log P relation for the Galactic Mira variables and obtained a relation of MK = -3.52 log P + (1.09 ± 0.14). Other long-period variables, including red supergiants, whose distances were determined with astrometric VLBI, were also compiled to explore the different sequences of the MK-log P relation.

  12. GAME - A small mission concept for high-precision astrometric test of General Relativity

    NASA Astrophysics Data System (ADS)

    Vecchiato, A.; Gai, Mario; Donati, Paolo; Morbidelli, Roberto; Lattanzi, Mario G.; Crosta, Mariateresa

    2010-11-01

    GAME (Gamma Astrometric Measurement Experiment) is a concept for a small mission whose main goal is to measure from space the γ parameter of the Parameterized Post-Newtonian formalism, Will (2001)) A satellite, looking as close as possible to the Solar limb, measures the gravitational bending of light in a way similar to that followed by past experiments from the ground during solar eclipses. In the cited formalism, deviations of the γ parameter from unity are interpreted as deviations from the predictions of General Relativity which are foreseen by several competing theories of gravity. In the present theoretical scenario, such deviations are expected to appear in the range between 10-5 and 10-7. The most stringent experimental constraints available up to now are those of the Cassini mission, that gives 1-γ≲10-5 Bertotti et al. (2003), while future space missions are expected to reach the 10-7 level of accuracy. (Vecchiato et al. (2003), Turyshev et al. (2004), Ni (2008)) Preliminary simulations have shown that the expected final accuracy of GAME can reach the 10-7 level, or better if the mission profile can be extended to fit a larger budget Vecchiato et al. (2009), Gai et al. (2009). This work, which has recently been extended to better assess the mission performances, has confirmed the previous results and has given indications on how further improve various aspects of the mission profile. Moreover, thanks to its flexible observation strategy, GAME is also able to target other interesting scientific goals in the realm of General Relativity, as well as in those involving observations of selected extrasolar systems in the brown dwarf and planetary regime.

  13. Parallax of a Mira variable R Ursae Majoris studied with astrometric VLBI

    NASA Astrophysics Data System (ADS)

    Nakagawa, Akiharu; Kurayama, Tomoharu; Matsui, Makoto; Omodaka, Toshihiro; Honma, Mareki; Shibata, Katsunori M.; Sato, Katsuhisa; Jike, Takaaki

    2016-08-01

    We have measured an annual parallax of the Mira variable R Ursae Majoris (R UMa) with the VLBI Exploration for Radio Astronomy (VERA). From the monitoring VLBI observations over a span of about two years, we detected H2O maser spots in the LSR velocity range from 37 to 42 km s-1. We derived an annual parallax of 1.97 ± 0.05 mas, and this gives a corresponding distance of 508 ± 13 pc. The VLBI maps revealed 72 maser spots distributed in an ˜110 au area around the expected stellar position. Circumstellar kinematics of the maser spots were also revealed by subtracting a systemic motion in the Hipparcos catalog from proper motions of each maser spot derived from our VLBI observations. Infrared photometry was also conducted to measure a K-band apparent magnitude, and we obtained a mean magnitude of mK = 1.19 ± 0.02 mag. Using the trigonometric distance, mK is converted to a K-band absolute magnitude of MK = -7.34 ± 0.06 mag. This result gives a much more accurate absolute magnitude for R UMa than previously provided. We solved a zero-point of the MK-log P relation for the Galactic Mira variables and obtained a relation of MK = -3.52 log P + (1.09 ± 0.14). Other long-period variables, including red supergiants, whose distances were determined with astrometric VLBI, were also compiled to explore the different sequences of the MK-log P relation.

  14. Hand Dominance Influences the Processing of Observed Bodies

    ERIC Educational Resources Information Center

    Gardner, Mark R.; Potts, Rosalind

    2010-01-01

    In motor tasks, subgroups of lefthanders have been shown to differ in the distribution of attention about their own bodies. The present experiment examined whether similar attentional biases also apply when processing observed bodies. Sixteen right handers (RHs), 22 consistent left handers (CLHs) and 11 relatively ambidextrous inconsistent left…

  15. External Influences on Modeled and Observed Cloud Trends

    NASA Technical Reports Server (NTRS)

    Marvel, Kate; Zelinka, Mark; Klein, Stephen A.; Bonfils, Celine; Caldwell, Peter; Doutriaux, Charles; Santer, Benjamin D.; Taylor, Karl E.

    2015-01-01

    Understanding the cloud response to external forcing is a major challenge for climate science. This crucial goal is complicated by intermodel differences in simulating present and future cloud cover and by observational uncertainty. This is the first formal detection and attribution study of cloud changes over the satellite era. Presented herein are CMIP5 (Coupled Model Intercomparison Project - Phase 5) model-derived fingerprints of externally forced changes to three cloud properties: the latitudes at which the zonally averaged total cloud fraction (CLT) is maximized or minimized, the zonal average CLT at these latitudes, and the height of high clouds at these latitudes. By considering simultaneous changes in all three properties, the authors define a coherent multivariate fingerprint of cloud response to external forcing and use models from phase 5 of CMIP (CMIP5) to calculate the average time to detect these changes. It is found that given perfect satellite cloud observations beginning in 1983, the models indicate that a detectable multivariate signal should have already emerged. A search is then made for signals of external forcing in two observational datasets: ISCCP (International Satellite Cloud Climatology Project) and PATMOS-x (Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmospheres - Extended). The datasets are both found to show a poleward migration of the zonal CLT pattern that is incompatible with forced CMIP5 models. Nevertheless, a detectable multivariate signal is predicted by models over the PATMOS-x time period and is indeed present in the dataset. Despite persistent observational uncertainties, these results present a strong case for continued efforts to improve these existing satellite observations, in addition to planning for new missions.

  16. The Astrometric Imaging Telescope - A space-based observatory for extra-solar planet detection

    NASA Technical Reports Server (NTRS)

    Pravdo, Steven H.

    1991-01-01

    The paper describes the objectives, techniques, instrumentation, and mission of the planned Astrometric Imaging Telescope. This space-based observatory is designed to detect and characterize extra-solar planetary systems. Results will contribute to the understanding of the astrophysics of stellar and planetary formation and provide an impetus for the study of exobiology.

  17. MODEST - JPL GEODETIC AND ASTROMETRIC VLBI MODELING AND PARAMETER ESTIMATION PROGRAM

    NASA Technical Reports Server (NTRS)

    Sovers, O. J.

    1994-01-01

    Observations of extragalactic radio sources in the gigahertz region of the radio frequency spectrum by two or more antennas, separated by a baseline as long as the diameter of the Earth, can be reduced, by radio interferometry techniques, to yield time delays and their rates of change. The Very Long Baseline Interferometric (VLBI) observables can be processed by the MODEST software to yield geodetic and astrometric parameters of interest in areas such as geophysical satellite and spacecraft tracking applications and geodynamics. As the accuracy of radio interferometry has improved, increasingly complete models of the delay and delay rate observables have been developed. MODEST is a delay model (MOD) and parameter estimation (EST) program that takes into account delay effects such as geometry, clock, troposphere, and the ionosphere. MODEST includes all known effects at the centimeter level in modeling. As the field evolves and new effects are discovered, these can be included in the model. In general, the model includes contributions to the observables from Earth orientation, antenna motion, clock behavior, atmospheric effects, and radio source structure. Within each of these categories, a number of unknown parameters may be estimated from the observations. Since all parts of the time delay model contain nearly linear parameter terms, a square-root-information filter (SRIF) linear least-squares algorithm is employed in parameter estimation. Flexibility (via dynamic memory allocation) in the MODEST code ensures that the same executable can process a wide array of problems. These range from a few hundred observations on a single baseline, yielding estimates of tens of parameters, to global solutions estimating tens of thousands of parameters from hundreds of thousands of observations at antennas widely distributed over the Earth's surface. Depending on memory and disk storage availability, large problems may be subdivided into more tractable pieces that are processed

  18. A magnetic isolation and pointing system for the astrometric telescope facility

    NASA Technical Reports Server (NTRS)

    Smith, Marcie; Hibble, William; Wolke, Patrick J.

    1993-01-01

    The astrometric telescope facility (ATF), a 20-meter telescope designed for long-term detection and observation of planetary systems outside of the solar system, is scheduled to be a major user of the Space Station's payload pointing system (PPS) capabilities. However, because the ATF has such a stringent pointing stability specification (as low as 0.01 arcsec error over the frequency range from 5 to 200 hertz) and requires +/- 180-degree roll rotation around the telescope's line of sight, the ATF's utilization of the PPS requires the addition of a mechanism or mechanisms to enhance the basic PPS capabilities. The results of a study conducted to investigate the ATF pointing performance achievable by the addition of a magnetic isolation and pointing (MIPS) system between the PPS upper gimbal and the ATF, and separately, by the addition of a passive isolation system between the Space Station and the PPS base are presented. In addition, the study produced requirements on magnetic force and gap motion as a function of the level of Space Station disturbance. These results were used to support the definition of a candidate MIPS. Pointing performance results from the study indicate that a MIPS can meet the ATF pointing requirements in the presence of a PPS base transitional acceleration of up to 0.018g, with reasonable restrictions placed on the isolation and pointing bandwidths. By contrast, the passive base isolator system must have an unrealistically low isolation bandwidth on all axes (less than 0.1 hertz) to meet ATF pointing requirements. The candidate MIPS is based on an assumed base translational disturbance of 0.01g. The system fits within the available annular region between the PPS and ATF while meeting power and weight limitations and providing the required payload roll motion. Payload data and power services are provided by noncontacting transfer devices.

  19. Observation of Influence of Cataract Surgery on the Ocular Surface

    PubMed Central

    Park, Yuli; Hwang, Hyung Bin; Kim, Hyun Seung

    2016-01-01

    Introduction To evaluate meibomian gland function, changes of lacrimal tears and ocular surface parameters and tear inflammatory mediators following cataract surgery. Methods 48 eyes of 34 patients who underwent uncomplicated phacoemulsification were involved and divided into 2 groups with those who had preexisting dry-eye before cataract surgery and those who did not. Ocular symptom score, Schirmer I test, tear film break-up time (TBUT), corneal sensitivity threshold, corneal staining, inflammatory cytokine activities, lid margin abnormalities, meibum expressibility, meibum quality and meibomian gland imaging were evaluated preoperatively, at 1 day, 1 and 2 months postoperatively. Results Ocular symptom scores were worse at 1 and 2 months postoperatively but, TBUT, corneal staining score and corneal sensitivity threshold showed gradual improvements at 1 month and 2 months postoperatively (p<0.05, respectively). Interestingly there were statistically significant improvements in TBUT, corneal staining score and corneal sensitivity threshold at 1 month postoperatively when topical eye drops were used compared to the period without topical therapy which is the months 2 postoperatively. There were statistically significant decreases in IL-1β, IL-6, IL-8, MCP-1, TNF-α and IFN-γ concentrations at 1 and 2 months postoperatively. Lid margin abnormalities, meibum quality and expressibility scores increased significantly (p < 0.05, respectively) at postoperative period. Compared with the no dry eye group, dry eye group revealed significantly higher ocular symptom scores, lower TBUT, higher lid margin abnormalities, meibum quality and expressibility scores after cataract surgery. There were significant correlations between IL-6 and parameters of dry eye, and between MGD parameters and ocular symptom scores. Conclusions Our study revealed that meibomian gland function is influenced after cataract surgery accompanying structural changes and these were correlated with

  20. Comparing Observed Hurricane Conditions Against Potential Future Climate Change Influences

    NASA Astrophysics Data System (ADS)

    Graham, W. D.

    2012-12-01

    Climate Adaptation Science Investigators: (CASI) is to advance and apply NASA's scientific expertise and products to develop climate adaptation strategies that support NASA's overall mission by minimizing risks to each center's operations, physical assets, and personnel. Using Hurricane Katrina observations as a baseline, we use ADCIRC to model surge extent with simple modifications of the storm track. We examine two time now (T0) scenarios of present-day climatological factors: 1) translating the 2005 path 7 km west; and 2) rotating the approach angle from due-north to WNW. Second, we examine two future time scenarios (TX) by infusing climate change conditions, such as sea level rise and increased storm intensity, into a T0 baseline to assess future impacts. The primary goal of this work entails planning and protecting NASA assets and infrastructure. The adjacent communities, state and local emergency managers, gain benefit from this NASA work as data and analysis includes the surrounding geography.

  1. The second release of the Large Quasar Astrometric Catalog (LQAC-2)

    NASA Astrophysics Data System (ADS)

    Souchay, J.; Andrei, A. H.; Barache, C.; Bouquillon, S.; Suchet, D.; Taris, F.; Peralta, R.

    2012-01-01

    Context. Since the first release of the LQAC (Large Quasar Astrometric Catalogue) a large number of quasars have been discovered through very dense observational surveys. As these objects constitute the cornerstones of modern astrometry by indicating quasi inertial directions, their spatial density and their astrometric quality must be studied in detail. Aims: Following the same procedure as in this first release of the LQAC, our aim is to compile all the quasars recorded until the present date, with the best determination of their equatorial coordinates in the ICRS, i.e. with respect to the newly established ICRF2 and with the maximum of information concerning their physical properties (redshift, photometry, absolute magnitudes). Methods: First of all we made a substantial review of the definitions and properties of quasars and AGN (active galactic nuclei), because the differenciation of these objects is unclear in the literature, even for specialists. Then we carried out the cross-identification between the nine catalogs of quasars chosen for their accuracy and their huge number of objects, including all the available data related to magnitudes, radiofluxes, and redshifts. Moreover, we computed the absolute magnitude of our extragalactic objects by taking the recent studies concerning the galactic absorption into account. In addition, substantial improvements were made with respect to the first release of the LQAC. First, an LQAC name is given for each object based on its equatorial coordinates with respect to the ICRS, following a procedure that creates no ambiguity in the identification. Second the equatorial coordinates of the objects were recomputed more accurately according to the algorithms used for the elaboration of the Large Quasar Reference Frame (LQRF). Third we introduce a morphological classification for the objects that in particular clearly defines if the object is point-like or extended. Results: Our final catalog, called LQAC-2, contains 187 504

  2. ASTROMETRIC STUDIES OF ALDEBARAN, ARCTURUS, VEGA, THE HYADES, AND OTHER REGIONS

    SciTech Connect

    Gatewood, George

    2008-07-15

    The results of astrometric studies in the regions of Groombridge 34A, the Hyades, Aldebaran, Ross 47, BD+5{sup 0} 1668, 81 Cancri, BD+15{sup 0} 2620, Arcturus, Vega, and Ross 248 are presented. Estimates of the absolute parallax of each star are presented and a mass estimate is present for 81 Cancri. Comments include the discussion of the apparent motions of a few previously suggested planetary systems.

  3. Astrometric Follow-Up of Faint Near Earth Objects

    NASA Technical Reports Server (NTRS)

    Morgan, T. (Technical Monitor); Spahr, Timothy

    2004-01-01

    The observing program at Mt. Hopkins using the 48" reflector and funded by the Near- Earth Object Observation Program continues to excel. As in the past, all requested observing time was granted. Minor improvements continue to be made. For example, the telescope is set up to track and non-sidereal rates. This allows the user to track on the target object, rather than relying exclusively on the shift- and-stack technique. Other improvements made by the staff include automatic focus routines, automatic seeing-measurement routines, and improvement in dome seeing and mirror stabilization. The net result is better focus, better seeing, and the ability to expose longer in order to acquire the faintest and most important objects. During the proposal period, this program ranked again very high worldwide in terms of faint Near Earth Objects observed. During this latest proposal cycle, fewer objects were observed than previous cycles, but this was due to the strict targeting of only the faintest observable objects. The follow-up programs of observatory codes 926 (led by P. Holvorcem) and 291 (led by Dr. B. McMillan) have greatly increased their capacity, and as a result less bright objects are in urgent need of follow-up than in years past. Even with this new object selection and additional competition, code 696 still ranked second to code 291 in terms of objects observed fainter than V = 20. Minimal scripting is now in place to allow the telescope to run autonomously for 30-45 minutes at a time.

  4. When Your Decisions Are Not (Quite) Your Own: Action Observation Influences Free Choices

    PubMed Central

    Cole, Geoff G.; Wright, Damien; Doneva, Silviya P.; Skarratt, Paul A.

    2015-01-01

    A growing number of studies have begun to assess how the actions of one individual are represented in an observer. Using a variant of an action observation paradigm, four experiments examined whether one person’s behaviour can influence the subjective decisions and judgements of another. In Experiment 1, two observers sat adjacent to each other and took turns to freely select and reach to one of two locations. Results showed that participants were less likely to make a response to the same location as their partner. In three further experiments observers were asked to decide which of two familiar products they preferred or which of two faces were most attractive. Results showed that participants were less likely to choose the product or face occupying the location of their partner’s previous reaching response. These findings suggest that action observation can influence a range of free choice preferences and decisions. Possible mechanisms through which this influence occurs are discussed. PMID:26024480

  5. Observational Conditioning in Flower Choice Copying by Bumblebees (Bombus terrestris): Influence of Observer Distance and Demonstrator Movement

    PubMed Central

    Avarguès-Weber, Aurore; Chittka, Lars

    2014-01-01

    Background Bumblebees use information provided inadvertently by conspecifics when deciding between different flower foraging options. Such social learning might be explained by relatively simple associative learning mechanism: the bee may learn to associate conspecifics with nectar or pollen reward through previous experience of foraging jointly. However, in some studies, observers were guided by choices of ‘demonstrators’ viewed through a screen, so no reward was given to the observers at the time of seeing other bees’ flowers choice and no demonstrator bee was present at the moment of decision. This behaviour, referred to observational conditioning, implies an additional associative step as the positive value of conspecific is transferred to the associated flower. Here we explore the role of demonstrator movement, and the distance between observers and demonstrators that is required for observation conditioning to take place. Methodology/Principal Findings We identify the conditions under which observational conditioning occurs in the widespread European species Bombus terrestris. The presence of artificial demonstrator bees leads to a significant change in individual colour preference toward the indicated colour if demonstrators were moving and observation distance was limited (15 cm), suggesting that observational conditioning could only influence relatively short-range foraging decisions. In addition, the movement of demonstrators is a crucial factor for observational conditioning, either due to the more life-like appearance of moving artificial bees or an enhanced detectability of moving demonstrators, and an increased efficiency at directing attention to the indicated flower colour. Conclusion Bumblebees possess the capacity to learn the quality of a flower by distal observation of other foragers’ choices. This confirms that social learning in bees involves more advanced processes than simple associative learning, and indicates that observational

  6. Automated image analysis for space debris identification and astrometric measurements

    NASA Astrophysics Data System (ADS)

    Piattoni, Jacopo; Ceruti, Alessandro; Piergentili, Fabrizio

    2014-10-01

    The space debris is a challenging problem for the human activity in the space. Observation campaigns are conducted around the globe to detect and track uncontrolled space objects. One of the main problems in optical observation is obtaining useful information about the debris dynamical state by the images collected. For orbit determination, the most relevant information embedded in optical observation is the precise angular position, which can be evaluated by astrometry procedures, comparing the stars inside the image with star catalogs. This is typically a time consuming process, if done by a human operator, which makes this task impractical when dealing with large amounts of data, in the order of thousands images per night, generated by routinely conducted observations. An automated procedure is investigated in this paper that is capable to recognize the debris track inside a picture, calculate the celestial coordinates of the image's center and use these information to compute the debris angular position in the sky. This procedure has been implemented in a software code, that does not require human interaction and works without any supplemental information besides the image itself, detecting space objects and solving for their angular position without a priori information. The algorithm for object detection was developed inside the research team. For the star field computation, the software code astrometry.net was used and released under GPL v2 license. The complete procedure was validated by an extensive testing, using the images obtained in the observation campaign performed in a joint project between the Italian Space Agency (ASI) and the University of Bologna at the Broglio Space center, Kenya.

  7. JASMINE-astrometric map of the galactic bulge .

    NASA Astrophysics Data System (ADS)

    Gouda, N.; Kobayashi, Y.; Yamada, Y.; Yano, T.; Tsujimoto, T.; Suganuma, M.; Niwa, Y.; Yamauchi, M.; Kawakatsu, Y.; Matsuhara, H.; Noda, A.; Tsuiki, A.; Utashima, M.; Ogawa, A.; Sako, N.; JASMINE working Group

    We introduce a Japanese plan of infrared (z-band:0.9mu m) space astrometry(JASMINE-project). JASMINE is the satellite (Japan Astrometry Satellite Mission for INfrared Exploration) which will measure distances and apparent motions of stars around the center of the Milky Way with yet unprecedented precision. It will measure parallaxes with the accuracy of 10 micro-arcsec and proper motions with the accuracy of 4 micro-arcsec/year for stars brighter than z=14mag. JASMINE can observe about ten million stars belonging to the bulge components of our Galaxy, which are hidden by the interstellar dust extinction in optical bands. Number of stars with sigma /pi <0.1 in the direction of the Galactic central bulge is about 1000 times larger than those observed in optical bands, where pi is a parallax and sigma is an error of the parallax. With the completely new map of the bulge in the Milky Way it is expected that many new exciting scientific results will be obtained in various fields of astronomy. We will introduce some scientific topics which will be obtained by JASMINE. Presently, JASMINE is in a development phase, with a target launch date around 2015. We adopt the following instrument design of JASMINE in order to get the accurate positions of many stars. We adopt a 3-mirrors optical system (modified Korsch system) with a primary mirror of 0.75m. On the astro-focal plane, we put dozens of new type of CCDs for z-band to get a wide field of view. JASMINE mission takes a frames-link method which can be applied for the survey of the Galactic bulge, as a observing strategy. The consideration of overall system (bus) design is now going on in cooperation with Japan Aerospace Exploration Agency (JAXA). The introduction of JASMINE and the present status of the project will be shown in the presentation.

  8. Astrometric observations of outer planets and minor planets 1982-1983

    NASA Astrophysics Data System (ADS)

    Klemola, A. R.; Harlan, E. A.

    1984-06-01

    The 0.51-m Carnegie double astrograph has been used to obtain direct photographs on which the equatorial coordinates for Uranus, Neptune, Pluto, Ceres, Pallas, Juno, Fortuna, Nemausa, and other minor planets can be measured. These measurements are intended for the refinement of predictions of possible stellar occultations by these objects.

  9. Multiple Shells Around Wolf-Rayet Stars: Space Based Astrometric Observing

    NASA Technical Reports Server (NTRS)

    Marston, Anthony P.

    1995-01-01

    The completion of a complementary optical emission-line survey of the nebulae associated with Wolf-Rayet stars in the southern sky is reported, along with the completion of a survey the large-scale environments of Wolf-Rayet stars using IRAS Skyflux data. HIRES IRAS maps in the four IRAS wavebands for appoximately half of all galactic Wolf-Rayet stars are created.

  10. JASMINE-Astrometric Map of the Galactic Bulge-

    NASA Astrophysics Data System (ADS)

    Gouda, N.; Kobayashi, Y.; Yamada, Y.; Yano, T.; Tsujimoto, T.; Suganuma, M.; Niwa, Y.; Yamauchi, M.; Kawakatsu, Y.; Matsuhara, H.; Moda, A.; Tsuiki, A.; Utashima, M.; Ogawa, A.; Sako, N.

    2006-08-01

    We introduce a Japanese plan of infrared(z-band:0.9μm) space astrometry (JASMINE-project). JASMINE is the satellite (Japan Astrometry Satellite Mission for INfrared Exploration) which will measure the distances and apparent motions of stars around the center of the Milky Way with yet unprecedented precision. It will measure parallaxes, positions with the accuracy of 10 micro-arcsec and proper motions with the accuracy of 4 micro-arcsec/year for stars brighter than z=14mag. JASMINE can observe about ten million stars belonging to the bulge components of our Galaxy, which are hidden by the interstellar dust extinction in optical bands. Number of stars with sigma/pi <0.1 in the direction of the Galactic central bulge is about 1000 times larger than those observed in optical bands, where pi is a parallax and sigma is an error of the parallax. With the completely new "map of the bulge in the Milky Way", it is expected that many new exciting scientific results will be obtained in various fields of astronomy. We will introduce some scientific topics which will be obtained by JASMINE. Presently, JASMINE is in a development phase, with a target launch date around 2015. We adopt the following instrument design of JASMINE in order to get the accurate positions of many stars. We adopt a 3-mirrors optical system (modified Korsch system) with a primary mirror of 0.75m. On the astro-focal plane, we put dozens of new type of CCDs for z-band to get a wide field of view. The consideration of overall system(bus) design is now going on in cooperation with Japan Aerospace Exploration Agency (JAXA). The introduction of JASMINE and the present status of the project will be shown in the presentation.

  11. A near-Infrared SETI Experiment: Alignment and Astrometric precision

    NASA Astrophysics Data System (ADS)

    Duenas, Andres; Maire, Jerome; Wright, Shelley; Drake, Frank D.; Marcy, Geoffrey W.; Siemion, Andrew; Stone, Remington P. S.; Tallis, Melisa; Treffers, Richard R.; Werthimer, Dan

    2016-06-01

    Beginning in March 2015, a Near-InfraRed Optical SETI (NIROSETI) instrument aiming to search for fast nanosecond laser pulses, has been commissioned on the Nickel 1m-telescope at Lick Observatory. The NIROSETI instrument makes use of an optical guide camera, SONY ICX694 CCD from PointGrey, to align our selected sources into two 200µm near-infrared Avalanche Photo Diodes (APD) with a field-of-view of 2.5"x2.5" each. These APD detectors operate at very fast bandwidths and are able to detect pulse widths extending down into the nanosecond range. Aligning sources onto these relatively small detectors requires characterizing the guide camera plate scale, static optical distortion solution, and relative orientation with respect to the APD detectors. We determined the guide camera plate scale as 55.9+- 2.7 milli-arcseconds/pixel and magnitude limit of 18.15mag (+1.07/-0.58) in V-band. We will present the full distortion solution of the guide camera, orientation, and our alignment method between the camera and the two APDs, and will discuss target selection within the NIROSETI observational campaign, including coordination with Breakthrough Listen.

  12. Optical system for an astrometric survey from space

    NASA Astrophysics Data System (ADS)

    Phillips, James D.; Reasenberg, Robert D.

    1998-08-01

    We present an optical design for a spaceborne instrument, of about half m aperture, to perform a combined astrometic and photometric survey via a scan similar to that of Hipparcos. A CCD detector array with time delayed integration will permit an astrometic mission accuracy better than 50 microarcseconds for stars brighter than 10th magnitude. 1 1/2 orders better than Hipparcos. The passband is nominally 0.4 to 0.9 microns. For the instrument to have both high measurements rate and high accuracy, the optical system just satisfy several requirements. It should have aberration well under diffraction, for high precision in centroiding and as a means of keeping unmolded shifts of the image centroids small. The system should have a wide field of view so that there is a large overlap of successive scans, have a large field of view for scientific throughput, and have low image distortion so that the stellar images moved at constant rate along columns of detector pixels. The design presented meets these requirements using aspheric surfaces that are manufacturable. We have demonstrated that the instrument will determine the temperature of an observed star without requiring a dispersive element or color filters. The design is thus free of transmissive elements, and protected from the systematic errors that they might have induced, e.g., due to thermal variation variation and to chromatic effects. This study was inspired by our previous consideration of scientific throughput. Our study of data reduction from a scanning astrometic survey mission demonstrated that there is a substantial gain in mission accuracy if the spacecraft precesses without discontinuities such as those that result from gas jet firings. Our study of methods of processing the spacecraft showed that smooth rotation would be possible using solar radiation pressure, but only if the spacecraft rotation rate were increased. Maintaining the integration time for each object would require an optical design of

  13. Astrometric Support for Space Situational Awareness and Space Control: The U.S. Naval Observatory

    NASA Astrophysics Data System (ADS)

    White, J.

    The United States Naval Observatory (USNO), founded in 1830 as the progenitor of warfighting Position, Time and Navigation (PNT) operations, is the DoD agency mandated by the Joint Chiefs to establish, maintain, and coordinate Precise Time (such as for GPS) and Astronomical Reference Frames used by all components for navigation, precise positioning and orientation, space operations, and command, control, communications, computers, intelligence, surveillance, and reconnaissance (C4ISR). Specifically, the USNO-charged astrometric programs address fundamental needs gaps in several key aspects of Space Situational Awareness (SSA), Space Control (SC), and space-borne Target Location Error/CEP -reduction systems. As part of its responsibility, the USNO is the developer and synthesizer of all astronomical catalogs, surveys, and databases used by the DoD. USNO then produces the products needed to satisfy both broad and mission-specific needs gaps for the warfighter in the field, the air, at sea, or on the high frontier of Space. USNO DoD programs specifically applicable to the latter include space object tracking, extreme accuracy/rapid orbit determination, offensive/defensive counterspace (OCS/DCS), multi-waveband non-resolved object characterization, space sensor calibration, and astrometric reference frame and stellar catalog definition, maintenance, and improvement. Indeed, USNO's unique capability to produce milli-arcsecond guidance data is foundational to SSA/SC, and precision targeting and munitions. USNO capabilities will be discussed, and a vision presented of how advancements in astrometric programs will close need gaps, enable future capabilities in Space Situational Awareness, Space Control and spaceborne ISR.

  14. Astrometric and Photometric Analysis of the September 2008 ATV-1 Re-Entry Event

    NASA Technical Reports Server (NTRS)

    Mulrooney, Mark K.; Barker, Edwin S.; Maley, Paul D.; Beaulieu, Kevin R.; Stokely, Christopher L.

    2008-01-01

    NASA utilized Image Intensified Video Cameras for ATV data acquisition from a jet flying at 12.8 km. Afterwards the video was digitized and then analyzed with a modified commercial software package, Image Systems Trackeye. Astrometric results were limited by saturation, plate scale, and imposed linear plate solution based on field reference stars. Time-dependent fragment angular trajectories, velocities, accelerations, and luminosities were derived in each video segment. It was evident that individual fragments behave differently. Photometric accuracy was insufficient to confidently assess correlations between luminosity and fragment spatial behavior (velocity, deceleration). Use of high resolution digital video cameras in future should remedy this shortcoming.

  15. Modulation of Brain Activity during Action Observation: Influence of Perspective, Transitivity and Meaningfulness

    PubMed Central

    Hétu, Sébastien; Mercier, Catherine; Eugène, Fanny; Michon, Pierre-Emmanuel; Jackson, Philip L.

    2011-01-01

    The coupling process between observed and performed actions is thought to be performed by a fronto-parietal perception-action system including regions of the inferior frontal gyrus and the inferior parietal lobule. When investigating the influence of the movements' characteristics on this process, most research on action observation has focused on only one particular variable even though the type of movements we observe can vary on several levels. By manipulating the visual perspective, transitivity and meaningfulness of observed movements in a functional magnetic resonance imaging study we aimed at investigating how the type of movements and the visual perspective can modulate brain activity during action observation in healthy individuals. Importantly, we used an active observation task where participants had to subsequently execute or imagine the observed movements. Our results show that the fronto-parietal regions of the perception action system were mostly recruited during the observation of meaningless actions while visual perspective had little influence on the activity within the perception-action system. Simultaneous investigation of several sources of modulation during active action observation is probably an approach that could lead to a greater ecological comprehension of this important sensorimotor process. PMID:21931832

  16. Affective Evaluations of Objects Are Influenced by Observed Gaze Direction and Emotional Expression

    ERIC Educational Resources Information Center

    Bayliss, Andrew P.; Frischen, Alexandra; Fenske, Mark J.; Tipper, Steven P.

    2007-01-01

    Gaze direction signals another person's focus of interest. Facial expressions convey information about their mental state. Appropriate responses to these signals should reflect their combined influence, yet current evidence suggests that gaze-cueing effects for objects near an observed face are not modulated by its emotional expression. Here, we…

  17. Influences of Teacher Delivery, Student Engagement, and Observation Focus on Preservice Teachers' Perceptions of Teaching Effectiveness

    ERIC Educational Resources Information Center

    Napoles, Jessica; MacLeod, Rebecca B.

    2016-01-01

    The purpose of this study was to examine how teacher delivery, student engagement, and observation focus influenced preservice teachers' ratings of teaching effectiveness. Participants (N = 84 preservice teachers) viewed short teaching excerpts of orchestral and choral rehearsals wherein the teacher displayed either high or low teacher delivery,…

  18. Influence of Previous Knowledge, Language Skills and Domain-specific Interest on Observation Competency

    NASA Astrophysics Data System (ADS)

    Kohlhauf, Lucia; Rutke, Ulrike; Neuhaus, Birgit

    2011-10-01

    Many epoch-making biological discoveries (e.g. Darwinian Theory) were based upon observations. Nevertheless, observation is often regarded as `just looking' rather than a basic scientific skill. As observation is one of the main research methods in biological sciences, it must be considered as an independent research method and systematic practice of this method is necessary. Because observation skills form the basis of further scientific methods (e.g. experiments or comparisons) and children from the age of 4 years are able to independently generate questions and hypotheses, it seems possible to foster observation competency at a preschool level. To be able to provide development-adequate individual fostering of this competency, it is first necessary to assess each child's competency. Therefore, drawing on the recent literature, we developed in this study a competency model that was empirically evaluated within learners ( N = 110) from different age groups, from kindergarten to university. In addition, we collected data on language skills, domain-specific interest and previous knowledge to analyse coherence between these skills and observation competency. The study showed as expected that previous knowledge had a high impact on observation competency, whereas the influence of domain-specific interest was nonexistent. Language skills were shown to have a weak influence. By utilising the empirically validated model consisting of three dimensions (`Describing', `Scientific reasoning' and `Interpreting') and three skill levels, it was possible to assess each child's competency level and to develop and evaluate guided play activities to individually foster a child's observation competency.

  19. A Global Astrometric Solution for Pan-STARRS Referenced to ICRF2

    NASA Astrophysics Data System (ADS)

    Berghea, C. T.; Makarov, V. V.; Frouard, J.; Hennessy, G. S.; Dorland, B. N.; Veillette, D. R.; Dudik, R. P.; Magnier, E. A.; Burgett, W. S.; Chambers, K. C.; Denneau, L.; Flewelling, H.; Kaiser, N.; Tonry, J. L.; Wainscoat, R. J.; Sesar, B.

    2016-09-01

    We describe the development and application of a Global Astrometric Solution (GAS) to the problem of Pan-STARRS1 (PS1) astrometry. Current PS1 astrometry is based on differential astrometric measurements using 2MASS reference stars, and thus PS1 astrometry inherits the errors of the 2MASS catalog. The GAS, based on a single, least-squares adjustment to approximately 750 k “grid stars” using over 3000 extragalactic objects as reference objects, avoids this catalog-to-catalog propagation of errors to a great extent. The GAS uses a relatively small number of quasi-stellar objects (QSOs, or distant active galactic nuclei) with very accurate (<1 mas) radio positions, referenced to the ICRF2. These QSOs provide a hard constraint in the global least-squares adjustment. Solving such a system provides absolute astrometry for all of the stars simultaneously. The concept is much cleaner than conventional astrometry but is not easy to perform for large catalogs. In this paper, we describe our method and its application to Pan-STARRS1 data. We show that large-scale systematic errors are easily corrected but our solution residuals for position (˜60 mas) are still larger than expected based on simulations (˜10 mas). We provide a likely explanation for the reason the small-scale residual errors are not corrected in our solution as would be expected.

  20. The U.S. Naval Observatory Robotic Astrometric Telescope 1st Catalog (URAT1)

    NASA Astrophysics Data System (ADS)

    Zacharias, Norbert; Finch, Charlie T.; Subasavage, John P.; Tilleman, Trudy; DiVittorio, Mike; Harris, Hugh C.; Rafferty, Ted; Wieder, Gary; Eric Ferguson, Chris Kilian, Albert Rhodes, Mike Schultheis

    2015-01-01

    The 1st USNO Robotic Astrometric Telescope Catalog (URAT1) is about tobe released. It contains accurate positions (typically 10 to 30 mas std.error) of 220 million stars, mainly on the northern hemisphere. Propermotions were obtained for 85% of these stars utilizing the 2MASS as 1stepoch. URAT1 is supplemented by 2MASS and APASS photometry. The URAT1catalog was derived from 2 years of operations (April 2012 to April 2014)of the USNO "redlens" astrograph with its 474 Mpx 4-shooter camera at theNaval Observatory Flagstaff Station (NOFS) in a joint effort betweenUSNO's Astrometry Department and NOFS. Due to a combination of longexposures and short exposures with objective grating, URAT1 observationscover the large 3 to 18.5 magnitude range in a single 680-750 nm bandpass.The catalog properties are presented together with a brief summary ofobservations and reductions methods. URAT1 has on average about 4-timesthe number of stars per square degree and is 4-times more accurate thanUCAC4. URAT1 will serve as the currently most accurate astrometric anddeep photometric optical reference star catalog until the delivery ofthe Gaia catalog.

  1. Astrometric and Photometric Accuracy of the 1.3 m Robotically Controlled Telescope on Kitt Peak

    NASA Astrophysics Data System (ADS)

    McGruder, Charles H.; Carini, M. T.; Engle, S. G.; Gelderman, R.; Guinan, E. F.; Laney, D.; Strolger, L.; Treffers, R. R.; Walter, D. K.

    2014-01-01

    The 1.3 m (50 inch) telescope on Kitt Peak has been refurbished and provided with an autonomous scheduler. It is operated by The Robotically Controlled Telescope (RCT) consortium whose members are: South Carolina State, Villanova and Western Kentucky Universities. The facility possesses 5 board (UBVRI) and 11 narrow-band filters. Attached to the RCT camera is a 2048 x 2048 SITe SI-424A back-illuminated CCD with 24 micrometer pixels. We used over 7,000 star measurements from 37, 198s R-images to compute the astrometric and photometric accuracy. The difference of the J2000 coordinates computed from the RCT images and the J2000 Nomad catalog coordinate values in right ascension peaks at 0.058”, while the declination peaks at -0.125”. We obtained these astrometric results using the simplest assumptions: linear relationship between standard coordinates and measured coordinates, no color or magnitude dependency and no differential refraction (all images taken in the zenith). We express the photometric accuracy in the following manner: The Signal-to-Noise-Ratio as a function of apparent magnitude shows that the RCT is not noise dominated at m < 20 magnitude.

  2. Recent Status of SIM Lite Astrometric Observatory Mission: Flight Engineering Risk Reduction Activities

    NASA Technical Reports Server (NTRS)

    Goullioud, Renaud; Dekens, Frank; Nemati, Bijan; An, Xin; Carson, Johnathan

    2010-01-01

    The SIM Lite Astrometric Observatory is a mission concept for a space-borne instrument to perform micro-arc-second narrow-angle astrometry to search 60 to 100 nearby stars for Earth-like planets, and to perform global astrometry for a broad astrophysics program. The instrument consists of two Michelson stellar interferometers and a telescope. The first interferometer chops between the target star and a set of reference stars. The second interferometer monitors the attitude of the instrument in the direction of the target star. The telescope monitors the attitude of the instrument in the other two directions. The main enabling technology development for the mission was completed during phases A & B. The project is currently implementing the developed technology onto flight-ready engineering models. These key engineering tasks will significantly reduce the implementation risks during the flight phases C & D of the mission. The main optical interferometer components, including the astrometric beam combiner, the fine steering optical mechanism, the path-length-control and modulation optical mechanisms, focal-plane camera electronics and cooling heat pipe, are currently under development. Main assemblies are built to meet flight requirements and will be subjected to flight qualification level environmental testing (random vibration and thermal cycling) and performance testing. This paper summarizes recent progress in engineering risk reduction activities.

  3. Influence of daylight and noise current on cloud and aerosol observations by spaceborne elastic scattering lidar.

    PubMed

    Nakajima, T Y; Imai, T; Uchino, O; Nagai, T

    1999-08-20

    The influence of daylight and noise current on cloud and aerosol observations by realistic spaceborne lidar was examined by computer simulations. The reflected solar radiations, which contaminate the daytime return signals of lidar operations, were strictly and explicitly estimated by accurate radiative transfer calculations. It was found that the model multilayer cirrus clouds and the boundary layer aerosols could be observed during the daytime and the nighttime with only a few laser shots. However, high background noise and noise current make it difficult to observe volcanic aerosols in middle and upper atmospheric layers. Optimal combinations of the laser power and receiver field of view are proposed to compensate for the negative influence that is due to these noises. For the computer simulations, we used a realistic set of lidar parameters similar to the Experimental Lidar in-Space Equipment of the National Space Development Agency of Japan.

  4. NEAT: an astrometric space telescope to search for habitable exoplanets in the solar neighborhood

    NASA Astrophysics Data System (ADS)

    Crouzier, A.; Malbet, F.; Kern, P.; Feautrier, P.; Preiss, O.; Martin, G.; Henault, F.; Stadler, E.; Lafrasse, S.; Behar, E.; Saintpe, M.; Dupont, J.; Potin, S.; Lagage, P.-O.; Cara, C.; Leger, A.; Leduigou, J.-M.; Shao, M.; Goullioud, R.

    2014-03-01

    The last decade has witnessed a spectacular development of exoplanet detection techniques, which led to an exponential number of discoveries and a great diversity of known exoplanets. However, it must be noted that the quest for the holy grail of astrobiology, i.e. a nearby terrestrial exoplanet in habitable zone around a solar type star, is still ongoing and proves to be very hard. Radial velocities will have to overcome stellar noise if there are to discover habitable planets around stars more massive than M ones. For very close systems, transits are impeded by their low geometrical probability. Here we present an alternative concept: space astrometry. NEAT (Nearby Earth Astrometric Telescope) is a concept of astrometric mission proposed to ESA which goal is to make a whole sky survey of close (less then 20 pc) planetary systems. The detection limit required for the instrument is the astrometric signal of an Earth analog (at 10 pc). Differential astrometry is a very interesting tool to detect nearby habitable exoplanets. Indeed, for F, G and K main sequence stars, the astrophysical noise is smaller than the astrometric signal, contrary to the case for radial velocities. The difficulty lies in the fact that the signal of an exo-Earth around a G type star at 10 pc is a tiny 0.3 micro arc sec, which is equivalent to a coin on the moon, seen from the Earth: the main challenge is related to instrumentation. In order to reach this specification, NEAT consists of two formation flying spacecraft at a 40m distance, one carries the mirror and the other one the focal plane. Thus NEAT has a configuration with only one optical surface: an off-axis parabola. Consequently, beamwalk errors are common to the whole field of view and have a small effect on differential astrometry. Moreover a metrology system projects young fringes on the focal plane, which can characterize the pixels whenever necessary during the mission. NEAT has two main scientific objectives: combined with

  5. The influence of observers' sex on attention-demanding performance depends on performers' sex.

    PubMed

    Wang, Lijun; Tan, Jinfeng; Chen, Jiangtao; Chen, Antao

    2015-01-01

    Post-error slowing (PES) indicates the slower responses after errors than after correct responses. Prior studies mainly focus on how the observation errors influence one own's performance, there is no study investigating how other's monitoring influence one own's performance. Additionally, the issue that whether social context influences the PES effect differently for females and males is still unclear. To address aforementioned issues, we required the participants to interact with a same-sex or opposite-sex partner to complete a color flanker task together (they sat next to each other, Experiment 1). One was the performer (perform the flanker task), and the other was the observer (monitor the error responses of performer). They alternated their roles in two successive blocks. To further verify the role of the interaction context, a control experiment was conducted in the individual context (Experiment 2). The results revealed that (1) larger PES effect was observed in females than in males in the interaction context; (2) the sex difference of PES effect mainly benefited from the opposite-sex interaction; (3) larger PES effect was observed in the interaction context than in the individual context; (4) females' performance was influenced after an interaction with a same-sex or opposite-sex partner, whereas males' performance was merely influenced after an interaction with an opposite-sex partner. Taken together, these findings may suggest that (1) interaction context modulates the PES effect differently for females and males; (2) females are more susceptible to social information and hence more effective to adjust the post-error behaviors. PMID:26379574

  6. Preliminary Light Curve Results of NEOs from the Characterization and Astrometric Follow-Up Program at Adler Planetarium

    NASA Astrophysics Data System (ADS)

    Brucker, Melissa J.; Nault, Kristie A.; Hammergren, Mark; Sieben, Jennifer; Gyuk, Geza; Solontoi, Michael R.

    2015-11-01

    We are nearing the halfway mark of a two-year program for near-Earth object (NEO) astrometric follow-up and characterization utilizing 500 hours of observing time per year with the Astrophysical Research Consortium (ARC) 3.5-meter telescope at Apache Point Observatory (APO). Our observing is divided into two-hour blocks approximately every other night for astrometry (see poster by K. A. Nault et al.) and several half-nights per month for spectroscopy (see poster by M. Hammergren et al.) and light curve studies.We present preliminary results from variable photometry observations as part of the characterization portion of the Adler Planetarium’s NEO program. The frequent scheduling of half-night observing time allows us to capture data for small NEOs near the time when they are closest to Earth before their apparent magnitudes rapidly diminish beyond the range of detectability. We searched for variability in newly discovered NEOs that had close approaches to Earth near the time of observation. These include 2014 RQ17, 2014 SB145, 2014 SF304, 2014 WO4, 2014 WY119, and 2015 BC. In addition, we observed 2340 Hathor and 2007 EC when they each made a close approach to Earth to compare with light curves and magnitude variation constraints from previous apparitions. We will construct light curves for all of the objects listed above and determine rotational periods for those with sufficient temporal coverage.The targets were selected from candidates in the JPL NEO Earth Close Approaches table, Arecibo planetary radar targets, and the Goldstone asteroid radar schedule. Due to the sensitivity of AGILE, we restricted our targets to those with apparent magnitudes in V less than 19 magnitudes.Observations were made using the frame transfer CCD camera AGILE on the ARC 3.5-meter telescope. AGILE has a field-of-view of 2.2'x2.2' and a plate scale of 0.258”/pixel with 2x2 binning.This work is based on observations obtained with the Apache Point Observatory 3.5-meter telescope

  7. Observations of deep convective influence on stratospheric water vapor and its isotopic composition

    NASA Astrophysics Data System (ADS)

    Hanisco, T. F.; Moyer, E. J.; Weinstock, E. M.; Dessler, A. E.; St. Clair, J. M.; Sayres, D. S.; Smith, J. B.; Lockwood, R.; Read, W. G.; Anderson, J. G.

    2006-12-01

    In situ observations of H2O and HDO from the NASA WB-57 and remote measurements of H2O from AURA MLS are used to evaluate the role of deep convection as a source of water to the overworld stratosphere (potential temperature above 380 K). Observations in different seasons and latitudes are used to identify and evaluate the different pathways by which convection influences water vapor and its isotopes, including convection above the 380 K surface in the tropics, subtropics, and midlatitudes. The water isotope observations show that water vapor in the overworld stratosphere in the tropics and mid-latitudes is isotopically heavy, an unambiguous signature of large scale convective influence on stratospheric water to near- tropopause altitudes. Model results constrained by MLS H2O and in situ H2O and HDO suggest that extratropical convection accounts for a large fraction of the observed water vapor in the summertime overworld stratosphere above the mid-North American continent. Discontinuities between the water isotope abundances in the tropical tropopause layer (TTL) and the overworld stratosphere suggest that local processes do not control the abundance of stratospheric water above the western tropical pacific. Observations of water vapor and water isotopes in the tropical stratosphere indicate a significant, but not yet quantified, role of convection.

  8. Brassboard Astrometric Beam Combiner (ABC) Development for the Space Interferometry Mission (SIM)

    NASA Technical Reports Server (NTRS)

    Jeganathan, Muthu; Kuan, Gary; Rud, Mike; Lin, Sean; Sutherland, Kristen; Moore, James; An, Xin

    2008-01-01

    The Astrometric Beam Combiner (ABC) is a critical element of the Space Interferometry Mission (SIM) that performs three key functions: coherently combine starlight from two siderostats; individually detect starlight for angle tracking; and disperse and detect the interferometric fringes. In addition, the ABC contains: a stimulus, cornercubes and shutters for in-orbit calibration; several tip/tilt mirror mechanisms for in-orbit alignment; and internal metrology beam launcher for pathlength monitoring. The detailed design of the brassboard ABC (which has the form, fit and function of the flight unit) is complete, procurement of long-lead items is underway, and assembly and testing is expected to be completed in Spring 2009. In this paper, we present the key requirements for the ABC, details of the completed optical and mechanical design as well as plans for assembly and alignment.

  9. Wide angle astrometric demonstration on the micro-arcsecond metrology testbed for the space interferometry mission

    NASA Technical Reports Server (NTRS)

    Goullioud, Renaud; Shen, Tsae-Pyng J.; Catanzarite, Joseph H.

    2004-01-01

    The Space Interferometry Mission (SIM) requires fringe measurements to the level of picometers in order to produce astrometric data at the micro-arc-second level. To be more specific, it is necessary to measure both the position of the starlight central fringe and the change in the internal optical path of the interferometer to a few hundreds of picometers. The internal path is measured with a small heterodyne metrology beam, whereas the starlight fringe position is estimated with a CCD sampling a large concentric annular beam. One major challenge for SIM is to align the metrology beam with the starlight beam to keep the consistency between these two sensors at the system level while articulating the instrument optics over the field of view.

  10. Quantifying the influence of observed global warming on the probability of unprecedented extreme climate events

    NASA Astrophysics Data System (ADS)

    Diffenbaugh, N. S.; Rajaratnam, B.; Charland, A.; Haugen, M.; Horton, D. E.; Singh, D.; Swain, D. L.; Tsiang, M.

    2014-12-01

    Now that observed global warming has been clearly attributed to human activities, there has been increasing interest in the extent to which that warming has influenced the occurrence and severity of individual extreme climate events. However, although trends in the extremes of the seasonal- and daily-scale distributions of climate records have been analyzed for many years, quantifying the contribution of observed global warming to individual events that are unprecedented in the observed record presents a particular scientific challenge. We will describe a modified method for leveraging observations and large climate model ensembles to quantify the influence of observed global warming on the probability of unprecedented extreme events. In this approach, we first diagnose the causes of the individual event in order to understand which climate processes to target in the probability quantification. We then use advanced statistical techniques to quantify the uncertainty in the return period of the event in the observed record. We then use large ensembles of climate model simulations to quantify the distribution of return period ratios between the current level of climate forcing and the pre-industrial climate forcing. We will compare the structure of this approach to other approaches that exist in the literature. We will then examine a set of individual extreme events that have been analyzed in the literature, and compare the results of our approach with those that have been previously published. We will conclude with a discussion of the observed agreement and disagreement between the different approaches, including implications for interpretation of the role of human forcing in shaping unprecedented extreme events.

  11. Astrometric and Photometric Data Fusion for Mass and Surface Material Estimation using Refined Bidirectional Reflectance Distribution Functions-Solar Radiation Pressure Model

    NASA Astrophysics Data System (ADS)

    Linares, R.; Jah, M.; Hill, K.; Crassidis, J.; Wetterer, C.

    2013-09-01

    This paper studies the inference of space object mass, which is made possible due to the coupled influence of solar radiation pressure (SRP) acceleration on the orbit of satellites and their observed brightness. This effect takes time to be observed in optical angle measurements given the combination of a priori kinematic state uncertainties and the magnitude of this effect relative to them and the sensor data noise. Therefore multiple nights of observations are typically required to extract this "weak" signal from collected measurements. From angles data alone, only effective albedo-area-to-mass can be estimated since this term appears in the SRP acceleration equation, but when photometric data is fused with the astrometric angle measurements, it provides observability of and thus constrains the albedo-area estimates. This inferred constraint makes mass the most open degree of freedom and thus the fused data eventually inform the filter of the mass. The observability of albedo-area products is provided by the photometric brightness measurements, since the brightness of the space object is a strong function of the albedo-areas. However, the relationship between the albedo-areas and both the photometric return and SRP involves knowledge of the Bidirectional Reflectance Distribution Function (BRDF) for the surface of the space object. If the BRDF in the photometric measurement model and the BRDF in the SRP model are not consistent with each other, then the resulting estimated albedo-areas and mass are inaccurate and biased. This work studies the use of physically consistent BRDF-SRP models for mass estimation where simulation studies are used to provide an indication of the benefits of using these new models. An unscented Kalman filter approach that includes BRDF and mass parameters in the state vector is used. The full set of estimated parameters are position, velocity, attitude, angular rates, mass, exponential factor (parameter in Ashikhmin-Shirley BRDF related to

  12. Influence of projection effects on the observed differential rotation rate in the UV corona

    PubMed Central

    Mancuso, Salvatore; Giordano, Silvio

    2012-01-01

    Following previous investigations by Giordano and Mancuso [1] and Mancuso and Giordano [2,3] on the differential rotation of the solar corona as obtained through the analysis of the intensity time series of the O VI 1032 Å spectral line observed by the UVCS/SOHO telescope during solar cycle 23, we analysed the possible influence of projection effects of extended coronal structures on the observed differential rotation rate in the ultraviolet corona. Through a simple geometrical model, we found that, especially at higher latitudes, the differential rotation may be less rigid than observed, since features at higher latitudes could be actually linked to much lower coronal structures due to projection effects. At solar maximum, the latitudinal rigidity of the UV corona, with respect to the differential rotating photosphere, has thus to be considered as an upper limit of the possible rigidity. At solar minimum and near the equatorial region throughout the solar cycle, projection effects are negligible. PMID:25685430

  13. Visual influences on sensorimotor EEG responses during observation of hand actions.

    PubMed

    Drew, Ashley R; Quandt, Lorna C; Marshall, Peter J

    2015-02-01

    There is growing interest within the field of social-cognitive neuroscience in the dynamics of sensorimotor EEG rhythms during the observation of actions performed by others. However, there remain important gaps in the literature regarding the effects of perceptual aspects of the observed hand movements. This study investigated two visual influences on the EEG response to hand actions. Specifically, the perspective of the action in relation to the participant (egocentric/allocentric) was varied and the effect of the hand used to carry out the action (left/right) was also assessed. While EEG was recorded, 28 undergraduate participants observed video clips showing an actor's hand reaching for, grasping, and lifting a cylindrical object across four conditions (right-hand egocentric, left-hand egocentric, right-hand allocentric, and left-hand allocentric). For actions viewed from an egocentric perspective, significantly greater event-related desynchronization (ERD) was present in the 7-9 Hz range over right mid-frontal, right central, and bilateral mid-parietal sites for right-handed actions compared to left-handed actions. In addition, greater ERD was observed within the 7-9 Hz band during the observation of right-handed egocentric actions compared to actions viewed from the allocentric perspective. This finding was present at bilateral central and mid-parietal sites, and emerged as an anticipatory effect prior to the onset of the observed hand movements.

  14. Influences of observer sex, facial masculinity, and gender role identification on first impressions of men's faces.

    PubMed

    Macapagal, Kathryn R; Rupp, Heather A; Heiman, Julia R

    2011-01-01

    Evaluations of male faces depend on attributes of the observer and target and may influence future social and sexual decisions. However, it is unknown whether adherence to hypertraditional gender roles may shape women's evaluations of potential sexual partners or men's evaluations of potential competitors. Using a photo task, we tested participants' judgments of attractiveness, trustworthiness, aggressiveness, and masculinity of male faces altered to appear more masculine or feminine. Findings revealed that higher hypermasculinity scores in male observers were correlated with higher attractiveness and trustworthiness ratings of the male faces; conversely, higher hyperfemininity scores in female observers were associated with lower ratings on those traits. Male observers also rated the faces as more aggressive than did female observers. Regarding ratings by face type, masculinized faces were rated more aggressive than feminized faces, and women's ratings did not discriminate between altered faces better than men's ratings. These results suggest that first impressions of men can be explained in part by socioculturally- and evolutionarily-relevant factors such as the observer's sex and gender role adherence, as well as the target's facial masculinity.

  15. Influences of observer sex, facial masculinity, and gender role identification on first impressions of men's faces.

    PubMed

    Macapagal, Kathryn R; Rupp, Heather A; Heiman, Julia R

    2011-01-01

    Evaluations of male faces depend on attributes of the observer and target and may influence future social and sexual decisions. However, it is unknown whether adherence to hypertraditional gender roles may shape women's evaluations of potential sexual partners or men's evaluations of potential competitors. Using a photo task, we tested participants' judgments of attractiveness, trustworthiness, aggressiveness, and masculinity of male faces altered to appear more masculine or feminine. Findings revealed that higher hypermasculinity scores in male observers were correlated with higher attractiveness and trustworthiness ratings of the male faces; conversely, higher hyperfemininity scores in female observers were associated with lower ratings on those traits. Male observers also rated the faces as more aggressive than did female observers. Regarding ratings by face type, masculinized faces were rated more aggressive than feminized faces, and women's ratings did not discriminate between altered faces better than men's ratings. These results suggest that first impressions of men can be explained in part by socioculturally- and evolutionarily-relevant factors such as the observer's sex and gender role adherence, as well as the target's facial masculinity. PMID:21874151

  16. Quantitative Assessment of Upstream Source Influences on TGM Observations at Three CAMNet Sites

    NASA Astrophysics Data System (ADS)

    Wen, D.; Lin, J. C.; Meng, F.; Gbor, P. K.; He, Z.; Sloan, J. J.

    2009-05-01

    Mercury is a persistent and toxic substance in the environment. Exposure to high levels of mercury can cause a range of adverse health effects, including damage to the nervous system, reproduction system and childhood development. Proper recognition and prediction of atmospheric levels of mercury can effectively avoid the adverse affect of Hg, however they cannot be achieved without accurate and quantitative identification of source influences, which is a great challenge due to the complexity of Hg in the air. The objective of this study is to present a new method to simulate Hg concentrations at the location of a monitoring site and quantitatively assess its upstream source influences. Hourly total gaseous mercury (TGM) concentrations at three CAMNet monitoring sites (receptors) in Ontario were predicted for four selected periods using the Stochastic Time-Inverted Lagrangian Transport (STILT) model, which is capable of representing near-field influences that are not resolved by typical grid sizes in transport models. The model was modified to deal with Hg depositions and point source Hg emissions. The model-predicted Hg concentrations were compared with observations, as well as with the results from a CMAQ-Hg simulation in which the same emission and meteorology inputs were used. The comparisons show that STILT-predicted Hg concentrations agree well with observations, and are generally closer to the observations than those predicted by CMAQ-Hg. The better performance of the STILT simulation can be attributed to its ability to account for near-field influences. STILT was also applied to assess quantitatively the relative importance of different upstream source regions for the selected episodes. The assessment was made based on emission fluxes and STILT footprints, i.e., sensitivities of atmospheric concentrations to upstream surface fluxes. The results indicated that the main source regions of observed low Hg concentrations were in Northeastern Ontario, whereas

  17. Influence of age and of desmotropic drugs on the step phenomenon observed in rat skin.

    PubMed

    Vogel, H G; Hilgner, W

    1979-03-31

    Comprehensive analysis of the mechanical properties of rat skin revealed the "step phenomenon". This particular observation was made after constant strain rate (analysis of stress strain curves) as well as after constant load (creep experiments). Relative low extensions or low loads were necessary to provoke the steps. In most cases two, sometimes three steps were observed. The step phenomenon was found mainly in skin strips punched out perpendicularly to the body axis. Probably some bonds in the fibrous network are broken giving way to additional elongation whereafter stronger links take over the stress. Since earlier studies demonstrated a pronounced influence of age and of desmotropic drugs on mechanical properties at ultimate load, e.g., tensile strength, ultimate modulus of elasticity, and ultimate strain, also the step phenomenon was studied under these conditions. In stress-strain experiments most of the steps were found at the ages of 2 and 4 months. Total stress loss and total work loss due to the steps were the highest at the age of 4 months. If, however, these values were calculated as percentage of ultimate values, the highest figures were found in young animals. Elongation gain due to the steps also showed a maximum at time of maturation, e.g., 4 months. Similar findings were achieved in creep experiments at medium load (200 g). After treatment with prednisolone acetate more steps and after treatment with D-penicillamine fewer steps were observed. In stress-strain experiments total stress loss and total work loss due to steps were more than twice as high than controls after prednisolone treatment and only one half after D-penicillamine. If calculated as percentage of ultimate stress or percentage of work input, these changes disappeared because of similar changes at ultimate load. However, elongation gain due to steps, which was not significantly influenced by prednisolone acetate but significantly decreased by D-penicillamine, showed the same changes

  18. Observational Learning without a Model Is Influenced by the Observer's Possibility to Act: Evidence from the Simon Task

    ERIC Educational Resources Information Center

    Iani, Cristina; Rubichi, Sandro; Ferraro, Luca; Nicoletti, Roberto; Gallese, Vittorio

    2013-01-01

    We assessed whether observational learning in perceptual-motor tasks is affected by the visibility of an action producing perceived environmental effects and by the observer's possibility to act during observation. To this end, we conducted three experiments in which participants were required to observe a spatial compatibility task in which only…

  19. Influence of the observation window size on the performance of multilayer traffic engineering

    NASA Astrophysics Data System (ADS)

    Yan, Qiang; De Maesschalck, Sophie; Colle, Didier; Puype, Bart; Lievens, Ilse; Pickavet, Mario; Demeester, Piet

    2003-08-01

    Although the Optical Transport Network, based on technologies such as Wavelength Division Multiplexing and Optical Cross-Connects, offers tremendous transportation capacity, its management requires frequent manual intervention. However, as the traffic pattern offered to today's transport networks is subject to continuous changes due to the Internet traffic dominance, an optical transport network with a smart, automatic and real-time control system, denoted as Intelligent Optical Network (ION) or Automatic Switched Optical Network (ASON), is desired by network operators. Duly and correctly retrieving the changing traffic load information is a very important factor for the successful deployment of an ION. In this paper, we discuss the influence of the observation window size used for collecting the traffic load information, on the performance of an ION. By comparing the performance of an ION using different traffic observation window sizes, we show that a smaller observation window harms the network stability; while a too large observation window worsens the network reliability. We demonstrate that a suitable traffic observation window size improves the offered Quality of Service (QoS) by reconfiguring the logical layer network at the right time and in the right way.

  20. Experimental observation of the strong influence of crystal orientation on Electron Rutherford Backscattering Spectra

    NASA Astrophysics Data System (ADS)

    Vos, Maarten; Aizel, Koceila; Winkelmann, Aimo

    2010-06-01

    In Electron Rutherford Backscattering Spectroscopy (ERBS) energetic electrons (in our case up to 40 keV) impinge on a target and one measures the energy of elastically scattered electrons. This energy depends on the mass of the scattering atom, due to the recoil effect. This technique thus provides information about the sample composition. For single crystals the interaction of the projectile electron with the crystal potential modifies the angular intensity distribution of the scattered electrons. This leads, for example, to the well-known Kikuchi patterns. Here we investigate if such modified angular distribution has any influence on the intensity ratio of the observed elastic peaks in ERBS. Dramatic effects are found. Implications of these observations for quantitative surface analysis using energetic electrons are discussed.

  1. Associations of group level popularity with observed behavior and influence in a dyadic context.

    PubMed

    Lansu, Tessa A M; Cillessen, Antonius H N

    2015-12-01

    This study examined the association between popularity in the peer group and adolescents' behavior in a dyadic context. After collecting peer nominations for popularity, 218 early adolescents (M(age) = 11.0 years) in 109 randomly composed same-sex dyads participated in a discussion task where they planned a party for their classroom. From digital recordings of the sessions, each participant's influence, involvement, skillful leadership, coercive resource control, submissiveness, positivity, and negativity were observed. Analyses with the actor-partner interdependence model (APIM) demonstrated that for girls high group level popularity was associated with a socially sensitive interaction style and influence in the dyadic context. For both boys and girls, the interaction partner's group level popularity negatively predicted their use of coercive resource control strategies and negative behavior in the dyad. For girls, in addition, the interaction partner's group level popularity also positively predicted their submissiveness and negatively predicted their task influence. These results indicate that, in particular for girls, adolescents' group level popularity plays an important role in the behavior of both peers in a cooperative dyadic context.

  2. Associations of group level popularity with observed behavior and influence in a dyadic context.

    PubMed

    Lansu, Tessa A M; Cillessen, Antonius H N

    2015-12-01

    This study examined the association between popularity in the peer group and adolescents' behavior in a dyadic context. After collecting peer nominations for popularity, 218 early adolescents (M(age) = 11.0 years) in 109 randomly composed same-sex dyads participated in a discussion task where they planned a party for their classroom. From digital recordings of the sessions, each participant's influence, involvement, skillful leadership, coercive resource control, submissiveness, positivity, and negativity were observed. Analyses with the actor-partner interdependence model (APIM) demonstrated that for girls high group level popularity was associated with a socially sensitive interaction style and influence in the dyadic context. For both boys and girls, the interaction partner's group level popularity negatively predicted their use of coercive resource control strategies and negative behavior in the dyad. For girls, in addition, the interaction partner's group level popularity also positively predicted their submissiveness and negatively predicted their task influence. These results indicate that, in particular for girls, adolescents' group level popularity plays an important role in the behavior of both peers in a cooperative dyadic context. PMID:26232593

  3. The influence of observation errors on analysis error and forecast skill investigated with an observing system simulation experiment

    NASA Astrophysics Data System (ADS)

    Privé, N. C.; Errico, R. M.; Tai, K.-S.

    2013-06-01

    The National Aeronautics and Space Administration Global Modeling and Assimilation Office (NASA/GMAO) observing system simulation experiment (OSSE) framework is used to explore the response of analysis error and forecast skill to observation quality. In an OSSE, synthetic observations may be created that have much smaller error than real observations, and precisely quantified error may be applied to these synthetic observations. Three experiments are performed in which synthetic observations with magnitudes of applied observation error that vary from zero to twice the estimated realistic error are ingested into the Goddard Earth Observing System Model (GEOS-5) with Gridpoint Statistical Interpolation (GSI) data assimilation for a 1 month period representing July. The analysis increment and observation innovation are strongly impacted by observation error, with much larger variances for increased observation error. The analysis quality is degraded by increased observation error, but the change in root-mean-square error of the analysis state is small relative to the total analysis error. Surprisingly, in the 120 h forecast, increased observation error only yields a slight decline in forecast skill in the extratropics and no discernible degradation of forecast skill in the tropics.

  4. The Influence of Observation Errors on Analysis Error and Forecast Skill Investigated with an Observing System Simulation Experiment

    NASA Technical Reports Server (NTRS)

    Prive, N. C.; Errico, R. M.; Tai, K.-S.

    2013-01-01

    The Global Modeling and Assimilation Office (GMAO) observing system simulation experiment (OSSE) framework is used to explore the response of analysis error and forecast skill to observation quality. In an OSSE, synthetic observations may be created that have much smaller error than real observations, and precisely quantified error may be applied to these synthetic observations. Three experiments are performed in which synthetic observations with magnitudes of applied observation error that vary from zero to twice the estimated realistic error are ingested into the Goddard Earth Observing System Model (GEOS-5) with Gridpoint Statistical Interpolation (GSI) data assimilation for a one-month period representing July. The analysis increment and observation innovation are strongly impacted by observation error, with much larger variances for increased observation error. The analysis quality is degraded by increased observation error, but the change in root-mean-square error of the analysis state is small relative to the total analysis error. Surprisingly, in the 120 hour forecast increased observation error only yields a slight decline in forecast skill in the extratropics, and no discernable degradation of forecast skill in the tropics.

  5. Balancing cognitive control: how observed movements influence motor performance in a task with balance constraints.

    PubMed

    Verrel, Julius; Lisofsky, Nina; Kühn, Simone

    2014-07-01

    We investigated the influence of observed movements on executed movements in a task requiring lifting one foot from the floor while maintaining whole-body balance. Sixteen young participants (20-30 years) performed foot lift movements, which were either cued symbolically by a letter (L/R, indicating to lift the left/right foot) or by a short movie showing a foot lift movement. In the symbol cue condition, stimuli from the movie cue condition were used as distractors, and vice versa. Anticipatory postural adjustments (APAs) and actual foot lifts were recorded using force plates and optical motion capture. Foot lift responses were generally faster in response to the movie compared to the symbol cue condition. Moreover, incongruent movement distractors interfered with performance in the symbol cue condition, as shown by longer response times and increased number of APAs. Latencies of the first (potentially wrong) APA in a trial were shorter for movie compared to symbol cues but were not affected by cue-distractor congruency. Amplitude of the first APA was smaller when it was followed by additional APAs compared to trials with a single APA. Our results show that automatic imitation tendencies are integrated with postural control in a task with balance constraints. Analysis of the number, timing and amplitude of APAs indicates that conflicts between intended and observed movements are not resolved at a purely cognitive level but directly influence overt motor performance, emphasizing the intimate link between perception, cognition and action. PMID:24880223

  6. Point source influence on observed extreme pollution levels in a monitoring network

    NASA Astrophysics Data System (ADS)

    Ensor, Katherine B.; Ray, Bonnie K.; Charlton, Sarah J.

    2014-08-01

    This paper presents a strategy to quantify the influence major point sources in a region have on extreme pollution values observed at each of the monitors in the network. We focus on the number of hours in a day the levels at a monitor exceed a specified health threshold. The number of daily exceedances are modeled using observation-driven negative binomial time series regression models, allowing for a zero-inflation component to characterize the probability of no exceedances in a particular day. The spatial nature of the problem is addressed through the use of a Gaussian plume model for atmospheric dispersion computed at locations of known emissions, creating covariates that impact exceedances. In order to isolate the influence of emitters at individual monitors, we fit separate regression models to the series of counts from each monitor. We apply a final model clustering step to group monitor series that exhibit similar behavior with respect to mean, variability, and common contributors to support policy decision making. The methodology is applied to eight benzene pollution series measured at air quality monitors around the Houston ship channel, a major industrial port.

  7. BDNF Val66Met Polymorphism Influences Visuomotor Associative Learning and the Sensitivity to Action Observation

    PubMed Central

    Taschereau-Dumouchel, Vincent; Hétu, Sébastien; Michon, Pierre-Emmanuel; Vachon-Presseau, Etienne; Massicotte, Elsa; De Beaumont, Louis; Fecteau, Shirley; Poirier, Judes; Mercier, Catherine; Chagnon, Yvon C.; Jackson, Philip L.

    2016-01-01

    Motor representations in the human mirror neuron system are tuned to respond to specific observed actions. This ability is widely believed to be influenced by genetic factors, but no study has reported a genetic variant affecting this system so far. One possibility is that genetic variants might interact with visuomotor associative learning to configure the system to respond to novel observed actions. In this perspective, we conducted a candidate gene study on the Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism, a genetic variant linked to motor learning in regions of the mirror neuron system, and tested the effect of this polymorphism on motor facilitation and visuomotor associative learning. In a single-pulse TMS study carried on 16 Met (Val/Met and Met/Met) and 16 Val/Val participants selected from a large pool of healthy volunteers, Met participants showed significantly less muscle-specific corticospinal sensitivity during action observation, as well as reduced visuomotor associative learning, compared to Val homozygotes. These results are the first evidence of a genetic variant tuning sensitivity to action observation and bring to light the importance of considering the intricate relation between genetics and associative learning in order to further understand the origin and function of the human mirror neuron system. PMID:27703276

  8. Interferometric, astrometric, and photometric studies of Epsilon Aurigae: Seeing the disk around a distant star

    NASA Astrophysics Data System (ADS)

    Kloppenborg, Brian

    2012-05-01

    Epsilon (epsilon) Aurigae is a binary star system that has baffled astronomers for 170 years. In 1821 it was first noticed that the star system had dimmed by nearly 50%. After many decades of photometric monitoring, the 27.1 year period was finally established in 1903. A few years later, in 1912, Henry Norris Russell published the first analytic methods for binary star analysis. Later application of these formulae came to an interesting conclusion; the system was composed of two stars: the visible F-type supergiant, and an equally massive, but yet photometrically and spectroscopically invisible, companion. Several theories were advanced to explain this low-light to high-mass conundrum, eventually settling on the notion that the companion object is obscured from view by a disk of opaque material. With this topic solved, the debate shifted the evolutionary state of the system. Two scenarios became dominant: the system is either relativity young, and composed of a massive, 15 Mo (solar mass), F-type supergiant and a nearly equally massive main sequence companion inside of the disk; or a much older and significantly less massive, 4 Mo, F-type post-asymptotic giant branch object with a more massive, 6 Mo, companion surrounded by a debris disk. In this dissertation I disentangle the two evolutionary states by comparing the photometric behavior of the F-type star to known supergiant and post-asymptotic giant branch objects; and deriving a dynamical mass for the two components using astrometric, radial velocity, and interferometric data. Along with this, I provide the first interferometric images during the eclipse which prove the 50% dimming is indeed caused by an opaque disk. The first chapter presents the reader with the status quo of epsilon Aurigae research and the topics I wish to address in this dissertation. Chapter two presents an analysis of nearly 30 years of photometry on the system, concluding the star periodically exhibits stable pulsation on 1/3 orbital

  9. Observational learning without a model is influenced by the observer's possibility to act: evidence from the Simon task.

    PubMed

    Iani, Cristina; Rubichi, Sandro; Ferraro, Luca; Nicoletti, Roberto; Gallese, Vittorio

    2013-07-01

    We assessed whether observational learning in perceptual-motor tasks is affected by the visibility of an action producing perceived environmental effects and by the observer's possibility to act during observation. To this end, we conducted three experiments in which participants were required to observe a spatial compatibility task in which only the effects of computer-generated responses were visible before executing a Simon task. In Experiment 1, we compared the effects of a passively observed practice with either a spatially compatible or incompatible stimulus-response (S-R) association. In Experiment 2, during the observed spatially incompatible practice participants were prevented from potentially acting, either because a plexiglas barrier separated the participant from the response device rendering it out of reach; or because the participant's hands were tied; or the device affording a response was absent. In Experiment 3, the plexiglas presented an opening that could allow the participant to potentially reach and interact with it. As when the practice is physically performed, we found an elimination of the Simon effect following a spatially incompatible observed practice, suggesting that participants learned an incompatible S-R association by observing and transferred this knowledge to the subsequent Simon task. No evidence of transfer of learning was found when, during passive observation, the participant's hands were tied, or a barrier prevented him/her from potentially interacting with the device, or no response device was present. Differently, a transfer-of-learning effect was observed when the barrier presented an opening. These results suggest that learning can derive from the mere observation of action effects, even when an action is not visible, as long as the observer has the potential to act.

  10. How do Biomass Burning Carbon Monixide Emissions from South America influence Satellite Observed Columns over Africa?

    NASA Astrophysics Data System (ADS)

    Krol, M. C.; van Leeuwen, T. T.; Aouizerats, B.; van der Werf, G.

    2015-12-01

    Large amounts of Carbon Monoxide (CO) are emitted during biomass burning events. These emissions severely perturb the atmospheric composition. For this reason, satellite observations of CO can help to constrain emissions from biomass burning. Other sources of CO, such as the production of CO from naturally emitted non-methane hydrocarbons, may interfere with CO from biomass burning and inverse modeling efforts to estimate biomass burning emissions have to account for these CO sources. The atmospheric lifetime of CO varies from weeks to months, depending on the availability of atmospheric OH for atmospheric oxidation of CO to carbon dioxide. This means that CO can be transported over relatively long distances. It also implies that satellite-observed CO does not necessarily originate from the underlying continent, but may be caused by distant emissions transported to the observation location. In this presentation we focus on biomass burning emissions from South America and Southern Africa during 2010. This year was particularly dry over South America with a large positive anomaly in biomass burning in the 2010 burning season (July-October). We will adress the question how CO plumes from South America biomass burning influence satellite observations from the Infrared Atmospheric Sounding Interferometer (IASI) instrument over Southern Africa. For this we employ the TM5 atmospheric chemistry model, with 1x1 degree zoom resolutions over Africa and South America. Also, we use the TM5-4DVAR code to estimate CO biomass burning emissions using IASI CO observations. The accompanying image shows IASI CO oberservations over Africa on August 27, 2010, compared to the columns simulated with TM5. Clear signs of intercontinental transport from South America are visible over the Southermost region.

  11. Solar wind influence on the Jovian inner magnetosphere observed by Hisaki/EXCEED

    NASA Astrophysics Data System (ADS)

    Murakami, G.; Yoshioka, K.; Yamazaki, A.; Tsuchiya, F.; Kimura, T.; Tao, C.; Kagitani, M.; Sakanoi, T.; Uemizu, K.; Kasaba, Y.; Yoshikawa, I.; Fujimoto, M.

    2015-12-01

    The dawn-dusk asymmetry of the Io plasma torus has been seen by several observations [e.g., Sandel and Broadfoot, 1982; Steffl et al., 2004]. Ip and Goertz [1983] explained this asymmetry can be caused by a dawn-to-dusk electric field in the Jupiter's inner magnetosphere. However, the question what physical process can impose such an electric field deep inside the strong magnetosphere still remains. The long-term monitoring of the Io plasma torus is a key observation to answer this question. The extreme ultraviolet (EUV) spectrometer EXCEED onboard the Hisaki satellite observed the Io plasma torus continuously during the two periods: from December 2013 to March 2014 and from November 2014 to May 2015. We found clear responses of the dawn-dusk asymmetry to rapid increases of the solar wind dynamic pressure. We statistically analyzed the relations between solar wind and IPT response. Furthermore, we investigated the influence of Io's volcanic activity, detected by Hisaki in January 2015, on the solar wind response of Jovian inner magnetosphere. We will report the initial results of this study.

  12. Influence of atmospheric relative humidity on ultraviolet flux and aerosol direct radiative forcing: Observation and simulation

    NASA Astrophysics Data System (ADS)

    Xia, Dong; Chen, Ling; Chen, Huizhong; Luo, Xuyu; Deng, Tao

    2016-08-01

    The atmospheric aerosols can absorb moisture from the environment due to their hydrophilicity and thus affect atmospheric radiation fluxes. In this article, the ultraviolet radiation and relative humidity (RH) data from ground observations and a radiative transfer model were used to examine the influence of RH on ultraviolet radiation flux and aerosol direct radiative forcing under the clear-sky conditions. The results show that RH has a significant influence on ultraviolet radiation because of aerosol hygroscopicity. The relationship between attenuation rate and RH can be fitted logarithmically and all of the R2 of the 4 sets of samples are high, i.e. 0.87, 0.96, 0.9, and 0.9, respectively. When the RH is 60%, 70%, 80% and 90%, the mean aerosol direct radiative forcing in ultraviolet is -4.22W m-2, -4.5W m-2, -4.82W m-2 and -5.4W m-2, respectively. For the selected polluted air samples the growth factor for computing aerosol direct radiative forcing in the ultraviolet for the RH of 80% varies from 1.19 to 1.53, with an average of 1.31.

  13. Type of gesture, valence, and gaze modulate the influence of gestures on observer's behaviors

    PubMed Central

    De Stefani, Elisa; Innocenti, Alessandro; Secchi, Claudio; Papa, Veronica; Gentilucci, Maurizio

    2013-01-01

    The present kinematic study aimed at determining whether the observation of arm/hand gestures performed by conspecifics affected an action apparently unrelated to the gesture (i.e., reaching-grasping). In 3 experiments we examined the influence of different gestures on action kinematics. We also analyzed the effects of words corresponding in meaning to the gestures, on the same action. In Experiment 1, the type of gesture, valence and actor's gaze were the investigated variables Participants executed the action of reaching-grasping after discriminating whether the gestures produced by a conspecific were meaningful or not. The meaningful gestures were request or symbolic and their valence was positive or negative. They were presented by the conspecific either blindfolded or not. In control Experiment 2 we searched for effects of the sole gaze, and, in Experiment 3, the effects of the same characteristics of words corresponding in meaning to the gestures and visually presented by the conspecific. Type of gesture, valence, and gaze influenced the actual action kinematics; these effects were similar, but not the same as those induced by words. We proposed that the signal activated a response which made the actual action faster for negative valence of gesture, whereas for request signals and available gaze, the response interfered with the actual action more than symbolic signals and not available gaze. Finally, we proposed the existence of a common circuit involved in the comprehension of gestures and words and in the activation of consequent responses to them. PMID:24046742

  14. Astrometric telescope facility. Preliminary systems definition study. Volume 3: Cost estimate

    NASA Technical Reports Server (NTRS)

    Sobeck, Charlie (Editor)

    1987-01-01

    The results of the Astrometric Telescope Facility (ATF) Preliminary System Definition Study conducted in the period between March and September 1986 are described. The main body of the report consists primarily of the charts presented at the study final review which was held at NASA Ames Research Center on July 30 and 31, 1986. The charts have been revised to reflect the results of that review. Explanations for the charts are provided on the adjoining pages where required. Note that charts which have been changed or added since the review are dated 10/1/86; unchanged charts carry the review date 7/30/86. In addition, a narrative summary is presented of the study results and two appendices. The first appendix is a copy of the ATF Characteristics and Requirements Document generated as part of the study. The second appendix shows the inputs to the Space Station Mission Requirements Data Base submitted in May 1986. The report is issued in three volumes. Volume 1 contains an executive summary of the ATF mission, strawman design, and study results. Volume 2 contains the detailed study information. Volume 3 has the ATF cost estimate, and will have limited distribution.

  15. NEAT: An Astrometric Mission to Detect and Characterize Nearby Habitable Planetary Systems

    NASA Astrophysics Data System (ADS)

    Malbet, Fabien; Crouzier, Antoine; Goullioud, Renaud; Lagage, Pierre-Olivier; Léger, Alain; Shao, Mike

    2014-04-01

    Many planets have been detected so far but very few around nearby stars that could allow characterization of their atmosphere thanks to their proximity. There are known exoplanets around less than 8.3% of the FGK stars of the Solar neighborhood (d<20 pc) and the vast majority of them are giant planets. Within the ESA Cosmic Vision 2015-2025 plan, the scientific goal of the NEAT (Nearby Earth Astrometric Telescope) mission is to detect and characterize planetary systems around these nearby stars in an exhaustive way down to 1 Earth-mass in the habitable zone. This survey would provide the actual planetary masses, the full characterization of the orbits including their inclination, for all the components of the planetary system down to the Earth-mass limit. NEAT will continue the work performed by Hipparcos and Gaia by reaching a precision that is improved by two orders of magnitude on pointed targets compared to Gaia. We present the free-flyer concept that has been submitted to the 2010 ESA call for M3 missions with two satellites flying in formation 40m apart.

  16. Habitable Worlds Around M Dwarf Stars: The CAPSCam Astrometric Planet Search

    NASA Astrophysics Data System (ADS)

    Boss, Alan P.; Weinberger, Alycia J.; Anglada-Escudé, Guillem; Thompson, Ian B.; Brahm, Rafael

    2014-04-01

    M dwarf stars are attractive targets in the search for habitable worlds as a result of their relative abundance and proximity, making them likely targets for future direct detection efforts. Hot super-Earths as well as gas giants have already been detected around a number of early M dwarfs, and the former appear to be the high-mass end of the population of rocky, terrestrial exoplanets. The Carnegie Astrometric Planet Search (CAPS) program has been underway since March 2007, searching ~ 100 nearby late M, L, and T dwarfs for gas giant planets on orbits wide enough for habitable worlds to orbit interior to them. The CAPSCam-N camera on the 2.5-m du Pont telescope at the Las Campanas Observatory has demonstrated the ability to detect planets as low in mass as Saturn orbiting at several AU around late M dwarfs within 15 pc. Over the next decade, the CAPS program will provide new constraints on the planetary census around late M dwarf stars, and hence on the suitability of these nearby planetary systems for supporting life.

  17. Astrometric Telescope Facility preliminary systems definition study. Volume 1: Executive summary

    NASA Astrophysics Data System (ADS)

    Sobeck, Charlie

    1987-03-01

    The Astrometric Telescope Facility (ATF) is a spaceborne observatory proposed for use on the Space Station (SS) as an Initial Operating Capability (IOC) payload. The primary objective of the ATF will be the search for extrasolar planetary systems and a detailed investigation of any discovered systems. In addition, it will have the capability of conducting other astrophysics investigations; e.g., measuring precise distances and motions of stars within our galaxy. The purposes of the study were to: (1) define mission and system requirements; (2) define a strawman system concept for the facility at the Prephase A level; (3) define the need for additional trade studies or technology development; and (4) estimate program cost for the strawman concept. It has been assumed for the study that the ATF will be a SS payload, will use a SS-provided Coarse Pointing System (CPS), will meet SS constraints, and will make maximum use of existing flight qualified designs or designs to be qualified by the SS program for general SS use.

  18. Global Astrometric Sphere Reconstruction in Gaia. Challenges and First Results of the Verification Unit

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Abbas, U.; Bucciarelli, B.; Lattanzi, M. G.; Morbidelli, R.

    2009-05-01

    Gaia will estimate the astrometric and physical data of approximately one billion objects. The core of this process, the global sphere reconstruction, is represented by the reduction of a subset of these objects, which will constitute the largest and most precise catalog of absolute astrometry in the history of Astronomy, and will put General Relativity to test by estimating the PPN parameter γ with unprecedented accuracy. As the Hipparcos mission showed, and as it is natural for all kind of absolute measurements, possible errors in the data reduction can hardly be identified at the end of the processing, and can lead to systematic errors in all the works which will use these results. In order avoid such kind of problems, a Verification Unit was established by the Gaia Data Processing and Analysis Consortium (DPAC). One of its jobs is to implement and perform an independent global sphere reconstruction, parallell to the baseline one, to compare the two results, and to report any significant difference. We will present here how we dealt with the challenges of such a task, and the first results obtained so far.

  19. Global astrometric sphere reconstruction in Gaia: challenges and first results of the Verification Unit

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Abbas, Ummi; Bucciarelli, Beatrice; Lattanzi, Mario G.; Morbidelli, Roberto

    2010-01-01

    Gaia will estimate the astrometric and physical data of approximately one billion objects. The core of this process, the global sphere reconstruction, is represented by the reduction of a subset of these objects, which will constitute the largest and most precise catalog of absolute astrometry in the history of Astronomy, and will put General Relativity to test by estimating the PPN parameter γ with unprecedented accuracy. As the Hipparcos mission showed, and as it is natural for all kind of absolute measurements, possible errors in the data reduction can hardly be identified at the end of the processing, and can lead to systematic errors in all the works which will use these results. In order to avoid such kind of problems, a Verification Unit was established by the Gaia Data Processing and Analysis Consortium (DPAC). One of its jobs is to implement and perform an independent global sphere reconstruction, parallel to the baseline one, to compare the two results, and to report any significant difference.

  20. A photometric and astrometric investigation of the brown dwarfs in Blanco 1

    NASA Astrophysics Data System (ADS)

    Casewell, S. L.; Baker, D. E. A.; Jameson, R. F.; Hodgkin, S. T.; Dobbie, P. D.; Moraux, E.

    2012-10-01

    We present the results of a photometric and astrometric study of the low-mass stellar and substellar population of the young open cluster Blanco 1. We have exploited J-band data, obtained recently with the Wide Field Camera (WFCAM) on the United Kingdom Infrared Telescope (UKIRT), and 10-year-old I- and z-band optical imaging from CFH12k on the Canada-France-Hawaii Telescope (CFHT), to identify 44 candidate low-mass stellar and substellar members, in an area of 2 deg2, on the basis of their colours and proper motions. This sample includes five sources which are newly discovered. We also confirm the lowest mass candidate member of Blanco 1 unearthed so far (29MJup). We determine the cluster mass function to have a slope of α = +0.93, assuming it to have a power-law form. This is high, but nearly consistent with previous studies of the cluster (to within the errors), and also that of its much better studied Northern hemisphere analogue, the Pleiades.

  1. New Astrometric Reduction of the USNO Photographic Plates of Planetary Satellites

    NASA Astrophysics Data System (ADS)

    de Cuyper, J.-P.; Winter, L.; de Decker, G.; Zacharias, N.; Pascu, D.; Arlot, J.-E.; Robert, V.; Lainey, V.

    2009-09-01

    An international collaboration has been set up between the US Naval Observatory (USNO) in Washington DC, the IMCCE of Paris Observatory (OBSPM) and the Royal Observatory of Belgium (ROB) to make a new astrometric reduction of the USNO archival photographic plates of planetary satellites. In order to obtain a better knowledge of their orbital motions these photographic plates are digitized with the new generation DAMIAN digitizer at the ROB, providing a geometric stability of better than 0.1 μm on the plates. We focus here on a subset of a few hundred photographic plates of the Galilean satellites, taken with the McCormick and the USNO 26-inch refractors between 1967 and 1998. Specific procedures and algorithms are used to obtain highly accurate positions using the Tycho2, UCAC2 (20 - 30 mas) and later the UCAC3 (10 - 20 mas) catalogues. A comparison with the MAMA digitizer of the Paris Observatory is made through the results obtained from digital mosaic images of the plates.

  2. Astrometric Telescope Facility preliminary systems definition study. Volume 1: Executive summary

    NASA Technical Reports Server (NTRS)

    Sobeck, Charlie

    1987-01-01

    The Astrometric Telescope Facility (ATF) is a spaceborne observatory proposed for use on the Space Station (SS) as an Initial Operating Capability (IOC) payload. The primary objective of the ATF will be the search for extrasolar planetary systems and a detailed investigation of any discovered systems. In addition, it will have the capability of conducting other astrophysics investigations; e.g., measuring precise distances and motions of stars within our galaxy. The purposes of the study were to: (1) define mission and system requirements; (2) define a strawman system concept for the facility at the Prephase A level; (3) define the need for additional trade studies or technology development; and (4) estimate program cost for the strawman concept. It has been assumed for the study that the ATF will be a SS payload, will use a SS-provided Coarse Pointing System (CPS), will meet SS constraints, and will make maximum use of existing flight qualified designs or designs to be qualified by the SS program for general SS use.

  3. Merger influence on the thermal SZ effect: Model, simulation and observation

    NASA Astrophysics Data System (ADS)

    Koch, P.

    XMM-Newton and Chandra reveal detailed structures and dynamical processes in clusters of galaxies. We propose an analytical model to calculate the influence of an ongoing merger on the thermal SZ effect. According to observations we distinguish between subsonic and transonic mergers. For both cases we estimate the new pressure distribution around the merging subcluster due to its movement. Depending on the geometrical shape of the subcluster, its extension and infall velocity, and also depending on the angle between the merger axis and the line of sight, the expected SZ distortion in the merger region is of the order of 3-15 percent higher than for a relaxed cluster. In addition to this new pressure distribution we also calculate the change in the thermal spectral SZ function, resulting from the bow shock accelerated electrons in a transonic or supersonic merger. The merger shock compression factor determines the power law tail of the new non-thermal electron population and it is directly related to a shift in the crossover frequency. This shift is typically a few percent towards higher frequencies. We compare our result with the expected relativistic corrections for the thermal SZ effect and we point out the different features. Our new pressure distribution is testet against simulations and expected forthcoming observations with our AMiBA instrument.

  4. Are Observed Variations of Topography of The '660' Influenced By Lateral Variations of An Underlying Interface ?

    NASA Astrophysics Data System (ADS)

    Castillo, J.; Mocquet, A.; Vacher, P.; Sotin, C.

    Most global studies of lateral variations of topography of the '660' have been per- formed so far with long-period data. This presentation assess the seismic signature of this region when studied with broadband data in the frequency range 0.1-1 Hz. When sampled with P-to-s converted phases, this region shows a complex pattern, associat- ing 3 interfaces at the average depths of 600, 650 and 715 km. First results indicate that lateral topography variations of the '650' fit previous observations by long-period data (Gu et al., 1998), except in some subduction zones, especially in East Asia, where vari- ation trends appear to behave in an opposite way. In such regions, better correlations are found with the behaviour of the '715'. We propose that the seismic signature of long-period waves generated at the bottom of the transition zone may be influenced by both interfaces. Because of the lateral variations of their thickness and velocity jump as a function of thermal context, the signature of one interface could prevail against the other. The transformation of garnet into perovskite, and dissociation of ringwood- ite are tested as possible candidates for the '715' and '650', respectively (Vacher et al., 1998), using available thermoelastic data. Synthetic modelling of converted phases on the velocity profiles computed in different thermal contexts can explain our broadband observations. References : Gu et al., EPSL, 157, 57-67, 1998 ; Vacher et al., PEPI, 106, 275-298, 1998.

  5. Influence of Observed Diurnal Cycles of Aerosol Optical Depth on Aerosol Direct Radiative Effect

    NASA Technical Reports Server (NTRS)

    Arola, A.; Eck, T. F.; Huttunen, J.; Lehtinen, K. E. J.; Lindfors, A. V.; Myhre, G.; Smirinov, A.; Tripathi, S. N.; Yu, H.

    2013-01-01

    The diurnal variability of aerosol optical depth (AOD) can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF) or aerosol direct radiative effect (ADRE). The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally.We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast) does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on 24 h ADRE was

  6. Influence of orographic and canopy conditions on friction velocities observed during frontal events using Doppler sodar observations

    SciTech Connect

    Kotroni, V.; Amory-Mazaudier, C. )

    1993-03-01

    Sodar friction velocities, obtained during frontal events traversing areas characterized by different orographic and canopy conditions (flat, bare ground, small hills and valleys with agricultural crops and trees, agricultural crops and forest on a flat ground, bare ground on the side of a mountain), are compared in order to identify the influence of topography on this parameter. For some case studies, sounding and sodar data are combined in order to provide a relation between the friction velocity and the low-level jet presence. For the cases analyzed in this paper, the following results are obtained: the frontal passage is associated with a decrease of the horizontal wind speed (about 50% in magnitude) in the surface layer, and an increase of the friction velocity before the frontal passage followed by a decrease just at the time of the frontal passage or with a little delay. Friction velocity is more intense in the cold side of the low-level jet and its maximum represents 2% of the low-level jet maximum magnitude. As it concerns the influence of the terrain conditions on friction velocity, mountain effects yield to more intense friction-velocity values and to a superposition of an oscillating behavior on the time variation of friction velocity, while forest effects induce a shift of the frontal signature on the time variation of friction velocity at higher height levels. 25 refs., 18 figs., 3 tabs.

  7. The Influence of Aerosol Composition on Photolysis Rates Based on Airborne Observations

    NASA Astrophysics Data System (ADS)

    Corr, C.; Barrick, J. D. W.; Beyersdorf, A. J.; Chen, G.; Crawford, J. H.; Jordan, C. E.; Moore, R.; Shook, M.; Thornhill, K. L., II; Winstead, E.; Ziemba, L. D.; Madronich, S.; Anderson, B. E.

    2015-12-01

    The potential variability in modeled photolysis rates introduced by aerosol optical properties measured at visible wavelengths is presented here. Aerosol scattering and absorption were measured aboard the NASA P-3B aircraft during the Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) using a TSI Nephelometer and a Radiance Research Particle Soot Absorption Photometer (PSAP), respectively. To isolate the effect of aerosols on photolysis rates, cloud-free case studies were identified using aircraft videos for the four DISCOVER-AQ deployments: Baltimore, MD-Washington, D.C. in July 2011, the California Central Valley in January/February 2013, Houston, TX in September 2013, and Denver, CO in July 2014. For these case studies, absorption measurements at 470 and 532 nm were extrapolated to the Nephelometer wavelengths (450 and 550nm) using the 470-532nm absorption Angstrom exponent (AAE470-532) to calculate aerosol extinction and SSAs at these wavelengths. Photolysis rates were modeled using the Tropospheric Ultraviolet model version 5.2 (TUV 5.2) for three scenarios: 1) an aerosol-free case, 2) using a spectrally-flat SSA at 550nm and 3) using a spectrally-dependent SSA derived from scattering and absorption measurements. Modeled photolysis rates were compared to those measured aboard the P-3B during DISCOVER-AQ. The relationship between airborne measurements of water soluble organic carbon (WSOC) made by a Particle-Into-Liquid-Sampler (PILS), AAE470-532 and model/measurement discrepancies were explored to assess the influence of aerosol composition on photolysis rates. Additional comparisons between photolysis rates modeled with vertically-resolved aerosol optical properties and those modeled using column-average values were performed to assess the influence of aerosol vertical distribution on photolysis rates.

  8. AN ASTROMETRIC SEARCH FOR A SUB-STELLAR COMPANION OF THE M8.5 DWARF TVLM 513–46546 USING VERY LONG BASELINE INTERFEROMETRY

    SciTech Connect

    Forbrich, Jan; Berger, Edo; Reid, Mark J.

    2013-11-01

    We conducted multi-epoch very long baseline interferometry observations to search for astrometric reflex motion that would be caused by a sub-stellar companion of the M8.5 dwarf TVLM 513–46546. The observations yield an absolute parallax corresponding to a distance of 10.762 ± 0.027 pc and a proper motion of 78.09 ± 0.17 mas yr{sup –1}. The averaged flux density per epoch varies by a factor of at least three. From the absence of significant residual motion, we place an upper limit on any reflex motion caused by a companion, extending the parameter space covered by previous near-infrared direct-imaging searches. The data exclude a phase space of companion masses and orbital periods ranging from 3.8 M{sub Jup} with an orbital radius of ∼0.05 AU (and an orbital period of 16 days) to 0.3 M{sub Jup} with an orbital radius of ∼0.7 AU (and an orbital period of 710 days)

  9. Science, Technology and Mission Design for the Laser Astrometric Test of Relativity

    NASA Astrophysics Data System (ADS)

    Turyshev, Slava G.

    2006-04-01

    The Laser Astrometric Test of Relativity (LATOR) is a Michelson-Morley-type experiment designed to improve current tests of Einstein's general theory of relativity by more than four orders of magnitude. The space experiment uses laser interferometry between two laser sources placed on two small spacecraft separated by 1 degree (as seen from the Earth), whose lines of sight several times pass close by the Sun, to measure accurately the deflection of light by the solar gravitational field. The key element of the experimental design is a redundant geometry optical truss provided by a long-baseline (˜100m) Michelson stellar optical interferometer that is used to measure the angle between the two spacecraft (with accuracy of 0.1 picoradian). The three arms of the light triangle formed by three space nodes are monitored with laser metrology (accurate to ˜1 cm). By using a combination of independent time-series of highly accurate measurements of gravitational deflection of light in the immediate proximity to the Sun, along with measurements of the Shapiro time delay on the interplanetary scales, LATOR will significantly improve our knowledge of relativistic gravity in the solar system. The experiment will measure the key post-Newtonian Eddington parameter γ with accuracy of 1 part in 10^9 and will also conduct a number of other unique measurements of the gravity effects on light propagation. This primary measurement pushes to unprecedented accuracy the search for cosmologically relevant scalar-tensor theories of gravity by looking for a remnant scalar field in today's solar system. LATOR will lead to very robust advances in the tests of fundamental physics: this mission could discover a violation or extension of general relativity and/or reveal the presence of an additional long range interaction in the physical law. In this talk we will discus the science, technology and mission design for the LATOR experiment.

  10. Deep Brain Stimulation of the Pedunculopontine Tegmental Nucleus (PPN) Influences Visual Contrast Sensitivity in Human Observers

    PubMed Central

    Strumpf, Hendrik; Noesselt, Toemme; Schoenfeld, Mircea Ariel; Voges, Jürgen; Panther, Patricia; Kaufmann, Joern; Heinze, Hans-Jochen; Hopf, Jens-Max

    2016-01-01

    The parapontine nucleus of the thalamus (PPN) is a neuromodulatory midbrain structure with widespread connectivity to cortical and subcortical motor structures, as well as the spinal cord. The PPN also projects to the thalamus, including visual relay nuclei like the LGN and the pulvinar. Moreover, there is intense connectivity with sensory structures of the tegmentum in particular with the superior colliculus (SC). Given the existence and abundance of projections to visual sensory structures, it is likely that activity in the PPN has some modulatory influence on visual sensory selection. Here we address this possibility by measuring the visual discrimination performance (luminance contrast thresholds) in a group of patients with Parkinson’s Disease (PD) treated with deep-brain stimulation (DBS) of the PPN to control gait and postural motor deficits. In each patient we measured the luminance-contrast threshold of being able to discriminate an orientation-target (Gabor-grating) as a function of stimulation frequency (high 60Hz, low 8/10, no stimulation). Thresholds were determined using a standard staircase-protocol that is based on parameter estimation by sequential testing (PEST). We observed that under low frequency stimulation thresholds increased relative to no and high frequency stimulation in five out of six patients, suggesting that DBS of the PPN has a frequency-dependent impact on visual selection processes at a rather elementary perceptual level. PMID:27167979

  11. Hierarchical Observing Protocol (HOP) for Asteroids

    NASA Astrophysics Data System (ADS)

    Bowell, E.; Koehn, B. W.; Wasserman, L. H.; Muinonen, K.

    1997-07-01

    From the standpoint of orbit improvement, we seek to answer two questions: (1) When is it best or necessary to make astrometric observations of a given asteroid? (2) Which are the best asteroids to observe at a given time? Answering these questions allows one to address a third: (3) How should we best marshal and optimize the use of limited resources in making astrometric observations of asteroids? Such issues are increasing in importance as the number of observers and astrometric data mushroom. We have developed two tools necessary for implementing HOP: (1) Observability of a chosen asteroid over a chosen time interval (consult the WWW at http://asteroid.lowell.edu/cgi-bin/koehn/obs), and (2) Observing strategy required to achieve the numbering of a chosen asteroid (http://asteroid.lowell.edu/cgi-bin/koehn/obsstrat). We find that four ``rules of thumb" can be used as precepts for HOP: The first concerns the numberability of asteroids, the second the rate of increase of ephemeris uncertainty of newly discovered asteroids, the third adduces that the improvement in an asteroid's orbit is proportional to the improvement in its ephemeris uncertainty that results from making an accurate observation, and the fourth states that peaks in ephemeris uncertainty generally occur near opposition. We give examples of the use of .../obs and .../obstrat, which indicate that, during the discovery apparition, observations are needed at time intervals that increase geometrically (generally, by a factor of 3 to 5), and subsequently that one or two nights' observation per apparition suffice for an asteroid to be numbered after two or three apparitions (NEAs), three or four apparitions (MBAs), or six or more apparitions (transneptunians). We plan to create a web site for observers to make ranked lists of astrometric targets for their own locations/instrumentation, and we show how observations can be coordinated so as to assure that important targets are observed in a timely manner and

  12. How does observation uncertainty influence which stream water samples are most informative for model calibration?

    NASA Astrophysics Data System (ADS)

    Wang, Ling; van Meerveld, Ilja; Seibert, Jan

    2016-04-01

    occurred, the mixing processes were more complex and the information content of streamflow samples decreased. Therefore, for these cases, samples taken at the start or end of overflow were most informative. We, furthermore, investigated how observation errors influenced the multi-criteria calibration process. Preliminary results show that more than two samples are needed to maintain a similar simulation performance when observation errors in precipitation or streamflow are included. These results provide guidance on suitable event-based sampling strategies for different conditions.

  13. The influence of regional surface soil moisture anomalies on forest fires in Siberia observed from satellites

    NASA Astrophysics Data System (ADS)

    Bartsch, A.; Balzter, H.; George, C.

    2009-10-01

    Forest fires are frequent in the Siberian taiga and are predicted to increase in frequency as a result of increased fire risk under drought conditions, and prolonged fire seasons caused by climate change. There is, however, some uncertainty as to the extent to which drought influences forest fire frequency at a regional scale. Here, we present an analysis of satellite derived soil moisture anomaly data from ERS-1/2 (ERS: Earth Resources Satellite) scatterometer data and burned area maps from MODIS/AVHRR/ATSR (Moderate Resolution Imaging Spectroradiometer/Advanced Very High Resolution Radiometer/Along-Track Scanning Radiometer) over Central Siberia for the years 1992-2000. The purpose of this study is to investigate the relationship of remotely sensed soil moisture deviations from the long-term mean and fire within the boreal biome on a sub-continental scale. Results show that wet surface soil moisture conditions limit the extent of burned area. They can prevent the outbreak of fires but the magnitude of a negative (dry) deviation does not determine the maximum size of fire affected areas. It is known from the literature, however, that an ignition is more likely to occur under low surface wetness conditions, such as those that we observed during July and August in both permafrost and non-permafrost regions. Although the burned area under drier conditions in July is lowest over non-permafrost, the actual number of fires is as high as over continuous permafrost. Approximately 80% of all events occurred under such conditions during that month. The fire size was below 50 km2 under moist conditions. Larger burned areas have in general not been detected when the surface wetness deviation exceeded +5%.

  14. Examining rater and occasion influences in observational assessments obtained from within the clinical environment

    PubMed Central

    Kreiter, Clarence D.; Wilson, Adam B.; Humbert, Aloysius J.; Wade, Patricia A.

    2016-01-01

    Background When ratings of student performance within the clerkship consist of a variable number of ratings per clinical teacher (rater), an important measurement question arises regarding how to combine such ratings to accurately summarize performance. As previous G studies have not estimated the independent influence of occasion and rater facets in observational ratings within the clinic, this study was designed to provide estimates of these two sources of error. Method During 2 years of an emergency medicine clerkship at a large midwestern university, 592 students were evaluated an average of 15.9 times. Ratings were performed at the end of clinical shifts, and students often received multiple ratings from the same rater. A completely nested G study model (occasion: rater: person) was used to analyze sampled rating data. Results The variance component (VC) related to occasion was small relative to the VC associated with rater. The D study clearly demonstrates that having a preceptor rate a student on multiple occasions does not substantially enhance the reliability of a clerkship performance summary score. Conclusions Although further research is needed, it is clear that case-specific factors do not explain the low correlation between ratings and that having one or two raters repeatedly rate a student on different occasions/cases is unlikely to yield a reliable mean score. This research suggests that it may be more efficient to have a preceptor rate a student just once. However, when multiple ratings from a single preceptor are available for a student, it is recommended that a mean of the preceptor's ratings be used to calculate the student's overall mean performance score. PMID:26925540

  15. Observations of muslim physicians regarding the influence of religion on health and their clinical approach.

    PubMed

    Al-Yousefi, Nada A

    2012-06-01

    Although most patients report wanting their physicians to address the religious aspects of their lives, most physicians do not initiate questions concerning religion with their patients. Although religion plays a major role in every aspect of the life of a Muslim, most of the data on the role of religion in health have been conducted in populations that are predominantly non-Muslim. The objectives of this study were to assess Muslim physicians' beliefs and behaviours regarding religious discussions in clinical practice and to understand the factors that facilitate or impede discussion of religion in clinical settings. The study is based on a cross-sectional survey. Muslim physicians working in a tertiary care hospital in Saudi Arabia were invited to complete a questionnaire that included demographic data; intrinsic level of religiosity; beliefs about the impact of religion on health; and observations, attitudes, behaviours, and barriers to attending to patients' religious needs. Out of 225 physicians, 91% agreed that religion had a positive influence on health, but 62.2% thought that religion could lead to the refusal of medically indicated therapy. Over half of the physicians queried never asked about religious issues. Family physicians were more likely to initiate religious discussions, and physicians with high intrinsic religiosity were more likely to share their own religious views. Residents and staff physicians tended to avoid such discussions. The study results highlight the fact that many physicians do not address patients' religious issues and that there is a need to clarify ethically sound means by which to address such needs in Islamic countries. Medical institutions should work to improve the capacity of medical personnel to appropriately address religious issues. The training of clinical religious advisors is a promising solution to this dilemma.

  16. Stellar, Remnant, Planetary, and Dark-Object Masses from Astrometric Microlensing

    NASA Technical Reports Server (NTRS)

    Gould, Andrew P.; Bennett, David P.; Boden, Andrew; Depoy, Darren L.; Gaudi, Scott B.; Griest, Kim; Han, Cheongho; Paczynski, Bohdan; Reid, I. Neill

    2004-01-01

    The primary goal of our project is to make a complete census of the stellar population of the Galaxy. We are broadening the term stellar here to include both ordinary stars and dark stars. Ordinary stars, burning their nuclear fuel and shining, can perhaps best be studied with traditional astronomical techniques, but dark stars, by which we include old brown dwarfs, black holes, old white dwarfs, neutron stars, and perhaps exotic objects such as mirror matter stars or primordial black holes, can only be studied by their gravitational effects. Traditionally, these objects have been probed in binaries, and thus selected in a way that may or may not be representative of their respective field populations. The only way to examine the field population of these stars is through microlensing, the deflection of light from a visible star in the background by an object (dark or not) in the foreground. When lensed, there are two images of the background star. Although these images cannot be resolved when the lens has a stellar mass, the lensing effect can be detected in two ways: photometrically, i.e. by measuring the magnification of the source by the lens, and astrometrically, i.e. by measuring the shift in the centroid of the two images. Photometric microlensing experiments have detected hundreds of microlensing events over the past decade. Despite its successes, photometric microlensing has so far been somewhat frustrating because these events are difficult to interpret. Almost nothing is known about the masses of individual lenses and very little is known about the statistical properties of the lenses treated as a whole, such as their average mass. Although probably over 100 of the lenses are in fact dark objects, we can't determine which they are, let alone investigate finer details such as what their masses are, and where they are in the Galaxy. With SIM, we will break the microlensing degeneracy, and allow detailed interpretation of individual microlensing events. We

  17. Advancing fundamental physics with the Laser Astrometric Test of Relativity. The LATOR mission

    NASA Astrophysics Data System (ADS)

    Turyshev, S. G.; Shao, M.; Nordtvedt, K. L.; Dittus, H.; Laemmerzahl, C.; Theil, S.; Salomon, C.; Reynaud, S.; Damour, T.; Johann, U.; Bouyer, P.; Touboul, P.; Foulon, B.; Bertolami, O.; Páramos, J.

    2009-12-01

    The Laser Astrometric Test of Relativity (LATOR) is an experiment designed to test the metric nature of gravitation—a fundamental postulate of the Einstein’s general theory of relativity. The key element of LATOR is a geometric redundancy provided by the long-baseline optical interferometry and interplanetary laser ranging. By using a combination of independent time-series of gravitational deflection of light in the immediate proximity to the Sun, along with measurements of the Shapiro time delay on interplanetary scales (to a precision respectively better than 0.1 picoradians and 1 cm), LATOR will significantly improve our knowledge of relativistic gravity and cosmology. The primary mission objective is i) to measure the key post-Newtonian Eddington parameter γ with accuracy of a part in 109. 1/2(1-γ) is a direct measure for presence of a new interaction in gravitational theory, and, in its search, LATOR goes a factor 30,000 beyond the present best result, Cassini’s 2003 test. Other mission objectives include: ii) first measurement of gravity’s non-linear effects on light to ˜0.01% accuracy; including both the traditional Eddington β parameter and also the spatial metric’s 2nd order potential contribution (never measured before); iii) direct measurement of the solar quadrupole moment J 2 (currently unavailable) to accuracy of a part in 200 of its expected size of ≃ 10 - 7; iv) direct measurement of the “frame-dragging” effect on light due to the Sun’s rotational gravitomagnetic field, to 0.1% accuracy. LATOR’s primary measurement pushes to unprecedented accuracy the search for cosmologically relevant scalar-tensor theories of gravity by looking for a remnant scalar field in today’s solar system. We discuss the science objectives of the mission, its technology, mission and optical designs, as well as expected performance of this experiment. LATOR will lead to very robust advances in the tests of fundamental physics: this mission could

  18. The Growth of Hydrological Understanding: Observations, Theories and Societal Influences that have Shaped the Field

    NASA Astrophysics Data System (ADS)

    Sivapalan, M.

    2009-12-01

    “Progress in science depends on new techniques, new discoveries and new ideas, probably in that order.” Sydney Brenner (1980). ______________ Science never progresses smoothly or uniformly on all fronts. History of science tells us that progress cannot be meticulously planned, and elaborate plans do not always end up at their intended targets. Breakthroughs tend to happen by themselves through human ingenuity, which cannot be precisely predicted nor pre-planned. All sciences go through periods of euphoria, stagnation, pessimism and then recovery. New theories/ideas, or new measurements/data sources or new analysis techniques have alternated in generating vital breakthroughs. Progress in science is also not immune from other societal and technological influences, including wars. Hydrology is no exception. However, at this point in time it is not clear if hydrologic science is limited by data (and our ability to measure or monitor water cycle dynamics) or by theories or vital ideas that can help us understand how the hydrologic system works and will evolve. We can map the surface of Mars in search of the presence of water, but cannot close the water balance here on Earth. We have instruments that can help us observe pore scale processes in the laboratory, but still cannot predict how these will evolve in time in real places, at much larger scales. We are dealing with a complex adaptive system that evolves at all time and space scales. There is a great need for data to close the water balance, but there is an even greater need to understand and predict in all places in such a dynamic environment. It sometimes happens that every time a new measurement technology or data analysis technique is introduced we get excited and pour enormous resources on their development only to be disappointed that we have gone down a narrow alley. In spite of occasional breakthroughs in our measurement capability, the bigger challenge remains our inability to extrapolate beyond the

  19. Observations of Spacecraft Targets, Unusual Asteroids, and Targets of Opportunity

    NASA Technical Reports Server (NTRS)

    Tholen, David J.

    1998-01-01

    Obtain physical and astrometric observations of: (1) spacecraft targets to support mission operations; (2) known asteroids with unusual orbits to help determine their origin; and (3) newly discovered minor planets (including both asteroids and comets) that represent a particular opportunity to add significant new knowledge of the Solar System.

  20. Distortion of the pixel grid in HST WFC3/UVIS and ACS/WFC CCD detectors and its astrometric correction

    NASA Astrophysics Data System (ADS)

    Kozhurina-Platais, Vera; Mackenty, John; Golimovski, David; Sirianni, Marco; Borncamp, David; Anderson, Jay; Grogin, Norman

    2016-07-01

    The geometric distortion of the CCD detectors used in the Hubble Space TelescopeWide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) instruments is characterized by both large and fine-scale distortions. The large-scale distortion, due to the complexity of the HST optical assembly, can be modeled by a high-order polynomial. The majority of fine-distortion is inherent to the CCD detectors themselves, which manifests itself as fine-scale, correlated systematic offsets in the residuals from the best-fit polynomial solution. Such systematic offsets across the CCD chip introduce astrometric errors at the level of about 0.1 pix (up to 1.5 μm within the 15 μm pixels). These fine-scale and low-amplitude distortions apparently arise from the spatial irregularities in the pixel grid. For the WFC3/UVIS CCD chips, there is a clear pattern of periodic skew in the lithographic-mask stencil imprinted onto the detector. Similar irregularities in the pixel grid of ACS/WFC CCD chips are even more pronounced by the narrow (68×2048 pixel) lithographic-mask stencil. To remove these distortions, a 2-D correction in the form of a look-up table has been developed using HST images of very dense stellar fields. The post-correction of fine-scale astrometric errors can be removed down to the level of 0.01 pix (0.15 μm) or better.

  1. Watching for Washback: Observing the Influence of the International English Language Testing System Academic Writing Test in the Classroom

    ERIC Educational Resources Information Center

    Green, Anthony

    2006-01-01

    Previous studies of washback (the influence of a test on teaching and learning) have provided insights into the complexity of educational systems and test use, especially in relation to the role of the teacher, but have given insufficient attention to the relationship between observed practices and test design features. In this article a washback…

  2. A Computer-Based Observational Assessment of the Teaching Behaviours that Influence Motivational Climate in Physical Education

    ERIC Educational Resources Information Center

    Morgan, Kevin; Sproule, John; Weigand, Daniel; Carpenter, Paul

    2005-01-01

    The primary purpose of this study was to use an established behavioural taxonomy (Ames, 1992b) as a computer-based observational coding system to assess the teaching behaviours that influence perceptions of the motivational climate in Physical Education (PE). The secondary purpose was to determine the degree of congruence between the behavioural…

  3. Reprocessing of GPS observations: influence of calibration models of antenna/radome combinations on permanent GPS station coordinates

    NASA Astrophysics Data System (ADS)

    Ishchenko, Marina

    2012-05-01

    Observations of the GPS satellites at permanent stations located in Ukraine and in the Eastern Europe were reprocessed at the GPS Analysis Center of the Main Astronomical Observatory with Bernese GPS Software ver. 5.0. The effect of influence of relative and absolute phase center variations of antenna/radome combinations to determination coordinates of permanent GPS stations are considered.

  4. The Functional Equivalence between Movement Imagery, Observation, and Execution Influences Imagery Ability

    ERIC Educational Resources Information Center

    Williams, Sarah E.; Cumming, Jennifer; Edwards, Martin G.

    2011-01-01

    Based on literature identifying movement imagery, observation, and execution to elicit similar areas of neural activity, research has demonstrated that movement imagery and observation successfully prime movement execution. To investigate whether movement and observation could prime ease of imaging from an external visual-imagery perspective, an…

  5. Witnessed aggression: influence of an observer's sex and values on aggressive responding.

    PubMed

    Borden, R J

    1975-03-01

    Two experiments investigated the effects of the presence of an observer on aggressive responding. In one experiment, male subjects observed by a male aggressed more than those observed by a female. When the male observer was removed from the situation, subjects' level of aggressiveness more closely matched the level manifested by the opponent. The removal of the female observer had little effect on the subjects' behavior. In the second experiment, the male or female observer of the subject's behavior was disguised as a member of an organization with explicit values (aggressive or pacifistic) regarding the use of aggression. In this case, significant differences in aggression were associated with the observer's values but not the observer's sex. Following the departure of the observer, the shock settings of subjects in the two aggressive-value observer groups showed a signifcant decrease. The average shock setting of subjects in the two pacifistic-value observer groups remained at about the same level. In sum, the results indicated that the subjects' aggressive behavior was apparently a function of their expectations of approval for such behavior, based on the inferred or explicit values of the observer. The results were further discussed in terms of social learning theory.

  6. Gravity and observer's body orientation influence the visual perception of human body postures.

    PubMed

    Lopez, Christophe; Bachofner, Christelle; Mercier, Manuel; Blanke, Olaf

    2009-05-04

    Since human behavior and perception have evolved within the Earth's gravitational field, humans possess an internal model of gravity. Although gravity is known to influence the visual perception of moving objects, the evidence is less clear concerning the visual perception of static objects. We investigated whether a visual judgment of the stability of human body postures (static postures of a human standing on a platform and tilted in the roll plane) may also be influenced by gravity and by the participant's orientation. Pictures of human body postures were presented in different orientations with respect to gravity and the participant's body. The participant's body was aligned to gravity (upright) or not (lying on one side). Participants performed stability judgments with respect to the platform, imagining that gravity operates in the direction indicated by the platform (that was or was not concordant with physical gravity). Such visual judgments were influenced by the picture's orientation with respect to physical gravity. When pictures were tilted by 90 degrees with respect to physical gravity, the human postures that were tilted toward physical gravity (down) were perceived as more unstable than similar postures tilted away from physical gravity (up). Stability judgments were also influenced by the picture's orientation with respect to the participant's body. This indicates that gravity and the participant's body position may influence the visual perception of static objects.

  7. First Results of Venus Express Spacecraft Observations with Wettzell

    NASA Technical Reports Server (NTRS)

    Calves, Guifre Molera; Wagner, Jan; Neidhardt, Alexander; Kronschnabl, Gerhard; Ayucar, Miguel Perez; Cimo, Giuseppe; Pogrebenko, Sergei

    2010-01-01

    The ESA Venus Express spacecraft was observed at X-band with the Wettzell radio telescope in October-December 2009 in the framework of an assessment study of the possible contribution of the European VLBI Network to the upcoming ESA deep space missions. A major goal of these observations was to develop and test the scheduling, data capture, transfer, processing, and analysis pipeline. Recorded data were transferred from Wettzell to Metsahovi for processing, and the processed data were sent from Mets ahovi to JIVE for analysis. A turnover time of 24 hours from observations to analysis results was achieved. The high dynamic range of the detections allowed us to achieve a milliHz level of spectral resolution accuracy and to extract the phase of the spacecraft signal carrier line. Several physical parameters can be determined from these observational results with more observational data collected. Among other important results, the measured phase fluctuations of the carrier line at different time scales can be used to determine the influence of the solar wind plasma density fluctuations on the accuracy of the astrometric VLBI observations.

  8. Direct laboratory observation of fluid distribution and its influence on acoustic properties of patchy saturated rocks

    NASA Astrophysics Data System (ADS)

    Lebedev, M.; Clennell, B.; Pervukhina, M.; Shulakova, V.; Mueller, T.; Gurevich, B.

    2009-04-01

    Porous rocks in hydrocarbon reservoirs are often saturated with a mixture of two or more fluids. Interpretation of exploration seismograms requires understanding of the relationship between distribution of the fluids patches and acoustic properties of rocks. The sizes of patches as well as their distribution affect significantly the seismic response. If the size of the fluid patch is smaller than the diffusion wavelength then pressure equilibration is achieved and the bulk modulus of the rock saturated with a mixture is defined by the Gassmann equations (Gassmann, 1951) with the saturation-weighted average of the fluid bulk modulus given by Wood's law (Wood, 1955, Mavko et al., 1998). If the fluid patch size is much larger than the diffusion wavelength then there is no pressure communication between different patches. In this case, fluid-flow effects can be neglected and the overall rock may be considered equivalent to an elastic composite material consisting of homogeneous parts whose properties are given by Gassmann theory with Hill's equation for the bulk modulus (Hill, 1963, Mavko et al., 1998). At intermediate values of fluid saturation the velocity-saturation relationship is significantly affected by the fluid patch distribution. In order to get an improved understanding of factors influencing the patch distribution and the resulting seismic wave response we performed simultaneous measurements of P-wave velocities and rock sample CT imaging. The CT imaging allows us to map the fluid distribution inside rock sample during saturation (water imbibition). We compare the experimental results with theoretical predictions. In this paper we will present results of simultaneous measurements of longitudinal wave velocities and imaging mapping of fluid distribution inside rock sample during sample saturation. We will report results of two kinds of experiments: "dynamic" and "quasi static" saturation. In both experiments Casino Cores Otway Basin sandstone, Australia core

  9. The Influence of Personality on Neural Mechanisms of Observational Fear and Reward Learning

    ERIC Educational Resources Information Center

    Hooker, Christine I.; Verosky, Sara C.; Miyakawa, Asako; Knight, Robert T.; D'Esposito, Mark

    2008-01-01

    Fear and reward learning can occur through direct experience or observation. Both channels can enhance survival or create maladaptive behavior. We used fMRI to isolate neural mechanisms of observational fear and reward learning and investigate whether neural response varied according to individual differences in neuroticism and extraversion.…

  10. Top-down influences on ambiguous perception: the role of stable and transient states of the observer

    PubMed Central

    Scocchia, Lisa; Valsecchi, Matteo; Triesch, Jochen

    2014-01-01

    The world as it appears to the viewer is the result of a complex process of inference performed by the brain. The validity of this apparently counter-intuitive assertion becomes evident whenever we face noisy, feeble or ambiguous visual stimulation: in these conditions, the state of the observer may play a decisive role in determining what is currently perceived. On this background, ambiguous perception and its amenability to top-down influences can be employed as an empirical paradigm to explore the principles of perception. Here we offer an overview of both classical and recent contributions on how stable and transient states of the observer can impact ambiguous perception. As to the influence of the stable states of the observer, we show that what is currently perceived can be influenced (1) by cognitive and affective aspects, such as meaning, prior knowledge, motivation, and emotional content and (2) by individual differences, such as gender, handedness, genetic inheritance, clinical conditions, and personality traits and by (3) learning and conditioning. As to the impact of transient states of the observer, we outline the effects of (4) attention and (5) voluntary control, which have attracted much empirical work along the history of ambiguous perception. In the huge literature on the topic we trace a difference between the observer's ability to control dominance (i.e., the maintenance of a specific percept in visual awareness) and reversal rate (i.e., the switching between two alternative percepts). Other transient states of the observer that have more recently drawn researchers' attention regard (6) the effects of imagery and visual working memory. (7) Furthermore, we describe the transient effects of prior history of perceptual dominance. (8) Finally, we address the currently available computational models of ambiguous perception and how they can take into account the crucial share played by the state of the observer in perceiving ambiguous displays. PMID

  11. Observations of Three-Dimensional Radiative Effects that Influence Satellite Retrievals of Cloud Properties

    NASA Technical Reports Server (NTRS)

    Varnai, Tamas; Marshak, Alexander; Lau, William K. M. (Technical Monitor)

    2001-01-01

    This paper examines three-dimensional (3D) radiative effects, which arise from horizontal radiative interactions between areas that have different cloud properties. Earlier studies have argued that these effects can cause significant uncertainties in current satellite retrievals of cloud properties, because the retrievals rely on one-dimensional (1D) theory and do not consider the effects of horizontal changes in cloud properties. This study addresses two questions: which retrieved cloud properties are influenced by 3D radiative effects, and where 3D effects tend to occur? The influence of 3D effects is detected from the wayside illumination and shadowing make clouds appear asymmetric: Areas appear brighter if the cloud top surface is tilted toward, rather than away from, the Sun. The analysis of 30 images by the Moderate Resolution Imaging Spectroradiometer (MODIS) reveals that retrievals of cloud optical thickness and cloud water content are most influenced by 3D effects, whereas retrievals of cloud particle size are much less affected. The results also indicate that while 3D effects are strongest at cloud edges, cloud top variability in cloud interiors, even in overcast regions, also produces considerable 3D effects. Finally, significant 3D effects are found in a wide variety of situations, ranging from thin clouds to thick ones and from low clouds to high ones.

  12. Motion trajectory information and agency influence motor learning during observational practice.

    PubMed

    Roberts, James W; Bennett, Simon J; Elliott, Digby; Hayes, Spencer J

    2015-07-01

    Fundamental to performing actions is the acquisition of motor behaviours. We examined if motor learning, through observational practice, occurs by viewing an agent displaying naturalistic or constant velocity, and whether motion trajectory, as opposed to end-state, information is required. We also investigated if observational practice is sensitive to belief regarding the origin of an agent. Participants had to learn a novel movement sequence timing task, which required upper-limb movements to a series of targets within a pre-specified absolute and relative time goal. Experiment 1 showed learning after viewing naturalistic and constant velocity, but not end-state information. For Experiment 2, in addition to learning the movement sequence, participants observed a series of movement stimuli that were either the trained or new sequences and asked to rate their confidence on whether the observed sequence was the same or different to observational practice. The results indicated that agency belief modulates how naturalistic and constant velocity is coded. This indicated that the processes associated with belief are part of an interpretative predictive coding system where the association between belief and observed motion is determined. When motion is constant velocity, or believed to be computer-generated, coding occurs through top-down processes. When motion is naturalistic velocity, and believed to be human-generated, it is most likely coded by gaining access to bottom-up sensorimotor processes in the action-observation network.

  13. Goal anticipation during action observation is influenced by synonymous action capabilities, a puzzling developmental study.

    PubMed

    Gredebäck, Gustaf; Kochukhova, Olga

    2010-04-01

    Eighteen- and 25-month-old human toddlers' ability to manually solve a puzzle and their ability to anticipate the goal during observation of similar actions were investigated. Results demonstrate that goal anticipation during action observation is dependent on manual ability, both on a group level (only 25-month-olds solved the manual task and anticipated the goal during observation) and individually within the older age group (r (xy) = 0.53). These findings suggests a connection between manual ability and the ability to anticipate the goal of others' actions in toddlers, in accordance with the direct matching hypothesis. PMID:20041233

  14. Observations of deep convective influence on stratospheric water vapor and its isotopic composition

    NASA Astrophysics Data System (ADS)

    Hanisco, Thomas F.; Moyer, E. J.; Weinstock, E. M.; St. Clair, J. M.; Sayres, D. S.; Smith, J. B.; Lockwood, R.; Anderson, J. G.; Dessler, A. E.; Keutsch, F. N.; Spackman, J. R.; Read, W. G.; Bui, T. P.

    2007-02-01

    In situ observations of H2O and HDO in the midlatitude stratosphere are used to evaluate the role of convection in determining the stratospheric water budget. The observations show that water vapor in the overworld stratosphere (potential temperature > 380 K) is isotopically heavier than expected. Measurements in an airmass with anomalously high concentrations of water vapor show isotopic water signatures that are characteristic of evaporated ice lofted from the troposphere during convective storms. Observed H2O and HDO concentrations in the plume of enhanced water and in the background stratosphere suggest that extratropical convection can account for a significant fraction of the observed water vapor in the summertime overworld stratosphere above the mid-North American continent.

  15. Observed Influence of Amazon rainfall on the Atlantic ITCZ and Atlantic Nino

    NASA Astrophysics Data System (ADS)

    Fu, R.; Wang, H.

    2007-05-01

    Most of previous studies on climate variabilities of the tropical Atlantic Ocean have been focused on remote and internal oceanic processes or atmosphere-ocean interaction. In comparison, relatively few studies have examined the influences from adjacent continents, especially the influence of rainfall over the South American continent. Using the Tropical Rainfall Measuring Mission (TRMM) daily rain-rate dada, the QuikSCAT ocean surface wind and PIRATA buoy data, we have found that convection developed over the Amazonia appears to propagate eastward across the Atlantic and then into Africa. Such changes modulate the intensity and location of the convection within the Atlantic ITCZ and result in a zonal oscillation of the ITCZ between the west and east equatorial Atlantic Ocean. The eastward propagating disturbances appear to be an atmospheric Kelvin wave with a period of 6 to 7 days and a phase speed of around 12 m s-1. Such convectively coupled Kelvin wave is particularly strong during boreal spring and dominates the synoptic variations of the lower and upper troposphere winds. Our results further suggest that the interannual changes of these convective coupled Kelvin waves have an important influence on trigging the onset of Atlantic Ninos. In particular, anomalously late northward withdraw of the South American rainfall in boreal spring lead to stronger Kelvin wave activities and stronger westerly wind anomalies in the western equatorial Atlantic. The latter triggers a change of the slope of the thermocline in the equatorial Atlantic Ocean and induces sea surface temperature anomalies in the eastern Atlantic. These changes contribute to the onset of the Atlantic Nino in earlier boreal summer.

  16. The Influence of Downscaling Models and Observations on Future Hydrochemistry Reponses of Forest Watersheds

    NASA Astrophysics Data System (ADS)

    Pourmokhtarian, A.; Driscoll, C. T.; Campbell, J. L.; Hayhoe, K.; Stoner, A. M. K.

    2014-12-01

    Most projections of climate change impacts on ecosystems rely on multiple climate model projections, but utilize only one downscaling approach trained on one set of observations. Here, we explore the extent to which modeled biogeochemical responses to changing climate are affected by the selection of the climate downscaling method and training observations used in the complex mountainous terrain of the Hubbard Brook Experimental Forest, New Hampshire, USA. We evaluated three different downscaling methods: the monthly delta method (or the "change factor method"); monthly quantile mapping (Bias Correction-Spatial Disaggregation, or BCSD); and daily quantile regression (Asynchronous Regional Regression Model, or ARRM). Additionally, we trained outputs, from four AOGCMs (CCSM3, HadCM3, PCM, and GFDL-CM2) driven by higher (A1fi) and lower (B1) future emission scenarios, on two sets of observations (1/8th degree resolution grid vs. individual weather station) to generate the high-resolution climate input for the hydrochemical model PnET-BGC (ensemble of 48 runs). The choice of downscaling approach and spatial resolution of the observations used to train the downscaling model both had a major impact on modeled soil moisture and streamflow which in turn affected forest growth, net nitrification and stream chemistry. Specifically, the delta method, the simplest downscaling approach evaluated, was highly sensitive to the observations used, resulting in projections that were significantly different than those produced with the BCSD and ARRM methods. Using spatially smoothed gridded observations and/or methods that do not resolve sub-monthly shifts in the distribution of temperature and/or precipitation can produce poor results in model applications run at higher temporal and/or spatial resolutions. These results underscore the importance of carefully considering the observations and downscaling method used to generate climate change projections for smaller scale modeling

  17. The magnitude of genetic and environmental influences on parental and observational measures of behavioral inhibition and shyness in toddlerhood.

    PubMed

    Smith, Ashley K; Rhee, Soo H; Corley, Robin P; Friedman, Naomi P; Hewitt, John K; Robinson, Joann L

    2012-09-01

    Behavioral inhibition is a temperamental trait that refers to slow approach to novel items, shyness towards new people, and fearfulness in new situations, and individuals may develop inhibited response styles by as early as 2 years of age. There are important methodological considerations in the assessment of early temperament, with parental report and observational measures providing both corroborative and unique data. The present study examined behavioral inhibition measured by parental report and observational measures in a genetically informative sample to delineate the agreement between the methods and the uniqueness of each method, and to estimate the magnitude of genetic and environmental influences on the common and unique variance. The biometric, psychometric, and rater bias models were conducted to study the covariance between measurement modalities. Overall, the results suggested a common phenotype was assessed by both parents and observers. The latent phenotype underlying parental and observational measures of behavioral inhibition was moderately to substantially heritable.

  18. Global dynamic topography observations reveal limited influence of large-scale mantle flow

    NASA Astrophysics Data System (ADS)

    Hoggard, M. J.; White, N.; Al-Attar, D.

    2016-06-01

    Convective circulation of the Earth's mantle maintains some fraction of surface topography that varies with space and time. Most predictive models show that this dynamic topography has peak amplitudes of about +/-2 km, dominated by wavelengths of 104 km. Here, we test these models against our comprehensive observational database of 2,120 spot measurements of dynamic topography that were determined by analysing oceanic seismic surveys. These accurate measurements have typical peak amplitudes of +/-1 km and wavelengths of approximately 103 km, and are combined with limited continental constraints to generate a global spherical harmonic model, the robustness of which has been carefully tested and benchmarked. Our power spectral analysis reveals significant discrepancies between observed and predicted dynamic topography. At longer wavelengths (such as 104 km), observed dynamic topography has peak amplitudes of about +/-500 m. At shorter wavelengths (such as 103 km), significant dynamic topography is still observed. We show that these discrepancies can be explained if short-wavelength dynamic topography is generated by temperature-driven density anomalies within a sub-plate asthenospheric channel. Stratigraphic observations from adjacent continental margins show that these dynamic topographic signals evolve quickly with time. More rapid temporal and spatial changes in vertical displacement of the Earth's surface have direct consequences for fields as diverse as mantle flow, oceanic circulation and long-term climate change.

  19. A novel opinion dynamics model based on expanded observation ranges and individuals’ social influences in social networks

    NASA Astrophysics Data System (ADS)

    Diao, Su-Meng; Liu, Yun; Zeng, Qing-An; Luo, Gui-Xun; Xiong, Fei

    2014-12-01

    In this paper, we propose an opinion dynamics model in order to investigate opinion evolution and interactions and the behavior of individuals. By introducing social influence and its feedback mechanism, the proposed model can highlight the heterogeneity of individuals and reproduce realistic online opinion interactions. It can also expand the observation range of affected individuals. Combining psychological studies on the social impact of majorities and minorities, affected individuals update their opinions by balancing social impact from both supporters and opponents. It can be seen that complete consensus is not always obtained. When the initial density of either side is greater than 0.8, the enormous imbalance leads to complete consensus. Otherwise, opinion clusters consisting of a set of tightly connected individuals who hold similar opinions appear. Moreover, a tradeoff is discovered between high interaction intensity and low stability with regard to observation ranges. The intensity of each interaction is negatively correlated with observation range, while the stability of each individual’s opinion positively affects the correlation. Furthermore, the proposed model presents the power-law properties in the distribution of individuals’ social influences, which is in agreement with people’s daily cognition. Additionally, it is proven that the initial distribution of individuals’ social influences has little effect on the evolution.

  20. Methods of use and presentation of the accurate astrometric data based on the modern terrestrial and celestial reference systems

    NASA Astrophysics Data System (ADS)

    Sekowski, M.; Krynski, J.

    2012-12-01

    The increasing precision of the modern astrometric data as well as changes from the introduction of a new paradigm for the relations of terrestrial and celestial systems, forces the changes in methods of the usage and presentation of the data. The paper presents the efforts undertaken to satisfy these needs in the 'Rocznik Astronomiczny'. Among the issues under consideration are: 1) identification and analysis of the sources of problems with interpolation of the high accuracy data; 2) reviewing the used interpolation methods; 3) development of the new methods of presenting of the high accuracy data, allowing their proper interpolation; 4) research on the need and the possibility to redefine the Besselian Numbers algorithm in calculations of the apparent places, to the form in which it could be used in the new paradigm (CIP/CIO).

  1. Influence of biomass aerosol on precipitation over the Central Amazon: an observational study

    NASA Astrophysics Data System (ADS)

    Gonçalves, W. A.; Machado, L. A. T.; Kirstetter, P.-E.

    2015-06-01

    Understanding the influence of biomass burning aerosol on clouds and precipitation in the Amazon is key to reducing uncertainties in simulations of climate change scenarios with regard to deforestation fires. Here, we associate rainfall characteristics obtained from an S-band radar in the Amazon with in situ measurements of biomass burning aerosol for the entire year of 2009. The most important results were obtained during the dry season (July-December). The results indicate that the influence of aerosol on precipitating systems is modulated by the atmospheric degree of instability. For less unstable atmospheres, the higher the aerosol concentration is, the lower the precipitation is over the region. In contrast, for more unstable cases, higher concentrations of black carbon are associated with greater precipitation, increased ice content, and larger rain cells; this finding suggests an association with long-lived systems. The results presented are statistically significant. However, due to limitations imposed by the available data set, important features, such as the contribution of each mechanism to the rainfall suppression, need further investigation. Regional climate model simulations with aircraft and radar measurements would help clarify these questions.

  2. Observational evidence of the influence of Antarctic stratospheric ozone variability on middle atmosphere dynamics

    NASA Astrophysics Data System (ADS)

    Venkateswara Rao, N.; Espy, P. J.; Hibbins, R. E.; Fritts, D. C.; Kavanagh, A. J.

    2015-10-01

    Modeling results have suggested that the circulation of the stratosphere and mesosphere in spring is strongly affected by the perturbations in heating induced by the Antarctic ozone hole. Here using both mesospheric MF radar wind observations from Rothera Antarctica (67°S, 68°W) as well as stratospheric analysis data, we present observational evidence that the stratospheric and mesospheric wind strengths are highly anti-correlated, and show their largest variability in November. We find that these changes are related to the total amount of ozone loss that occurs during the Antarctic spring ozone hole and particularly with the ozone gradients that develop between 57.5°S and 77.5°S. The results show that with increasing ozone loss during spring, winter conditions in the stratosphere and mesosphere persist longer into the summer. These results are discussed in the light of observations of the onset and duration of the Antarctic polar mesospheric cloud season.

  3. Implications of cavity, topographic and geologic influences on tilt and strain observations

    NASA Technical Reports Server (NTRS)

    Harrison, J. C.

    1978-01-01

    Tilt and strain observations are importantly (pathologically at the 100%, typically at the few 10s% level) affected by cavities, topography, and geological inhomogenities; gravity observation are practically unaffected. The traditional earth tide observatory and abandoned mine or tunnel is a very poor place to measure body tides because of the complicated cavities, topography and geology. Instead, the ideal site for observing the body tide is in flat terrain with horizontally layered, mechanically homogeneous geology. Strain will be measured with long surface- or trench-mounted laser strain meters and tilt with long, surface- or trench mounted liquid levels, or with borehole tiltmeters. Horizontal geological discontinuities can produce large perturbations of the tilt and strain tides, and these perturbations, using the known homogeneous tidal strains and tilts, can be used in exploring local structure in favorable cases and, through possible time variations of tidal admittances, in predicting earthquakes.

  4. Adolescent, Parent, and Observer Perceptions of Parenting: Genetic and Environmental Influences on Shared and Distinct Perceptions.

    ERIC Educational Resources Information Center

    Feinberg, Mark; Neiderhiser, Jenae; Howe, George; Hetherington, E. Mavis

    2001-01-01

    Examined low interrater agreement by decomposing common and unique variance among parent, adolescent, and observer reports of parental warmth and negativity into genetic and environmental factors. Model-fitting analyses findings generally supported predictions for warmth and negativity at Family and Individual levels. At the Social level, genetic…

  5. The influence of visual perspective on the somatosensory steady-state response during pain observation

    PubMed Central

    Canizales, Dora L.; Voisin, Julien I. A.; Michon, Pierre-Emmanuel; Roy, Marc-André; Jackson, Philip L.

    2013-01-01

    The observation and evaluation of other’s pain activate part of the neuronal network involved in the actual experience of pain, including those regions subserving the sensori-discriminative dimension of pain. This was largely interpreted as evidence showing that part of the painful experience can be shared vicariously. Here, we investigated the effect of the visual perspective from which other people’s pain is seen on the cortical response to continuous 25 Hz non-painful somatosensory stimulation (somatosensory steady-state response: SSSR). Based on the shared representation framework, we expected first-person visual perspective (1PP) to yield more changes in cortical activity than third-person visual perspective (3PP) during pain observation. Twenty healthy adults were instructed to rate a series of pseudo-dynamic pictures depicting hands in either painful or non-painful scenarios, presented either in 1PP (0–45° angle) or 3PP (180° angle), while changes in brain activity was measured with a 128-electode EEG system. The ratings demonstrated that the same scenarios were rated on average as more painful when observed from the 1PP than from the 3PP. As expected from previous works, the SSSR response was decreased after stimulus onset over the left caudal part of the parieto-central cortex, contralateral to the stimulation side. Moreover, the difference between the SSSR was of greater amplitude when the painful situations were presented from the 1PP compared to the 3PP. Together, these results suggest that a visuospatial congruence between the viewer and the observed scenarios is associated with both a higher subjective evaluation of pain and an increased modulation in the somatosensory representation of observed pain. These findings are discussed with regards to the potential role of visual perspective in pain communication and empathy. PMID:24367323

  6. Spacebased Observations of Oceanic Influence on the Annual Variation of South American Water Balance

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy; Xie, Xiaosu; Tang, Wenqing; Zlotnicki, Victor

    2006-01-01

    The mass change of South America (SA) continent measured by the Gravity Recovery and Climate Experiment (GRACE) imposes a constraint on the uncertainties in estimating the annual variation of rainfall measured by Tropical Rain Measuring Mission (TRMM) and ocean moisture influx derived from QuikSCAT data. The approximate balance of the mass change rate with the moisture influx less climatological river discharge, in agreement with the conservation principle, bolsters not only the credibility of the spacebased measurements, but supports the characterization of ocean's influence on the annual variation of continental water balance. The annual variation of rainfall is found to be in phase with the mass change rate in the Amazon and the La Plata basins, and the moisture advection across relevant segments of the Pacific and Atlantic coasts agrees with the annual cycle of rainfall in the two basins and the Andes mountains.

  7. Boy-lovers and their influence on boys: distorted research and anecdotal observations.

    PubMed

    Brongersma, E

    1990-01-01

    A wide experience with boy-lovers has convinced the author that one can often learn more about them from reading some excellent novels than from so-called scientific studies. All too often research is unreliable because (1) it assumes pedosexual activity is a positive indicator of pedophilia; (2) no distinction is drawn between pseudo-pedophiles and real pedophiles; (3) no difference is recognized between boys and girls as partners; and (4) it is highly distorted by bias. Representative samples for research cannot be drawn from members of boy-love organizations. The incidence of violence is very low in pedophile contacts with boys. The influence can be strong in lasting relationships; it can be either wholesome or unwholesome. Within a relationship, sex is usually only a secondary element, although it can be important in sexual instruction and education. The impact of the law, the hostility of parents and the problem of the partners' inequality are discussed.

  8. Rock climbing: observations on heart rate and plasma catecholamine concentrations and the influence of oxprenolol.

    PubMed Central

    Williams, E. S.; Taggart, P.; Carruthers, M.

    1978-01-01

    Observations are presented on the electrocardiogram and plasma catecholamine concentrations of 11 healthy men monitored during two rock climbing ascents. A placebo was administered prior to the first climb and an oral dose of the beta blocking agent oxprenolol ("Trasicor") prior to the second. Mean heart rates were 166 (+/- 20.4 SD) and 120 (+/- 10.2) respectively. Median plasma adrenaline concentrations were 0.05 microgram/1 and 0.33 microgram/1 before and after the climbs following the placebo. No significant difference was observed in the adrenaline concentrations before and after climbing following oxprenolol, or of noradrenaline concentrations on either occasion. These results are interpreted as suggesting that this popular sport represents more an anxiety-type of psychological stress than a physical stress and as such is likely to increase moral fibre rather than muscle fibre. PMID:719320

  9. The Influence of Wind Turbines on Radio Astronomical Observations in Irbene

    NASA Astrophysics Data System (ADS)

    Bezrukovs, D.

    2016-04-01

    The reflection and diffraction of external communication and navigational transmitters from tall constructions and moving blades of wind turbines produce some short-pulse additional electromagnetic interference strong enough to fully disturb radio astronomical observations. The problem of short-pulse electromagnetic interference is distinctive to all radio telescopes surrounded by wind turbines. This problem became significant for Ventspils International Radio Astronomy Centre (VIRAC) after new wind park "Platene" of Winergy Ltd. was built in 2012 and radio telescopes RT-16 and RT-32 renovated and equipped with cryogenic high sensitive receivers. The paper deals with the analysis and evaluation of intensities and probabilities of short-pulse interferences produced by wind park "Platene" and its possible impact on radio astronomical observations at VIRAC radio telescopes.

  10. Influence of ocean tides on the diurnal and semidiurnal earth rotation variations from VLBI observations

    NASA Astrophysics Data System (ADS)

    Gubanov, V. S.; Kurdubov, S. L.

    2015-05-01

    The International astrogeodetic standard IERS Conventions (2010) contains a model of the diurnal and semidiurnal variations in Earth rotation parameters (ERPs), the pole coordinates and the Universal Time, arising from lunisolar tides in the world ocean. This model was constructed in the mid-1990s through a global analysis of Topex/Poseidon altimetry. The goal of this study is to try to estimate the parameters of this model by processing all the available VLBI observations on a global network of stations over the last 35 years performed within the framework of IVS (International VLBI Service) geodetic programs. The complexity of the problemlies in the fact that the sought-for corrections to the parameters of this model lie within 1 mm and, thus, are at the limit of their detectability by all currently available methods of ground-based positional measurements. This requires applying universal software packages with a high accuracy of reduction calculations and a well-developed system of controlling the simultaneous adjustment of observational data to analyze long series of VLBI observations. This study has been performed with the QUASAR software package developed at the Institute of Applied Astronomy of the Russian Academy of Sciences. Although the results obtained, on the whole, confirm a high accuracy of the basic model in the IERS Conventions (2010), statistically significant corrections that allow this model to be refined have been detected for some harmonics of the ERP variations.

  11. The influence of student characteristics on the dependability of behavioral observation data.

    PubMed

    Briesch, Amy M; Volpe, Robert J; Ferguson, Tyler David

    2014-06-01

    Although generalizability theory has been used increasingly in recent years to investigate the dependability of behavioral estimates, many of these studies have relied on use of general education populations as opposed to those students who are most likely to be referred for assessment due to problematic classroom behavior (e.g., inattention, disruption). The current study investigated the degree to which differences exist in terms of the magnitude of both variance component estimates and dependability coefficients between students nominated by their teachers for Tier 2 interventions due to classroom behavior problems and a general classroom sample (i.e., including both nominated and non-nominated students). The academic engagement levels of 16 (8 nominated, 8 non-nominated) middle school students were measured by 4 trained observers using momentary time-sampling procedures. A series of G and D studies were then conducted to determine whether the 2 groups were similar in terms of the (a) distribution of rating variance and (b) number of observations needed to achieve an adequate level of dependability. Results suggested that the behavior of students in the teacher-nominated group fluctuated more across time and that roughly twice as many observations would therefore be required to yield similar levels of dependability compared with the combined group. These findings highlight the importance of constructing samples of students that are comparable to those students with whom the measurement method is likely to be applied when conducting psychometric investigations of behavioral assessment tools.

  12. Direct observations of the influence of solution composition on magnesite dissolution

    NASA Astrophysics Data System (ADS)

    King, Helen E.; Putnis, Christine V.

    2013-05-01

    In situ observations during atomic force microscopy experiments and ex situ observations after static and flow-through experiments were used to explore the effect of three different electrolytes on magnesite (MgCO3) dissolution at pH 2. The experiments showed that the magnesite dissolution rate varied in the order NO3->Cl>SO42- when these anions were present in solution. Under the experimental conditions magnesite dissolution occurred via the removal of successive single surface layers, where changes in magnesite reactivity in the presence of different electrolytes could be observed as variations in the cycle length for the removal of one unit cell layer. The cycles began with the formation of sporadically distributed etch pits followed by the nucleation of homogeneously distributed etch pits. Coalescence of the etch pits formed isolated sections of the remnant surface, which then dissolved away. The timing of sporadic and homogeneous etch pit nucleation was constant despite the presence of different anions. However, the cycles in surface roughness and etch pit spreading rates indicate that the different anions affect step retreat rates and hence dissolution rates. Differences in magnesite reactivity can be attributed to the direct interaction of sulphate with the magnesite surface and the indirect effects of chloride and nitrate on the magnesite surface hydration and hydration of the Mg2+ ion in solution. In all experiments during the dissolution process evidence for the precipitation of a new phase was observed, either directly as precipitates forming on the magnesite surface in the AFM and after the experiments, seen in SEM analysis, or as changes in the Mg outlet concentration during flow-through experiments. EDX and Raman spectroscopy were used to analyse the composition of the precipitate and although it could not be definitively identified, considering previous observations the precipitate is most likely a hydrated Mg-carbonate phase with a MgCO3·xH2O

  13. VizieR Online Data Catalog: USNO Martian observations (Robert+, 2015)

    NASA Astrophysics Data System (ADS)

    Robert, V.; Lainey, V.; Pascu, D.; Pasewaldt, A.; Arlot, J.-E.; de Cuyper, J.-P.; Dehant, V.; Thuillot, W.

    2015-08-01

    Astrometric and measured data of Mars, Phobos and Deimos taken with the U.S. Naval Observatory 61-inch astrometric reflector and 26-inch refractor from 1967 to 1997. Astrometric (RA,DEC) positions are geocentric observed positions reduced from stars and refer to the ICRF. They were corrected for all instrumental and spherical effects, except for the light time propagation. Measured (x,y) positions are raw data of the stars and satellites. They were obtained from initial extraction from the plates, thus no instrumental or spherical effects were corrected. (x,y) positions refer to the measured center of the planet. One should select/reject available references carefully to ensure the most accurate plate constants for the reduction process. (5 data files).

  14. The joint influence of albedo and insulation on roof performance: An observational study

    DOE PAGES

    Ramamurthy, P.; Sun, T.; Rule, K.; Bou-Zeid, E.

    2015-02-23

    We focus on understanding the temperature and heat flux fields in building roofs, and how they are modulated by the interacting influences of albedo and insulation at annual, seasonal and diurnal scales. High precision heat flux plates and thermocouples were installed over multiple rooftops of varying insulation thickness and albedo in the Northeastern United States to monitor the temperature and the heat flux into and out of the roof structures for a whole year. This analysis shows that while membrane reflectivity (albedo) plays a dominant role in reducing the heat conducted inward through the roof structures during the warmer months,more » insulation thickness becomes the main roof attribute in preventing heat loss from the buildings during colder months. On a diurnal scale, the thermal state of the white roof structures fluctuated little compared to black roof structures; membrane temperature over white roofs ranged between 10 °C and 45 °C during summer months compared to black membranes that ranged between 10 °C and 80 °C. Insulation thickness, apart from reducing the heat conducted through the roof structure, also delayed the transfer of heat, owing to the thermal inertia of the insulation layer. Furthermore, this has important implications for determining the peak heating and cooling times.« less

  15. The joint influence of albedo and insulation on roof performance: An observational study

    SciTech Connect

    Ramamurthy, P.; Sun, T.; Rule, K.; Bou-Zeid, E.

    2015-02-23

    We focus on understanding the temperature and heat flux fields in building roofs, and how they are modulated by the interacting influences of albedo and insulation at annual, seasonal and diurnal scales. High precision heat flux plates and thermocouples were installed over multiple rooftops of varying insulation thickness and albedo in the Northeastern United States to monitor the temperature and the heat flux into and out of the roof structures for a whole year. This analysis shows that while membrane reflectivity (albedo) plays a dominant role in reducing the heat conducted inward through the roof structures during the warmer months, insulation thickness becomes the main roof attribute in preventing heat loss from the buildings during colder months. On a diurnal scale, the thermal state of the white roof structures fluctuated little compared to black roof structures; membrane temperature over white roofs ranged between 10 °C and 45 °C during summer months compared to black membranes that ranged between 10 °C and 80 °C. Insulation thickness, apart from reducing the heat conducted through the roof structure, also delayed the transfer of heat, owing to the thermal inertia of the insulation layer. Furthermore, this has important implications for determining the peak heating and cooling times.

  16. The influence of ionospheric thin shell height on TEC retrieval from GPS observation

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Lan; Wan, Qing-Tao; Ma, Guan-Yi; Li, Jing-Hua; Fan, Jiang-Tao

    2016-07-01

    We investigate the influence of assumed height for the thin shell ionosphere model on the Total Electron Content (TEC) derived from a small scale Global Positioning System (GPS) network. TEC and instrumental bias are determined by applying a grid-based algorithm to the data on several geomagnetically quiet days covering a 10 month period in 2006. Comparisons of TEC and instrumental bias are made among assumed heights from 250 km to 700 km with an interval of 10 km. While the TEC variations with time follow the same trend, TEC tends to increase with the height of the thin shell. The difference in TEC between heights 250 km and 700 km can be as large as ∼ 8 TECU in both daytime and nighttime. The times at which the TEC reaches its peak or valley do not vary much with the assumed heights. The instrumental biases, especially bias from the satellite, can vary irregularly with assumed height. Several satellites show a large deviation of ∼ 3 ns for heights larger than 550 km. The goodness of fit for different assumed heights is also examined. The data can be generally well-fitted for heights from 350 km to 700 km. A large deviation happens at heights lower than 350 km. Using the grid-based algorithm, there is no consensus on assumed height as related to data fitting. A thin shell height in the range 350 – 500 km can be a reasonable compromise between data fitting and peak height of the ionosphere.

  17. The influence of ionospheric thin shell height on TEC retrieval from GPS observation

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Lan; Wan, Qing-Tao; Ma, Guan-Yi; Li, Jing-Hua; Fan, Jiang-Tao

    2016-07-01

    We investigate the influence of assumed height for the thin shell ionosphere model on the Total Electron Content (TEC) derived from a small scale Global Positioning System (GPS) network. TEC and instrumental bias are determined by applying a grid-based algorithm to the data on several geomagnetically quiet days covering a 10 month period in 2006. Comparisons of TEC and instrumental bias are made among assumed heights from 250 km to 700 km with an interval of 10 km. While the TEC variations with time follow the same trend, TEC tends to increase with the height of the thin shell. The difference in TEC between heights 250 km and 700 km can be as large as ˜ 8 TECU in both daytime and nighttime. The times at which the TEC reaches its peak or valley do not vary much with the assumed heights. The instrumental biases, especially bias from the satellite, can vary irregularly with assumed height. Several satellites show a large deviation of ˜ 3 ns for heights larger than 550 km. The goodness of fit for different assumed heights is also examined. The data can be generally well-fitted for heights from 350 km to 700 km. A large deviation happens at heights lower than 350 km. Using the grid-based algorithm, there is no consensus on assumed height as related to data fitting. A thin shell height in the range 350 - 500 km can be a reasonable compromise between data fitting and peak height of the ionosphere.

  18. The influence of ionospheric thin shell height on TEC retrieval from GPS observation

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Lan; Wan, Qing-Tao; Ma, Guan-Yi; Li, Jing-Hua; Fan, Jiang-Tao

    2016-07-01

    We investigate the influence of assumed height for the thin shell ionosphere model on the Total Electron Content (TEC) derived from a small scale Global Positioning System (GPS) network. TEC and instrumental bias are determined by applying a grid-based algorithm to the data on several geomagnetically quiet days covering a 10 month period in 2006. Comparisons of TEC and instrumental bias are made among assumed heights from 250 km to 700 km with an interval of 10 km. While the TEC variations with time follow the same trend, TEC tends to increase with the height of the thin shell. The difference in TEC between heights 250 km and 700 km can be as large as ˜ 8 TECU in both daytime and nighttime. The times at which the TEC reaches its peak or valley do not vary much with the assumed heights. The instrumental biases, especially bias from the satellite, can vary irregularly with assumed height. Several satellites show a large deviation of ˜ 3 ns for heights larger than 550 km. The goodness of fit for different assumed heights is also examined. The data can be generally well-fitted for heights from 350 km to 700 km. A large deviation happens at heights lower than 350 km. Using the grid-based algorithm, there is no consensus on assumed height as related to data fitting. A thin shell height in the range 350 – 500 km can be a reasonable compromise between data fitting and peak height of the ionosphere.

  19. The influence of personality on neural mechanisms of observational fear and reward learning

    PubMed Central

    Hooker, Christine I.; Verosky, Sara C.; Miyakawa, Asako; Knight, Robert T.; D’Esposito, Mark

    2012-01-01

    Fear and reward learning can occur through direct experience or observation. Both channels can enhance survival or create maladaptive behavior. We used fMRI to isolate neural mechanisms of observational fear and reward learning and investigate whether neural response varied according to individual differences in neuroticism and extraversion. Participants learned object-emotion associations by observing a woman respond with fearful (or neutral) and happy (or neutral) facial expressions to novel objects. The amygdala-hippocampal complex was active when learning the object-fear association, and the hippocampus was active when learning the object-happy association. After learning, objects were presented alone; amygdala activity was greater for the fear (vs. neutral) and happy (vs. neutral) associated object. Importantly, greater amygdala-hippocampal activity during fear (vs. neutral) learning predicted better recognition of learned objects on a subsequent memory test. Furthermore, personality modulated neural mechanisms of learning. Neuroticism positively correlated with neural activity in the amygdala and hippocampus during fear (vs. neutral) learning. Low extraversion/high introversion was related to faster behavioral predictions of the fearful and neutral expressions during fear learning. In addition, low extraversion/high introversion was related to greater amygdala activity during happy (vs. neutral) learning, happy (vs. neutral) object recognition, and faster reaction times for predicting happy and neutral expressions during reward learning. These findings suggest that neuroticism is associated with an increased sensitivity in the neural mechanism for fear learning which leads to enhanced encoding of fear associations, and that low extraversion/high introversion is related to enhanced conditionability for both fear and reward learning. PMID:18573512

  20. The influence of PMCs on water vapor and drivers behind PMC variability from SOFIE observations

    NASA Astrophysics Data System (ADS)

    Hervig, Mark E.; Siskind, David E.; Bailey, Scott M.; Russell, James M.

    2015-09-01

    Observations from the Solar Occultation For Ice Experiment (SOFIE) are used to quantify relationships between polar mesospheric clouds (PMC) and their environment. Dehydration due to ice growth is found to be greatest ∼1.8 km above the height of peak ice mass density on average, and H2O enhancement due to sublimation is greatest near the bottom of the PMC layer. The dehydration and hydration layers contain a similar amount of H2O, although less than is found in ice layers, a difference that may be due to meridional transport. Because PMCs modify the surrounding water vapor, PMC-H2O relationships can be misleading and recommendations are made for dealing with this issue. The dependence of PMCs on water vapor and temperature was quantified, accounting for the effects of ice on water vapor. The approach examined inter-annual variations and considered the subset of PMCs detected by the Solar Backscatter Ultraviolet (SBUV) instruments, which are less sensitive than SOFIE. Results in the Northern Hemisphere indicate that PMC variations are dominated by temperature, but that a combination of temperature and water vapor provides the best explanation of the observations. In the Southern Hemisphere PMC variability is attributed primarily to temperature, with water vapor playing a minor role. The subset of SBUV PMCs are found to be one third as sensitive to changing temperature as the entire PMC population observed by SOFIE. Finally, an approach is presented which allows temperature and water vapor anomalies to be estimated from various PMC data sets such as SBUV. Using recently reported SBUV PMC trends at 64-74°N latitude with the results of this study indicates a cooling trend of -0.27±0.14 K decade-1 and a water vapor increase of +0.66±0.34% decade-1 (both at 80-84 km). This cooling trend agrees with reports based on observations in the middle atmosphere at similar latitudes. The water vapor increase is lower than expected due to increasing methane, although this

  1. Researching of sea waves influence on a coastal line transformation (based on field observation results)

    NASA Astrophysics Data System (ADS)

    Chernov, A.; Kouznetsov, K.; Kurkin, A.; Shevchenko, G.

    2009-04-01

    The long duration registrations of bottom pressure, temperature and meteorological data took place in June - October 2007 on the shelf near 104th - 110th kilometer of interstate road Yuzhno-Sakhalinsk - Okha. Sediment transport and abrasion processes are observed in this place, it is a dangerous factor for road and railroad constructions, it can also be threat for some buildings of Vzmorie town. Distributed network of autonomous pressure gauges was installed for wave structure studying. Gauges were installed in tree lines with 100, 150 and 200 meters far from each other. Gathered data contains information about different wave's regimes under different weather conditions, it's allowed us to make analysis. Different data rows for different wave regimes were taken for analysis. Transformation of wave field along shoreline and opposite was observed. The results of observation are showed that disposition of waves was determined by swell waves with period 8-9 second. Wind waves were weaker than swell waves, conceivably because of big depths in the studied area. Much more interesting results were found in the infragravity waves range (0.5 - 5 min). For example, peaks with period above 150 and 75 seconds are presented in the spectral estimation of record from gauge 23. The same peaks were not observed in other gauges to the North and to the South from 23. However, low frequency peak was much stronger at the storm weather, but 75 seconds peak was stayed non-changed under the different weather conditions. For understanding mechanism of infra-gravitation waves generation group structure of waves were studied. Spectrum characteristics of different data rows for different wave regimes and also for their envelopes were provided. Results of this research allow us to consider that wave packets with common period 7 - 8 seconds make infra-gravitation waves with period above 5 minutes which forcing sediment transport processes. Satellite images of studied place were used in this

  2. Observational evidence of planetary wave influences on ozone enhancements over upper troposphere North Africa

    NASA Astrophysics Data System (ADS)

    Mengistu Tsidu, Gizaw; Ture, Kassahun; Sivakumar, V.

    2013-07-01

    MOZAIC instrument measured enhanced ozone on two occasions in February, 1996 and 1997 at cruise altitude over North Africa. The cause and source of ozone enhancements over the region are investigated using additional reanalysis data from ERA-Interim. The ERA-Interim reprocessed GOME ozone indicated existence of enhancement as well. Both observational data revealed that the increase in ozone has wider latitudinal coverage extending from North Europe upto North Africa. The geopotential heights and zonal wind from ERA-Interim have indicated existence of planetary-scale flow that allowed meridional airmass exchanges between subtropics and higher latitudes. The presence of troughs-ridge pattern are attributable to large amplitude waves of zonal wavenumber 1-5 propagating eastward in the winter hemisphere westerly current as determined from Hayashi spectra as well as local fractional variance spectra determined from Multitaper Method-Singular Value Decomposition (MTM-SVD) spectral method. MTM-SVD is also used to understand the role of these waves on ozone enhancement and variability during the observation period in a mechanistic approach. A joint analysis of driving field, such as wind and potential vorticity (PV) for which only signals of the dominant zonal wavenumbers of prevailing planetary waves are retained, has revealed strong linkage between wave activity and ozone enhancement over the region at a temporal cycle of 5.8 days. One of these features is the displacement of the polar vortex southward during the enhancements, allowing strong airmass, energy and momentum exchanges. Evidence of cutoff laws that are formed within the deep trough, characteristics of Rossby wave breaking, is also seen in the ozone horizontal distribution at different pressure levels during the events. The reconstruction of signals with the cycle of 5.8 days has shown that the time and strength of enhancement depend on the circulation patterns dictated by planetary-scale flow relative to the

  3. Surface observations of aerosols and vertical ozone profiling: Influence from the Indo Gangetic Plain, biomass burning and LRT

    NASA Astrophysics Data System (ADS)

    Naja, M. K.; Kotamarthi, V. R.; Singh, N.; Phani, D. V.; Dumka, U. C.; Kumar, R.; Ojha, N.; Bhardhwaj, P.; Lal, S.

    2013-12-01

    South Asia is the home to one of the most populated and polluted region (The Indo-Gangetic Plain, IGP) of the world and variety of anthropogenic and biogenic emission sources are exiting in the same region. Despite of the poor understanding of the physical, chemical, and dynamical processes in the lower atmosphere over this region, there are very limited ground based observations in South Asia. In view of this, an observational facility was setup at ARIES, Nainital (29.4N, 79.5E; 1950 m) in the central Himalayas and at two sites in the IGP region for the surface based trace gases and aerosols observations as well as balloon-borne ozone observations. Further, First Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF1), DOE, was setup at ARIES during a GVAX campaign (June 2011-March 2012) and extensive observations of vertical profiling was also carried out using balloons, doppler Lidar, microwave radiometer, wind profiler and ceilometers. Observations of trace gases and aerosols show a clear enhancement during pre-monsoon and a secondary peak during post-monsoon period. The average scattering Angstrom exponent suggests dominance of relatively larger size particles and single scattering albedo indicates more scattering or less absorbing aerosols in this region. Events of the long-range transport are seen, when concentrations of bigger particle are observed to be higher. Apart from LRT, events of downward transport of ozone rich but drier air-masses are also observed. Extensive in-situ observations of ozone, CO, BC, aerosol absorption, scattering and number-concentration, along with back-air trajectories and MODIS fire-counts have been used to demonstrate evidences of the influence of biomass burning over this region. Aerosol organic enrichment and subsequent evolution to predominantly accumulation mode have been observed. This enrichment and its simultaneous size-growth caused it to get brighter during the biomass burning season. A very clear enhancement (20

  4. Traces across the body: influence of music-dance synchrony on the observation of dance.

    PubMed

    Woolhouse, Matthew Harold; Lai, Rosemary

    2014-01-01

    In previous studies investigating entrainment and person perception, synchronized movements were found to enhance memory for incidental person attributes. Although this effect is robust, including in dance, the process by which it is actuated are less well understood. In this study, two hypotheses are investigated: that enhanced memory for person attributes is the result of (1) increased gaze time between in-tempo dancers; and/or (2) greater attentional focus between in-tempo dancers. To explore these possible mechanisms in the context of observing dance, an eye-tracking study was conducted in which subjects watched videos of pairs of laterally positioned dancers; only one of the dancers was synchronized with the music, the other being asynchronous. The results were consistent with the first hypothesis-music-dance synchrony gives rise to increased visual inspection times. In addition, there was a preference for upper-body fixations over lower-body fixations across both synchronous and asynchronous conditions. A subsequent, single-dancer eye-tracking study investigated fixations across different body regions, including head, torso, legs and feet. Significantly greater dwell times were recorded for head than torso and legs; feet attracted significantly less dwell time than any other body region. Lastly, the study sought to identify dance gestures responsible for torso- and head-directed fixations. Specifically we asked whether there are features in dance that are specially designed to direct an observer's gaze towards the face-the main "communicative portal" with respect to the transmission of intent, affect and empathy.

  5. Asymmetry and nonlinearity of the influence of ENSO on the northern winter stratosphere: 1. Observations

    NASA Astrophysics Data System (ADS)

    Rao, Jian; Ren, Rongcai

    2016-08-01

    The El Niño-Southern Oscillation (ENSO) has significant effects on the extratropical stratosphere. This study explores the nonlinearity and the asymmetry of these influences by distinguishing the different effects of four types of ENSO: "moderate El Niño," "strong El Niño," "moderate La Niña," and "strong La Niña." It is revealed that the moderate El Niño and the strong La Niña are much more efficient than the strong El Niño and the moderate La Niña, respectively, in modulating the northern winter stratospheric variability, resulting in significant nonlinearity and asymmetry. The tropical rainfall anomalies induced by a moderate El Niño or a strong La Niña are centered over the central equatorial Pacific region near the dateline, while the convection responses to a strong El Niño or a moderate La Niña are centered farther eastward. Accordingly, the anomalous Pacific-North America wave train pattern is modulated by ENSO in a nonlinear and asymmetric way, which leads to the large nonlinear and asymmetric components of the vertical Eliassen-Palm (E-P) flux responses to ENSO. The increase of planetary wave activity in the extratropical stratosphere in moderate El Niño winters is thus greater than in strong El Niño winters, whereas a strong La Niña gives a larger decrease in propagation than a moderate La Niña. The relatively strong (weak) E-P flux responses to moderate (strong), El Niño and strong (moderate) La Niña explains the remarkable nonlinearity and asymmetry in the response of the extratropical stratosphere to ENSO.

  6. Influence of duty cycle on the power-duration relationship: observations and potential mechanisms.

    PubMed

    Broxterman, R M; Ade, C J; Wilcox, S L; Schlup, S J; Craig, J C; Barstow, T J

    2014-02-01

    The highest sustainable rate of aerobic metabolism [critical power (CP)] and the finite amount of work that can be performed above CP (W' [curvature constant]) were determined under two muscle contraction duty cycles. Eight men completed at least three constant-power handgrip tests to exhaustion to determine CP and W' for 50% and 20% duty cycles, while brachial artery blood flow (Q̇BA) and deoxygenated-[hemoglobin + myoglobin] (deoxy-[Hb+Mb]) were measured. CP was lower for the 50% duty cycle (3.9 ± 0.9 W) than the 20% duty cycle (5.1 ± 0.8 W; p < 0.001), while W' was not significantly different (50% duty cycle: 452 ± 141 J vs. 20% duty cycle: 432 ± 130 J; p > 0.05). At the same power output, Q̇BA and deoxy-[Hb + Mb] achieved higher end-exercise values for the 20% duty cycle (9.87 ± 1.73 ml·s(-1); 51.7 ± 4.7 μM) than the 50% duty cycle (7.37 ± 1.76 ml·s(-1), p < 0.001; 44.3 ± 2.4 μM, p < 0.03). These findings indicate that blood flow influences CP, but not W'.

  7. Dependence of aerosol scattering coefficients on relative humidity observed at two coastal sites on the East China Sea: Comparison to remote observations and influence of chemical composition

    NASA Astrophysics Data System (ADS)

    Kanaya, Y.; Taketani, F.; Irie, H.; Komazaki, Y.; Takashima, H.; Xiaole, P.; Takami, A.; Wang, Z.

    2011-12-01

    We employed an integrating nephelometer equipped with a humidifier (where the relative humidity (RH) was scanned between 40 and 90%) to measure the aerosol scattering coefficients and their dependence on RH at Fukue Island (32.75N, 128.68E), west of Japan, in May 2009 and at Rudong, Jiangsu, China (32.26N, 121.37E) in May/June 2010, aiming at better characterization of optical properties of the regional-scale aerosol pollution over East Asia. The two coastal sites are located east and west of the East China Sea and are separated by about 700 km. The observed scattering coefficients are normalized by the concurrently measured PM2.5 mass concentrations and thereby behaviors of the mass scattering coefficients are discussed. At Fukue, the mass scattering coefficients under the ambient RH conditions were >1.5 times higher than those observed under the dry condition (RH = 40%), suggesting that the RH effect was crucial in determining optical properties under ambient conditions. The coefficients under the ambient RH conditions, rather than the dry values, agreed better with the extinction coefficients determined by MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy) technique based on remote measurements of O4 optical depths. The single-scattering albedo (SSA), estimated in combination to the absorption coefficients determined by a MAAP (Multi-Angle Absorption Photometer) instrument, had similar average values (~0.95) at the two sites. The SSA values at the two sites were commonly lowered (to below 0.90) when the air traveled from the North China Plain region. At Fukue, the RH dependence was found to be weakened when the organics/sulfate ratio increased (as observed by an Aerodyne Aerosol Mass Spectrometer), while such influence of chemical composition was less clear at Rudong, possibly masked by large temporal variations in the particle size distributions.

  8. A Comet Engulfs Mars: MAVEN Observations of Comet Siding Spring's Influence on the Martian Magnetosphere

    NASA Technical Reports Server (NTRS)

    Espley, Jared R.; Dibraccio, Gina A.; Connerney, John E. P.; Brain, David; Gruesbeck, Jacob; Soobiah, Yasir; Halekas, Jasper S.; Combi, Michael; Luhmann, Janet; Ma, Yingjuan

    2015-01-01

    The nucleus of comet C/2013 A1 (Siding Spring) passed within 141,000?km of Mars on 19 October 2014. Thus, the cometary coma and the plasma it produces washed over Mars for several hours producing significant effects in the Martian magnetosphere and upper atmosphere. We present observations from Mars Atmosphere and Volatile EvolutioN's (MAVEN's) particles and field's instruments that show the Martian magnetosphere was severely distorted during the comet's passage. We note four specific major effects: (1) a variable induced magnetospheric boundary, (2) a strong rotation of the magnetic field as the comet approached, (3) severely distorted and disordered ionospheric magnetic fields during the comet's closest approach, and (4) unusually strong magnetosheath turbulence lasting hours after the comet left. We argue that the comet produced effects comparable to that of a large solar storm (in terms of incident energy) and that our results are therefore important for future studies of atmospheric escape, MAVEN's primary science objective.

  9. CRT diagnosis of pulmonary disease: influence of monitor brightness and room illuminance on observer performance.

    PubMed

    Ishihara, Shunichi; Shimamoto, Kazuhiro; Ikeda, Mitsuru; Kato, Katsuhiko; Mori, Yoshine; Ishiguchi, Tsuneo; Ishigaki, Takeo

    2002-01-01

    Using a 21-in. cathode ray tube (CRT) monitor (2048 x 2560 x 8bits), six radiologists interpreted 12 images with interstitial lung disease under six conditions of CRT luminance (50 and 400 cd/m(2)) and room illuminance (20, 120 and 480lx), and 10 radiologists interpreted 25 images with pulmonary nodules under nine conditions of CRT luminance (50, 200 and 500 cd/m(2)) and room illuminance (20, 120 and 480lx). Observer's performance for interstitial disease was relatively better at 120lx. Four hundred and eighty lux illuminance with 50 cd/m(2) CRT luminance, which degraded the detectability of pulmonary nodule significantly (p<0.05), should be avoided for clinical use.

  10. A comet engulfs Mars: MAVEN observations of comet Siding Spring's influence on the Martian magnetosphere

    NASA Astrophysics Data System (ADS)

    Espley, Jared R.; DiBraccio, Gina A.; Connerney, John E. P.; Brain, David; Gruesbeck, Jacob; Soobiah, Yasir; Halekas, Jasper; Combi, Michael; Luhmann, Janet; Ma, Yingjuan; Jia, Yingdong; Jakosky, Bruce

    2015-11-01

    The nucleus of comet C/2013 A1 (Siding Spring) passed within 141,000 km of Mars on 19 October 2014. Thus, the cometary coma and the plasma it produces washed over Mars for several hours producing significant effects in the Martian magnetosphere and upper atmosphere. We present observations from Mars Atmosphere and Volatile EvolutioN's (MAVEN's) particles and field's instruments that show the Martian magnetosphere was severely distorted during the comet's passage. We note four specific major effects: (1) a variable induced magnetospheric boundary, (2) a strong rotation of the magnetic field as the comet approached, (3) severely distorted and disordered ionospheric magnetic fields during the comet's closest approach, and (4) unusually strong magnetosheath turbulence lasting hours after the comet left. We argue that the comet produced effects comparable to that of a large solar storm (in terms of incident energy) and that our results are therefore important for future studies of atmospheric escape, MAVEN's primary science objective.

  11. Quantifying the influence of sea ice on ocean microseism using observations from the Bering Sea, Alaska

    USGS Publications Warehouse

    Tsai, V.C.; McNamara, D.E.

    2011-01-01

    Microseism is potentially affected by all processes that alter ocean wave heights. Because strong sea ice prevents large ocean waves from forming, sea ice can therefore significantly affect microseism amplitudes. Here we show that this link between sea ice and microseism is not only a robust one but can be quantified. In particular, we show that 75-90% of the variability in microseism power in the Bering Sea can be predicted using a fairly crude model of microseism damping by sea ice. The success of this simple parameterization suggests that an even stronger link can be established between the mechanical strength of sea ice and microseism power, and that microseism can eventually be used to monitor the strength of sea ice, a quantity that is not as easily observed through other means. Copyright 2011 by the American Geophysical Union.

  12. Quantifying the influence of sea ice on ocean microseism using observations from the Bering Sea, Alaska

    USGS Publications Warehouse

    Tsai, Victor C.; McNamara, Daniel E.

    2011-01-01

    Microseism is potentially affected by all processes that alter ocean wave heights. Because strong sea ice prevents large ocean waves from forming, sea ice can therefore significantly affect microseism amplitudes. Here we show that this link between sea ice and microseism is not only a robust one but can be quantified. In particular, we show that 75–90% of the variability in microseism power in the Bering Sea can be predicted using a fairly crude model of microseism damping by sea ice. The success of this simple parameterization suggests that an even stronger link can be established between the mechanical strength of sea ice and microseism power, and that microseism can eventually be used to monitor the strength of sea ice, a quantity that is not as easily observed through other means.

  13. Democratic Parenting Beliefs and Observed Parental Sensitivity: Reciprocal Influences Between Coparents

    PubMed Central

    Schofield, Thomas; Weaver, Jennifer

    2016-01-01

    Three hundred and sixty-five two-parent families from the NICHD Study of Early Child Care and Youth Development were rated by trained observers on their parenting behavior at six assessments ranging from six months after the child's birth to when the child was in fifth grade (M = 10.4 years old at fifth grade). Across assessments, parents reported on their parenting beliefs and mothers reported on the child's externalizing behavior problems. Parenting beliefs predicted change in parenting behavior, and to a lesser degree parenting behavior predicted change in parenting beliefs. Parenting behavior and parenting beliefs both showed reciprocal effects between coparents, after controlling for child externalizing behavior and parent education. PMID:26551656

  14. Traces across the body: influence of music-dance synchrony on the observation of dance.

    PubMed

    Woolhouse, Matthew Harold; Lai, Rosemary

    2014-01-01

    In previous studies investigating entrainment and person perception, synchronized movements were found to enhance memory for incidental person attributes. Although this effect is robust, including in dance, the process by which it is actuated are less well understood. In this study, two hypotheses are investigated: that enhanced memory for person attributes is the result of (1) increased gaze time between in-tempo dancers; and/or (2) greater attentional focus between in-tempo dancers. To explore these possible mechanisms in the context of observing dance, an eye-tracking study was conducted in which subjects watched videos of pairs of laterally positioned dancers; only one of the dancers was synchronized with the music, the other being asynchronous. The results were consistent with the first hypothesis-music-dance synchrony gives rise to increased visual inspection times. In addition, there was a preference for upper-body fixations over lower-body fixations across both synchronous and asynchronous conditions. A subsequent, single-dancer eye-tracking study investigated fixations across different body regions, including head, torso, legs and feet. Significantly greater dwell times were recorded for head than torso and legs; feet attracted significantly less dwell time than any other body region. Lastly, the study sought to identify dance gestures responsible for torso- and head-directed fixations. Specifically we asked whether there are features in dance that are specially designed to direct an observer's gaze towards the face-the main "communicative portal" with respect to the transmission of intent, affect and empathy. PMID:25520641

  15. Influence of nuclear de-excitation on observables relevant for space exploration

    NASA Astrophysics Data System (ADS)

    Mancusi, Davide; Boudard, Alain; Cugnon, Joseph; David, Jean-Christophe; Leray, Sylvie

    The composition of the space radiation environment inside spacecrafts is modified by the inter-action with shielding material, with equipment and even with the astronauts' bodies. Accurate quantitative estimates of the effects of nuclear reactions are necessary, for example, for dose estimation and prediction of single-event upset rates. To this end, it is necessary to construct predictive models for nuclear reactions, which usually consist of an intranuclear-cascade or quantum-molecular-dynamics stage, followed by a nuclear de-excitation stage. While it is generally acknowledged that it is necessary to accurately simulate the first reaction stage, transport-code users often neglect or underestimate the importance of the choice of the de-excitation code. The purpose of this work is to prove that the de-excitation model is in fact a non-negligible source of uncertainty for the prediction of several observables of crucial importance for space applications. For some particular observables, such as fragmentation cross sections, the systematic uncertainty due to the de-excitation model actually dominates the theoretical error. Our point will be illustrated by making use of calculations performed with several intranuclear-cascade/de-excitation models, such as the Li`ge Intranuclear Cascade model (INCL) and Isabel (for the cascade part) and ABLA, GEMINI++ and SMM (on the de-excitation side). We will also rely on the results of the recent IAEA intercomparison of spallation models, which can be used as informative groundwork for the evaluation of the global uncertainties involved in nucleon-nucleus reactions.

  16. The major influence of the atmosphere on intracranial pressure: an observational study

    NASA Astrophysics Data System (ADS)

    Herbowski, Leszek

    2016-06-01

    The impact of the atmosphere on human physiology has been studied widely within the last years. In practice, intracranial pressure is a pressure difference between intracranial compartments and the surrounding atmosphere. This means that gauge intracranial pressure uses atmospheric pressure as its zero point, and therefore, this method of pressure measurement excludes the effects of barometric pressure's fluctuation. The comparison of these two physical quantities can only take place through their absolute value relationship. The aim of this study is to investigate the direct effect of barometric pressure on the absolute intracranial pressure homeostasis. A prospective observational cross-sectional open study was conducted in Szczecin, Poland. In 28 neurosurgical patients with suspected normal-pressure hydrocephalus, intracranial intraventricular pressure was monitored in a sitting position. A total of 168 intracranial pressure and atmospheric pressure measurements were performed. Absolute atmospheric pressure was recorded directly. All values of intracranial gauge pressure were converted to absolute pressure (the sum of gauge intracranial pressure and local absolute atmospheric pressure). The average absolute mean intracranial pressure in the patients is 1006.6 hPa (95 % CI 1004.5 to 1008.8 hPa, SEM 1.1), and the mean absolute atmospheric pressure is 1007.9 hPa (95 % CI 1006.3 to 1009.6 hPa, SEM 0.8). The observed association between atmospheric and intracranial pressure is strongly significant (Spearman correlation r = 0.87, p < 0.05) and all the measurements are perfectly reliable (Bland-Altman coefficient is 4.8 %). It appears from this study that changes in absolute intracranial pressure are related to seasonal variation. Absolute intracranial pressure is shown to be impacted positively by atmospheric pressure.

  17. Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations.

    PubMed

    Alvarez-Mozos, Jesús; Verhoest, Niko E C; Larrañaga, Arantzazu; Casalí, Javier; González-Audícana, María

    2009-01-01

    Radar-based surface soil moisture retrieval has been subject of intense research during the last decades. However, several difficulties hamper the operational estimation of soil moisture based on currently available spaceborne sensors. The main difficulty experienced so far results from the strong influence of other surface characteristics, mainly roughness, on the backscattering coefficient, which hinders the soil moisture inversion. This is especially true for single configuration observations where the solution to the surface backscattering problem is ill-posed. Over agricultural areas cultivated with winter cereal crops, roughness can be assumed to remain constant along the growing cycle allowing the use of simplified approaches that facilitate the estimation of the moisture content of soils. However, the field scale spatial variability and temporal variations of roughness can introduce errors in the estimation of soil moisture that are difficult to evaluate. The objective of this study is to assess the impact of roughness spatial variability and roughness temporal variations on the retrieval of soil moisture from radar observations. A series of laser profilometer measurements were performed over several fields in an experimental watershed from September 2004 to March 2005. The influence of the observed roughness variability and its temporal variations on the retrieval of soil moisture is studied using simulations performed with the Integral Equation Model, considering different sensor configurations. Results show that both field scale roughness spatial variability and its temporal variations are aspects that need to be taken into account, since they can introduce large errors on the retrieved soil moisture values.

  18. Influence of muscle mass and bone mass on the mobility of elderly women: an observational study

    PubMed Central

    2014-01-01

    Background The purpose of this study was to investigate the influence of muscle mass and bone mineral density on markers of mobility in dwelling elderly women. Methods This cross-sectional study included 99 elderly women, who were 65 years old or above, in Campinas-SP, Brazil. To collect data, we used sociodemographic data, the body mass index (BMI), health status, comorbidities, use of medications, mobility tests (TUG and gait speed) and examinations of the body composition (densitometry with dual-emission X-ray absorptiometry “DXA”). In order to examine the relationship between muscle and bone mass with mobility (gait speed and TUG), we applied the Spearman correlation coefficient. Also was applied the analysis of covariance (ANCOVA) adjusted for age and comorbidities. To identify the factors associated with mobility, we used the univariate and multivariate logistic regression analysis. The level of significance for statistical tests was P < 0.05. Results The correlation between sarcopenia and bone mineral density with mobility tests showed a significant relationship only between sarcopenia and TUG (r = 0.277, P = 0.006) in Spearman correlation coefficient. The result of the correlation analysis (ANCOVA) showed that sarcopenia was associated with gait speed (r2 = 0.0636, P = 0.0018) and TUG (r2 = 0.0898, P = 0.0027). The results of the multivariate analysis showed that age (P = 0.034, OR = 1.081) was associated with worse performance on gait speed. By highlighting the TUG test, the results of the multivariate analysis showed that the age (P = 0.004, OR = 1.111) and BMI in overweight (P = 0.011, OR = 7.83) and obese (P < 0.001, OR = 7.84) women were associated with lower performance of the functionality of the lower limbs. Conclusion The findings with regard to mobility tests which were analyzed in this study indicate the association of variables related to the aging process that contribute to the

  19. Factors influencing the quality of postoperative epidural analgesia: an observational multicenter study

    PubMed Central

    Wranicz, Piotr; Andersen, Hege; Nordbø, Arve; Kongsgaard, Ulf E

    2014-01-01

    Background Epidural analgesia (EDA) is used widely for postoperative pain treatment. However, studies have reported a failure rate of EDA of up to 30%. We aimed to evaluate the quality of postoperative EDA in patients undergoing a laparotomy in five Norwegian hospitals. Methods This was a multicenter observational study in patients undergoing a laparotomy with epidural-based postoperative analgesia. Data were registered at three time points. Technical aspects, infusion rates, pain intensity, assessment procedures, side effects, and satisfaction of patients and health personnel were recorded. The use of other pain medications and coanalgesics was registered. Results Three hundred and seventeen patients were included. Pain control at rest was satisfactory in 89% of patients at 24 hours and in 91% at 48 hours. Pain control when coughing was satisfactory in 62% at 24 hours and in 59% at 48 hours. The spread of hypoesthesia was consistent for each individual patient but varied between patients. The hypoesthetic area was not associated with pain intensity, and the precision of the EDA insertion point was not associated with the pain score. Few side effects were reported. EDA was regarded as effective and functioning well by 64% of health personnel. Conclusion EDA was an effective method for postoperative pain relief at rest but did not give sufficient pain relief during mobilization. The use of cold stimulation to assess the spread of EDA had limited value as a clinical indicator of the efficacy of postoperative pain control. Validated tools for the control of EDA quality are needed. PMID:25206312

  20. The clouds of Venus. II - An investigation of the influence of coagulation on the observed droplet size distribution

    NASA Technical Reports Server (NTRS)

    Rossow, W. B.

    1977-01-01

    An approximate numerical technique is used to investigate the influence of coagulation, sedimentation and turbulent motions on the observed droplet size distribution in the upper layers of the Venus clouds. If the cloud mass mixing ratio is less than 0.000001 at 250 K or the eddy diffusivity throughout the cloud is greater than 1,000,000 sq cm per sec, then coagulation is unimportant. In this case, the observed droplet size distribution is the initial size distribution produced by the condensation of the droplets. It is found that all cloud models with droplet formation near the cloud top (e.g., a photochemical model) must produce the observed droplet size distribution by condensation without subsequent modification by coagulation. However, neither meteoritic or surface dust can supply sufficient nucleating particles to account for the observed droplet number density. If the cloud droplets are formed near the cloud bottom, the observed droplet size distribution can be produced solely by the interaction of coagulation and dynamics; all information about the initial size distribution is lost. If droplet formation occurs near the cloud bottom, the lower atmosphere of Venus is oxidizing rather than reducing.

  1. Vegetation influence on runoff and sediment yield in the Andes region: observation and modelling

    NASA Astrophysics Data System (ADS)

    Braud, I.; Vich, A. I. J.; Zuluaga, J.; Fornero, L.; Pedrani, A.

    2001-12-01

    The Precordillera of the Andes Mountains (Mendoza, Argentina) is prone to severe flash floods, caused by heavy rainfall events of short duration and high intensities. Two catchments were instrumented in order to study the rainfall-runoff process and soil management impact on runoff and/or sediment yield. In the first catchment (Divisadero Largo, DL, 5.47 km 2), characterized by a large heterogeneity of surface geology, a data set of about 50 rainfall-runoff events covering the 1983-1994 period was available. Vegetation cover changed significantly after the catchment was enclosed in 1989-1990. This change was successfully mapped using Landsat TM image analysis. The second catchment (Cuenca Aluvional Piloto, CAP, 35 ha), the soil of which was homogeneous, was instrumented in 1992 for total runoff and sediment yield measurements. Three small plots of 3×10 m 2 (bare soil, 42 and 60% vegetation cover) and three sub catchments (2-4.5 ha) were delimited with different average vegetation cover. Data analysis showed the difficulty in relating runoff volume and sediment yield to simple descriptors of the catchments such as the average slope and/or the average vegetation cover. The DL and CAP catchments were modelled using the Areal Non Point Source Watershed Environment Response Simulation (ANSWERS) model with contrasting results. Good agreement between model and observation could be achieved after calibration on the 3×10 m 2 plots, but the model failed to correctly reproduce runoff on the three 2-4.5 ha CAP sub-catchments using the values calibrated on the small plots. Better results were obtained on the larger and heterogeneous DL basin, where surface geology variations and rainfall variability seemed to be the most influential factors. In this case, no sensitivity to vegetation coverage changes, induced when enclosing the catchment, was found. On the other hand, the model proved sensitive to differences in vegetation cover at smaller scales when the geology was

  2. Traces across the body: influence of music-dance synchrony on the observation of dance

    PubMed Central

    Woolhouse, Matthew Harold; Lai, Rosemary

    2014-01-01

    In previous studies investigating entrainment and person perception, synchronized movements were found to enhance memory for incidental person attributes. Although this effect is robust, including in dance, the process by which it is actuated are less well understood. In this study, two hypotheses are investigated: that enhanced memory for person attributes is the result of (1) increased gaze time between in-tempo dancers; and/or (2) greater attentional focus between in-tempo dancers. To explore these possible mechanisms in the context of observing dance, an eye-tracking study was conducted in which subjects watched videos of pairs of laterally positioned dancers; only one of the dancers was synchronized with the music, the other being asynchronous. The results were consistent with the first hypothesis—music-dance synchrony gives rise to increased visual inspection times. In addition, there was a preference for upper-body fixations over lower-body fixations across both synchronous and asynchronous conditions. A subsequent, single-dancer eye-tracking study investigated fixations across different body regions, including head, torso, legs and feet. Significantly greater dwell times were recorded for head than torso and legs; feet attracted significantly less dwell time than any other body region. Lastly, the study sought to identify dance gestures responsible for torso- and head-directed fixations. Specifically we asked whether there are features in dance that are specially designed to direct an observer’s gaze towards the face—the main “communicative portal” with respect to the transmission of intent, affect and empathy. PMID:25520641

  3. Sudden Stratospheric Warming (SSW) and its immediate and broader influence on tropical dynamics using COSMIC Observations

    NASA Astrophysics Data System (ADS)

    Dhaka, Surendra

    2016-07-01

    We have analyzed temperature changes in troposphere and stratosphere from polar to tropical region during major sudden stratospheric warming (SSW) using data derived from COSMIC over a period of 2007-2014. During peak period of SSW, a large variability noted in temperature structure, rise in temperature occurred down to the tropopause height (~8 km height) in polar region. At around 40 km altitudes (as data is available to this height), temperature increased by several tens of degrees within few days of SSW. After SSW termination, temperature decreased up to ~ 80°C in strong SSW cases. After about a week of SSW event, descending cold anomalies emerged at polar region. These features are emerging normally known as polar night jet oscillations (PJO). The cooling phase was much longer along with large spatial coverage than the warm phase. Due to SSW, polar T-CPT and H-CPT alter significantly. As a consequence of SSW, bottom of stratospheric region expands and hence the tropospheric region shrunk by the same height. A rapid atmospheric response is identified between polar and tropical region possibly through set up of strong meridional circulation. During occurrence of SSW, at 40 km altitude in polar region, large increase in temperature noted, while in the tropics temperature dropped at similar heights. After termination of SSW, descending warm anomalies observed over the tropical region for a longer duration, while the long cold phase persisted at the polar region. These warm anomalies at tropical region are much longer and deeper in comparison to those of the cold anomalies. It is concluded that SSW event at polar region connects to the entire tropical tropopause region across the equator in SH up to 40° S. Hence these processes need to be understood thoroughly to contribute to the temperature change.

  4. The ICQ Guide to Observing Comets.

    NASA Astrophysics Data System (ADS)

    Green, D. W. E.

    1997-01-01

    The following topics were dealt with: basic information (comet names and designation nomenclature, basic anatomy of a comet, composition of comets and techniques for deriving this information, orbital characteristics of comets, the stellar-magnitude scale and general remarks on comet magnitudes, typical comet behaviors, and the role of solar activity, time and its role in observing comets, locating and identifying known comets, what to do if you discover a comet); a historical overview of the observation of comets (perceptions of comets via naked-eye observations prior to Halley, issues regarding the reading and interpretation of historical observations); visual observing (the human eye as a light detector, observing conditions and observing-site selection, instrumentation and observing "assessories", comet hunting, discovery, and follow-up, estimating a comet's total magnitude, estimating the comet's other physical parameters, drawing comets, daytime observations of comets); non-visual optical observations (CCD observations, photography of comets, narrow-band photometry, spectroscopy and spectrophotometry, occultations); observations outside the visual region (ground-based observations at non-optical wavelengths, satellite-based observations of comets); astrometry of comets (astrometric measurement of photographs and CCD frames, general measurement procedures and astrometric reductions, reporting of comet astrometry, radar astrometry, dealing with older astrometry). Appendices (list of numbered periodic comets, star catalogues, atlases, and charts).

  5. A Prolific Warm Rain Process and its Possible Influence on Ice Nucleation as Observed During ICE-T

    NASA Astrophysics Data System (ADS)

    Lasher-Trapp, S.; DeMott, P. J.; Heymsfield, A.; Hudson, J. G.; Jensen, J. B.; Johnson, A. V.; Leon, D.; McMeeking, G.; Rogers, D. C.; Toohey, D. W.; Twohy, C. H.

    2011-12-01

    of supercooled water present in these clouds, and its possible influence on ice nucleation. Preliminary numerical modeling results constrained by these observations will also be presented to understand if raindrops formed by the warm rain process could be initiating the first ice, and if the cloud conditions and time scales of the microphysical processes are consistent with those observed.

  6. The influence of speed, cyclists' age, pedaling frequency, and observer age on observers' time to arrival judgments of approaching bicycles and e-bikes.

    PubMed

    Schleinitz, Katja; Petzoldt, Tibor; Krems, Josef F; Gehlert, Tina

    2016-07-01

    Given their potential to reach higher speed levels than conventional bicycles, the growing market share of e-bikes has been the reason for increased concerns regarding road safety. Previous studies have shown a clear relationship between object approach speed and an observers' judgment of when the object would reach a predefined position (i.e., time to arrival, TTA), with higher speed resulting in longer TTA estimates. Since TTA estimates have been linked to road users' decisions of whether or not to cross or turn in front of approaching vehicles, the higher potential speeds of e-bikes might result in an increased risk for traffic conflicts. The goal of the two experiments presented in this paper was to examine the influence of speed and a variety of other factors on TTA estimation for conventional bicycles and for e-bikes. In both experiments, participants from two age groups (20-45 years old and 65 years or older) watched video sequences of bicycles approaching at different speeds (15-25km/h) and were asked to judge the TTA at the moment the video was stopped. The results of both experiments showed that an increase in bicycle approach speed resulted in longer TTA estimates (measured as the proportion of estimated TTA relative to actual TTA) for both bicycle types (ηp(2)Exp.1=.489, ηp(2)Exp.2=.705). Compared to younger observers, older observers provided shorter estimates throughout (Exp. I: MDiff=0.35, CI [0.197, 0.509], ηp(2)=.332, Exp. II: MDiff=0.50, CI [.317, 0.682], ηp(2)=.420). In Experiment I, TTA estimates for the conventional bicycle were significantly shorter than for the e-bike (MDiff=0.03, CI [.007, 0.044], ηp(2)=.154), as were the estimates for the elder cyclist compared to the younger one (MDiff=0.05, CI [.025, 0.066], ηp(2)=.323). We hypothesized that the cause for this effect might lie in the seemingly reduced pedaling effort for the e-bike as a result of the motor assistance it provides. Experiment II was able to show that a high pedaling

  7. The influence of speed, cyclists' age, pedaling frequency, and observer age on observers' time to arrival judgments of approaching bicycles and e-bikes.

    PubMed

    Schleinitz, Katja; Petzoldt, Tibor; Krems, Josef F; Gehlert, Tina

    2016-07-01

    Given their potential to reach higher speed levels than conventional bicycles, the growing market share of e-bikes has been the reason for increased concerns regarding road safety. Previous studies have shown a clear relationship between object approach speed and an observers' judgment of when the object would reach a predefined position (i.e., time to arrival, TTA), with higher speed resulting in longer TTA estimates. Since TTA estimates have been linked to road users' decisions of whether or not to cross or turn in front of approaching vehicles, the higher potential speeds of e-bikes might result in an increased risk for traffic conflicts. The goal of the two experiments presented in this paper was to examine the influence of speed and a variety of other factors on TTA estimation for conventional bicycles and for e-bikes. In both experiments, participants from two age groups (20-45 years old and 65 years or older) watched video sequences of bicycles approaching at different speeds (15-25km/h) and were asked to judge the TTA at the moment the video was stopped. The results of both experiments showed that an increase in bicycle approach speed resulted in longer TTA estimates (measured as the proportion of estimated TTA relative to actual TTA) for both bicycle types (ηp(2)Exp.1=.489, ηp(2)Exp.2=.705). Compared to younger observers, older observers provided shorter estimates throughout (Exp. I: MDiff=0.35, CI [0.197, 0.509], ηp(2)=.332, Exp. II: MDiff=0.50, CI [.317, 0.682], ηp(2)=.420). In Experiment I, TTA estimates for the conventional bicycle were significantly shorter than for the e-bike (MDiff=0.03, CI [.007, 0.044], ηp(2)=.154), as were the estimates for the elder cyclist compared to the younger one (MDiff=0.05, CI [.025, 0.066], ηp(2)=.323). We hypothesized that the cause for this effect might lie in the seemingly reduced pedaling effort for the e-bike as a result of the motor assistance it provides. Experiment II was able to show that a high pedaling

  8. Computer-automated caries detection in digital bitewings: consistency of a program and its influence on observer agreement.

    PubMed

    Wenzel, A

    2001-01-01

    The aim of this study was to evaluate a decision-support, caries detection program and its influence on observer agreement in caries diagnosis. 130 patients were examined by digital bitewing radiography (RVG XL sensor, Trophy Radiologie Inc.). Fifty-four approximal surfaces (27 in premolars and 27 in molars) were selected by the author: 24 surfaces (9 in molars and 15 in premolars) scored as sound, 16 surfaces (9 in molars and 7 in premolars) scored as carious in enamel, and 14 surfaces (9 in molars and 5 in premolars) scored as carious in dentine. The Logicon Caries Detector (LCD) program (Logicon Inc., USA) was assessed by repeating the automated analysis ten times for each surface. The two most varying outcomes for lesion probability (Lp(min) and Lp(max)) were saved. Five observers scored the 54 surfaces independently as sound, caries in enamel or caries in dentine before and after the use of LCD. In more than one third of all surfaces the program indicated different lesion probability, from sound at Lp(min) to the presence of a carious lesion at Lp(max). The 5 observers changed their caries score after the use of LCD in a total of 31 surfaces (only 2 of these were in the same surface). Mean kappa value for inter-observer agreement for caries scores before the use of LCD was 0.47 (range 0. 39-0.61) and after LCD 0.48 (range 0.37-0.69). It was concluded that the automated caries detection program was not very consistent and provided different opinions on the caries status in a surface. Inter-observer agreement in caries diagnosis did not improve using the program.

  9. Video Surveillance Captures Student Hand Hygiene Behavior, Reactivity to Observation, and Peer Influence in Kenyan Primary Schools

    PubMed Central

    Pickering, Amy J.; Blum, Annalise G.; Breiman, Robert F.; Ram, Pavani K.; Davis, Jennifer

    2014-01-01

    Background In-person structured observation is considered the best approach for measuring hand hygiene behavior, yet is expensive, time consuming, and may alter behavior. Video surveillance could be a useful tool for objectively monitoring hand hygiene behavior if validated against current methods. Methods Student hand cleaning behavior was monitored with video surveillance and in-person structured observation, both simultaneously and separately, at four primary schools in urban Kenya over a study period of 8 weeks. Findings Video surveillance and in-person observation captured similar rates of hand cleaning (absolute difference <5%, p = 0.74). Video surveillance documented higher hand cleaning rates (71%) when at least one other person was present at the hand cleaning station, compared to when a student was alone (48%; rate ratio  = 1.14 [95% CI 1.01–1.28]). Students increased hand cleaning rates during simultaneous video and in-person monitoring as compared to single-method monitoring, suggesting reactivity to each method of monitoring. This trend was documented at schools receiving a handwashing with soap intervention, but not at schools receiving a sanitizer intervention. Conclusion Video surveillance of hand hygiene behavior yields results comparable to in-person observation among schools in a resource-constrained setting. Video surveillance also has certain advantages over in-person observation, including rapid data processing and the capability to capture new behavioral insights. Peer influence can significantly improve student hand cleaning behavior and, when possible, should be exploited in the design and implementation of school hand hygiene programs. PMID:24676389

  10. VizieR Online Data Catalog: 2nd Cat. of Radial Velocities with Astrometric Data (Kharchenko+, 2007)

    NASA Astrophysics Data System (ADS)

    Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Roeser, S.; Schilbach, E.

    2007-06-01

    The catalogue of radial velocities of Galactic stars with high precision astrometric data, 2nd version (CRVAD-2), is the result of a merging of star lists from the All-Sky Compiled Catalogue of 2.5 Million Stars (ASCC-2.5, Cat. I/280) with the General Catalogue of Radial Velocities (GCRV, Cat. III/213) and with other recently published radial velocity lists and catalogues. Cross identification of objects was carried out with help of coordinate, magnitude, colour and/or spectral type criteria. Data from the Catalogue of Components of Double and Multiple Stars (CCDM, Cat. I/274) were taken into account for the identification of multiple system components. Altogether 54907 stars from the ASCC-2.5 were identified with 51762 stars from the RV source catalogues, 3085 stars have secondary components and 30 stars have 3rd components in multiple systems. The CRVAD-2 includes accurate J2000 equatorial coordinates, proper motions and trigonometric parallaxes in the Hipparcos system, Johnson's BV photometric data, spectral types, radial velocities, multiplicity and variability flags. Stars are sorted in the order of increasing right ascension J2000. This catalogue supersedes the previous version numbered . (1 data file).

  11. Influence of operational parameters on the fluid-side mass transfer resistance observed in a packed bed bioreactor.

    PubMed

    Hussain, Amir; Kangwa, Martin; Abo-Elwafa, Ahmed Gad; Fernandez-Lahore, Marcelo

    2015-01-01

    The influence of mass transfer on productivity as well as the performance of packed bed bioreactor was determined by varying a number of parameters; flow rate, glucose concentration and polymers (chitosan). Saccharomyces cerevisiae cells were immobilized in chitosan and non-chitosan coated alginate beads to demonstrate the effect on external mass transfer by substrate consumption time, lag phase and ethanol production. The results indicate that coating has a significant effect on the lag phase duration, being 30-40 min higher than non-coated beads. After lag phase, no significant change was observed in both types of beads on consumption of glucose with the same flow rate. It was observed that by increasing flow rates; lag phase and glucose consumption time decreased. The reason is due to the reduction of external mass transfer as a result of increase in flow rate as glucose is easily transported to and from the beads surface by diffusion. It is observed that chitosan acts as barrier for transfer of substrate and products, in and out of beads, at initial time of fermentation as it shows longer lag phase for chitosan coated beads than non-coated. Glucose consumption at low flow rate was lower as compared to higher flow rates. The optimum combination of parameters consisting of higher flow rates 30-90 ml/min and between 10 and 20 g/l of glucose was found for maximum production of ethanol.

  12. Investigating the Influence of Anthropogenic Forcing on Observed Mean and Extreme Sea Level Pressure Trends over the Mediterranean Region

    DOE PAGES

    Barkhordarian, Armineh

    2012-01-01

    We investigate whether the observed mean sea level pressure (SLP) trends over the Mediterranean region in the period from 1975 to 2004 are significantly consistent with what 17 models projected as response of SLP to anthropogenic forcing (greenhouse gases and sulphate aerosols, GS). Obtained results indicate that the observed trends in mean SLP cannot be explained by natural (internal) variability. Externally forced changes are detectable in all seasons, except spring. The large-scale component (spatial mean) of the GS signal is detectable in all the 17 models in winter and in 12 of the 17 models in summer. However, the small-scalemore » component (spatial anomalies about the spatial mean) of GS signal is only detectable in winter within 11 of the 17 models. We also show that GS signal has a detectable influence on observed decreasing (increasing) tendency in the frequencies of extremely low (high) SLP days in winter and that these changes cannot be explained by internal climate variability. While the detection of GS forcing is robust in winter and summer, there are striking inconsistencies in autumn, where analysis points to the presence of an external forcing, which is not GS forcing.« less

  13. Influence of upper ocean on Indian summer monsoon rainfall: studies by observation and NCEP climate forecast system (CFSv2)

    NASA Astrophysics Data System (ADS)

    Chaudhari, Hemantkumar S.; Pokhrel, Samir; Rahman, H.; Dhakate, A.; Saha, Subodh K.; Pentakota, S.; Gairola, R. M.

    2016-08-01

    This study explores the role played by ocean processes in influencing Indian summer monsoon rainfall (ISMR) and compares the observed findings with National Centers for Environmental Prediction (NCEP)-coupled model Climate Forecast System, version 2 (CFSv2). The excess and deficit ISMR clearly brings out the distinct signatures in sea surface height (SSH) anomaly, thermocline and mixed layer depth over north Indian Ocean. CFSv2 is successful in simulating SSH anomalies, especially over Arabian Sea and Bay of Bengal region. CFSv2 captures observed findings of SSH anomalies during flood and drought (e.g., Rossby wave propagation which reaches western Bay of Bengal (BoB) during flood years, Rossby wave propagation which did not reach western BoB during drought). It highlights the ability of CFSv2 to simulate the basic ocean processes which governs the SSH variability. These differences are basically generated by upwelling and downwelling caused by the equatorial and coastal Kelvin and Rossby waves, thereby causing difference in SSH anomaly and thermocline, and subsequently modifying the convection centers, which dictates precipitation over the Indian subcontinent region. Since the observed SSH anomaly and thermal structure show distinct characteristic features with respect to strong and weak ISMR variability, the assimilation of real ocean data in terms of satellite products (like SSHA from AVISO/SARAL) bestow great promise for the future improvement.

  14. The influence of diffuse scattered light. II. Observations of galaxy haloes and thick discs and hosts of blue compact galaxies

    NASA Astrophysics Data System (ADS)

    Sandin, Christer

    2015-05-01

    Studies of deep photometry of galaxies have presented discoveries of excess light in surface-brightness and colour profiles at large radii in the form of diffuse faint haloes and thick discs. In a majority of the cases, it has seemed necessary to use exotic stellar populations or alternative physical solutions to explain the excess. Few studies have carefully scrutinized the role of scattered light in this context. I explore the influence of scattered light on ground-based observations of haloes and thick discs around edge-on galaxies, haloes around face-on disc galaxies, host galaxies around blue compact galaxies (BCGs), and haloes around elliptical galaxies. Surface-brightness structures of all considered types of galaxies are modelled and analysed to compare scattered-light haloes and thick discs with measurements. I simulate the influence of scattered light and accurate sky subtraction on simplified Sérsic-type and face-on disc galaxy models. All galaxy models are convolved with both lower-limit and brighter point spread functions (PSFs); for a few galaxies it was possible to use dedicated PSFs. The results show bright scattered-light haloes and high amounts of red excess at large radii and faint surface brightnesses for nearly all types of galaxies; exceptions are the largest elliptical-type galaxies where the influence of scattered light is smaller. Studies have underestimated the role of scattered light to explain their surface-brightness profiles. My analysis shows surface-brightness profiles that include scattered light that are very similar to and overlap measurements at all radii. The derivation of physical properties of haloes, thick discs, and BCG hosts from diffuse data is misleading since accurate and radially extended PSFs are non-existent. Significantly improved analyses that include new measurements of PSFs are required to study diffuse faint structures further.

  15. Influence of aerosols on the life cycle of a radiation fog event. A numerical and observational study

    NASA Astrophysics Data System (ADS)

    Stolaki, S.; Haeffelin, M.; Lac, C.; Dupont, J.-C.; Elias, T.; Masson, V.

    2015-01-01

    Despite the knowledge gained on the physical processes dominating the formation, development and dissipation of radiation fog events, uncertainties still exist about the role of the microphysical processes related to aerosol characteristics. The objective of this work is to analyze the sensitivity of fog to aerosols through their impacts on the fog droplets. A radiation fog event that formed on 15/11/2011 at the SIRTA Observatory near Paris in the context of the 2011-2012 ParisFog field campaign is the basis of this study. The selected case is one that initially forms a few hundred meters above the surface and within half an hour lowers down to the surface. A combination of SIRTA's sophisticated observations and 1D numerical simulations is employed with the aim of better understanding the influence of thermodynamics and microphysics on the life-cycle of the fog event and the degree to which aerosol characteristics such as concentration of potentially activated aerosols, size and solubility affect its characteristics. It results that the model simulates fairly well the fog life cycle, with only one half hour advance in the onset and one hour in the dissipation at the surface. The quality of the reference simulation is evaluated against several in-situ and remote sensing measurements. A numerical sensitivity analysis shows that the fog characteristics are strongly influenced by the aerosols. Doubling (halving) the cloud condensation nuclei (CCN) number translates into a 160% increase (65% decrease) in the production of fog droplets, and a 60% increase (40% decrease) of the liquid water path (LWP). The aerosols influence up to 10% the fog geometrical thickness. The necessity for more detailed local forcings that will produce better thermohygrometric conditions in the upper levels above the formed fog layer is underlined, as well as the addition of microphysical measurements in the vertical that will allow to improve two-moment microphysics schemes.

  16. Apparent tidal influence on magmatic activity at Oldoinyo Lengai volcano, Tanzania, as observed in Moderate resolution Imaging Spectroradiometer (MODIS) data

    NASA Astrophysics Data System (ADS)

    van Manen, Saskia M.; Kervyn, Matthieu; Blake, Stephen; Ernst, Gerald G. J.

    2010-01-01

    This paper investigates the relative timing of solid Earth tides and thermal anomalies associated with volcanic activity at Oldoinyo Lengai (OL), Tanzania, from 2000 to 2008. The low viscosity of OL's carbonatite magmas may make it particularly susceptible to tidal stresses. Thermal data from the Moderate resolution Imaging Spectroradiometer (MODIS) were filtered using the MODLEN algorithm and Earth tides were modeled using TSoft. Application of the Schuster and Chi-squared tests resulted in apparent correlations between times of thermal anomalies and the phase of the semi-diurnal and biannual solid Earth tides. However, for semi-diurnal and biannual tides limited acquisition times of the MODIS data account for the apparent correlations. Re-examining the data while accounting for the bias introduced by the limited acquisition times, correlations are no longer found. Onset times of eruptive events and times of thermal anomalies show no statistically significant correlation with the fortnightly tide, indicating this is not an influence on activity at OL. Tidal influences on magmatic activity, if at all present, cannot be observed in coarse resolution thermal data on semi-diurnal and fortnightly time scales. Based on the available data, correlations on biannual timescales cannot be ruled out.

  17. A molecular picture: How composition influences the dynamic and static properties in a polyolefin blend, as observed with molecular simulation

    NASA Astrophysics Data System (ADS)

    May, Andrew

    2005-03-01

    We use molecular dynamics simulation to investigate dynamic and static properties in a blend of poly(ethylene-propylene) [PEP] and poly(ethylene-butene) [PEB]: this is a simple model for blend dynamics because the mixture behaves athermally and each component has similar pure packing characteristics and glass transition temperatures. The use of simulation allows us to examine a full spectrum of compositions, ranging from the dilute (single chain) to concentrated limits (all but one chain). As composition is varied, mobility is observed through the self-intermediate scattering function, while the pair distribution function and local concentrations are used to examine static features. Attention is given to both average values and the distribution within the average. Despite the simplicity of this system, the influence of composition varies between the two components, most noticeable in the dilute region. Molecular packing and concentrations on a local length scale are investigated as a possible source for this variation.

  18. The Influence of Pumping on Observed Bacterial Counts in Groundwater Samples: Implications for Sampling Protocol and Water Quality Interpretation

    NASA Astrophysics Data System (ADS)

    Kozuskanich, J.; Novakowski, K.; Anderson, B.

    2008-12-01

    Drinking water quality has become an important issue in Ontario following the events in Walkerton in 2000. Many rural communities are reliant on private groundwater wells for drinking water, and it is the responsibility of the owner to have the water tested to make sure it is safe for human consumption. Homeowners can usually take a sample to the local health unit for total coliform and E. Coli analysis at no charge to determine if the water supply is being tainted by surface water or fecal matter, both of which could indicate the potential for negative impacts on human health. However, is the sample coming out of the tap representative of what is going on the aquifer? The goal of this study is to observe how bacterial counts may vary during the course of well pumping, and how those changing results influence the assessment of water quality. Multiple tests were conducted in bedrock monitoring wells to examine the influence of pumping rate and pumped volume on observed counts of total coliform, E. Coli, fecal streptococcus, fecal coliform and heterotrophic plate count. Bacterial samples were collected frequently during the course of continuous purging events lasting up to 8 hours. Typical field parameters (temperature, salinity, pH, dissolved oxygen and ORP) were also continuously monitored during the course of each test. Common practice in groundwater studies is to wait until these parameters have stabilized or three well volumes have been removed prior to sampling, to ensure the sample is taken from new water entering the well from the aquifer, rather than the original water stored in the borehole prior to the test. In general, most bacterial counts were low, but did go above the drinking water standard of 0 counts/100mL (total coliform and E. Coli) at times during the tests. Results show the greatest variability in the observed bacterial counts at the onset of pumping prior to the removal of three well volumes. Samples taken after the removal of three well

  19. Astrometric Positioning of the Venezuelan Satellite VeneSat-1 "PASAVEN"

    NASA Astrophysics Data System (ADS)

    Otero, S.; Abad, C.; Hernández, R.

    2014-06-01

    By means of this document we inform regarding the collaboration between the Venezuelan institutions, Bolivarian Agency for Space Activities (ABAE) and the Astronomy Research Center (CIDA) with the purpose of using astrometry for the tracking of the Venezuelan Geostationary Satellite Venesat1 by means of optical observation. For this purpose two small astronomical observatories shall be installed on the space tracking ground stations owned by the ABAE in Venezuela and we hope that in a short term they shall be producing the expected results, and also that these observations may be extended to future Venezuelan satellites and to the determination of the geostationary space debris trajectories.

  20. VizieR Online Data Catalog: Astrometric catalogue of stars KMAC3 (Lazorenko+, 2016)

    NASA Astrophysics Data System (ADS)

    Karbovsky, V.; Lazorenko, P.; Buromsky, M.; Kasjan, S.; Svachii, L.

    2016-09-01

    The KMAC3 catalogue contain positions (J2000.0) and V magnitudes in equatorial sky area. Positions are given at mean epoch of observations. The limiting magnitude is V=17mag. The estimated accuracies are 60-80mag in positions and 0.04-0.08mag in photometry for V<15mag stars. (1 data file).

  1. Influence of subsurface heterogeneity on observed borehole temperatures at a mountain permafrost site in the Upper Engadine, Swiss Alps

    NASA Astrophysics Data System (ADS)

    Schneider, S.; Hoelzle, M.; Hauck, C.

    2012-04-01

    Permafrost in high mountain areas occurs in a large variety of surface and subsurface material within short distances. This work presents a nine-year (2002 - 2011) data set of borehole temperatures for five different (sub-) surface materials from the high alpine permafrost area, Murtèl-Corvatsch, Switzerland (Haeberli et al. (1988) and Hanson & Hoelzle (2005)). The influence of the material on the thermal regime was investigated by borehole temperature data, the temperature at the top of the permafrost (TTOP-concept) and the apparent thermal diffusivity (ATD). The results show no consistent subsurface temperature trends since 2002 within the uppermost 6 meters. Rather, the thermal regime is predominantly influenced by the composition of the subsurface material and the thickness and duration of the snow cover. At all sites the subsurface temperatures were the lowest when the snow thickness was less than 1m. As pointed out in Luetschg et al. (2008), it could be confirmed, that the longer the non-insulating snow cover lasts in autumn, the colder is the ground surface temperature (GST) through the entire year. At all sites the cooling during autumn/ winter and the duration of the zero curtain in spring had a stronger influence on the interannual variability of the thermal regime than the temperature increase during summer. At coarse blocky, ice-rich sites no changes in active layer depth were observed. Rather, the ATD values of the active layer and the high temperature transport rate of 5.6 K m-1 d-1 confirm a high thermal response of the active layer. Within coarse blocky material, the air ventilation (as described in Wakonigg (1996)) and the seasonal production of ice seem to be the main factors for permafrost occurrence in high alpine regions. While temperatures within the talus slope are close to 0 °C and a stable permafrost regime is observed, the subsurface of the fine-grained site (where convective and advective airflow can be neglected) showed positive

  2. Prediction of local concentration statistics in variably saturated soils: Influence of observation scale and comparison with field data

    NASA Astrophysics Data System (ADS)

    Graham, Wendy; Destouni, Georgia; Demmy, George; Foussereau, Xavier

    1998-07-01

    The methodology developed in Destouni and Graham [Destouni, G., Graham, W.D., 1997. The influence of observation method on local concentration statistics in the subsurface. Water Resour. Res. 33 (4) 663-676.] for predicting locally measured concentration statistics for solute transport in heterogeneous porous media under saturated flow conditions is applied to the prediction of conservative nonreactive solute transport in the vadose zone where observations are obtained by soil coring. Exact analytical solutions are developed for both the mean and variance of solute concentrations measured in discrete soil cores using a simplified physical model for vadose-zone flow and solute transport. Theoretical results show that while the ensemble mean concentration is relatively insensitive to the length-scale of the measurement, predictions of the concentration variance are significantly impacted by the sampling interval. Results also show that accounting for vertical heterogeneity in the soil profile results in significantly less spreading in the mean and variance of the measured solute breakthrough curves, indicating that it is important to account for vertical heterogeneity even for relatively small travel distances. Model predictions for both the mean and variance of locally measured solute concentration, based on independently estimated model parameters, agree well with data from a field tracer test conducted in Manatee County, Florida.

  3. Detection method and observed data of high-energy gamma rays under the influence of quantum gravity

    SciTech Connect

    Kifune, T.

    2014-05-20

    The interaction of high-energy particles affected by quantum gravity is argued from the experimental viewpoint of raising a question, 'our detection method for high-energy γ-rays supplies trustworthy observation data and we are now seeing the true image of the universe through high-energy γ-rays?' The modified dispersion relation (MDR) for particles' energy and momentum is applied to the equation of energy-momentum conservation in particle reactions, to study the restriction imposed on the kinematic state of high-energy particles by the Lorentz invariance violation (LIV) due to quantum gravity, as a function of the incident particle energy of the reaction. The result suggests that the interaction utilized for γ-ray detection is not free from the effect of quantum gravity when γ-ray energy is higher than 10{sup 13} ∼ 10{sup 17} eV depending on models of MDR. Discussion is presented on the prospect of finding clear evidence of the LIV effect from γ-ray observations, as well as on the radiation and propagation mechanism of γ-rays under the influence of the LIV effect.

  4. Influence of mental practice and movement observation on motor memory, cognitive function and motor performance in the elderly

    PubMed Central

    Altermann, Caroline D. C.; Martins, Alexandre S.; Carpes, Felipe P.; Mello-Carpes, Pâmela B.

    2014-01-01

    Background With aging, it is important to maintain cognitive and motor functions to ensure autonomy and quality of life. During the acquisition of motor skills, it is necessary for the elderly to understand the purpose of the proposed activities. Physical and mental practice, as well as demonstrations, are strategies used to learn movements. Objectives To investigate the influence of mental practice and the observation of movement on motor memory and to understand the relationship between cognitive function and motor performance in the execution of a sequence of digital movements in the elderly. Method This was a cross-sectional study conducted with 45 young and 45 aged subjects. The instruments used were Mini-Mental State Examination (MMSE), Manual Preference Inventory and a Digital Motor Task (composed of a training of a sequence of movements, an interval and a test phase). The subjects were divided into three subgroups: control, mental practice and observation of movement. Results The elderly depend more strongly on mental practice for the acquisition of a motor memory. In comparing the performances of people in different age groups, we found that in the elderly, there was a negative correlation between the MMSE score and the execution time as well as the number of errors in the motor task. Conclusions For the elderly, mental practice can advantage motor performance. Also, there is a significant relationship between cognitive function, learning and the execution of new motor skills. PMID:24839046

  5. Eclipses of the inner satellites of Jupiter observed in 2015

    NASA Astrophysics Data System (ADS)

    Saquet, E.; Emelyanov, N.; Colas, F.; Arlot, J.-E.; Robert, V.; Christophe, B.; Dechambre, O.

    2016-06-01

    Aims: During the 2014-2015 campaign of mutual events, we recorded ground-based photometric observations of eclipses of Amalthea (JV) and, for the first time, Thebe (JXIV) by the Galilean moons. We focused on estimating whether the positioning accuracy of the inner satellites determined with photometry is sufficient for dynamical studies. Methods: We observed two eclipses of Amalthea and one of Thebe with the 1 m telescope at Pic du Midi Observatory using an IR filter and a mask placed over the planetary image to avoid blooming features. A third observation of Amalthea was taken at Saint-Sulpice Observatory with a 60 cm telescope using a methane filter (890 nm) and a deep absorption band to decrease the contrast between the planet and the satellites. After background removal, we computed a differential aperture photometry to obtain the light flux, and followed with an astrometric reduction. Results: We provide astrometric results with an external precision of 53 mas for the eclipse of Thebe, and 20 mas for that of Amalthea. These observation accuracies largely override standard astrometric measurements. The (O - C)s for the eclipse of Thebe are 75 mas on the X-axis and 120 mas on the Y-axis. The (O - C)s for the total eclipses of Amalthea are 95 mas and 22 mas, along the orbit, for two of the three events. Taking into account the ratio of (O - C) to precision of the astrometric results, we show a significant discrepancy with the theory established by Avdyushev and Ban'shikova in 2008, and the JPL JUP 310 ephemeris. Three of the four eclipse observations where recorded at the 1 m telescope of Pic du Midi Observatory (S2P), the other at Saint-Sulpice Observatory.

  6. VizieR Online Data Catalog: Astrometric catalogue of stars KMAC2 (Lazorenko+, 2015)

    NASA Astrophysics Data System (ADS)

    Lazorenko, P.; Karbovsky, V.; Buromsky, M.; Svachii, L.; Kasjan, S.

    2016-01-01

    The KMAC2 catalogue contain positions (J2000.0) and V magnitudes in equatorial sky area. Positions are given at mean epoch of observations. The limiting magnitude is V=17mag. The estimated accuracies are 50-70mag in positions and 0.05-0.08mag in photometry for V<15mag stars. We add also proper motions taken from the USNO-A2.0 catalogue. (1 data file).

  7. Observables and Goals for Coronagraphic Characterization of Earth Analogs

    NASA Technical Reports Server (NTRS)

    Stapelfelt, Karl R.

    2012-01-01

    On a suitably large and stable telescope, direct coronagraphic imaging can make numerous important measurements of terrestrial exoplanets. Astrometric time-series observations will be of primary importance: Only when the planet orbital elements are known can 1) the effects of the planet's illumination phase and asterocentric distance be accounted for in the observed planetary fluxes, and 2) the planet's location relative to the habitable zone be established. Planetary colors and spectra will allow characterization of the planet's atmosphere and possibly even its surface, while time-variable fluxes may indicate surface contrast features or seasonal changes. Imaging will also reveal the context of other planets and dust belts in the system, both of which can affect habitability. Requirements on astrometric precision, number of visits, and telescope aperture will be discussed.

  8. KLENOT - Near Earth and other unusual objects observations

    NASA Astrophysics Data System (ADS)

    Kocer, Michal; Tichá, Jana; Tichý, Miloš

    2005-02-01

    The KLENOT project is a project of the Klet Observatory, Czech Republic, devoted to astrometric observations of Near-Earth objects, distant objects and comets. The improved effort of the large NEO surveys resulting in an increasing number of newly discovered NEOs calls for continuous follow-up astrometry to secure an accurate orbit determination of discovered bodies first in discovery opposition and then during next apparitions. Considering this urgent need of astrometric follow-up, the fact that many of these targets are fainter then magnitude 20.0 V and our results and experience in minor planet and comet CCD astrometry done at Klet since 1993, we decided to bring into operation a new 1-m class facility working on a permanent basis - the KLENOT telescope. The regular observing of the telescope started in March 2002 (the MPC code 246). Beside methods and techniques we use for follow-up astrometry we present most important results of the project.

  9. The influence of expertise on brain activation of the action observation network during anticipation of tennis and volleyball serves

    PubMed Central

    Balser, Nils; Lorey, Britta; Pilgramm, Sebastian; Naumann, Tim; Kindermann, Stefan; Stark, Rudolf; Zentgraf, Karen; Williams, A. Mark; Munzert, Jörn

    2014-01-01

    In many daily activities, and especially in sport, it is necessary to predict the effects of others' actions in order to initiate appropriate responses. Recently, researchers have suggested that the action–observation network (AON) including the cerebellum plays an essential role during such anticipation, particularly in sport expert performers. In the present study, we examined the influence of task-specific expertise on the AON by investigating differences between two expert groups trained in different sports while anticipating action effects. Altogether, 15 tennis and 16 volleyball experts anticipated the direction of observed tennis and volleyball serves while undergoing functional magnetic resonance imaging (fMRI). The expert group in each sport acted as novice controls in the other sport with which they had only little experience. When contrasting anticipation in both expertise conditions with the corresponding untrained sport, a stronger activation of AON areas (SPL, SMA), and particularly of cerebellar structures, was observed. Furthermore, the neural activation within the cerebellum and the SPL was linearly correlated with participant's anticipation performance, irrespective of the specific expertise. For the SPL, this relationship also holds when an expert performs a domain-specific anticipation task. Notably, the stronger activation of the cerebellum as well as of the SMA and the SPL in the expertise conditions suggests that experts rely on their more fine-tuned perceptual-motor representations that have improved during years of training when anticipating the effects of others' actions in their preferred sport. The association of activation within the SPL and the cerebellum with the task achievement suggests that these areas are the predominant brain sites involved in fast motor predictions. The SPL reflects the processing of domain-specific contextual information and the cerebellum the usage of a predictive internal model to solve the anticipation

  10. Understanding the influence of assimilating satellite-derived observations on mesoscale analyses and forecasts of tropical cyclone track and structure

    NASA Astrophysics Data System (ADS)

    Wu, Ting-Chi

    This dissertation research explores the influence of assimilating satellite-derived observations on mesoscale numerical analyses and forecasts of tropical cyclones (TC). The ultimate goal is to provide more accurate mesoscale analyses of TC and its surrounding environment for superior TC track and intensity forecasts. High spatial and temporal resolution satellite-derived observations are prepared for two TC cases, Typhoon Sinlaku and Hurricane Ike (both 2008). The Advanced Research version of the Weather and Research Forecasting Model (ARW-WRF) is employed and data is assimilated using the Ensemble Adjustment Kalman Filter (EAKF) implemented in the Data Assimilation Research Testbed. In the first part of this research, the influence of assimilating enhanced atmospheric motion vectors (AMVs) derived from geostationary satellites is examined by comparing three parallel WRF/EnKF experiments. The control experiment assimilates the same AMV dataset assimilated in NCEP operational analysis along with conventional observations from radiosondes, aircraft, and advisory TC position data. During Sinlaku and Ike, the Cooperative Institute for Meteorological Satellite Studies (CIMSS) generates hourly AMVs along with Rapid-Scan (RS) AMVs when the satellite RS mode is activated. With an order of magnitude more AMV data assimilated, the assimilation of hourly CIMSS AMV dataset exhibit superior initial TC position, intensity and structure estimates to the control analyses and the subsequent short-range forecasts. When RS AMVs are processed and assimilated, the addition of RS AMVs offers additional modification to the TC and its environment and leads to Sinlaku's recurvature toward Japan, albeit prematurely. The results demonstrate the promise of assimilating enhanced AMV data into regional TC models. The second part of this research continues the work in the first part and further explores the influence of assimilating enhanced AMV datasets by conducting parallel data-denial WRF

  11. EMCCD SPECKLE INTERFEROMETRY WITH THE 6 m TELESCOPE: ASTROMETRIC MEASUREMENTS, DIFFERENTIAL PHOTOMETRY, AND ORBITS

    SciTech Connect

    Docobo, Jose A.; Tamazian, Vakhtang S.; Melikian, Norair D. E-mail: vakhtang.tamazian@usc.e E-mail: nmelikia@bao.sci.a

    2010-10-15

    Results of the EMCCD-based speckle interferometric observations and differential photometry for 46 visual binaries obtained in 2007 June and July with the 6 m telescope of the Special Astrophysical Observatory (Russia) are presented. First preliminary orbits for COU 401, COU 1281, and COU 1037 as well as improved orbits for CHR 137, COU 100, COU 1136, COU 798, CHR 51, CHR 55, COU 315, COU 206, and ADS 13961, along with their dynamical mass estimates, are reported. On the basis of dynamical parallax information, first distance estimates for COU 100, COU 1136, COU 798, COU 206, and COU 1037 are calculated.

  12. Possible influence of cosmic rays on climate through thunderstorm clouds, 2. Observations in different cosmic ray components

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.; Dorman, I. V.; Iucci, N.; Ne'eman, Yu.; Parisi, M.; Pustil'nik, L. A.; Signoretti, F.; Sternlieb, A.; Villoresi, G.; Zukerman, I. G.

    We compare observed in many experiments effects of atmospheric electric field in cosmic rays. On the basis of cosmic ray and atmospheric electric field one minute data obtained by NM and EFS of Emilio Segre' Observatory (hight 2025 m above s.l., cosmic ray cut-off rigidity for vertical direction 10.8 GV) we determine the atmospheric electric field effect in CR for total neutron intensity and for multiplicities m ≥ 1, m ≥ 2, m ≥ 3, m ≥ 4, m ≥ 5, m ≥ 6, m ≥ 7, and m ≥ 8, as well as for m = 1, m = 2, m = 3, m = 4, m = 5, m = 6, and m = 7. For comparison and excluding primary CR variations we use also one minute data on neutron multiplicities obtained by NM in Rome and other cosmic ray stations. According to the theoretical calculations of Dorman and Dorman (2004) the electric field effect in the NM counting rate must be caused mainly by captchuring of slow negative muons by lead nucleus with escaping few neutrons. As it was shown in Dorman and Dorman (2004), the biggest electric field effect is expected in the multiplicity m = 1, much smaller in m = 2 and negligible effect is expected in higher multiplicities. We control this conclusion on the basis of our experimental data. Obtained results give a possibility to estimate total acceleration and deceleration of CR particles by the atmospheric electric field. We consider also the possible influence of CR air ionization (especially by secondary energetic electrons) on thunderstorms and lightnings, and through this -- on climate. References: Dorman L.I. and I.V. Dorman ``Possible influence of cosmic rays on climate through thunderstorm clouds, 1. Theory on cosmic ray connection with atmospheric electric field phenomenon''. Report on the Session D2.1/C2.2/E3.1 of COSPAR-2004.

  13. The Orbit of Pheobe from Earthbased and Voyager Observations

    NASA Technical Reports Server (NTRS)

    Jacobson, R. A.

    1996-01-01

    This article presents the results of a fit of a numerically integrated orbit for the Saturnian satellite Pheobe to Earthbased astrometric observations (from 1904 to 1996) and imaging data acquired by the Voyager 2 spacecraft during its encounter with Saturn. The primary results are the epoch state vector used in the integration and a set of mean elements which provide a geometrical representation of the orbit. We also assess the quality of the fit and the accuracy of the orbit.

  14. On the influence of biomass burning on the seasonal CO2 signal as observed at monitoring stations

    USGS Publications Warehouse

    Wittenberg, U.; Heimann, Martin; Esse, G.; McGuire, A.D.; Sauf, W.

    1998-01-01

    We investigated the role of biomass burning in simulating the seasonal signal in both prognostic and diagnostic analyses. The prognostic anaysis involved the High-Resolution Biosphere Model, a prognostic terrestrial biosphere model, and the coupled vegetation fire module, which together produce a prognostic data set of biomass burning. The diagnostic analysis invovled the Simple Diagnostic Biosphere Model (SDBM) and the Hao and Liu [1994] diagnostic data set of bimass burning, which have been scaled to global 2 and 4 Pg C yr-1, respectively. The monthly carbon exchange fields between the atmosphere and the biosphere with a spatial resolution of 0.5?? ?? 0.5??, the seasonal atmosphere-ocean exchange fields, and the emissions from fossil fuels have been coupled to the three-dimensional atmospheric transport model TM2. We have chosen eight monitoring stations of the National Oceanic and Atmospheric Administration network to compare the predicted seasonal atmospheric CO2 signals with those deduced from atmosphere-biosphere carbon exchange fluxes without any contribution from biomass burning. The prognostic analysis and the diagnostic analysis with global burning emissions of 4 Pg C yr-1 agree with respect to the change in the amplitude of the seasonal CO2 concentration introduced through biomass burning. We find that the seasonal CO2 signal at stations in higher northern latitudes (north of 30??N) is marginally influenced by biomass burning. For stations in tropical regions an increase in the CO2 amplitude of more an 1 oppmv (up to 50% with respect to the observed trough to peak amplitude) has been calculated. Biomass burning at stations farther south accounts for an increase in the CO2 amplitude of up to 59% (0.6 ppmv). A change in the phase of the seasonal CO2 signal at tropical and southern stations has been shown to be strongly influenced by the onset of biomass burning in southern tropical Africa and America. Comparing simulated and observed seasonal CO2 signals

  15. Radio-source structure in astrometric and geodetic very long baseline interferometry

    SciTech Connect

    Charlot, P. Institut Geographique National, Saint Mande )

    1990-04-01

    An algorithm to calculate source structure corrections for bandwidth synthesis delays and delay rates is used to refer the position of extragalacitc radio sources to a specific feature of each source's morphology. The delay and delay rate are obtained from VBLI observations. The algorithm and its theoretical basis are described, and simulations for a simple two-component source are discussed. VLBI data for the complex radio source NRAO 140 are analyzed. For this source, structure corrections are calculated with maps from three different VLBI imaging techniques: the hybrid-CLEAN algorithm, the maximum entropy method, and model fitting. The calculated structure corrections are compared with brightness distributions to the actual data. The results are used to map NRAO 140. It is found that the CLEAN map produces the most accurate structure corrections. 27 refs.

  16. SIMULATION AND ANALYSIS OF SUB-{mu}as PRECISION ASTROMETRIC DATA FOR PLANET FINDING

    SciTech Connect

    Savransky, Dmitry; Kasdin, N. Jeremy

    2010-10-01

    We present a vector formulation of an interferometric observation of a star, including the effects of the barycentric motion of the observatory, the proper motions of the star, and the reflex motions of the star due to orbiting planets. We use this model to empirically determine the magnitude and form of the signal due to a single Earth-mass planet orbiting about a Sun-mass star. Using bounding values for the known components of the model, we perform a series of expansions, comparing the residuals to this signal. We demonstrate why commonly used first-order linearizations of similar measurement models are insufficient for signals of the magnitude of the one due to an Earth-mass planet, and present a consistent expansion which is linear in the unknown quantities, with residuals multiple orders of magnitude below the Earth-mass planet signal. We also discuss numerical issues that can arise when simulating or analyzing these measurements.

  17. Factors influencing response to Botulinum toxin type A in patients with idiopathic cervical dystonia: results from an international observational study

    PubMed Central

    Ehler, Edvard; Zakine, Benjamin; Maisonobe, Pascal; Simonetta-Moreau, Marion

    2012-01-01

    Objectives Real-life data on response to Botulinum toxin A (BoNT-A) in cervical dystonia (CD) are sparse. An expert group of neurologists was convened with the overall aim of developing a definition of treatment response, which could be applied in a non-interventional study of BoNT-A-treated subjects with CD. Design International, multicentre, prospective, observational study of a single injection cycle of BoNT-A as part of normal clinical practice. Setting 38 centres across Australia, Belgium, Czech Republic, France, Germany, The Netherlands, Portugal, Russia and the UK. Participants 404 adult subjects with idiopathic CD. Most subjects were women, aged 41–60 years and had previously received BoNT-A. Outcome measures Patients were classified as responders if they met all the following four criteria: magnitude of effect (≥25% improvement Toronto Western Spasmodic Torticollis Rating Scale), duration of effect (≥12-week interval between the BoNT-A injection day and subject-reported waning of treatment effect), tolerability (absence of severe related adverse event) and subject's positive Clinical Global Improvement (CGI). Results High rates of response were observed for magnitude of effect (73.6%), tolerability (97.5%) and subject's clinical global improvement (69.8%). The subjective duration of effect criterion was achieved by 49.3% of subjects; 28.6% of subjects achieved the responder definition. Factors most strongly associated with response were age (<40 years; OR 3.9, p<0.05) and absence of baseline head tremor (OR 1.5; not significant). Conclusions Three of four criteria were met by most patients. The proposed multidimensional definition of response appears to be practical for routine practice. Unrealistically high patient expectation and subjectivity may influence the perception of a quick waning of effect, but highlights that this aspect may be a hurdle to response in some patients. Clinical registration number (NCT00833196; ClinicalTrials.gov). PMID

  18. Observational Constraints on Terpene Oxidation with and without Anthropogenic Influence in the Amazon using Speciated Measurements from SV-TAG

    NASA Astrophysics Data System (ADS)

    Yee, L.; Isaacman, G. A.; Kreisberg, N. M.; Liu, Y.; McKinney, K. A.; de Sá, S. S.; Martin, S. T.; Alexander, M. L.; Palm, B. B.; Hu, W.; Campuzano Jost, P.; Day, D. A.; Jimenez, J. L.; Viegas, J.; Springston, S. R.; Wurm, F.; Ferreira De Brito, J.; Artaxo, P.; Manzi, A. O.; Machado, L.; Longo, K.; Oliveira, M. B.; Souza, R. A. F. D.; Hering, S. V.; Goldstein, A. H.

    2014-12-01

    Biogenic volatile organic compounds (BVOCs) from the Amazon forest represent the largest regional source of organic carbon emissions to the atmosphere. These BVOC emissions dominantly consist of volatile and semi-volatile terpenoid compounds that undergo chemical transformations in the atmosphere to form oxygenated condensable gases and secondary organic aerosol (SOA). However, the oxidation pathways of these compounds are still not well understood, and are expected to differ significantly between "pristine" conditions, as is common in Amazonia, and polluted conditions caused by emissions from growing cities. Our focus is to elucidate how anthropogenic emissions influence BVOC chemistry and BSOA formation through speciated measurements of their oxidation products. We have deployed the Semi-Volatile Thermal desorption Aerosol Gas Chromatograph (SV-TAG) at the rural T3 site located west of the urban center of Manaus, Brazil as part of the Green Ocean Amazon (GoAmazon) 2014 field campaign to measure hourly concentrations of semi-volatile BVOCs and their oxidation products during the wet and dry seasons. Primary BVOC concentrations measured by the SV-TAG include sesquiterpenes and diterpenes, which have rarely been speciated with high time-resolution. We observe sesquiterpenes to be anti-correlated with ozone, indicative of sesquiterpene oxidation playing a major role in the regional oxidant budget. The role of sesquiterpenes in atmospheric SOA formation are of interest due to their high aerosol yields and high reactivity with ozone, relative to more commonly measured BVOCs (e.g. monoterpenes). We explore relative concentrations of sesquiterpenes and monoterpenes and their roles as precursors to SOA formation by combining SV-TAG measurements with those from an additional suite of VOC and particle measurements deployed in the Amazon. We also report the first ever hourly observations of the gas-particle partitioning of speciated terpene oxidation products in the Amazon

  19. An observational study on the influence of solvent composition on the architecture of drug-layered pellets.

    PubMed

    McConnell, Emma L; Macfarlane, Calum B; Basit, Abdul W

    2009-10-01

    Pelletization for the manufacture of modified release multiparticulate drug delivery systems is often considered to be well defined and robust. However, small differences in formulation conditions can lead to surprising changes to the expected outcomes. We observed that extended release tramadol hydrochloride pellets, prepared by solution layering an ethanolic solution of drug on a non-pareil, resulted in highly unusual pellet architecture with deep indentations which prevented the application of a homogeneous outer coating of ethylcellulose and talc, and negatively influenced the desired modified release characteristics. Modification of outer coating thickness and process temperature showed no improvement in release characteristics. A solution to the problem was found in the incorporation of 10% v/v water into the ethanolic drug layering solution, resulting in the production of drug-loaded pellets with a smooth morphology which allowed the application of a coherent outer coating able to retard drug release. The surprising difference in pellet morphology between the two solvent drug layering systems may be attributed to differences in solvent evaporation rates. This demonstrates that established techniques are sometimes less straightforward than thought as small changes in formulation have significant effects on the resulting product in a way which is not always well understood. PMID:19589378

  20. Influence of the actions observed on cervical motion in patients with chronic neck pain: a pilot study.

    PubMed

    de-la-Puente-Ranea, Lucía; García-Calvo, Beatriz; La Touche, Roy; Fernández-Carnero, Josué; Gil-Martínez, Alfonso

    2016-08-01

    The aim of the present pilot study was to prove if the action-observation (AOb) improved the cervical range of motion (CROM) in patients with nonspecific chronic neck pain (CNP). Double blind pilot study. A total of 28 subjects were randomly assigned to an effective-movement group (n=14) and an ineffective-movement group (n=14). The follow-up consisted of: pretreatment, posttreatment and 10 min after second measurement (motor imagery). Outcome measures were CROM, and pres-sure pain detection thresholds (PPDTs). No statistical differences were found in baseline on CROM and on the PPDT. Test for independent groups revealed significant changes in cervical rotation movement. Both groups in posttreatment (P=0.042; Cohen d=0.81) and after 10 min (P=0.019; Cohen d=0.9). For intragroup PPDT, the Wilcoxon test revealed significant effects in the effective movement at C2 of the pre to 10-min post (P=0.040). However, the ineffective movement revealed a significant reduction in PPDT in zygapophyseal joint of C5-C6 as the pre to post (P=0.010) as the pre to 10-min post (P=0.041) periods. In conclusions this pilot study demonstrated that the effective AOb produced significant changes versus ineffective AOb in the CROM and it could influences in PPT in subject with CNP immediately. PMID:27656633

  1. Influence of the actions observed on cervical motion in patients with chronic neck pain: a pilot study

    PubMed Central

    de-la-Puente-Ranea, Lucía; García-Calvo, Beatriz; La Touche, Roy; Fernández-Carnero, Josué; Gil-Martínez, Alfonso

    2016-01-01

    The aim of the present pilot study was to prove if the action-observation (AOb) improved the cervical range of motion (CROM) in patients with nonspecific chronic neck pain (CNP). Double blind pilot study. A total of 28 subjects were randomly assigned to an effective-movement group (n=14) and an ineffective-movement group (n=14). The follow-up consisted of: pretreatment, posttreatment and 10 min after second measurement (motor imagery). Outcome measures were CROM, and pres-sure pain detection thresholds (PPDTs). No statistical differences were found in baseline on CROM and on the PPDT. Test for independent groups revealed significant changes in cervical rotation movement. Both groups in posttreatment (P=0.042; Cohen d=0.81) and after 10 min (P=0.019; Cohen d=0.9). For intragroup PPDT, the Wilcoxon test revealed significant effects in the effective movement at C2 of the pre to 10-min post (P=0.040). However, the ineffective movement revealed a significant reduction in PPDT in zygapophyseal joint of C5–C6 as the pre to post (P=0.010) as the pre to 10-min post (P=0.041) periods. In conclusions this pilot study demonstrated that the effective AOb produced significant changes versus ineffective AOb in the CROM and it could influences in PPT in subject with CNP immediately. PMID:27656633

  2. Influence of the actions observed on cervical motion in patients with chronic neck pain: a pilot study

    PubMed Central

    de-la-Puente-Ranea, Lucía; García-Calvo, Beatriz; La Touche, Roy; Fernández-Carnero, Josué; Gil-Martínez, Alfonso

    2016-01-01

    The aim of the present pilot study was to prove if the action-observation (AOb) improved the cervical range of motion (CROM) in patients with nonspecific chronic neck pain (CNP). Double blind pilot study. A total of 28 subjects were randomly assigned to an effective-movement group (n=14) and an ineffective-movement group (n=14). The follow-up consisted of: pretreatment, posttreatment and 10 min after second measurement (motor imagery). Outcome measures were CROM, and pres-sure pain detection thresholds (PPDTs). No statistical differences were found in baseline on CROM and on the PPDT. Test for independent groups revealed significant changes in cervical rotation movement. Both groups in posttreatment (P=0.042; Cohen d=0.81) and after 10 min (P=0.019; Cohen d=0.9). For intragroup PPDT, the Wilcoxon test revealed significant effects in the effective movement at C2 of the pre to 10-min post (P=0.040). However, the ineffective movement revealed a significant reduction in PPDT in zygapophyseal joint of C5–C6 as the pre to post (P=0.010) as the pre to 10-min post (P=0.041) periods. In conclusions this pilot study demonstrated that the effective AOb produced significant changes versus ineffective AOb in the CROM and it could influences in PPT in subject with CNP immediately.

  3. Influence of the actions observed on cervical motion in patients with chronic neck pain: a pilot study.

    PubMed

    de-la-Puente-Ranea, Lucía; García-Calvo, Beatriz; La Touche, Roy; Fernández-Carnero, Josué; Gil-Martínez, Alfonso

    2016-08-01

    The aim of the present pilot study was to prove if the action-observation (AOb) improved the cervical range of motion (CROM) in patients with nonspecific chronic neck pain (CNP). Double blind pilot study. A total of 28 subjects were randomly assigned to an effective-movement group (n=14) and an ineffective-movement group (n=14). The follow-up consisted of: pretreatment, posttreatment and 10 min after second measurement (motor imagery). Outcome measures were CROM, and pres-sure pain detection thresholds (PPDTs). No statistical differences were found in baseline on CROM and on the PPDT. Test for independent groups revealed significant changes in cervical rotation movement. Both groups in posttreatment (P=0.042; Cohen d=0.81) and after 10 min (P=0.019; Cohen d=0.9). For intragroup PPDT, the Wilcoxon test revealed significant effects in the effective movement at C2 of the pre to 10-min post (P=0.040). However, the ineffective movement revealed a significant reduction in PPDT in zygapophyseal joint of C5-C6 as the pre to post (P=0.010) as the pre to 10-min post (P=0.041) periods. In conclusions this pilot study demonstrated that the effective AOb produced significant changes versus ineffective AOb in the CROM and it could influences in PPT in subject with CNP immediately.

  4. A Characterization of Arctic Aerosols as Derived from Airborne Observations and their Influence on the Surface Radiation Budget

    NASA Astrophysics Data System (ADS)

    Herber, A.; Stone, R.; Liu, P. S.; Li, S.; Sharma, S.; Neuber, R.; Birnbaumn, G.; Vitale, V.

    2011-12-01

    Arctic climate is influenced by aerosols that affect the radiation balance at the surface and within the atmosphere. Impacts depend on the composition and concentration of aerosols that determine opacity, which is quantified by the measure of aerosol optical depth (AOD). During winter and spring, aerosols are transported into the Arctic from lower latitude industrial regions. Trans-Arctic flight missions PAMARCMiP (Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project) of the German POLAR 5 during spring 2009 and spring 2011 provided opportunities to collect a comprehensive data set from which properties of the aerosol were derived, including AOD. Measurements were made from near the surface to over 4 km in altitude during flights between Svalbard, Norway and Pt. Barrow, Alaska. These, along with measurements of particle size and concentration, and black carbon content (BC) provide a three-dimensional characterization of the aerosols encountered along track. The horizontal and vertical distribution of Arctic haze, in particular, was evaluated. During April 2009, the Arctic atmosphere was variably turbid with total column AOD (at 500 nm) ranging from ~ 0.12 to > 0.35, where clean background values are typically < 0.06 (Stone et al., 2010). The haze was concentrated within and just above the surface-based temperature inversion layer. Few, distinct elevated aerosol layers were observed, also with an aerosol airborne Lidar. The presence of these haze layers in the Arctic atmosphere during spring reduced the diurnally averaged net shortwave irradiance, which can cause cooling of the surface, depending on its Albedo (reflectivity). An overview of both campaigns will be given with results presented in the context of historical observations and current thinking about the impact aerosols have on the Arctic climate. Stone, R.S., A. Herber, V. Vitale, M. Mazzola, A. Lupi, R. Schnell, E.G. Dutton, P. Liu, S.M. Li, K. Dethloff, A. Lampert, C. Ritter

  5. Temperature Observation Time and Type Influence Estimates of Heat-Related Mortality in Seven U.S. Cities

    PubMed Central

    Davis, Robert E.; Hondula, David M.; Patel, Anjali P.

    2015-01-01

    -mortality was more closely coupled to afternoon and maximum temperatures in most cities we examined, particularly those typically prone to heat-related mortality. Citation: Davis RE, Hondula DM, Patel AP. 2016. Temperature observation time and type influence estimates of heat-related mortality in seven U.S. cities. Environ Health Perspect 124:795–804; http://dx.doi.org/10.1289/ehp.1509946 PMID:26636734

  6. Short-term Influences on Suspended Particulate Matter Distribution in the Northern Gulf of Mexico: Satellite and Model Observations

    PubMed Central

    D'Sa, Eurico J.; Ko, Dong S.

    2008-01-01

    Energetic meteorological events such as frontal passages and hurricanes often impact coastal regions in the northern Gulf of Mexico that influence geochemical processes in the region. Satellite remote sensing data such as winds from QuikSCAT, suspended particulate matter (SPM) concentrations derived from SeaWiFS and the outputs (sea level and surface ocean currents) of a nested navy coastal ocean model (NCOM) were combined to assess the effects of frontal passages between 23-28 March 2005 on the physical properties and the SPM characteristics in the northern Gulf of Mexico. Typical changes in wind speed and direction associated with frontal passages were observed in the latest 12.5 km wind product from QuikSCAT with easterly winds before the frontal passage undergoing systematic shifts in direction and speed and turning northerly, northwesterly during a weak and a strong front on 23 and 27 March, respectively. A quantitative comparison of model sea level results with tide gauge observations suggest better correlations near the delta than in the western part of the Gulf with elevated sea levels along the coast before the frontal passage and a large drop in sea level following the frontal passage on 27 March. Model results of surface currents suggested strong response to wind forcing with westward and onshore currents before the frontal passage reversing into eastward, southeastward direction over a six day period from 23 to 28 March 2005. Surface SPM distribution derived from SeaWiFS ocean color data for two clear days on 23 and 28 March 2005 indicated SPM plumes to be oriented with the current field with increasing concentrations in nearshore waters due to resuspension and discharge from the rivers and bays and its seaward transport following the frontal passage. The backscattering spectral slope γ, a parameter sensitive to particle size distribution also indicated lower γ values (larger particles) in nearshore waters that decreased offshore (smaller particles

  7. Reduction of astrometric plates

    NASA Technical Reports Server (NTRS)

    Stock, J.

    1984-01-01

    A rapid and accurate method for the reduction of comet or asteroid plates is described. Projection equations, scale length correction, rotation of coordinates, linearization, the search for additional reference stars, and the final solution are examined.

  8. Phobos Ephemeris Improvement from Recent Spacecraft Observations

    NASA Technical Reports Server (NTRS)

    Bills, B. G.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

    2004-01-01

    Despite 127 years of observations, there is still room for improvement in the ephemeris of the Martian satellite Phobos. Early in this history, Earth-based astrometric observations of Phobos and Deimos were used to estimate the mass and oblateness of Mars. As more data accumulated, it became clear that a secular acceleration in the longitude of Phobos was occurring, and this was attributed to tidal dissipation within Mars, yielding rough estimates of the tidal quality factor, or Q. At the epoch of the earliest spacecraft observations of Phobos, from Mariner 9 and the Viking Orbiters and Landers, the gravitational field of Mars, and resulting forces on Phobos, were still not particularly well known. Thus observations of natural and artificial satellite motions continued to contribute, each in their own way, to knowledge of the mass distribution within Mars. Improvements in tracking system accuracy, and the placement of satellites, like the 1996 Mars Global Surveyor and 2001 Mars Odyssey, in circular polar orbits has lead to dramatic improvements to knowledge of the Mars gravity field. The direct gravitational influence on Phobos is no longer expected to be a limiting factor in predicting its orbital motion. Despite that progress, a variety of observations of Phobos from recent orbiters and landers suggest that the best satellite ephemeris still has along-track orbit errors which are accumulating at a rate of 1.75 kilometers per year, with Phobos gaining on the predicted positions. These recent observations alone do not span sufficient time to separately resolve the positional error into changes in mean motion and changes in secular acceleration. However, combining them with earlier observations will allow improvements in both the mean motion and its first derivative. This latter parameter is particularly interesting, as it relates to tidal dissipation, and thus uniquely constrains the internal structure of Mars. The current best estimate of the secular acceleration

  9. ALMA Observations of TNOs

    NASA Astrophysics Data System (ADS)

    Butler, Bryan J.; Brown, Michael E.

    2016-10-01

    Some of the most fundamental properties of TNOs are still quite poorly constrained, including diameter and density. Observations at long thermal wavelengths, in the millimeter and submillimeter, hold promise for determining these quantities, at least for the largest of these bodies (and notably for those with companions). Knowing this information can then yield clues as to the formation mechanism of these bodies, allowing us to distinguish between pairwise accretion and other formation scenarios.We have used the Atacama Large Millimeter/Submillimeter Array (ALMA) to observe Orcus, Quaoar, Salacia, and 2002 UX25 at wavelengths of 1.3 and 0.8 mm, in order to constrain the sizes of these bodies. We have also used ALMA to make astrometric observations of the Eris-Dysnomia system, in an attempt to measure the wobble of Eris and hence accurately determine its density. Dysnomia should also be directly detectable in those data, separate from Eris (ALMA has sufficient resolution in the configuration in which the observations were made). Results from these observations will be presented and discussed.

  10. Influence of the Southeast Asian biomass burnings on the atmospheric persistent organic pollutants observed at near sources and receptor site

    NASA Astrophysics Data System (ADS)

    Chang, Shun-Shiang; Lee, Wen-Jhy; Wang, Lin-Chi; Lin, Neng-Huei; Chang-Chien, Guo-Ping

    2013-10-01

    Persistent organic pollutants (POPs) such as PCDD/Fs, PCBs, PBDD/Fs, PBBs and PBDEs are bio-accumulative, toxic, and susceptible to long-range transport (LRT). This study is the first that comprehensively discusses the long-range atmospheric transport behavior of these five groups of POPs. The main goal is to investigate the atmospheric characteristics of these POPs at the biomass burning sites of Chiang Mai in Thailand, and Da Nang in Vietnam, as well as the influence of the Southeast Asian biomass burnings on the Lulin Atmospheric Background Station (LABS) in Taiwan. Biomass burning in Southeast Asia is usually carried to remove the residues of agricultural activities. The ambient air in Da Nang seems to be more seriously affected by the local biomass burnings than that in Chiang Mai. The elevated atmospheric brominated POP (PBDD/Fs, PBBs and PBDEs) concentrations in Da Nang were attributed to the biomass burning and viewed as mostly unrelated to the local use of brominated flame retardants. In the spring of 2010, the mean atmospheric concentrations in LABS during the first and second Intensive Observation Periods (IOPs) were 0.00428 and 0.00232 pg I-TEQ Nm-3 for PCDD/Fs, 0.000311 and 0.000282 pg WHO-TEQ m-3 for PCBs, 0.000379 and 0.000449 pg TEQ Nm-3 for total PBDD/Fs, 0.0208 and 0.0163 pg Nm-3 for total PBBs, and 109 and 18.2 pg Nm-3 for total PBDEs, respectively. These values represent the above concentrations due to the Southeast Asian biomass burnings. The affected atmospheric POP concentrations at the LABS were still at least one order lower than those in other atmospheric environments, except for the PBDE concentrations during the first IOP (109 pg Nm-3), which was surprisingly higher than those in Taiwanese metal complex areas (93.9 pg Nm-3) and urban areas (34.7 pg Nm-3). Atmospheric POP concentrations do not seem to dramatically decrease during long-range transport, and the reasons for this need to be further investigated.

  11. A comparison of individual versus community influences on youth smoking behaviours: a cross-sectional observational study

    PubMed Central

    Adachi-Mejia, Anna M; Carlos, Heather A; Berke, Ethan M; Tanski, Susanne E; Sargent, James D

    2012-01-01

    Objectives To compare individual with community risk factors for adolescent smoking. Design A cross-sectional observational study with multivariate analysis. Setting National telephone survey. Participants 3646 US adolescents aged 13–18 years in 2007 recruited through a random digit-dial survey. Outcome measures Ever tried smoking and, among experimental smokers, smoking intensity (based on smoking in past 30 days). Results One-third of participants (35.6%, N=1297) had tried smoking. After controlling for individual risk factors, neither tobacco outlet density nor proximity were associated with tried smoking or smoking intensity. Associations with trying smoking included age (adjusted OR (AOR)=1.23, 95% CI 1.16 to 1.31), lower socioeconomic status (AOR=0.82, 95% CI 0.74 to 0.91), sibling smoking (AOR=2.13, 95% CI 1.75 to 2.59), friend smoking (AOR=2.60, 95% CI 2.19 to 3.10 for some and AOR=7.01, 95% CI 5.05 to 9.74 for most), movie smoking exposure (AOR=2.66, 95% CI 1.95 to 3.63), team sports participation (AOR=0.69, 95% CI 0.54 to 0.89) and sensation seeking (AOR=7.72, 95% CI 5.26 to 11.34). Among experimental smokers, age (AOR=1.32, 95% CI 1.21 to 1.44), minority status (AOR=0.48, 95% CI 0.30 to 0.79 for Black; AOR=0.46, 95% CI 0.31 to 0.69 for Hispanic; AOR=0.53, 95% CI 0.43 to 0.85 for mixed race/other), friend smoking (AOR=3.37, 95% CI 2.37 to 4.81 for some; AOR=20.27, 95% CI 13.22 to 31.08 for most), team sports participation (AOR=0.38, 95% CI 0.26 to 0.55) and sensation seeking (AOR=6.57, 95% CI 3.71 to 11.64) were associated with smoking intensity. Conclusions The study suggests that interventions and policies to prevent and reduce youth smoking should focus on individual risk factors for smoking, including supporting participation in team sports, minimising exposure to movie smoking, addressing the social influence of friend smoking and addressing experience seeking among high sensation-seekers. PMID:22942229

  12. SPECKLE INTERFEROMETRY AT THE USNO FLAGSTAFF STATION: OBSERVATIONS OBTAINED IN 2008 AND NINE NEW ORBITS

    SciTech Connect

    Hartkopf, William I.; Mason, Brian D. E-mail: bdm@usno.navy.mil

    2011-08-15

    Results are presented for 299 speckle interferometric observations of double stars, obtained in 2008 at the USNO Flagstaff Station using the 1.55 m Kaj Strand Astrometric Reflector. Separations range from 0.''15 to 9.''88, with a median of 2.''22. This observing run concentrated on neglected systems, as well as systems in need of improved orbital elements; new orbital solutions have been determined for nine systems as a result.

  13. Discovery, Observational Data and the Orbit of the Amor Group Asteroid 2010 BT3

    NASA Astrophysics Data System (ADS)

    Černis, K.; Zdanavičius, J.; Wlodarczyk, I.; Stonkutė, E.

    A project devoted to astrometric and photometric observations of asteroids at the Molėtai Observatory is described. One of its most important results is the discovery of the asteroid 2010 BT3 belonging to the Amor group of the near-Earth objects. The results of astrometric and photometric observations of the asteroid are presented. The brightness variations of the asteroid are found to be about 0.2 mag in R. The orbit of the asteroid was computed from 96 observations. This orbit, combined with the apparent brightness, gives the absolute magnitude 21.34 mag and the diameter between 160 m and 360 m, taking albedos of S-type and C-type asteroids, respectively.

  14. To Blame or Not to Blame: Influences of Target Race and Observer Sex on Rape Blame Attribution

    ERIC Educational Resources Information Center

    Donovan, Roxanne A.

    2007-01-01

    There is a paucity of research on the influence of racist and sexist stereotypes in rape blame attribution, including the jezebel and matriarch stereotypes of Black women. This study extends the literature by examining how victim race, perpetrator race, and participant sex affect perceptions of a rape survivor's promiscuity (jezebel stereotype)…

  15. Using Art to Teach Students Science Outdoors: How Creative Science Instruction Influences Observation, Question Formation, and Involvement

    NASA Astrophysics Data System (ADS)

    Cone, Christina Schull

    Elementary education has become increasingly divided into subjects and focused on the demand for high math and reading scores. Consequently, teachers spend less time devoted to science and art instruction. However, teaching art and science is crucial to developing creative and rational thinking, especially for observation and questioning skills. In this study, third grade students attending an urban school in Portland, Oregon received instruction of an art strategy using observational and quantifying drawing techniques. This study examines, "Will an art strategy observing the local environment help students make observations and ask questions?" and "In what ways are student learning and perspectives of science affected by the art strategy?" The independent variable is the art strategy developed for this study. There are three dependent variables: quality of student observations, quality of questions, and themes on student learning and perspectives of science. I predicted students would develop strong observation and questioning skills and that students would find the strategy useful or have an increased interest in science. The art scores were high for relevance and detail, but not for text. There were significant correlations between art scores and questions. Interviews revealed three themes: observations create questions, drawing is helpful and challenging, and students connected to science. By examining science through art, students were engaged and created strong observations and questions. Teachers need to balance unstructured drawing time with scaffolding for optimal results. This study provides an integrated science and art strategy that teachers can use outdoors or adapt for the classroom.

  16. Statistical analysis of observational study of the influence of radon and other risk factors on lung cancer incidence.

    PubMed

    Zhukovsky, Michael; Varaksin, Anatole; Pakholkina, Olga

    2014-07-01

    An observational study is a type of epidemiological study when the researcher observes the situation but is not able to change the conditions of the experiment. The statistical analysis of the observational study of the population of Lermontov city (North Caucasus) was conducted. In the initial group, there were 121 people with lung cancer diagnosis and 196 people of the control group. Statistical analysis was performed only for men (95 cases and 76 controls). The use of logistic regression with correction on age gives the value of odds ratio 1.95 (0.87÷4.37; 90% CI) per 100 working levels per month of combined (occupational and domestic) radon exposure. It was demonstrated that chronic lung diseases are an additional risk factor for uranium miners but it is not a significant risk factor for general population. Thus, the possibility of obtaining statistically reliable results in the observational studies when using the correct methods of analysis is demonstrated.

  17. Towards a Fundamental Astrometric Reference System behind the Magellanic Clouds: Spectroscopic Confirmation of New Quasar Candidates Selected in the Near-infrared

    NASA Astrophysics Data System (ADS)

    Ivanov, V. D.; Cioni, M.-R. L.; Bekki, K.; de Grijs, R.; Emerson, J.; Gibson, B. K.; Kamath, D.; van Loon, J. Th.; Piatti, A. E.; For, B.-Q.

    2016-03-01

    Quasi-stellar objects (quasars) located behind nearby galaxies provide an excellent absolute reference system for astrometric studies, but they are difficult to identify because of fore- and background contamination. We have embarked on a programme to expand the quasar reference system behind the Large and Small Magellanic Clouds, the Magellanic Bridge and Magellanic Stream. Hundreds of quasar candidates were selected, based on their near-infrared colours and variability properties from the ESO VISTA Magellanic Clouds (VMC) Public Survey. A subset of 49 objects was followed up with optical spectroscopy with FORS2. We confirmed the quasar nature of 37 objects (34 new identifications) that span a redshift range from z ~ 0.5 to 4.1.

  18. High-precision follow-up observations of Near-Earth Objects

    NASA Astrophysics Data System (ADS)

    Ramanjooloo, Yudish; Tholen, David J.; Fohring, Dora; Hung, Denise

    2016-10-01

    We present the latest results of ongoing high-precision astrometric follow-up observations of Near-Earth Objects (NEOs) using the University of Hawaii 2.24 metre telescope (currently 7.5 arcmin FOV), the Canada-France-Hawaii Telescope (CFHT; 1 degree FOV) with MegaPrime, and the Subaru Hyper Suprime-Cam (1.5 degree FOV). The combination of excellent observing conditions at Maunakea, and the use of no filter to maximise our throughput efficiency, allows us to recover targets having V < 24, and sometimes V < 25 under ideal conditions. We frequently achieve astrometric accuracy limited by the reference catalog and plan to improve on this capability with the implementation of the GAIA catalog. This work is funded by NASA grant NXX13AI64G.

  19. Gravity wave and tidal influences on equatorial spread F based on observations during the Spread F Experiment (SpreadFEx)

    NASA Astrophysics Data System (ADS)

    Fritts, D. C.; Vadas, S. L.; Riggin, D. M.; Abdu, M. A.; Batista, I. S.; Takahashi, H.; Medeiros, A.; Kamalabadi, F.; Liu, H.-L.; Fejer, B. G.; Taylor, M. J.

    2008-10-01

    The Spread F Experiment, or SpreadFEx, was performed from September to November 2005 to define the potential role of neutral atmosphere dynamics, primarily gravity waves propagating upward from the lower atmosphere, in seeding equatorial spread F (ESF) and plasma bubbles extending to higher altitudes. A description of the SpreadFEx campaign motivations, goals, instrumentation, and structure, and an overview of the results presented in this special issue, are provided by Fritts et al. (2008a). The various analyses of neutral atmosphere and ionosphere dynamics and structure described in this special issue provide enticing evidence of gravity waves arising from deep convection in plasma bubble seeding at the bottomside F layer. Our purpose here is to employ these results to estimate gravity wave characteristics at the bottomside F layer, and to assess their possible contributions to optimal seeding conditions for ESF and plasma instability growth rates. We also assess expected tidal influences on the environment in which plasma bubble seeding occurs, given their apparent large wind and temperature amplitudes at these altitudes. We conclude 1) that gravity waves can achieve large amplitudes at the bottomside F layer, 2) that tidal winds likely control the orientations of the gravity waves that attain the highest altitudes and have the greatest effects, 3) that the favored gravity wave orientations enhance most or all of the parameters influencing plasma instability growth rates, and 4) that gravity wave and tidal structures acting together have an even greater potential impact on plasma instability growth rates and plasma bubble seeding.

  20. The thermal influence of the subducting slab beneath South America from 410 and 660 km discontinuity observations

    NASA Astrophysics Data System (ADS)

    Collier, J. D.; Helffrich, G. R.

    2001-11-01

    Regional seismic network data from deep South American earthquakes to western United States and western European seismic arrays is slant stacked to detect weak near-source interactions with upper mantle discontinuities. These observations are complemented by an analysis of earlier work by Sacks & Snoke (1977) who observed S to P conversions from deep events to stations in South America, and similar observations from 1994-95 events using the BANJO and SEDA networks. Observations of the depth of the 410km discontinuity are made beneath central South America in the vicinity of the aseismic region of the subducting Nazca Plate. These results image the 410km discontinuity over a lateral extent of up to 850km perpendicular to the slab and over a distance of 2700km along the length of the slab. Away from the subducting slab the discontinuity is mainly seen near its global average depth, whilst inside the slab there is evidence for its elevation by up to around 60km but with significant scatter in the data. These results are consistent with the presence of a continuous slab through the aseismic region with a thermal anomaly of 900°C at 350km depth. This value is in good agreement with simple thermal models though our data are too sparse to accurately constrain them. Sparse observations of the 660km discontinuity agree with tomographic models suggesting penetration of the lower mantle by the slab in the north but stagnation at the base of the transition zone in the south. The geographical distribution of the data, however, does not allow us to rule out the possibility of slab stagnation at the base of the transition zone in the north. These observations, together with the presence of deep earthquakes, require more complicated thermal models than previously used to explain them, possibly including changes in slab dip and age with depth.

  1. Discovering New Ways of Moving: Observational Analysis of Motor Creativity while Dancing Contact Improvisation and the Influence of the Partner

    ERIC Educational Resources Information Center

    Torrents, Carlota; Castaner, Marta; Dinusova, Maria; Anguera, M. Teresa

    2010-01-01

    Contact improvisation (CI) is a form of dance based on motor creativity, improvisation and the physical contact between different improvisers dancing together. This will generate different ways of moving and a varied use of motor creativity depending on the dancers involved. This study aims to observe the differences in movement generation…

  2. VISIBILITY OF STRUCTURES OF RELEVANCE FOR PATIENTS WITH CYSTIC FIBROSIS IN CHEST TOMOSYNTHESIS: INFLUENCE OF ANATOMICAL LOCATION AND OBSERVER EXPERIENCE.

    PubMed

    Meltzer, Carin; Båth, Magnus; Kheddache, Susanne; Ásgeirsdóttir, Helga; Gilljam, Marita; Johnsson, Åse Allansdotter

    2016-06-01

    The aims of this study were to assess the visibility of pulmonary structures in patients with cystic fibrosis (CF) in digital tomosynthesis (DTS) using computed tomography (CT) as reference and to investigate the dependency on anatomical location and observer experience. Anatomical structures in predefined regions of CT images from 21 patients were identified. Three observers with different levels of experience rated the visibility of the structures in DTS by performing a head-to-head comparison with visibility in CT. Visibility of the structures in DTS was reported as equal to CT in 34 %, inferior in 52 % and superior in 14 % of the ratings. Central and peripheral lateral structures received higher visibility ratings compared with peripheral structures anteriorly, posteriorly and surrounding the diaphragm (p ≤ 0.001). Reported visibility was significantly higher for the most experienced observer (p ≤ 0.01). The results indicate that minor pathology can be difficult to visualise with DTS depending on location and observer experience. Central and peripheral lateral structures are generally well depicted.

  3. How does our choice of observable influence our estimation of the centre of a galaxy cluster? Insights from cosmological simulations

    NASA Astrophysics Data System (ADS)

    Cui, Weiguang; Power, Chris; Biffi, Veronica; Borgani, Stefano; Murante, Giuseppe; Fabjan, Dunja; Knebe, Alexander; Lewis, Geraint F.; Poole, Greg B.

    2016-03-01

    Galaxy clusters are an established and powerful test-bed for theories of both galaxy evolution and cosmology. Accurate interpretation of cluster observations often requires robust identification of the location of the centre. Using a statistical sample of clusters drawn from a suite of cosmological simulations in which we have explored a range of galaxy formation models, we investigate how the location of this centre is affected by the choice of observable - stars, hot gas, or the full mass distribution as can be probed by the gravitational potential. We explore several measures of cluster centre: the minimum of the gravitational potential, which would expect to define the centre if the cluster is in dynamical equilibrium; the peak of the density; the centre of brightest cluster galaxy (BCG); and the peak and centroid of X-ray luminosity. We find that the centre of BCG correlates more strongly with the minimum of the gravitational potential than the X-ray defined centres, while active galactic nuclei feedback acts to significantly enhance the offset between the peak X-ray luminosity and minimum gravitational potential. These results highlight the importance of centre identification when interpreting clusters observations, in particular when comparing theoretical predictions and observational data.

  4. Influence of Perspective of Action Observation Training on Residual Limb Control in Naïve Prosthesis Usage.

    PubMed

    Lawson, Delisa T; Cusack, William F; Lawson, Regan; Hardy, Ashley; Kistenberg, Robert; Wheaton, Lewis A

    2016-01-01

    Prior work in amputees and partial limb immobilization have shown improved neural and behavioral outcomes in using their residual limb with prosthesis when undergoing observation-based training with a prosthesis-using actor compared to an intact limb. It was posited that these improvements are due to an alignment of user with the actor. It may be affected by visual angles that allow emphasis of critical joint actions which may promote behavioral changes. The purpose of this study was to examine how viewing perspective of observation-based training effects prosthesis adaptation in naïve device users. Twenty nonamputated prosthesis users learned how to use an upper extremity prosthetic device while viewing a training video from either a sagittal or coronal perspective. These views were chosen as they place visual emphasis on different aspects of task performance to the device. The authors found that perspective of actions has a significant role in adaptation of the residual limb while using upper limb prostheses. Perspectives that demonstrate elbow adaptations to prosthesis usage may enhance the functional motor outcomes of action observation therapy. This work has potential implications on how prosthetic device operation is conveyed to persons adapting to prostheses through action observation based therapy. PMID:27253208

  5. VISIBILITY OF STRUCTURES OF RELEVANCE FOR PATIENTS WITH CYSTIC FIBROSIS IN CHEST TOMOSYNTHESIS: INFLUENCE OF ANATOMICAL LOCATION AND OBSERVER EXPERIENCE

    PubMed Central

    Meltzer, Carin; Båth, Magnus; Kheddache, Susanne; Ásgeirsdóttir, Helga; Gilljam, Marita; Johnsson, Åse Allansdotter

    2016-01-01

    The aims of this study were to assess the visibility of pulmonary structures in patients with cystic fibrosis (CF) in digital tomosynthesis (DTS) using computed tomography (CT) as reference and to investigate the dependency on anatomical location and observer experience. Anatomical structures in predefined regions of CT images from 21 patients were identified. Three observers with different levels of experience rated the visibility of the structures in DTS by performing a head-to-head comparison with visibility in CT. Visibility of the structures in DTS was reported as equal to CT in 34 %, inferior in 52 % and superior in 14 % of the ratings. Central and peripheral lateral structures received higher visibility ratings compared with peripheral structures anteriorly, posteriorly and surrounding the diaphragm (p ≤ 0.001). Reported visibility was significantly higher for the most experienced observer (p ≤ 0.01). The results indicate that minor pathology can be difficult to visualise with DTS depending on location and observer experience. Central and peripheral lateral structures are generally well depicted. PMID:26842827

  6. Solar wind influence on the dawn-dusk asymmetry of the Io plasma torus observed by HISAKI/EXCEED

    NASA Astrophysics Data System (ADS)

    Murakami, G.; Yoshioka, K.; Kimura, T.; Yamazaki, A.; Tsuchiya, F.; Kagitani, M.; Tao, C.; Yoshikawa, I.; Fujimoto, M.

    2014-12-01

    The dawn-dusk asymmetry of the Io plasma torus has been seen by several observations [e.g., Sandel and Broadfoot, 1982; Steffl et al., 2004]. Ip and Goertz [1983] explained this asymmetry can be caused by a dawn-to-dusk electric field in the Jupiter's inner magnetosphere. However, the question what physical process can impose such an electric field deep inside the strong magnetosphere still remains. The long-term monitoring of the Io plasma torus is a key observation to answer this question. The extreme ultraviolet (EUV) spectrometer EXCEED onboard the HISAKI satellite was launched in 2013 and observed the Io plasma torus from December 2013 to March 2014 (75 days). We investigated the temporal variation of the dawn/dusk ratio of EUV brightness. Then we compared it to the solar wind dynamic pressure extrapolated from that observed around Earth by using magnetohydrodynamic (MHD) simulation. As a result we found clear responses of the dawn-dusk asymmetry to rapid increases of the solar wind dynamic pressure. We will present the initial results of this study.

  7. The "Quasar" Network Observations in e-VLBI Mode Within the Russian Domestic VLBI Programs

    NASA Technical Reports Server (NTRS)

    Finkelstein, Andrey; Ipatov, Alexander; Kaidanovsky, Michael; Bezrukov, Ilia; Mikhailov, Andrey; Salnikov, Alexander; Surkis, Igor; Skurikhina, Elena

    2010-01-01

    The purpose of the Russian VLBI "Quasar" Network is to carry out astrometrical and geodynamical investigations. Since 2006 purely domestic observational programs with data processing at the IAA correlator have been carried out. To maintain these geodynamical programs e-VLBI technology is being developed and tested. This paper describes the IAA activity of developing a real-time VLBI system using high-speed digital communication links.

  8. Regional and Local Influences on Surface O3 over Beijing: Constraints from Integrated Surface observations and Modeling

    NASA Astrophysics Data System (ADS)

    Wang, Y.; McElroy, M. B.; Munger, W.; Hao, J.; Ma, H.; Chen, Y.

    2007-05-01

    Beijing, the Chinese capital, faces the challenge of improving its atmospheric environment while seeing an annual growth rate of 15% in the number of personal vehicles on the road. Among many pollutants, surface ozone is of particular concern for Beijing as it will host the "green" Olympics Games in summer 2008. Continuous measurements of surface O3 and CO at Miyun (a rural site 50km northeast of Beijing) in 2006 are analyzed using a 3-dimensional chemical transport model (GEOS-Chem) to improve our understanding of regional and local factors contributing to changes in tropospheric O3 in the Beijing area. The location of the site was selected to sample both clean continental air and pollution included in the plume from Beijing. To our knowledge, this is the first station in mainland China providing continuous measurements of O3 and related species (CO and CO2) over a relatively long period (years). Observations show that O3 peaks in June and September, while CO has a broad maximum in winter. Using updated emissions for China, the model successfully reproduces the seasonal variability in O3, CO, and their correlations observed at Miyun. Regional O3 levels representative of north China are identified from observations using concurrent measurements of CO. Events with daytime peak O3 concentrations exceeding 100 ppb were observed mainly in summer (JJA) and in September. A major discrepancy of the model is an overestimate of O3 in July. Observations show a decrease of 16 ppb in mean (median) O3 from June to July, presumably associated with enhanced precipitation and cloudiness in July. Implications of high levels of O3 for crop production will be discussed.

  9. Experimental observation of the influence of furnace temperature profile on convection and segregation in the vertical Bridgman crystal growth technique

    NASA Technical Reports Server (NTRS)

    Neugebauer, G. T.; Wilcox, W. R.

    1990-01-01

    Azulene-doped naphtalene was directionally solidified using the vertical Bridgman-Stockbarger technique. Doping homogeneity and convection are determined as a function of the temperature profile in the furnace and the freezing rate. Convective velocities are two orders of magnitude lower when the temperature increases with height. The cross sectional variation in azulene concentration tends to be asymmetric. Neither rotation of the ampoule nor deliberate introduction of thermal asymmetries during solidification had a significant influence on cross sectional variations in doping. It is predicted that slow directional solidification under microgravity conditions can produce greater inhomogeneities than on earth. Thus when low freezing rates are necessary in order to avoid constitutional supercooling, it may be necessary to combine microgravity and magnetic fields in order to achieve homogeneous crystals.

  10. Winter- and summertime continental influences on tropospheric O3 and CO observed by TES over the western North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Hegarty, J.; Mao, H.; Talbot, R.

    2010-04-01

    The distributions of tropospheric ozone (O3) and carbon monoxide (CO), and the synoptic factors regulating these distributions over the western North Atlantic Ocean during winter and summer were investigated using profile retrievals from the Tropospheric Emission Spectrometer (TES) for 2004-2006. Seasonal composites of TES retrievals, reprocessed to remove the influence of the a priori on geographical and seasonal structure, exhibited strong seasonal differences. At the 681 hPa level during winter months of December, January and February (DJF) the composite O3 mixing ratios were uniformly low (~45 ppbv), but continental export was evident in a channel of enhanced CO (100-110 ppbv) flowing eastward from the US coast. In summer months June, July, and August (JJA) O3 mixing ratios were variable (45-65 ppbv) and generally higher due to increased photochemical production. The summer distribution also featured a channel of enhanced CO (95-105 ppbv) flowing northeastward around an anticyclone and exiting the continent over the Canadian Maritimes around 50° N. Offshore O3-CO slopes were generally 0.15-0.20 mol mol-1 in JJA, indicative of photochemical O3 production. Composites for 4 predominant synoptic patterns or map types in DJF suggested that export to the lower free troposphere (681 hPa level) was enhanced by the warm conveyor belt airstream of mid-latitude cyclones while stratospheric intrusions increased TES O3 levels at 316 hPa. A major finding in the DJF data was that offshore 681 hPa CO mixing ratios behind cold fronts could be enhanced up to >150 ppbv likely by lofting from the surface via shallow convection resulting from rapid destabilization of cold air flowing over much warmer ocean waters. In JJA composites for 3 map types showed that the general export pattern of the seasonal composites was associated with a synoptic pattern featuring the Bermuda High. However, weak cyclones and frontal troughs could enhance offshore 681 hPa CO mixing ratios to >110 ppbv

  11. OBSERVATIONS AND ORBITAL ANALYSIS OF THE GIANT WHITE DWARF BINARY SYSTEM HR 5692

    SciTech Connect

    Stefanik, Robert P.; Torres, Guillermo; Latham, David W.; Landsman, Wayne; Craig, Nathaniel; Murrett, James

    2011-05-15

    We report spectroscopic observations of the red giant star HR 5692, previously known to be a binary system both from other spectroscopic work and from deviations in the astrometric motion detected by the Hipparcos satellite. Earlier International Ultraviolet Explorer (IUE) observations had shown the presence of a hot white dwarf companion to the giant primary. We have combined our radial velocity observations with other existing measurements and with the Hipparcos intermediate astrometric data to determine a complete astrometric-spectroscopic orbital solution, providing the inclination angle for the first time. We also determine an improved parallax for the system of 10.12 {+-} 0.67 mas. We derive the physical properties of the primary, and with an estimate of its mass from stellar evolution models (1.84 {+-} 0.40 M{sub sun}), we infer the mass of the white dwarf companion to be M{sub WD} = 0.59 {+-} 0.12 M{sub sun}. An analysis of an IUE white dwarf spectrum, using our parallax, yields T{sub eff} = 30, 400 {+-} 780 K, log g = 8.25 {+-} 0.15, and a mass M{sub WD} = 0.79 {+-} 0.09 M{sub sun}, in marginal agreement with the dynamical mass.

  12. Experimental observation of the influence of furnace temperature profile on convection and segregation in the vertical Bridgman crystal growth technique

    NASA Technical Reports Server (NTRS)

    Neugebauer, G. T.; Wilcox, William R.

    1992-01-01

    Azulene-doped naphthalene was directionally solidified during the vertical Bridgman-Stockbarger technique. Doping homogeneity and convection were determined as a function of the temperature profile in the furnace and the freezing rate. Convection velocities were two orders of magnitude lower when the temperature increased with height. Rarely was the convection pattern axisymmetric, even though the temperature varied less than 0.1 K around the circumference of the growth ampoule. Correspondingly the cross sectional variation in azulene concentration tended to be asymmetric, especially when the temperature increased with height. This cross sectional variation changed dramatically along the ingot, reflecting changes in convection presumably due to the decreasing height of the melt. Although there was large scatter and irreproducibility in the cross sectional variation in doping, this variation tended to be least when the growth rate was low and the convection was vigorous. It is expected that compositional variations would also be small at high growth rates with weak convection and flat interfaces, although this was not investigated in the present experiments. Neither rotation of the ampoule nor deliberate introduction of thermal asymmetries during solidification had a significant influence on cross sectional variations in doping. It is predicted that slow directional solidification under microgravity conditions could produce greater inhomogeneities than on Earth. Combined use of microgravity and magnetic fields would be required to achieve homogeneity when it is necessary to freeze slowly in order to avoid constitutional supercooling.

  13. Chemical and physical influences on aerosol activation in liquid clouds: an empirical study based on observations from the Jungfraujoch, Switzerland

    NASA Astrophysics Data System (ADS)

    Hoyle, C. R.; Webster, C. S.; Rieder, H. E.; Hammer, E.; Gysel, M.; Bukowiecki, N.; Weingartner, E.; Steinbacher, M.; Baltensperger, U.

    2015-06-01

    A simple empirical model to predict the number of aerosols which activate to form cloud droplets in a warm, free tropospheric cloud has been established, based on data from four summertime Cloud and Aerosol Characterisation Experiments (CLACE) campaigns at the Jungfraujoch (JFJ). It is shown that 76% of the observed variance in droplet numbers can be represented by a model accounting only for the number of potential CCN (defined as number of particles larger than 90 nm in diameter), while the mean errors in the model representation may be reduced by the addition of further explanatory variables, such as the mixing ratios of O3, CO and the height of the measurements above cloud base. The model has similar ability to represent the observed droplet numbers in each of the individual years, as well as for the two predominant local wind directions at the JFJ (north west and south east). Given the central European location of the JFJ, with air masses in summer being representative of the free troposphere with regular boundary layer in-mixing via convection, we expect that this model is applicable to warm, free tropospheric clouds over the European continent.

  14. An observation-based assessment of the influences of air temperature and snow depth on soil temperature in Russia

    NASA Astrophysics Data System (ADS)

    Park, Hotaek; Sherstiukov, Artem B.; Fedorov, Alexander N.; Polyakov, Igor V.; Walsh, John E.

    2014-05-01

    This study assessed trends in the variability of soil temperature (TSOIL) using spatially averaged observation records from Russian meteorological land stations. The contributions of surface air temperature (SAT) and snow depth (SND) to TSOIL variation were quantitatively evaluated. Composite time series of these data revealed positive trends during the period of 1921-2011, with accelerated increases since the 1970s. The TSOIL warming rate over the entire period was faster than the SAT warming rate in both permafrost and non-permafrost regions, suggesting that SND contributes to TSOIL warming. Statistical analysis revealed that the highest correlation between SND and TSOIL was in eastern Siberia, which is underlain by permafrost. SND in this region accounted for 50% or more of the observed variation in TSOIL. TSOIL in the non-permafrost region of western Siberia was significantly correlated with changes in SAT. Thus, the main factors associated with TSOIL variation differed between permafrost and non-permafrost regions. This finding underscores the importance of including SND data when assessing historical and future variations and trends of permafrost in the Northern Hemisphere.

  15. Interfacial kinematics and governing mechanisms under the influence of high strain rate impact conditions: Numerical computations of experimental observations

    NASA Astrophysics Data System (ADS)

    Raoelison, R. N.; Sapanathan, T.; Padayodi, E.; Buiron, N.; Rachik, M.

    2016-11-01

    This paper investigates the complex interfacial kinematics and governing mechanisms during high speed impact conditions. A robust numerical modelling technique using Eulerian simulations are used to explain the material response of the interface subjected to a high strain rate collision during a magnetic pulse welding. The capability of this model is demonstrated using the predictions of interfacial kinematics and revealing the governing mechanical behaviours. Numerical predictions of wave formation resulted with the upward or downward jetting and complex interfacial mixing governed by wake and vortex instabilities corroborate the experimental observations. Moreover, the prediction of the material ejection during the simulation explains the experimentally observed deposited particles outside the welded region. Formations of internal cavities along the interface is also closely resemble the resulted confined heating at the vicinity of the interface appeared from those wake and vortex instabilities. These results are key features of this simulation that also explains the potential mechanisms in the defects formation at the interface. These results indicate that the Eulerian computation not only has the advantage of predicting the governing mechanisms, but also it offers a non-destructive approach to identify the interfacial defects in an impact welded joint.

  16. Tidal influence on O(1S) airglow emission rate distributions at the geographic equator as observed by WINDII

    NASA Technical Reports Server (NTRS)

    Shephere, G. G.; Mclandress, C.; Solheim, B. H.

    1995-01-01

    WINDII, the Wind Imaging Interferometer on the Upper Atmosphere Research Satellite, observes winds, temperatures and emission rates in the upper mesosphere and thermosphere. In this paper we report on nighttime observations of the vertical distribution of the O(1S) 557.7 nm emission near the geographic equator for March/April, 1993. The airglow volume emission rate distribution is found to be strongly dependent on local time. Beginning at dusk, an intense airglow emission layer descends from a mean altitude of 95 km, reaching 89 km by midnight after which the emission rapidly decays. Shortly after midnight it reappears weakly at a higher altitude and remains at this level as the emission rate gradually increases towards dawn. This strong local time dependence leads us to conclude that the effect is tidally driven. Comparison with the Forbes (1982a,b) model suggest that total density perturbations and changes in the atomic oxygen mixing ratio may the cause of the changes in emission rate distribution between dusk and midnight. The reappearance of the emission after midnight may be caused by downward winds bringing oxygen-rich air from above.

  17. Pluto: improved astrometry from 19 years of observations

    NASA Astrophysics Data System (ADS)

    Benedetti-Rossi, G.; Vieira Martins, R.; Camargo, J. I. B.; Assafin, M.; Braga-Ribas, F.

    2014-10-01

    Context. We present astrometric positions of Pluto, consistent with the International Celestial Reference System, from 4412 CCD frames observed over 120 nights with three telescopes at the Observatório do Pico dos Dias in Brazil, covering a time span from 1995 to 2013, and also 145 frames observed over 11 nights in 2007 and 2009 with the ESO/MPG 2.2m telescope equipped with the Wide Field Imager (WFI). Aims: Our aim is to contribute to the study and improvement of the orbit of Pluto with new astrometric methods and positions. Methods: All astrometric positions of Pluto were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as the reference catalog. We also used the planetary ephemeris DE421+plu021 for comparisons. The positions were corrected for differential chromatic refraction. The (x, y) center of Pluto was determined from corrections to the measured photocenter, which was contaminated by Charon. The corrections were obtained with an original procedure based on analytical expressions derived from a two-dimensional Gaussian function i.e. the point spread function PSF fitted to the images to derive the (x, y) measurements. Results: We obtained mean values of 4 mas and 37 mas for right ascension and declination, and standard deviations of σα = 45 mas and σδ = 49 mas, for the offsets in the sense observed minus ephemeris position, after the corrections. We confirm the presence of a linear drift in the ephemeris declinations from 2005 on, also obtained from stellar occultations. Conclusions: We present astrometric positions of Pluto for 19 years of observations in Brazil. The positions, corrected for differential chromatic refraction and Pluto/Charon photocenter effects, presented the same behavior as obtained from stellar occultations, with a drift in declinations of about 100 mas since 2005. The results indicate that the DE421 Pluto ephemeris used in this work need to be

  18. The influence of sea-level rise on fringing reef sediment dynamics: field observations and numerical modeling

    USGS Publications Warehouse

    Storlazzi, Curt D.; Field, Michael E.; Elias, Edwin; Presto, M. Katherine

    2011-01-01

    While most climate projections suggest that sea level may rise on the order of 0.5-1.0 m by 2100, it is not clear how fluid flow and sediment transport on fringing reefs might change in response to this rapid sea-level rise. Field observations and numerical modeling suggest that an increase in water depth on the order of 0.5-1.0 m on a fringing reef flat would result in larger significant wave heights and wave-driven shear stresses, which, in turn, would result in an increase in both the size and quantity of sediment that can be resuspended from the seabed or eroded from coastal plain deposits. Greater wave- and wind-driven currents would develop on the reef flat with increasing water depth, increasing the offshore flux of water and sediment from the inner reef flat to the outer reef flat and fore reef where coral growth is typically greatest.

  19. Dust particles in controlled fusion devices: morphology, observations in the plasma and influence on the plasma performance

    NASA Astrophysics Data System (ADS)

    Rubel, M.; Cecconello, M.; Malmberg, J. A.; Sergienko, G.; Biel, W.; Drake, J. R.; Hedqvist, A.; Huber, A.; Philipps, V.

    2001-08-01

    The formation and release of particle agglomerates, i.e. debris and dusty objects, from plasma facing components and the impact of such materials on plasma operation in controlled fusion devices has been studied in the Extrap T2 reversed field pinch and the TEXTOR tokamak. Several plasma diagnostic techniques, camera observations and surface analysis methods were applied for in situ and ex situ investigation. The results are discussed in terms of processes that are decisive for dust transfer: localized power deposition connected with wall locked modes causing emission of carbon granules, brittle destruction of graphite and detachment of thick flaking co-deposited layers. The consequences for large next step devices are also addressed.

  20. Chemical and physical influences on aerosol activation in liquid clouds: a study based on observations from the Jungfraujoch, Switzerland

    NASA Astrophysics Data System (ADS)

    Hoyle, Christopher R.; Webster, Clare S.; Rieder, Harald E.; Nenes, Athanasios; Hammer, Emanuel; Herrmann, Erik; Gysel, Martin; Bukowiecki, Nicolas; Weingartner, Ernest; Steinbacher, Martin; Baltensperger, Urs

    2016-03-01

    A simple statistical model to predict the number of aerosols which activate to form cloud droplets in warm clouds has been established, based on regression analysis of data from four summertime Cloud and Aerosol Characterisation Experiments (CLACE) at the high-altitude site Jungfraujoch (JFJ). It is shown that 79 % of the observed variance in droplet numbers can be represented by a model accounting only for the number of potential cloud condensation nuclei (defined as number of particles larger than 80 nm in diameter), while the mean errors in the model representation may be reduced by the addition of further explanatory variables, such as the mixing ratios of O3, CO, and the height of the measurements above cloud base. The statistical model has a similar ability to represent the observed droplet numbers in each of the individual years, as well as for the two predominant local wind directions at the JFJ (northwest and southeast). Given the central European location of the JFJ, with air masses in summer being representative of the free troposphere with regular boundary layer in-mixing via convection, we expect that this statistical model is generally applicable to warm clouds under conditions where droplet formation is aerosol limited (i.e. at relatively high updraught velocities and/or relatively low aerosol number concentrations). A comparison between the statistical model and an established microphysical parametrization shows good agreement between the two and supports the conclusion that cloud droplet formation at the JFJ is predominantly controlled by the number concentration of aerosol particles.

  1. Influence of Dust and Black Carbon on the Snow Albedo in the NASA Goddard Earth Observing System Version 5 Land Surface Model

    NASA Technical Reports Server (NTRS)

    Yasunari, Teppei J.; Koster, Randal D.; Lau, K. M.; Aoki, Teruo; Sud, Yogesh C.; Yamazaki, Takeshi; Motoyoshi, Hiroki; Kodama, Yuji

    2011-01-01

    Present-day land surface models rarely account for the influence of both black carbon and dust in the snow on the snow albedo. Snow impurities increase the absorption of incoming shortwave radiation (particularly in the visible bands), whereby they have major consequences for the evolution of snowmelt and life cycles of snowpack. A new parameterization of these snow impurities was included in the catchment-based land surface model used in the National Aeronautics and Space Administration Goddard Earth Observing System version 5. Validation tests against in situ observed data were performed for the winter of 2003.2004 in Sapporo, Japan, for both the new snow albedo parameterization (which explicitly accounts for snow impurities) and the preexisting baseline albedo parameterization (which does not). Validation tests reveal that daily variations of snow depth and snow surface albedo are more realistically simulated with the new parameterization. Reasonable perturbations in the assigned snow impurity concentrations, as inferred from the observational data, produce significant changes in snowpack depth and radiative flux interactions. These findings illustrate the importance of parameterizing the influence of snow impurities on the snow surface albedo for proper simulation of the life cycle of snow cover.

  2. The Influence of African Dust on Air Quality in the Caribbean Basin: An Integrated Analysis of Satellite Retrievals, Ground Observations, and Model Simulations

    NASA Astrophysics Data System (ADS)

    Yu, H.; Prospero, J. M.; Chin, M.; Randles, C. A.; da Silva, A.; Bian, H.

    2015-12-01

    Long-term surface measurements in several locations extending from northeastern coast of South America to Miami in Florida have shown that African dust arrives in the Greater Caribbean Basin throughout a year. This long-range transported dust frequently elevates the level of particulate matter (PM) above the WHO guideline for PM10, which raises a concern of possible adverse impact of African dust on human health in the region. There is also concern about how future climate change might affect dust transport and its influence on regional air quality. In this presentation we provide a comprehensive characterization of the influence of African dust on air quality in the Caribbean Basin via integrating the ground observations with satellite retrievals and model simulations. The ground observations are used to validate and evaluate satellite retrievals and model simulations of dust, while satellite measurements and model simulations are used to extend spatial coverage of the ground observations. An analysis of CALIPSO lidar measurements of three-dimensional distribution of aerosols over 2007-2014 yields altitude-resolved dust mass flux into the region. On a basis of 8-year average and integration over the latitude zone of 0°-30°N, a total of 76 Tg dust is imported to the air above the Greater Caribbean Basin, of which 34 Tg (or 45%) is within the lowest 1 km layer and most relevant to air quality concern. The seasonal and interannual variations of the dust import are well correlated with ground observations of dust in Cayenne, Barbados, Puerto Rico, and Miami. We will also show comparisons of the size-resolved dust amount from both NASA GEOS-5 aerosol simulation and MERRA-2 aerosol reanalysis (i.e., column aerosol loading being constrained by satellite measurements of radiance at the top of atmosphere) with the ground observations and satellite measurement.

  3. Observed and modeled ecosystem isoprene fluxes from an oak-dominated temperate forest and the influence of drought stress

    SciTech Connect

    Potosnak, M.; LeStourgeon, Lauren; Pallardy, Stephen G.; Hosman, Kevin P.; Gu, Lianghong; Karl, Thomas; Geron, Chris; Guenther, Alex B.

    2014-02-19

    Ecosystem fluxes of isoprene emission were measured during the majority of the 2011 growing season at the University of Missouri's Baskett Wildlife Research and Education Area in centralMissouri, USA (38.7° N, 92.2° W). This broadleaf deciduous forest is typical of forests common in theOzarks region of the central United States. The goal of the isoprene flux measurements was to test ourunderstanding of the controls on isoprene emission from the hourly to the seasonal timescale using a state-of-the-art emission model, MEGAN (Model of Emissions of Gases and Aerosols from Nature). Isoprene emission rates were very high from the forest with a maximum of 50.9 mg m-2 hr-1 (208 nmol m-2 s-1), which to our knowledge exceeds all other reports of canopy-scale isoprene emission. The fluxes showed a clear dependence on the previous temperature and light regimes which was successfully captured by the existing algorithms in MEGAN. During a period of drought, MEGAN was unable to reproduce the time-dependent response of isoprene emission to water stress. Overall, the performance of MEGAN was robust and could explain 87% of the observed variance in the measured fluxes, but the response of isoprene emission to drought stress is a major source of uncertainty.

  4. Runoff production in a small agricultural catchment in Lao PDR : influence of slope, land-use and observation scale.

    NASA Astrophysics Data System (ADS)

    Patin, J.; Ribolzi, O.; Mugler, C.; Valentin, C.; Mouche, E.

    2009-04-01

    We study the surface and sub-surface hydrology of a small agricultural catchment (60ha) located in the Luang Prabang province of Lao PDR. This catchment is representative of the rural mountainous south east Asia. It exhibits steep slopes (up to 100% and more) under a monsoon climate. After years of traditional slash and burn cultures, it is now under high land pressures due to population resettling and environment preservation policies. This evolution leads to rapid land-use changes such as shifting cultivation reduction or growing of teak forest instead of classical crops. This catchment is a benchmark site of the Managing Soil Erosion Consortium since 1998. The international consortium aims to understand the effects of agricultural changes on the catchment hydrology and soil erosion in south east Asia. The Huay Pano catchment is subdivided into small sub-catchments that are gauged and monitored. Differ- ent agricultural practices where tested along the years. At a smaller scale, plot of 1m2 are instrumented to follow runoff and detachment of soil under natural rainfall along the monsoon season. Our modeling work aims to develop a distributed hydrological model integrating experimental data at the different scales. One of the objective is to understand the impact of land-use, soil properties (slope, crust, etc) and rainfall (dry and wet seasons) on surface and subsurface flows. We present here modeling results of the runoff plot experiments (1m2 scale) performed from 2002 to 2007. The plots distribution among the catchment and over the years gives a good representativity of the different runoff responses. The role of crust, slope and land-use on runoff is examined. Finally we discuss how this plot scale will be integrated in a sub-catchment model, with a particular attention on the observed paradox: how to explain that runoff coefficients at the catchment scale are much slower than at the plot scale ?

  5. CHARACTERIZING ULTRAVIOLET AND INFRARED OBSERVATIONAL PROPERTIES FOR GALAXIES. I. INFLUENCES OF DUST ATTENUATION AND STELLAR POPULATION AGE

    SciTech Connect

    Mao Yewei; Kong Xu; Kennicutt, Robert C. Jr.; Hao, Cai-Na; Zhou Xu E-mail: xkong@ustc.edu.cn

    2012-09-20

    The correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color (or ultraviolet spectral slope), i.e., the IRX-UV (or IRX-{beta}) relation, found in studies of starburst galaxies is a prevalent recipe for correcting extragalactic dust attenuation. Considerable dispersion in this relation discovered for normal galaxies, however, complicates its usability. In order to investigate the cause of the dispersion and to have a better understanding of the nature of the IRX-UV relation, in this paper, we select five nearby spiral galaxies, and perform spatially resolved studies on each of the galaxies, with a combination of ultraviolet and infrared imaging data. We measure all positions within each galaxy and divide the extracted regions into young and evolved stellar populations. By means of this approach, we attempt to discover separate effects of dust attenuation and stellar population age on the IRX-UV relation for individual galaxies. In this work, in addition to dust attenuation, stellar population age is interpreted to be another parameter in the IRX-UV function, and the diversity of star formation histories is suggested to disperse the age effects. At the same time, strong evidence shows the need for more parameters in the interpretation of observational data, such as variations in attenuation/extinction law. Fractional contributions of different components to the integrated luminosities of the galaxies suggest that the integrated measurements of these galaxies, which comprise different populations, would weaken the effect of the age parameter on IRX-UV diagrams. The dependence of the IRX-UV relation on luminosity and radial distance in galaxies presents weak trends, which offers an implication of selective effects. The two-dimensional maps of the UV color and the infrared-to-ultraviolet ratio are displayed and show a disparity in the spatial distributions between the two galaxy parameters, which offers a spatial interpretation of the scatter

  6. Sampling Design Influences the Observed Dominance of Culex tritaeniorhynchus: Considerations for Future Studies of Japanese Encephalitis Virus Transmission.

    PubMed

    Lord, Jennifer S; Al-Amin, Hasan Mohammad; Chakma, Sumit; Alam, Mohammad Shafiul; Gurley, Emily S; Pulliam, Juliet R C

    2016-01-01

    Mosquito sampling during Japanese encephalitis virus (JEV)-associated studies, particularly in India, has usually been conducted via aspirators or light traps to catch mosquitoes around cattle, which are dead-end hosts for JEV. High numbers of Culex tritaeniorhynchus, relative to other species, have often been caught during these studies. Less frequently, studies have involved sampling outdoor resting mosquitoes. We aimed to compare the relative abundance of mosquito species between these two previously used mosquito sampling methods. From September to December 2013 entomological surveys were undertaken in eight villages in a Japanese encephalitis (JE) endemic area of Bangladesh. Light traps were used to collect active mosquitoes in households, and resting boxes and a Bina Pani Das hop cage were used near oviposition sites to collect resting mosquitoes. Numbers of humans and domestic animals present in households where light traps were set were recorded. In five villages Cx. tritaeniorhynchus was more likely to be selected from light trap samples near hosts than resting collection samples near oviposition sites, according to log odds ratio tests. The opposite was true for Cx. pseudovishnui and Armigeres subalbatus, which can also transmit JEV. Culex tritaeniorhynchus constituted 59% of the mosquitoes sampled from households with cattle, 28% from households without cattle and 17% in resting collections. In contrast Cx. pseudovishnui constituted 5.4% of the sample from households with cattle, 16% from households with no cattle and 27% from resting collections, while Ar. subalbatus constituted 0.15%, 0.38%, and 8.4% of these samples respectively. These observations may be due to differences in timing of biting activity, host preference and host-seeking strategy rather than differences in population density. We suggest that future studies aiming to implicate vector species in transmission of JEV should consider focusing catches around hosts able to transmit JEV. PMID

  7. Tidal influence on gas bubble emissions from permanent seafloor observations at Ocean Networks Canada's cabled array NEPTUNE

    NASA Astrophysics Data System (ADS)

    Roemer, M.; Scherwath, M.; Heesemann, M.; Spence, G.; Riedel, M.

    2015-12-01

    Sonar data from the northern Cascadia margin correlate well with tidal pressure changes and not so well with currents, seafloor shaking from storms or earthquakes, or temperature changes. These data are available from Ocean Networks Canada which operates the NEPTUNE observatory with power and communications to gas hydrate sites on the continental slope, allowing 24/7 monitoring of the dynamic gas hydrate activity. Clayoquot Slope at Cascadia's Bullseye Vent and Bubbly Gulch, is equipped with a variety of sensors including a 270 kHz Imagenex 100 m range multibeam sonar, as well as Conductivity-Temperature-Depth (CTD) sensors, high precision Bottom Pressure Recorders (BPR), current meter and Ocean Bottom Seismograph (OBS). This enables statistically meaningful correlation of these data. Hourly sonar data were collected showing venting activity in the form of gas plumes of various strengths. For four years the sonar was located at what appears to be a transient gas site, with longer periods of absolutely no venting observed activity. Here, the strongest correlation of gas bubbling is with rapid decreasing tidal pressure, where subsequent increasing tidal pressure is shutting down the degassing. In May 2014, the sonar was moved by 500 m to a more actively venting site termed Gastown Alley, over a zone of seismic blanking interpreted as having high subsurface gas content. This site is continuously emitting gas bubbles albeit with varying numbers of plumes and intensities. The strongest correlation of gas discharge is with absolute pressures, with maximum flows at higher tidal pressures, hinting at a steady subsurface rise of gas that is squeezed out stronger at high tides, partially emptying the shallow reservoirs, and with subsiding tidal pressure the venting activity also decreases again. Thus, the two sonar sites, though only 500 m apart, show a different behavior in degassing, however, both reacting most strongly to tidal pressure changes.

  8. Sampling Design Influences the Observed Dominance of Culex tritaeniorhynchus: Considerations for Future Studies of Japanese Encephalitis Virus Transmission

    PubMed Central

    Lord, Jennifer S.; Al-Amin, Hasan Mohammad; Chakma, Sumit; Alam, Mohammad Shafiul; Gurley, Emily S.; Pulliam, Juliet R. C.

    2016-01-01

    Mosquito sampling during Japanese encephalitis virus (JEV)-associated studies, particularly in India, has usually been conducted via aspirators or light traps to catch mosquitoes around cattle, which are dead-end hosts for JEV. High numbers of Culex tritaeniorhynchus, relative to other species, have often been caught during these studies. Less frequently, studies have involved sampling outdoor resting mosquitoes. We aimed to compare the relative abundance of mosquito species between these two previously used mosquito sampling methods. From September to December 2013 entomological surveys were undertaken in eight villages in a Japanese encephalitis (JE) endemic area of Bangladesh. Light traps were used to collect active mosquitoes in households, and resting boxes and a Bina Pani Das hop cage were used near oviposition sites to collect resting mosquitoes. Numbers of humans and domestic animals present in households where light traps were set were recorded. In five villages Cx. tritaeniorhynchus was more likely to be selected from light trap samples near hosts than resting collection samples near oviposition sites, according to log odds ratio tests. The opposite was true for Cx. pseudovishnui and Armigeres subalbatus, which can also transmit JEV. Culex tritaeniorhynchus constituted 59% of the mosquitoes sampled from households with cattle, 28% from households without cattle and 17% in resting collections. In contrast Cx. pseudovishnui constituted 5.4% of the sample from households with cattle, 16% from households with no cattle and 27% from resting collections, while Ar. subalbatus constituted 0.15%, 0.38%, and 8.4% of these samples respectively. These observations may be due to differences in timing of biting activity, host preference and host-seeking strategy rather than differences in population density. We suggest that future studies aiming to implicate vector species in transmission of JEV should consider focusing catches around hosts able to transmit JEV. PMID

  9. The Observed Relationship Between Water Vapor and Ozone in the Tropical Tropopause Saturation Layer and the Influence of Meridional Transport

    NASA Technical Reports Server (NTRS)

    Selkirk, Henry B.; Schoeberl, M. R.; Olsen, M. A.; Douglass, A. R.

    2011-01-01

    We examine balloonsonde observations of water vapor and ozone from three Ticosonde campaigns over San Jose, Costa Rica [10 N, 84 W] during northern summer and a fourth during northern winter. The data from the summer campaigns show that the uppermost portion of the tropical tropopause layer between 360 and 380 K, which we term the tropopause saturation layer or TSL, is characterized by water vapor mixing ratios from proximately 3 to 15 ppmv and ozone from approximately 50 ppbv to 250 ppbv. In contrast, the atmospheric water vapor tape recorder at 380 K and above displays a more restricted 4-7 ppmv range in water vapor mixing ratio. From this perspective, most of the parcels in the TSL fall into two classes - those that need only additional radiative heating to rise into the tape recorder and those requiring some combination of additional dehydration and mixing with drier air. A substantial fraction of the latter class have ozone mixing ratios greater than 150 ppbv, and with water vapor greater than 7 ppmv this air may well have been transported into the tropics from the middle latitudes in conjunction with high-amplitude equatorial waves. We examine this possibility with both trajectory analysis and transport diagnostics based on HIRDLS ozone data. We apply the same approach to study the winter season. Here a very different regime obtains as the ozone-water vapor scatter diagram of the sonde data shows the stratosphere and troposphere to be clearly demarcated with little evidence of mixing in of middle latitude air parcels.

  10. Influence of Radical Recyling on Spatial Distributions of HOx in the Planetary Boundary Layer - Zeppelin-Based Observations

    NASA Astrophysics Data System (ADS)

    Hofzumahaus, A.; Gomm, S.; Broch, S.; Fuchs, H.; Holland, F.; Bohn, B.; Häseler, R.; Keutsch, F. N.; Li, X.; Lu, K.; Lohse, I.; Rohrer, F.; Tillmann, R.; Wegener, R.; Mentel, T. F.; Kiendler-Scharr, A.; Wahner, A.; Kaiser, J.; Jäger, J.; Wolfe, G.

    2015-12-01

    Tropospheric OH is the most important oxidant in the chemical degradation of atmospheric pollutants leading to a large variety of oxidised products. Often, OH reactions produce hydroperoxy radicals (HO2) which can recycle OH by reaction with NO or O3. The chemical interconversion of OH and HO2(collectively HOx) occurs on a fast time scale of seconds to minutes. Owing to their high reactivity and short chemical lifetime, substantial spatial variability of HOx is expected in ambient air with inhomogeneous trace-gas distribution. This is particularly the case in the planetary boundary layer (PBL) where most tropospheric pollutants are emitted near Earth's surface and are then distributed by transport. In summer 2012, a Zeppelin NT was used as an airborne platform to investigate the spatial variation of HOx and other trace gases in the PBL in the Po Valley (Italy) as part of the Pan-European Gas-AeroSOls-climate interaction Study (PEGASOS). HOx and OH reactivity were measured by laser-induced fluorescence. Other on-board measurements included O3, CO, NO, NO2, HCHO, HONO, VOCs, photolysis frequencies, particle number concentration, and meteorological parameters. Due to the slow flight speed and precise navigation of the Zeppelin, the concentrations of HOx and trace gases could be measured with high spatial resolution. Vertical profiles were recorded repeatedly at altitudes between 75 m and 900m above ground. In the morning, measured vertical distributions of trace gases such as CO, NOx or VOCs visualise the dynamically evolving structure of the PBL. They show a pronounced effect on the radical cycling of HOx and therefore on the concentration profiles of OH and HO2. This presentation will show examples of the Zeppelin-based observations and discuss the role of HOx radical recycling in the evolving PBL.

  11. Influence of the Aure valley on the boundary-layer features observed during the BLLAST experimental field campaign

    NASA Astrophysics Data System (ADS)

    Jimenez, Maria A.; Cuxart, Joan; Martinez-Villagrasa, Daniel

    2016-04-01

    Under clear-skies and weak-synoptic pressure gradients, the organization of the flow at lower levels is mainly controlled by the local effects, such as terrain or surface heterogeneities. This is the case of the thermal differences between the air adjacent to the slopes, within a valley and over the nearby plains that generate slope, valley and mountain winds with an opposite direction between day and night. The Aure valley, located at the north of the Pyrenees with the main axis pointing to North, and the surrounding foothills are selected to study the temporal and spatial scales of the thermally-driven flows during the BLLAST experimental field campaign (June-July 2011). A combined inspection of the observations in Lannemezan (located over a plateau at about 5 km from the exit of the Aure valley) and high-resolution mesoscale simulations is used to evaluate the effect of the Aure valley on the boundary-layer characteristics over Lannemezan. The inspection of some selected IOPs (clear-skies, no rain) show that the interaction between the Aure valley and the Lannemezan plateau takes place depending on the direction and intensity of the large-scale wind, enhancing or diminishing the thermally-driven flow. During day, a convective boundary layer is formed with associated strong turbulence at the foothills, valleys and plain. However, during the night-time turbulence is in general weaker with some episodes of strong turbulence associated to wind shear related to the presence of the exit valley jet of the drainage winds. It is found that when large-scale winds are weak the exit valley jet reach Lannemezan close to midnight and interacts with the locally-generated downslope winds already present. It is found that IOP11 shows a Foehn effect in the valley, that is warmer than the plain, resulting in up-valley flows during the night. The BLLAST dataset is an useful tool to evaluate the performance of the mesoscale model in a complex region, such as the valleys and

  12. Comparison of modeled and observed environmental influences on the stable oxygen and hydrogen isotope composition of leaf water in Phaseolus vulgaris L

    SciTech Connect

    Flanagan, L.B.; Comstock, J.P.; Ehleringer, J.R. )

    1991-06-01

    In this paper the authors describe how a model of stable isotope fractionation processes, originally developed by H. Craig and L.I. Gordon for evaporation of water from the ocean, can be applied to leaf transpiration. The original model was modified to account for turbulent conditions in the leaf boundary layer. Experiments were conducted to test the factors influencing the stable isotopic composition of leaf water under controlled environment conditions. At steady state, the observed leaf water isotopic composition was enriched above that of stem water with the extent of the enrichment dependent on the leaf-air vapor pressure difference (VPD) and the isotopic composition of atmospheric water vapor (AMV). The higher the VPD, the larger was the observed heavy isotope content of leaf water. At a constant VPD, leaf water was relatively enriched in heavy isotopes when exposed to AWV with a large heavy isotope composition. However, the observed heavy isotope composition of leaf water was always less than that predicted by the model. The extent of the discrepancy between the modeled and observed leaf water isotopic composition was a strong linear function of the leaf transpiration rate.

  13. Comparison of Modeled and Observed Environmental Influences on the Stable Oxygen and Hydrogen Isotope Composition of Leaf Water in Phaseolus vulgaris L.

    PubMed

    Flanagan, L B; Comstock, J P; Ehleringer, J R

    1991-06-01

    In this paper we describe how a model of stable isotope fractionation processes, originally developed by H. Craig and L. I. Gordon ([1965] in E Tongiorgi, ed, Proceedings of a Conference on Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, Italy, pp 9-130) for evaporation of water from the ocean, can be applied to leaf transpiration. The original model was modified to account for turbulent conditions in the leaf boundary layer. Experiments were conducted to test the factors influencing the stable isotopic composition of leaf water under controlled environment conditions. At steady state, the observed leaf water isotopic composition was enriched above that of stem water with the extent of the enrichment dependent on the leaf-air vapor pressure difference (VPD) and the isotopic composition of atmospheric water vapor (AWV). The higher the VPD, the larger was the observed heavy isotope content of leaf water. At a constant VPD, leaf water was relatively depleted in heavy isotopes when exposed to AWV with a low heavy isotope composition, and leaf water was relatively enriched in heavy isotopes when exposed to AWV with a large heavy isotope composition. However, the observed heavy isotope composition of leaf water was always less than that predicted by the model. The extent of the discrepancy between the modeled and observed leaf water isotopic composition was a strong linear function of the leaf transpiration rate. PMID:16668226

  14. Numerical simulations of barnacle larval dispersion coupled with field observations on larval abundance, settlement and recruitment in a tropical monsoon influenced coastal marine environment

    NASA Astrophysics Data System (ADS)

    Gaonkar, Chetan A.; Samiksha, S. V.; George, Grinson; Aboobacker, V. M.; Vethamony, P.; Anil, Arga Chandrashekar

    2012-06-01

    Larval abundance in an area depends on various factors which operate over different spatial and temporal scales. Identifying the factors responsible for variations in larval supply and abundance is important to understand the settlement and recruitment variability of their population in a particular area. In view of this, observations were carried out to monitor the larval abundance, settlement and recruitment of barnacles on a regular basis for a period of two years. The results were then compared with the numerical modelling studies carried out along the west coast of India. Field observations of larval abundance showed temporal variations. The least abundance of larvae was mostly observed during the monsoon season and the peak in abundance was mostly observed during the pre-monsoon season. Numerical simulations also showed a seasonal change in larval dispersion and retention patterns. During pre-monsoon season the larval movement was mostly found towards south and the larvae released from the northern release sites contributed to larval abundance within the estuaries, whereas during the monsoon season the larval movement was mostly found towards north and the larvae released from southern release sites contributed to larval abundance within the estuary. During post-monsoon season, the larval movement was found towards the north in the beginning of the season and is shifted towards the south at the end of the season, but the movement was mostly restricted near to the release sites. Larval supply from the adjacent rocky sites to the estuaries was higher during the pre-monsoon season and the retention of larvae released from different sites within the estuaries was found to be highest during the late post-monsoon and early pre-monsoon season. Maximum larval supply and retention during the pre-monsoon season coincided with maximum larval abundance, settlement and recruitment of barnacles observed in the field studies. These observations showed that the pattern of

  15. OBSERVING GRAVITATIONAL LENSING EFFECTS BY Sgr A* WITH GRAVITY

    SciTech Connect

    Bozza, V.; Mancini, L. E-mail: mancini@mpia-hd.mpg.de

    2012-07-01

    The massive black hole Sgr A* at the Galactic center is surrounded by a cluster of stars orbiting around it. Light from these stars is bent by the gravitational field of the black hole, giving rise to several phenomena: astrometric displacement of the primary image, the creation of a secondary image that may shift the centroid of Sgr A*, and magnification effects on both images. The soon-to-be second-generation Very Large Telescope Interferometer instrument GRAVITY will perform observations in the near-infrared of the Galactic center at unprecedented resolution, opening the possibility of observing such effects. Here we investigate the observability limits for GRAVITY of gravitational lensing effects on the S-stars in the parameter space 1[D{sub LS}, {gamma}, K], where D{sub LS} is the distance between the lens and the source, {gamma} is the alignment angle of the source, and K is the source's apparent magnitude in the K band. The easiest effect to observe in future years is the astrometric displacement of primary images. In particular, the shift of the star S17 from its Keplerian orbit will be detected as soon as GRAVITY becomes operative. For exceptional configurations, it will be possible to detect effects related to the spin of the black hole or post-Newtonian orders in the deflection.

  16. Water quality observations of ice-covered, stagnant, eutrophic water bodies and analysis of influence of ice-covered period on water quality

    NASA Astrophysics Data System (ADS)

    sugihara, K.; Nakatsugawa, M.

    2013-12-01

    The water quality characteristics of ice-covered, stagnant, eutrophic water bodies have not been clarified because of insufficient observations. It has been pointed out that climate change has been shortening the duration of ice-cover; however, the influence of climate change on water quality has not been clarified. This study clarifies the water quality characteristics of stagnant, eutrophic water bodies that freeze in winter, based on our surveys and simulations, and examines how climate change may influence those characteristics. We made fixed-point observation using self-registering equipment and vertical water sampling. Self-registering equipment measured water temperature and dissolved oxygen(DO).vertical water sampling analyzed biological oxygen demand(BOD), total nitrogen(T-N), nitrate nitrogen(NO3-N), nitrite nitrogen(NO2-N), ammonium nitrogen(NH4-N), total phosphorus(TP), orthophosphoric phosphorus(PO4-P) and chlorophyll-a(Chl-a). The survey found that climate-change-related increases in water temperature were suppressed by ice covering the water area, which also blocked oxygen supply. It was also clarified that the bottom sediment consumed oxygen and turned the water layers anaerobic beginning from the bottom layer, and that nutrient salts eluted from the bottom sediment. The eluted nutrient salts were stored in the water body until the ice melted. The ice-covered period of water bodies has been shortening, a finding based on the analysis of weather and water quality data from 1998 to 2008. Climate change was surveyed as having caused decreases in nutrient salts concentration because of the shortened ice-covered period. However, BOD in spring showed a tendency to increase because of the proliferation of phytoplankton that was promoted by the climate-change-related increase in water temperature. To forecast the water quality by using these findings, particularly the influence of climate change, we constructed a water quality simulation model that

  17. Influence of a source line position on results of EM observations applied to the diagnostics of underground heating system pipelines in urban area

    NASA Astrophysics Data System (ADS)

    Vetrov, A.

    2009-05-01

    The condition of underground constructions, communication and supply systems in the cities has to be periodically monitored and controlled in order to prevent their breakage, which can result in serious accident, especially in urban area. The most risk of damage have the underground construction made of steal such as pipelines widely used for water, gas and heat supply. To ensure the pipeline survivability it is necessary to carry out the operative and inexpensive control of pipelines condition. Induced electromagnetic methods of geophysics can be applied to provide such diagnostics. The highly developed surface in urbane area is one of cause hampering the realization of electromagnetic methods of diagnostics. The main problem is in finding of an appropriate place for the source line and electrodes on a limited surface area and their optimal position relative to the observation path to minimize their influence on observed data. Author made a number of experiments of an underground heating system pipeline diagnostics using different position of the source line and electrodes. The experiments were made on a 200 meters section over 2 meters deep pipeline. The admissible length of the source line and angle between the source line and the observation path were determined. The minimal length of the source line for the experiment conditions and accuracy made 30 meters, the maximum admissible angle departure from the perpendicular position made 30 degrees. The work was undertaken in cooperation with diagnostics company DIsSO, Saint-Petersburg, Russia.

  18. X-ray Astrometric Confirmation of Association of the Candidate Tidal Disruption Event ASASSN-14li with its Host Nucleus

    NASA Astrophysics Data System (ADS)

    Maksym, W. P.; Miller, J. M.; Cenko, S. B.; Drake, J. J.; Gezari, S.; Mushotzky, R.; Irwin, J.; Gultekin, K.; Kaastra, J.; Paerels, F.; Ramirez-Ruiz, E.; Reynolds, M.

    2014-12-01

    We report on the use of the 0th order images from the Chandra HRC-LETG DDT observations of ASSASN-14li (Miller et al., 2014; ATel #6800) to locate this likely tidal disruption event (TDE; Jose et al., 2014; ATel #6777) with respect to its host nucleus.

  19. Observation of the inverse trans influence (ITI) in a uranium(V) imide coordination complex: an experimental study and theoretical evaluation.

    PubMed

    Lam, Oanh P; Franke, Sebastian M; Nakai, Hidetaka; Heinemann, Frank W; Hieringer, Wolfgang; Meyer, Karsten

    2012-06-01

    An inverse trans influence has been observed in a high-valent U(V) imide complex, [(((Ad)ArO)(3)N)U(NMes)]. A thorough theoretical evaluation has been employed in order to corroborate the ITI in this unusual complex. Computations on the target complex, [(((Ad)ArO)(3)N)U(NMes)], and the model complexes [(((Me)ArO)(3)N)U(NMes)] and [(NMe(3))(OMe(2))(OMe)(3)U(NPh)] are discussed along with synthetic details and supporting spectroscopic data. Additionally, the syntheses and full characterization data of the related U(V) trimethylsilylimide complex [(((Ad)ArO)(3)N)U(NTMS)] and U(IV) azide complex [(((Ad)ArO)(3)N)U(N(3))] are also presented for comparison.

  20. Investigating the influence of long-range transport on surface O3 in Nevada, USA, using observations from multiple measurement platforms.

    PubMed

    Fine, Rebekka; Miller, Matthieu B; Yates, Emma L; Iraci, Laura T; Gustin, Mae Sexauer

    2015-10-15

    The current United States (US) National Ambient Air Quality Standard (NAAQS) for O3 (75 ppb) is expected to be revised to between 60 and 70 ppb. As the NAAQS becomes more stringent, characterizing the extent of O3 and precursors transported into the US is increasingly important. Given the high elevation, complex terrain, and location in the Intermountain West, the State of Nevada is ideally situated to intercept air transported into the US. Until recently, measurements of O3 and associated pollutants were limited to areas in and around the cities of Las Vegas and Reno. In 2011, the Nevada Rural Ozone Initiative began and through this project 13 surface monitoring sites were established. Also in 2011, the NASA Ames Alpha Jet Atmospheric eXperiment (AJAX) began making routine aircraft measurements of O3 and other greenhouse gases in Nevada. The availability of aircraft and surface measurements in a relatively rural, remote setting in the Intermountain West presented a unique opportunity to investigate sources contributing to the O3 observed in Nevada. Our analyses indicate that stratosphere to troposphere transport, long-range transport of Asian pollution, and regional emissions from urban areas and wildfires influence surface observations. The complexity of sources identified here along with the fact that O3 frequently approaches the threshold being considered for a revised NAAQS indicate that interstate and international cooperation will be necessary to achieve compliance with a more stringent regulatory standard. Further, on a seasonal basis we found no significant difference between daily 1-h maximum O3 at surface sites, which ranged in elevation from 888 to 2307 m, and aircraft measurements of O3 <2500 m which suggests that similar processes influence daytime O3 across rural Nevada and indicates that column measurements from Railroad Valley, NV are useful in understanding these processes. PMID:25845306

  1. The pattern of growth observed for Clostridium botulinum type A1 strain ATCC 19397 is influenced by nutritional status and quorum sensing: a modelling perspective

    PubMed Central

    Ihekwaba, Adaoha E. C.; Mura, Ivan; Peck, Michael W.; Barker, G. C.

    2015-01-01

    Botulinum neurotoxins (BoNTs) produced by the anaerobic bacterium Clostridium botulinum are the most poisonous substances known to mankind. However, toxin regulation and signals triggering synthesis as well as the regulatory network and actors controlling toxin production are unknown. Experiments show that the neurotoxin gene is growth phase dependent for C. botulinum type A1 strain ATCC 19397, and toxin production is influenced both by culture conditions and nutritional status of the medium. Building mathematical models to describe the genetic and molecular machinery that drives the synthesis and release of BoNT requires a simultaneous description of the growth of the bacterium in culture. Here, we show four plausible modelling options which could be considered when constructing models describing the pattern of growth observed in a botulinum growth medium. Commonly used bacterial growth models are unsuitable to fit the pattern of growth observed, since they only include monotonic growth behaviour. We find that a model that includes both the nutritional status and the ability of the cells to sense their surroundings in a quorum-sensing manner is most successful at explaining the pattern of growth obtained for C. botulinum type A1 strain ATCC 19397. PMID:26449712

  2. The pattern of growth observed for Clostridium botulinum type A1 strain ATCC 19397 is influenced by nutritional status and quorum sensing: a modelling perspective.

    PubMed

    Ihekwaba, Adaoha E C; Mura, Ivan; Peck, Michael W; Barker, G C

    2015-12-01

    Botulinum neurotoxins (BoNTs) produced by the anaerobic bacterium Clostridium botulinum are the most poisonous substances known to mankind. However, toxin regulation and signals triggering synthesis as well as the regulatory network and actors controlling toxin production are unknown. Experiments show that the neurotoxin gene is growth phase dependent for C. botulinum type A1 strain ATCC 19397, and toxin production is influenced both by culture conditions and nutritional status of the medium. Building mathematical models to describe the genetic and molecular machinery that drives the synthesis and release of BoNT requires a simultaneous description of the growth of the bacterium in culture. Here, we show four plausible modelling options which could be considered when constructing models describing the pattern of growth observed in a botulinum growth medium. Commonly used bacterial growth models are unsuitable to fit the pattern of growth observed, since they only include monotonic growth behaviour. We find that a model that includes both the nutritional status and the ability of the cells to sense their surroundings in a quorum-sensing manner is most successful at explaining the pattern of growth obtained for C. botulinum type A1 strain ATCC 19397.

  3. Kinematic relative velocity with respect to stationary observers in Schwarzschild spacetime

    NASA Astrophysics Data System (ADS)

    Bolós, Vicente J.

    2013-04-01

    We study the kinematic relative velocity of general test particles with respect to stationary observers (using spherical coordinates) in Schwarzschild spacetime, obtaining that its modulus does not depend on the observer, unlike Fermi, spectroscopic, and astrometric relative velocities. We study some fundamental particular cases, generalizing some results given in other work about stationary and radial free-falling test particles. Moreover, we give a new result about test particles with circular geodesic orbits: the modulus of their kinematic relative velocity with respect to any stationary observer depends only on the radius of the circular orbit, and so it remains constant.

  4. CCD Camera Observations

    NASA Astrophysics Data System (ADS)

    Buchheim, Bob; Argyle, R. W.

    One night late in 1918, astronomer William Milburn, observing the region of Cassiopeia from Reverend T.H.E.C. Espin's observatory in Tow Law (England), discovered a hitherto unrecorded double star (Wright 1993). He reported it to Rev. Espin, who measured the pair using his 24-in. reflector: the fainter star was 6.0 arcsec from the primary, at position angle 162.4 ^{circ } (i.e. the fainter star was south-by-southeast from the primary) (Espin 1919). Some time later, it was recognized that the astrograph of the Vatican Observatory had taken an image of the same star-field a dozen years earlier, in late 1906. At that earlier epoch, the fainter star had been separated from the brighter one by only 4.8 arcsec, at position angle 186.2 ^{circ } (i.e. almost due south). Were these stars a binary pair, or were they just two unrelated stars sailing past each other? Some additional measurements might have begun to answer this question. If the secondary star was following a curved path, that would be a clue of orbital motion; if it followed a straight-line path, that would be a clue that these are just two stars passing in the night. Unfortunately, nobody took the trouble to re-examine this pair for almost a century, until the 2MASS astrometric/photometric survey recorded it in late 1998. After almost another decade, this amateur astronomer took some CCD images of the field in 2007, and added another data point on the star's trajectory, as shown in Fig. 15.1.

  5. Mid infrared observations of Van Maanen 2: no substellar companion.

    SciTech Connect

    Farihi, J; Becklin, E; Macintosh, B

    2004-11-03

    The results of a comprehensive infrared imaging search for the putative 0.06 M{sub {circle_dot}} astrometric companion to the 4.4 pc white dwarf van Mannen 2 are reported. Adaptive optics images acquired at 3.8 {micro}m reveal a diffraction limited core of 0.09 inch and no direct evidence of a secondary. Models predict that at 5 Gyr, a 50 M{sub J} brown dwarf would be only 1 magnitude fainter than van Maanen 2 at this wavelength and the astrometric analysis suggested a separation of 0.2 inch. In the case of a chance alignment along the line of sight, a 0.4 mag excess should be measured. An independent photometric observation at the same wavelength reveals no excess. In addition, there exist published ISO observations of van Maanen 2 at 6.8 {micro}m and 15.0 {micro}m which are consistent with photospheric flux of a 6750 K white dwarf. If recent brown dwarf models are correct, there is no substellar companion with T{sub eff} {approx}> 500 K.

  6. Influence of regional biomass burning on the highly elevated organic carbon concentrations observed at Gosan, South Korea during a strong Asian dust period.

    PubMed

    Nguyen, Duc Luong; Kim, Jin Young; Ghim, Young Sung; Shim, Shang-Gyoo

    2015-03-01

    PM2.5 carbonaceous particles were measured at Gosan, South Korea during 29 March-11 April 2002 which includes a pollution period (30 March-01 April) when the highest concentrations of major anthropogenic species (nss-SO4 (2-), NO3 (-), and NH4 (+)) were observed and a strong Asian dust (AD) period (08-10 April) when the highest concentrations of mainly dust-originated trace elements (Al, Ca, Mg, and Fe) were seen. The concentrations of elemental carbon (EC) measured in the pollution period were higher than those measured in the strong AD period, whereas an inverse variation in the concentrations of organic carbon (OC) was observed. Based on the OC/EC ratios, the possible source that mainly contributed to the highly elevated OC concentrations measured in the strong AD period was biomass burning. The influence of the long-range transport of smoke plumes emitted from regional biomass burning sources was evaluated by using MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data for fire locations and the potential source contribution function analysis. The most potential source regions of biomass burning were the Primorsky and Amur regions in Far Eastern Russia and southeastern and southwestern Siberia, Russia. Further discussion on the source characteristics suggested that the high OC concentrations measured in the strong AD period were significantly affected by the smoldering phase of biomass burning. In addition to biomass burning, secondary OC (SOC) formed during atmospheric long-range transport should be also considered as an important source of OC concentration measured at Gosan. Although this study dealt with the episodic case of the concurrent increase of dust and biomass burning particles, understanding the characteristics of heterogeneous mixing aerosol is essential in assessing the radiative forcing of aerosol. PMID:25253054

  7. The Influences of Withdrawal and Daily Dose Reduction of Pioglitazone on Metabolic Parameters in Patients With Type 2 Diabetes: A Retrospective Longitudinal Observational Study

    PubMed Central

    Katsuyama, Hisayuki; Fukunaga, Takayuki; Hamasaki, Hidetaka; Adachi, Hiroki; Moriyama, Sumie; Kawaguchi, Akiko; Mishima, Shuichi; Sako, Akahito; Yanai, Hidekatsu

    2016-01-01

    Background The aim of the study was to understand the influences of withdrawal or dose reduction of pioglitazone in patients with type 2 diabetes. Methods We retrospectively picked up patients who had undergone withdrawal or daily dose reduction of pioglitazone after a continuous prescription for 3 months or longer between January 2010 and March 2014. We compared the data before the withdrawal or dose reduction of pioglitazone with the data at 3 or 6 months after those by a chart-based analysis. Results Among 713 patients taking pioglitazone at least once during the studied period, 20 patients had undergone withdrawal of pioglitazone (group A) and 51 patients had undergone daily dose reduction (group B). The mean pioglitazone dose at baseline was 23 mg in subjects of group A, and 30 mg in group B. The number of subjects who had taken high-dose metformin (≥ 1,000 mg) and dipeptidyl peptidase-4 (DPP-4) inhibitors increased after the withdrawal or dose reduction of pioglitazone in both groups. Although no significant change was observed in plasma glucose and HbA1c levels, body weight significantly decreased at 3 and 6 months after the dose reduction in group B. The same tendency was observed in group A. Serum high-density lipoprotein-cholesterol (HDL-C) levels significantly decreased at 3 and 6 months after the withdrawal in group A. The serum alanine aminotransferase levels significantly increased 3 months after the withdrawal in group A. Conclusions Present study demonstrated that the withdrawal of pioglitazone exacerbated serum HDL-C and liver function in patients with type 2 diabetes, although glycemic control could be maintained by using high-dose metformin or DPP-4 inhibitors. PMID:27429679

  8. Gender as a Modifying Factor Influencing Myotonic Dystrophy Type 1 Phenotype Severity and Mortality: A Nationwide Multiple Databases Cross-Sectional Observational Study

    PubMed Central

    Hamroun, Dalil; Varet, Hugo; Fabbro, Marianne; Rougier, Felix; Amarof, Khadija; Arne Bes, Marie-Christine; Bedat-Millet, Anne-Laure; Behin, Anthony; Bellance, Remi; Bouhour, Françoise; Boutte, Celia; Boyer, François; Campana-Salort, Emmanuelle; Chapon, Françoise; Cintas, Pascal; Desnuelle, Claude; Deschamps, Romain; Drouin-Garraud, Valerie; Ferrer, Xavier; Gervais-Bernard, Helene; Ghorab, Karima; Laforet, Pascal; Magot, Armelle; Magy, Laurent; Menard, Dominique; Minot, Marie-Christine; Nadaj-Pakleza, Aleksandra; Pellieux, Sybille; Pereon, Yann; Preudhomme, Marguerite; Pouget, Jean; Sacconi, Sabrina; Sole, Guilhem; Stojkovich, Tanya; Tiffreau, Vincent; Urtizberea, Andoni; Vial, Christophe; Zagnoli, Fabien; Caranhac, Gilbert; Bourlier, Claude; Riviere, Gerard; Geille, Alain; Gherardi, Romain K.; Eymard, Bruno; Puymirat, Jack; Katsahian, Sandrine; Bassez, Guillaume

    2016-01-01

    Background Myotonic Dystrophy type 1 (DM1) is one of the most heterogeneous hereditary disease in terms of age of onset, clinical manifestations, and severity, challenging both medical management and clinical trials. The CTG expansion size is the main factor determining the age of onset although no factor can finely predict phenotype and prognosis. Differences between males and females have not been specifically reported. Our aim is to study gender impact on DM1 phenotype and severity. Methods We first performed cross-sectional analysis of main multiorgan clinical parameters in 1409 adult DM1 patients (>18y) from the DM-Scope nationwide registry and observed different patterns in males and females. Then, we assessed gender impact on social and economic domains using the AFM-Téléthon DM1 survey (n = 970), and morbidity and mortality using the French National Health Service Database (n = 3301). Results Men more frequently had (1) severe muscular disability with marked myotonia, muscle weakness, cardiac, and respiratory involvement; (2) developmental abnormalities with facial dysmorphism and cognitive impairment inferred from low educational levels and work in specialized environments; and (3) lonely life. Alternatively, women more frequently had cataracts, dysphagia, digestive tract dysfunction, incontinence, thyroid disorder and obesity. Most differences were out of proportion to those observed in the general population. Compared to women, males were more affected in their social and economic life. In addition, they were more frequently hospitalized for cardiac problems, and had a higher mortality rate. Conclusion Gender is a previously unrecognized factor influencing DM1 clinical profile and severity of the disease, with worse socio-economic consequences of the disease and higher morbidity and mortality in males. Gender should be considered in the design of both stratified medical management and clinical trials. PMID:26849574

  9. Observations of a two-layer soil moisture influence on surface energy dynamics and planetary boundary layer characteristics in a semiarid shrubland

    NASA Astrophysics Data System (ADS)

    Sanchez-Mejia, Zulia Mayari; Papuga, Shirley A.

    2014-01-01

    We present an observational analysis examining soil moisture control on surface energy dynamics and planetary boundary layer characteristics. Understanding soil moisture control on land-atmosphere interactions will become increasingly important as climate change continues to alter water availability. In this study, we analyzed 4 years of data from the Santa Rita Creosote Ameriflux site. We categorized our data independently in two ways: (1) wet or dry seasons and (2) one of the four cases within a two-layer soil moisture framework for the root zone based on the presence or absence of moisture in shallow (0-20 cm) and deep (20-60 cm) soil layers. Using these categorizations, we quantified the soil moisture control on surface energy dynamics and planetary boundary layer characteristics using both average responses and linear regression. Our results highlight the importance of deep soil moisture in land-atmosphere interactions. The presence of deep soil moisture decreased albedo by about 10%, and significant differences were observed in evaporative fraction even in the absence of shallow moisture. The planetary boundary layer height (PBLh) was largest when the whole soil profile was dry, decreasing by about 1 km when the whole profile was wet. Even when shallow moisture was absent but deep moisture was present the PBLh was significantly lower than when the entire profile was dry. The importance of deep moisture is likely site-specific and modulated through vegetation. Therefore, understanding these relationships also provides important insights into feedbacks between vegetation and the hydrologic cycle and their consequent influence on the climate system.

  10. Lidar Ratio Derived for Pure Dust Aerosols: Multi-Year Micro Pulse Lidar Observations in a Saharan Dust-Influenced Region

    NASA Astrophysics Data System (ADS)

    Córdoba-Jabonero, Carmen; Adame, José Antonio; Campbell, James R.; Cuevas, Emilio; Díaz, Juan Pedro; Expósito, Francisco; Gil-Ojeda, Manuel

    2016-06-01

    A seasonal distribution of the Lidar Ratio (LR, extinction-to-backscattering coefficient ratio) for pure Saharan dust particles has been achieved. Simultaneous MPLNET/Micro Pulse lidar measurements in synergy with AERONET sun-photometer data were collected in the Tenerife area, a Saharan dust-influenced region, from June 2007 to November 2009. Dusty cases were mostly observed in summertime (71.4 % of total dusty cases). No differences were found among the LR values derived for spring, summertime and autumn times (a rather consistent seasonally averaged LR value of 57 sr is found). In wintertime, however, a higher mean LR is derived (65 sr), associated likely with a potential contamination from fine biomass burning particles coming from Sahel area during wintertime deforestation fires period. Results, obtained from a free-tropospheric pristine station (AEMET/Izaña Observatory) under Saharan dust intrusion occurrence, provide a more realistic perspective about LR values to be used in elastic lidar-derived AOD inversion for Saharan pure dust particles, and hence in improving CALIPSO AOD retrievals.

  11. Submersible- and lander-observed community patterns in the Mariana and New Britain trenches: Influence of productivity and depth on epibenthic and scavenging communities

    NASA Astrophysics Data System (ADS)

    Gallo, Natalya D.; Cameron, James; Hardy, Kevin; Fryer, Patricia; Bartlett, Douglas H.; Levin, Lisa A.

    2015-05-01

    Deep-sea trenches remain one of the least explored ocean ecosystems due to the unique challenges of sampling at great depths. Five submersible dives conducted using the DEEPSEA CHALLENGER submersible generated video of undisturbed deep-sea communities at bathyal (994 m), abyssal (3755 m), and hadal (8228 m) depths in the New Britain Trench, bathyal depths near the Ulithi atoll (1192 m), and hadal depths in the Mariana Trench Challenger Deep (10908 m). The New Britain Trench is overlain by waters with higher net primary productivity (~3-fold) than the Mariana Trench and nearby Ulithi, and receives substantially more allochthonous input from terrestrial sources, based on the presence of terrestrial debris in submersible video footage. Comparisons between trenches addressed how differences in productivity regime influence benthic and demersal deep-sea community structure. In addition, the scavenger community was studied using paired lander deployments to the New Britain (8233 m) and Mariana (10918 m) trenches. Differences in allochthonous input were reflected in epibenthic community abundance, biodiversity, and lifestyle representation. More productive locations were characterized by higher faunal abundances (~2-fold) at both bathyal and hadal depths. In contrast, biodiversity trends showed a unimodal pattern with more food-rich areas exhibiting reduced bathyal diversity and elevated hadal diversity. Hadal scavenging communities exhibited similar higher abundance but also ~3-fold higher species richness in the more food-rich New Britain Trench compared to the Mariana Trench. High species- and phylum-level diversity observed in the New Britain Trench suggest that trench environments may foster higher megafaunal biodiversity than surrounding abyssal depths if food is not limiting. However, the absence of fish at our hadal sites suggests that certain groups do have physiological depth limits. Submersible video footage allowed novel in situ observation of holothurian

  12. The Revised Pole Model and New Observations of Triton

    NASA Astrophysics Data System (ADS)

    Zhang, H.-Y.; Shen, K.-X.; Qiao, R.-Ch; Dourneau, G.; Yu, Y.

    2015-10-01

    We used 3108 Earth-based astrometric observations from the Natural Satellite Data Center (NSDC) over more than 30 years time span from 1975 to 2006 for determining the epoch state vectors of the Neptunes largest satellite Triton. In integrating the perturbation equation, the barycentric frame of Neptune-Triton system is adopted, and in considering the oblateness perturbation due to Neptune, a revised pole model describing the precession of the Neptune's pole is used in our calculation. Moreover, a total of 1095 new observed positions of Triton were collected during 46 nights of observations in 2007, 2008 and 2009. We compared our observations to two ephemerides of Triton and most of the available planetary ephemerides of Neptune.

  13. Observations of Planet Crossing Asteroids

    NASA Technical Reports Server (NTRS)

    Tholen, David J.; Whiteley, Robert J.; Lambert, Joy; Connelley, Michael; Salyk, Colette

    2002-01-01

    The goals of this research were the physical and dynamical characterization of planet crossing asteroids (Earth crossers, Mars crossers, Centaurs, and Pluto crossers, meaning trans-Neptunian objects), including colorimetry, rotational studies, and astrometry. Highlights are listed as follows: 1) Produced one doctoral dissertation (R. J. Whiteley, A Compositional and Dynamical Survey of the Near-Earth Asteroids). A key result is the fraction of Q-type asteroids among the near-Earth population was found to be about one-third; 2) Had prediscovery image showing the binary nature of trans-Neptunian object 1998 WW31, which is the first TNO to have a satellite found in orbit around it; 3) Discovery of shortest known rotation period for any asteroid (2000 D08, rotation period 78 seconds); it is just one of several fast-rotating small asteroids observed during the course of this project; 4) Discovery of a Centaur asteroid (1998 QM107) with, at the time, the smallest known orbital eccentricity among the Centaurs (0.13) and nearly in a 1:1 resonance with Uranus (semimajor axis of 19.9 AU); 5) Discovery of Apollo-type asteroid 1999 OW3, with a surprisingly bright absolute magnitude of 14.6 (estimated diameter of 4.6 km), brightest Apollo found in that calendar year; 6) Discovery of Aten-type asteroid 2000 SG344, which has the highest cumulative Earth impact probability among the near-Earth asteroids and a very Earth-similar orbit; 7) Instrumental in repairing the orbit of a numbered near-Earth asteroid for which prediscovery observations had been mis-attributed to it (2000 VN2); 8) Second-opposition recovery of 30-meter diameter Apollo-type asteroid 1998 KY26 in early 2002 when it was at a favorable magnitude of 24.8; 9) Primary contributor of astrometric observations of the CONTOUR fragments to the CONTOUR project following the failure of the spacecraft s kick motor; and 10) Development of orbit and ephemeris computation code that handles short observational arcs

  14. Orbital Debris Observations with WFCAM

    NASA Technical Reports Server (NTRS)

    Bold, Matthew; Cross, Nick; Irwin, Mike; Kendrick, Richard; Kerr, Thomas; Lederer, Susan; Mann, Robert; Sutorius, Eckhard

    2014-01-01

    The United Kingdom Infrared Telescope has been operating for 35 years on the summit of Mauna Kea as a premier Infrared astronomical facility. In its 35th year the telescope has been turned over to a new operating group consisting of University of Arizona, University of Hawaii and the LM Advanced Technology Center. UKIRT will continue its astronomical mission with a portion of observing time dedicated to orbital debris and Near Earth Object detection and characterization. During the past 10 years the UKIRT Wide Field CAMera (WFCAM) has been performing large area astronomical surveys in the J, H and K bands. The data for these surveys have been reduced by the Cambridge Astronomical Survey Unit in Cambridge, England and archived by the Wide Field Astronomy Unit in Edinburgh, Scotland. During January and February of 2014 the Wide Field CAMera (WFCAM) was used to scan through the geostationary satellite belt detecting operational satellites as well as nearby debris. Accurate photometric and astrometric parameters have been developed by CASU for each of the detections and all data has been archived by WFAU.

  15. Orbital Debris Observations with WFCAM

    NASA Astrophysics Data System (ADS)

    Kendrick, R.; Mann, B.; Read, M.; Kerr, T.; Irwin, M.; Cross, N.; Bold, M.,; Varricatt, W.; Madsen, G.

    2014-09-01

    The United Kingdom Infrared Telescope has been operating for 35 years on the summit of Mauna Kea as a premier Infrared astronomical facility. In its 35th year the telescope has been turned over to a new operating group consisting of University of Arizona, University of Hawaii and the LM Advanced Technology Center. UKIRT will continue its astronomical mission with a portion of observing time dedicated to orbital debris and Near Earth Object detection and characterization. During the past 10 years the UKIRT Wide Field CAMera (WFCAM) has been performing large area astronomical surveys in the J, H and K bands. The data for these surveys have been reduced by the Cambridge Astronomical Survey Unit in Cambridge, England and archived by the Wide Field Astronomy Unit in Edinburgh, Scotland. During January and February of 2014 the Wide Field CAMera (WFCAM) was used to scan through the geostationary satellite belt detecting operational satellites as well as nearby debris. Accurate photometric and astrometric parameters have been developed by CASU for each of the detections and all data has been archived by WFAU. This paper will present the January and February results of the orbital debris surveys with WFCAM.

  16. The Influence of Time from Injury to Surgery on Motor Recovery and Length of Hospital Stay in Acute Traumatic Spinal Cord Injury: An Observational Canadian Cohort Study

    PubMed Central

    Noonan, Vanessa K.; Fallah, Nader; Fisher, Charles G.; Finkelstein, Joel; Kwon, Brian K.; Rivers, Carly S.; Ahn, Henry; Paquet, Jérôme; Tsai, Eve C.; Townson, Andrea; Attabib, Najmedden; Bailey, Christopher S.; Christie, Sean D.; Drew, Brian; Fourney, Daryl R.; Fox, Richard; Hurlbert, R. John; Johnson, Michael G.; Linassi, A.G.; Parent, Stefan; Fehlings, Michael G.

    2015-01-01

    Abstract To determine the influence of time from injury to surgery on neurological recovery and length of stay (LOS) in an observational cohort of individuals with traumatic spinal cord injury (tSCI), we analyzed the baseline and follow-up motor scores of participants in the Rick Hansen Spinal Cord Injury Registry to specifically assess the effect of an early (less than 24 h from injury) surgical procedure on motor recovery and on LOS. One thousand four hundred and ten patients who sustained acute tSCIs with baseline American Spinal Injury Association Impairment Scale (AIS) grades A, B, C, or D and were treated surgically were analyzed to determine the effect of the timing of surgery (24, 48, or 72 h from injury) on motor recovery and LOS. Depending on the distribution of data, we used different types of generalized linear models, including multiple linear regression, gamma regression, and negative binomial regression. Persons with incomplete AIS B, C, and D injuries from C2 to L2 demonstrated motor recovery improvement of an additional 6.3 motor points (SE=2.8 p<0.03) when they underwent surgical treatment within 24 h from the time of injury, compared with those who had surgery later than 24 h post-injury. This beneficial effect of early surgery on motor recovery was not seen in the patients with AIS A complete SCI. AIS A and B patients who received early surgery experienced shorter hospital LOS. While the issues of when to perform surgery and what specific operation to perform remain controversial, this work provides evidence that for an incomplete acute tSCI in the cervical, thoracic, or thoracolumbar spine, surgery performed within 24 h from injury improves motor neurological recovery. Early surgery also reduces LOS. PMID:25333195

  17. STEPS: JPL's Astrometric Exoplanet Survey

    NASA Technical Reports Server (NTRS)

    Shaklan, Stuart; Pravdo, Steve

    2008-01-01

    Presentation topics include: STEPS ground-based astrometry at Hale Telescope; the instrument; why astronomy and why M-dwarfs; motion of center of light about center of mass in photocentric orbit; photocentric motion vs. fractional mass; high-resolution imaging of STEPS targets; GU 802 p one possible orbit plotted with data, Keplerian frame; GJ 802 results; STEPS future; and a bibliography of STEPS papers.

  18. Quaternions as astrometric plate constants

    NASA Technical Reports Server (NTRS)

    Jefferys, William H.

    1987-01-01

    A new method for solving problems in relative astrometry is proposed. In it, the relationship between the measured quantities and the components of the position vector of a star is modeled using quaternions, in effect replacing the plate constants of a standard four-plate-constant solution with the four components of a quaternion. The method allows a direct solution for the position vectors of the stars, and hence for the equatorial coordinates. Distortions, magnitude, and color effects are readily incorporated into the formalism, and the method is directly applicable to overlapping-plate problems. The advantages of the method include the simplicity of the resulting equations, their freedom from singularities, and the fact that trigonometric functions and tangential point transformations are not needed to model the plate material. A global solution over the entire sky is possible.

  19. Storm Observations of Persistent Three-Dimensional Shoreline Morphology and Bathymetry Along a Geologically Influenced Shoreface Using X-Band Radar (BASIR)

    NASA Astrophysics Data System (ADS)

    Brodie, K. L.; McNinch, J. E.

    2008-12-01

    Accurate predictions of shoreline response to storms are contingent upon coastal-morphodynamic models effectively synthesizing the complex evolving relationships between beach topography, sandbar morphology, nearshore bathymetry, underlying geology, and the nearshore wave-field during storm events. Analysis of "pre" and "post" storm data sets have led to a common theory for event response of the nearshore system: pre-storm three-dimensional bar and shoreline configurations shift to two-dimensional, linear forms post- storm. A lack of data during storms has unfortunately left a gap in our knowledge of how the system explicitly changes during the storm event. This work presents daily observations of the beach and nearshore during high-energy storm events over a spatially extensive field site (order of magnitude: 10 km) using Bar and Swash Imaging Radar (BASIR), a mobile x-band radar system. The field site contains a complexity of features including shore-oblique bars and troughs, heterogeneous sediment, and an erosional hotspot. BASIR data provide observations of the evolution of shoreline and bar morphology, as well as nearshore bathymetry, throughout the storm events. Nearshore bathymetry is calculated using a bathymetry inversion from radar- derived wave celerity measurements. Preliminary results show a relatively stable but non-linear shore-parallel bar and a non-linear shoreline with megacusp and embayment features (order of magnitude: 1 km) that are enhanced during the wave events. Both the shoreline and shore-parallel bar undulate at a similar spatial frequency to the nearshore shore- oblique bar-field. Large-scale shore-oblique bars and troughs remain relatively static in position and morphology throughout the storm events. The persistence of a three-dimensional shoreline, shore-parallel bar, and large-scale shore-oblique bars and troughs, contradicts the idea of event-driven shifts to two- dimensional morphology and suggests that beach and nearshore response

  20. La influencia de la rotación terrestre en el método de los arcos aplicado a observaciones VLBI

    NASA Astrophysics Data System (ADS)

    de Biasi, M. S.; Arias, E. F.

    We analyze the influence of the model or Earth's rotation in the arclength method envisioned to analyze VLBI astrometric observations. We particulary focus in the case of quasi-simultaneous observations.

  1. Observational data and orbits of the asteroids discovered at the Baldone Observatory in 2008--2013

    NASA Astrophysics Data System (ADS)

    Černis, K.; Wlodarczyk, I.; Eglitis, I.

    The paper presents statistics of the asteroids observed and discovered at the Baldone Observatory, Latvia, in 2008--2013 within the project for astrometric observations of the near-Earth objects (NEOs), the main belt asteroids and comets. CCD observations of the asteroids were obtained with the 0.80/1.20 m, f/3 Schmidt telescope and a ST-10XME 15 × 10 mm CCD camera. In the Minor Planet Circulars and the Minor Planet Electronic Circulars (2008--2013) we published 3511 astrometric positions of 826 asteroids. Among them, 43 asteroids were newly discovered at Baldone. For 36 of these asteroids the precise orbits are calculated. Because of short observational arc and small number of observations, a few asteroids have low-precision orbits and their tracks have been lost. For seven objects with poorly known orbits we present their ephemerides for 2015--2016. The orbits and the evolution of orbital elements of two asteroids, (428694) 2008 OS9 from the Apollo group and the Centaur (330836) Orius (2009 HW77), are recalculated including new observations obtained after 2011.

  2. Observations of the Natural Planetary Satellites for Dynamical and Physical Purpose

    NASA Astrophysics Data System (ADS)

    Arlot, J. E.; Thuillot, W.; Fienga, A.; Bec-Borsenberger, A.; Baron, N.; Berthier, J.; Colas, F.; Descamps, P.

    1999-12-01

    At the Institut de mecanique celeste-Bureau des longitudes, we started several programs of observation of the natural planetary satellites. First, we took the opportunity of the transit of the Earth and the Sun in the equatorial plane of Jupiter to observe the mutual phenomena of the Galilean satellites. These observations provide astrometric data of high accuracy useful for dynamical studies of the motions of the satellites and photometric data allowing to characterize the surfaces of the satellites. A campaign was organized leading to 400 light curves made throughout the world in about 40 countries. Second, we started astrometric CCD observations of the faint satellites of Jupiter JVI to JXIII and of the satellite of Saturn Phoebe (SIX) for dynamical purpose at Observatoire de Haute Provence using the 120cm-telescope. PPM, Hipparcos and USNO A.2 catalogue were used for calibration in order to get absolute J2000 R.A. and declination of these objects. In August and December, 1998, CCD observations provided 43 absolute positions of JVI, 23 of JVII, 53 of JVIII, 35 of JIX, 29 of JX, 27 of JXI, 18 of JXII, 16 of JXIII and 135 of SIX (Phoebe). A campaign will also take place in 1999.

  3. SIM instrument integration and test challenges: PKT & FAST testbed influence

    NASA Astrophysics Data System (ADS)

    Drosdat, Helmuth; Duncan, Alan L.

    2003-02-01

    At first glance the SIM concept seems deceptively simple. After all, its primary task is just to lock two interferometers on to a couple of bright guide stars and let the third integrate photons from a dim 'science' star to gather astrometric data. The difficulty is of course in the details of the performance requirements and overall integration and test risk associated with their verification. The challenge is to provide a meaningful verification of the SIM functionality on the ground that can be extrapolated to show satisfaction of the on-orbit performance requirements. The associated difficulties relate to the ability to provide a reasonable simulation of (1) the space environment with all the implications and (2) the creation of simulated target stars for each interferometer input optics that meet the associated wave front characteristic and star position knowledge requirements. The difficulty and complexity of the simulation of target stars itself is a major development challenge and program risk. In order to reduce this risk early development test beds are created to evolve the optical verification concept and build the actual devices needed for the flight system performance evaluation. The role of the PKT and FAST (Flight System Astrometric Test bed) test beds and their influence on flight integration risk reduction and test process is presented.

  4. Masses of the components of SB2s observed with Gaia - II. Masses derived from PIONIER interferometric observations for Gaia validation

    NASA Astrophysics Data System (ADS)

    Halbwachs, J.-L.; Boffin, H. M. J.; Le Bouquin, J.-B.; Kiefer, F.; Famaey, B.; Salomon, J.-B.; Arenou, F.; Pourbaix, D.; Anthonioz, F.; Grellmann, R.; Guieu, S.; Sana, H.; Guillout, P.; Jorissen, A.; Lebreton, Y.; Mazeh, T.; Tal-Or, L.; Gómez-Morán, A. Nebot

    2016-01-01

    In anticipation of the Gaia astrometric mission, a sample of spectroscopic binaries is being observed since 2010 with the Spectrograph pour l'Observation des PHénomènes des Intérieurs stellaires et des Exoplanètes (SOPHIE) spectrograph at the Haute-Provence Observatory. Our aim is to derive the orbital elements of double-lined spectroscopic binaries (SB2s) with an accuracy sufficient to finally obtain the masses of the components with relative errors as small as 1 per cent when combined with Gaia astrometric measurements. In order to validate the masses derived from Gaia, interferometric observations are obtained for three SB2s in our sample with F-K components: HIP 14157, HIP 20601 and HIP 117186. The masses of the six stellar components are derived. Due to its edge-on orientation, HIP 14157 is probably an eclipsing binary. We note that almost all the derived masses are a few per cent larger than the expectations from the standard spectral type-mass calibration and mass-luminosity relation. Our calculation also leads to accurate parallaxes for the three binaries, and the Hipparcos parallaxes are confirmed.

  5. Optical observations of comet 67P/Churyumov-Gerasimenko with the Nordic Optical Telescope. Comet activity before the solar conjunction

    NASA Astrophysics Data System (ADS)

    Zaprudin, B.; Lehto, H. J.; Nilsson, K.; Pursimo, T.; Somero, A.; Snodgrass, C.; Schulz, R.

    2015-11-01

    Context. 67P/Churyumov-Gerasimenko (67P) is a short-period Jupiter-family comet that was chosen as a target for the Rosetta mission by the European Space Agency (ESA). Monitoring of 67P with the Nordic Optical Telescope (NOT; La Palma, Spain) intends to aid this mission by providing ground-based reference information about the overall activity of the target and its astrometric position before the rendezvous. One motivation for our observations was to monitor sudden major increases in activity because they might have affected the Rosetta mission planning. None were observed. Ground-based photometric observations register the global activity of the comet, while the Rosetta spacecraft mostly measures local events. These data combined can lead to new insights into the comet behavior. Aims: The aim of this work is to perform the photometric and the astrometric monitoring of comet 67P with the NOT and to compare the results with the latest predictions for its position and activity. A new method of fitting extended-source components to the target surface brightness distribution was developed and applied to the data to estimate the size and contribution of the coma to the total brightness of the target. Methods: Comet 67P was monitored by the NOT in service mode during the period between 12.5.2013 and 11.11.2014. The very first observations were performed in the V band alone, but in the latest observations, the R band was used as well to estimate the color and nature of activity of the target. We applied a new method for estimating the coma size by deconvolving the point spread function profile from the image, which used Markov chain Monte Carlo and Bayesian statistics. This method will also be used for coma size estimations in further observations after the solar conjunction of 67P. Results: Photometric magnitudes in two colors were monitored during the period of observations. At the end of April 2014, the beginning of activity was observed. In late September 2014, a

  6. OBSERVATIONS OF HIERARCHICAL SOLAR-TYPE MULTIPLE STAR SYSTEMS

    SciTech Connect

    Roberts, Lewis C. Jr.; Tokovinin, Andrei; Mason, Brian D.; Hartkopf, William I.; Riddle, Reed L.

    2015-10-15

    Twenty multiple stellar systems with solar-type primaries were observed at high angular resolution using the PALM-3000 adaptive optics system at the 5 m Hale telescope. The goal was to complement the knowledge of hierarchical multiplicity in the solar neighborhood by confirming recent discoveries by the visible Robo-AO system with new near-infrared observations with PALM-3000. The physical status of most, but not all, of the new pairs is confirmed by photometry in the Ks band and new positional measurements. In addition, we resolved for the first time five close sub-systems: the known astrometric binary in HIP 17129AB, companions to the primaries of HIP 33555, and HIP 118213, and the companions to the secondaries in HIP 25300 and HIP 101430. We place the components on a color–magnitude diagram and discuss each multiple system individually.

  7. Astrometry of the main satellites of Uranus: 18 years of observations

    NASA Astrophysics Data System (ADS)

    Camargo, J. I. B.; Magalhães, F. P.; Vieira-Martins, R.; Assafin, M.; Braga-Ribas, F.; Dias-Oliveira, A.; Benedetti-Rossi, G.; Gomes-Júnior, A. R.; Andrei, A. H.; da Silva Neto, D. N.

    2015-10-01

    Context. We contribute to developing dynamical models of the motions of Uranus' main satellites. Aims: We determine accurate positions of the main satellites of Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon. Positions of Uranus, as derived from those of these satellites, are also determined. The observational period spans from 1992 to 2011. All runs were made at the Pico dos Dias Observatory, Brazil. Methods: We used the software called Platform for Reduction of Astronomical Images Automatically (PRAIA) to perform a digital coronography to minimise the influence of the scattered light of Uranus on the astrometric measurements and to determine accurate positions of the main satellites. The positions of Uranus were then indirectly determined by computing the mean differences between the observed and ephemeris positions of these satellites. A series of numerical filters was applied to filter out spurious data. These filters are mostly based on (a) the comparison between the positions of Oberon with those of the other satellites and on (b) the offsets as given by the differences between the observed and ephemeris positions of all satellites. Results: We have, for the overall offsets of the five satellites, -29 mas (±63 mas) in right ascension and -27 mas (±46 mas) in declination. For the overall difference between the offsets of Oberon and those of the other satellites, we have +3 mas (±30 mas) in right ascension and -2 mas (±28 mas) in declination. Ephemeris positions for the satellites were determined from DE432+ura111. Comparisons using other modern ephemerides for the solar system - INPOP13c - and for the motion of the satellites - NOE-7-2013 - were also made. They confirm that the largest contribution to the offsets we find comes from the motion of the barycenter of the Uranus system around the barycenter of the solar system, as given by the planetary ephemerides. For the period from 1992 to 2011, our final catalogues contain 584 observed positions of

  8. A comparison of radiometric fluxes influenced by parameterization cirrus clouds with observed fluxes at the Southern Great Plains (SGP) cloud and radiation testbed (CART) site

    SciTech Connect

    Mace, G.G.; Ackerman, T.P.; George, A.T.

    1996-04-01

    The data from the Atmospheric Radiation Measurement (ARM) Program`s Southern Great plains Site (SCP) is a valuable resource. We have developed an operational data processing and analysis methodology that allows us to examine continuously the influence of clouds on the radiation field and to test new and existing cloud and radiation parameterizations.

  9. Experiments for observation of the total solar eclipse on July 22, 2009, China

    NASA Astrophysics Data System (ADS)

    Stoeva, Penka; Stoev, Alexey; Kuzin, Sergey; Stoyanov, Nikolay; Pertsov, Andrey

    Scientific expedition for observation of the July 22, 2009 total solar eclipse was organized by the Solar-Terrestrial Influences Institute, BAS and the Yuri Gagarin Public Astronomical Observatory, and displaced near the observing station of the Shanghai Observatory, which belongs to the Chinese Academy of Sciences and is very close to the central line of the eclipse. The following experiments were conducted: 1. Determination of the absolute intensity of the red coronal line FeX 6374A with a spectro-grph mounted together with a 130/2000 Macsutov -Cassegrain telescope with a 20mm eyelense. The spectrogrph is designed and developed by specialists from Solar-Terrestrial Influences In-stitute, Stara Zagora Department, Bulgaria, Lebedev Physical Institute, Moscow, Russia and Yuri Gagarin Public Astronomical Observatory, Stara Zagora, Bulgaria, in the frames of the Bulgarian-Russian project of joint scientific research "CORONA". The aim of the experiment is to obtain images of the inner corona in the visible region of the spectrum simultaneously with images in the X ray region from the THESIS telescope on CORONAS -PHOTON helio-spheric satellite (launched in January 2009). This gives the unique possibility of determining the distribution of the light emission of the plasma with the temperature (detailed diagnostics of the thermal and nonthermal heating of the solar corona). 2. Investigation of the white-light corona from photographs with 250 mm and 2000mm objec-tives. 3. Investigation of the response of the Earth's atmosphere during the particular sircumstances in which solar light is totally being blocked by the Moon. Atmospheric temperature and pressure rapidly change during total solar eclipses which produce meteorological anomalies typical in this kind of phenomena. That is why the basic climatic parameters have to be measured with high sensitive meteorological instruments. Conducting measurements of the temperature of the soil and the air at three different levels

  10. Observation studies on the influence of atmospheric boundary layer characteristics associate with air quality in dry season over the Pearl River Delta, China

    NASA Astrophysics Data System (ADS)

    Fan, Shaojia; Wu, Meng; Li, Haowen; Liao, Zhiheng; Fan, Qi; Zhu, Wei

    2016-04-01

    The characteristics of atmospheric boundary layer (ABL) is the very important factors influence on air quality in dry season over the Pearl River Delta (PRD), China. Based on the sounding data at six stations (Xinken,Dongguan, Sanshui, Nanhai, Shunde, and Heshan) which obtained from three times ABL experiments carried in dry season over PRD, the influence of wind and temperature vertical structure to the air quality over PRD has been studied with wind and temperature profiles, inversion layer, recirculation factor (RF), atmospheric boundary layer height (ABLH) and ventilation index (VI). It was found that the vertical wind of PRD could be divided in typical three layers according two wind shears appeared in 800 m and 1300 m. The thickness of calm or lower wind speed layer in pollution days was 500-1000m thicker than that of clean days, and its last time also much longer than that of clean days. The frequency of surface inversion in pollution days was about 35%,the mean thickness was about 100 m. With the influence of sea breeze, the frequency and thickness of surface inversion layer at Xinken station was a little lower than that in inland. Influenced by sea-land breezes and urban heat-island circulation, the RF of pollution days in coastal and urban area was quite smaller than that of clean days. During sea-land breezes days, the pollutants would be transported back to inland in nighttime with the influence of sea breeze, and resulted in 72.7% sea-land breezes was pollution days. The evolution of ABL was very typical in PRD during dry season. In pollution days, daily ABLH in PRD was lower than 500 m, daily VI was about 500-1500 m2/s. In clean days, daily VI was much larger than 2500 m2/s. An improved conceptual model of ABL influence on poor air quality and the parameters of the ABL characteristics associate with poor air quality in dry season over PRD had been summarized.

  11. SIM PlanetQuest Key Project Precursor Observations to Detect Gas Giant Planets Around Young Stars

    NASA Technical Reports Server (NTRS)

    Tanner, Angelle; Beichman, Charles; Akeson, Rachel; Ghez, Andrea; Grankin, Konstantin N.; Herbst, William; Hillenbrand, Lynne; Huerta, Marcos; Konopacky, Quinn; Metchev, Stanimir; Mohanty, Subhanjoy; Prato, L.; Simon, Michal

    2008-01-01

    We present a review of precursor observing programs for the SIM PlanetQuest Key project devoted to detecting Jupiter mass planets around young stars. In order to ensure that the stars in the sample are free of various sources of astrometric noise that might impede the detection of planets, we have initiated programs to collect photometry, high contrast images, interferometric data and radial velocities for stars in both the Northern and Southern hemispheres. We have completed a high contrast imaging survey of target stars in Taurus and the Pleiades and found no definitive common proper motion companions within one arcsecond (140 AU) of the SIM targets. Our radial velocity surveys have shown that many of the target stars in Sco-Cen are fast rotators and a few stars in Taurus and the Pleiades may have sub-stellar companions. Interferometric data of a few stars in Taurus show no signs of stellar or sub-stellar companions with separations of <5 mas. The photometric survey suggests that approximately half of the stars initially selected for this program are variable to a degree (1(sigma) >0.1 mag) that would degrade the astrometric accuracy achievable for that star. While the precursor programs are still a work in progress, we provide a comprehensive list of all targets ranked according to their viability as a result of the observations taken to date. By far, the observable that removes the most targets from the SIM-YSO program is photometric variability.

  12. Some observations of the influence of δ-ferrite content on the hardness, galling resistance, and fracture toughness of selected commercially available iron-based hardfacing alloys

    NASA Astrophysics Data System (ADS)

    Cockeram, B. V.

    2002-11-01

    Iron-based weld hardfacing deposits are used to provide a wear-resistant surface for a structural base material. Iron-based hardfacing alloys that are resistant to corrosion in oxygenated aqueous environments contain high levels of chromium and carbon, which results in a dendritic microstructure with a high volume fraction of interdendrite carbides which provide the needed wear resistance. The ferrite content of the dendrites depends on the nickel content and base composition of the iron-based hardfacing alloy. The amount of ferrite in the dendrites is shown to have a significant influence on the hardness and galling wear resistance, as determined using ASTM G98 methods. Fracture-toughness ( K IC) testing in accordance with ASTM E399 methods was used to quantify the damage tolerance of various iron-based hardfacing alloys. Fractographic and microstructure examinations were used to determine the influence of microstructure on the wear resistance and fracture toughness of the iron-based hardfacing alloys. A crack-bridging toughening model was shown to describe the influence of ferrite content on the fracture toughness. A higher ferrite content in the dendrites of an iron-based hardfacing alloy reduces the tendency for plastic stretching and necking of the dendrites, which results in improved wear resistance, high hardness, and lower fracture-toughness values. A NOREM 02 hardfacing alloy has the most-optimum ferrite content, which results in the most-desired balance of galling resistance and high K IC values.

  13. Observer age and the social transmission of attractiveness in humans: Younger women are more influenced by the choices of popular others than older women.

    PubMed

    Little, Anthony C; Caldwell, Christine A; Jones, Benedict C; DeBruine, Lisa M

    2015-08-01

    Being paired with an attractive partner increases perceptual judgements of attractiveness in humans. We tested experimentally for prestige bias, whereby individuals follow the choices of prestigious others. Women rated the attractiveness of photographs of target males which were paired with either popular or less popular model female partners. We found that pairing a photo of a man with a woman presented as his partner positively influenced the attractiveness of the man when the woman was presented as more popular (Experiment 1). Further, this effect was stronger in younger participants compared to older participants (Experiment 1). Reversing the target and model such that women were asked to rate women paired with popular and less popular men revealed no effect of model popularity and this effect was unrelated to participant age (Experiment 2). An additional experiment confirmed that participant age and not stimulus age primarily influenced the tendency to follow others' preferences in Experiment 1 (Experiment 3). We also confirmed that our manipulations of popularity lead to variation in rated prestige (Experiment 4). These results suggest a sophisticated model-based bias in social learning whereby individuals are most influenced by the choices of those who have high popularity/prestige. Furthermore, older individuals moderate their use of such social information and so this form of social learning appears strongest in younger women. PMID:25314951

  14. Influence of observers and stream flow on northern two-lined salamander (Eurycea bislineata bislineata) relative abundance estimates in Acadia and Shenandoah National Parks, USA

    USGS Publications Warehouse

    Crocker, J.B.; Bank, M.S.; Loftin, C.S.; Jung Brown, R.E.

    2007-01-01

    We investigated effects of observers and stream flow on Northern Two-Lined Salamander (Eurycea bislineata bislineata) counts in streams in Acadia (ANP) and Shenandoah National Parks (SNP). We counted salamanders in 22 ANP streams during high flow (May to June 2002) and during low flow (July 2002). We also counted salamanders in SNP in nine streams during high flow (summer 2003) and 11 streams during low flow (summers 2001?02, 2004). In 2002, we used a modified cover-controlled active search method with a first and second observer. In succession, observers turned over 100 rocks along five 1-m belt transects across the streambed. The difference between observers in total salamander counts was not significant. We counted fewer E. b. bislineata during high flow conditions, confirming that detection of this species is reduced during high flow periods and that assessment of stream salamander relative abundance is likely more reliable during low or base flow conditions.

  15. Influence of Educational Level, Stage, and Histological Type on Survival of Oral Cancer in a Brazilian Population: A Retrospective Study of 10 Years Observation.

    PubMed

    Dantas, Thinali Sousa; de Barros Silva, Paulo Goberlânio; Sousa, Eric Fernandes; da Cunha, Maria do Pss; de Aguiar, Andréa Silvia Walter; Costa, Fábio Wildson Gurgel; Mota, Mário Rogério Lima; Alves, Ana Paula Negreiros Nunes; Sousa, Fabrício Bitu

    2016-01-01

    The mortality rate associated with oral cancer is estimated at approximately 12,300 deaths per year, and the survival rate is only 40% to 50% for diagnosed patients and is closely related to the duration of time between disease perception and its diagnosis and treatment. Socioeconomic risk factors are determinants of the incidence and mortality related to oral cancer. We conducted a retrospective, cross-sectional study of 573 records of patients with oral cancer at Haroldo Juaçaba Hospital - Cancer Institute of Ceará from 2000 to 2009 to evaluate the influence of socioeconomic factors on survival and epidemiological behavior of this neoplasia in a Brazilian population. In this study, patients with oral cancer were males greater than 60 years of age, presented squamous cell carcinoma in the floor of mouth and were characterized by low education levels. A total of 573 lesions were found in oral cavities. Cox proportional hazards regression model showed that the histological type, tumor stage, and low degree of education significantly influenced survival. A lower patient survival rate was correlated with a more advanced stage of disease and a worse prognosis. Squamous cell carcinoma is associated with a higher mortality when compared with other histological types of malign neoplasia. PMID:26817864

  16. Sequential compression devices in postoperative urologic patients: an observational trial and survey study on the influence of patient and hospital factors on compliance

    PubMed Central

    2013-01-01

    Background Sequential compression devices (SCDs) are commonly used for thromboprophylaxis in postoperative patients but compliance is often poor. We investigated causes for noncompliance, examining both hospital and patient related factors. Methods 100 patients undergoing inpatient urologic surgery were enrolled. All patient had SCD sleeves placed preoperatively. Postoperative observations determined SCD compliance and reasons for non-compliance. Patient demographics, length of stay, inpatient unit type, and surgery type were recorded. At discharge, a patient survey gauged knowledge and attitudes regarding SCDs and bother with SCDs. Statistical analysis was performed to correlate SCD compliance with patient demographics; patient knowledge and attitudes regarding SCDs; and patient self-reported bother with SCDs. Results Observed overall compliance was 78.6%. The most commonly observed reasons for non-compliance were SCD machines not being initially available on the ward (71% of non-compliant observations on post-operative day 1) and SCD use not being restarted promptly after return to bed (50% of non-compliant observations for entire hospital stay). Mean self-reported bother scores related to SCDs were low, ranging from 1–3 out of 10 for all 12 categories of bother assessed. Patient demographics, knowledge, attitudes and bother with SCD devices were not significantly associated with non-compliance. Conclusions Patient self-reported bother with SCD devices was low. Hospital factors, including SCD machine availability and timely restarting of devices by nursing staff when a patient returns to bed, played a greater role in SCD non-compliance than patient factors. Identifying and addressing hospital related causes for poor SCD compliance may improve postoperative urologic patient safety. PMID:23578129

  17. The PHESAT95 catalogue of observations of the mutual events of the Saturnian satellites

    NASA Astrophysics Data System (ADS)

    Thuillot, W.; Arlot, J.-E.; Ruatti, C.; Berthier, J.; Blanco, C.; Colas, F.; Czech, W.; Damani, M.; D'Ambrosio, V.; Descamps, P.; Dourneau, G.; Emelianov, N.; Foglia, S.; Helmer, G.; Irsmambetova, T. R.; James, N.; Laques, P.; Lecacheux, J.; Le Campion, J.-F.; Ledoux, C.; Le Floch, J.-C.; Oprescu, G.; Rapaport, M.; Riccioli, R.; Starosta, B.; Tejfel, V. G.; Trunkovsky, E. M.; Viateau, B.; Veiga, C. H.; Vu, D. T.

    2001-05-01

    In 1994-1996 the Sun and the Earth passed through the equatorial plane of Saturn and therefore through the orbital planes of its main satellites. During this period, phenomena involving seven of these satellites were observed. Light curves of eclipses by Saturn and of mutual eclipses and occultations were recorded by the observers of the international campaign PHESAT95 organized by the Institut de mécanique céleste, Paris, France. Herein, we report 66 observations of 43 mutual events from 16 sites. For each observation, information is given about the telescope, the receptor, the site and the observational conditions. This paper gathers together all these data and gives a first estimate of the precision providing accurate astrometric data useful for the development of dynamical models.

  18. The PHEMU97 catalogue of observations of the mutual phenomena of the Galilean satellites of Jupiter

    NASA Astrophysics Data System (ADS)

    Arlot, J.-E.; Thuillot, W.; Ruatti, C.; Akasawa, H.; Baroni, S.; Beisker, W.; Berthier, J.; Blanco, C.; Boonstra, J.; Bourgeois, J.; Bulder, H.; Casas, R.; Castano, J. G.; Colas, F.; Collins, D.; Cuypers, J.; Czech, W.; D'Ambrosio, V.; Denzau, H.; Descamps, P.; Dimitrescu, A.; Dinakarian, N.; Dourneau, G.; Emelyanov, N.; Enriquez, J. M.; Fernandez, J. M.; Fernandez-Barba, D.; Flatres, T.; Foglia, S.; Goncalves, M.; Guhl, K.; Helmer, G.; Hirose, T.; Irsmambetova, T. R.; Krobusek, B. A.; Lecacheux, J.; Le Campion, J.-F.; Lou, M.; Mallama, A.; Marchis, F.; Navarro, M. A. S.; Nelson, P.; Okura, N.; Park, J.; Pauwels, T.; Pluchino, S.; Priban, V.; Rapaport, M.; Sacré, J.-J.; Salvaggio, F.; Sanchez, M. A.; Sanchez-Bajo, F.; Stefanescu, G.; Tanga, P.; Tejfel, V. G.; Trisan, J. L.; Trunkovsky, E. M.; van Gestel, J.; Vandenbulcke, G.; Vasundhara, R.; Vass, G.; Vingerhoets, P.; Vu, D. T.; Wilds, R. T.

    2006-05-01

    In 1997 the Sun and the Earth passed through the equatorial plane of Jupiter and therefore through the orbital planes of its main satellites. During this period, mutual eclipses and occultations occurred and were observed. We investigate the precision of the catalogue to produce improved data for the development of dynamical models. Light curves of mutual eclipses and occultations were recorded by the observers of the international campaign PHEMU97 organized by the Institut de Mécanique Céleste, Paris, France. We made 275 observations of 148 mutual events from 42 sites. For each observation, information is given about the telescope, the receiver, the site and the observational conditions. This paper gathers together the data and gives a first estimate of the precision. The catalogue of these rare events represents a collection of improved accurate astrometric data useful for the development of dynamical models.

  19. The influence of normal stress and sliding velocity on the frictional behaviour of calcite at room temperature: insights from laboratory experiments and microstructural observations

    NASA Astrophysics Data System (ADS)

    Carpenter, B. M.; Collettini, C.; Viti, C.; Cavallo, A.

    2016-04-01

    The presence of calcite in and near faults, as the dominant material, cement, or vein fill, indicates that the mechanical behaviour of carbonate-dominated material likely plays an important role in shallow- and mid-crustal faulting. To better understand the behaviour of calcite, under loading conditions relevant to earthquake nucleation, we sheared powdered gouge of Carrara Marble, >98 per cent CaCO3, at constant normal stresses between 1 and 100 MPa under water-saturated conditions at room temperature. We performed slide-hold-slide tests, 1-3000 s, to measure the amount of static frictional strengthening and creep relaxation, and velocity-stepping tests, 0.1-1000 μm s-1, to evaluate frictional stability. We observe that the rates of frictional strengthening and creep relaxation decrease with increasing normal stress and diverge as shear velocity is increased from 1 to 3000 μm s-1 during slide-hold-slide experiments. We also observe complex frictional stability behaviour that depends on both normal stress and shearing velocity. At normal stresses less than 20 MPa, we observe predominantly velocity-neutral friction behaviour. Above 20 MPa, we observe strong velocity-strengthening frictional behaviour at low velocities, which then evolves towards velocity-weakening friction behaviour at high velocities. Microstructural analyses of recovered samples highlight a variety of deformation mechanisms including grain size reduction and localization, folding of calcite grains and fluid-assisted diffusion mass transfer processes promoting the development of calcite nanograins in the highly deformed portions of the experimental fault. Our combined analyses indicate that calcite fault gouge transitions from brittle to semi-brittle behaviour at high normal stress and slow sliding velocities. This transition has important implications for earthquake nucleation and propagation on faults in carbonate-dominated lithologies.

  20. Biomass Burning Influences on the Composition of the Remote South Pacific Troposphere: Analysis Based on Observations from PEM Tropics-A

    NASA Technical Reports Server (NTRS)

    Singh, H. B.; Viezee, W.; Chen, Y.; Bradshaw, J.; Sandholm, S.; Blake, D.; Blake, N.; Heikes, B.; Snow, J.; Talbot, R.; Sachse, G.; Vay, S.

    1999-01-01

    Airborne, in-situ measurements from PEM-Tropics-A (September/October 1996) are analyzed to show the presence of distinct pollution plumes in the middle-tropical troposphere of the remote South Pacific (10-30degS). These elevated plumes cause a relative maximum at about 5-7km attitude in the vertical distribution of primary and secondary species characteristic of fuel combustion and biomass burning (CO, C2H2, C2H6, CH3Cl, PAN, O3). Similar plumes were also observed at mid-latitudes in the middle troposphere during three flights east of New Zealand (40-45degS). In all, pollution plumes with CO larger than 100 ppb were observed 24 times on 7 separate flight days south of the equator. The observed plumes were generally embedded in very dry air. Ten-day back trajectory analysis supports the view that these originated from the biomass burning regions of South Africa (and South America) and were transported to the South Pacific along long-distance subsiding trajectories. The chemical composition of the southern Pacific troposphere analyzed from the PEM-Tropics-A data is compared with data from the tropical regions of the northern Pacific (PEM-West-A) and southern Atlantic (TRACE-A) during the same Sept/Oct time period. Sizable perturbations in the abundance of ozone and its key precursors, resulting from the transport of pollution originating from biomass burning sources, are observed in much of the Southern Hemispheric troposphere.

  1. Study on the influence of ground and satellite observations on the numerical air-quality for PM10 over Romanian territory

    NASA Astrophysics Data System (ADS)

    Dumitrache, Rodica Claudia; Iriza, Amalia; Maco, Bogdan Alexandru; Barbu, Cosmin Danut; Hirtl, Marcus; Mantovani, Simone; Nicola, Oana; Irimescu, Anisoara; Craciunescu, Vasile; Ristea, Alina; Diamandi, Andrei

    2016-10-01

    The numerical forecast of particulate matter concentrations in general, and PM10 in particular is a theme of high socio-economic relevance. The aim of this study was to investigate the impact of ground and satellite data assimilation of PM10 observations into the Weather Research and Forecasting model coupled with Chemistry (WRF-CHEM) numerical air quality model for Romanian territory. This is the first initiative of the kind for this domain of interest. Assimilation of satellite information - e.g. AOT's in air quality models is of interest due to the vast spatial coverage of the observations. Support Vector Regression (SVR) techniques are used to estimate the PM content from heterogeneous data sources, including EO products (Aerosol Optical Thickness), ground measurements and numerical model data (temperature, humidity, wind, etc.). In this study we describe the modeling framework employed and present the evaluation of the impact from the data assimilation of PM10 observations on the forecast of the WRF-CHEM model. Integrations of the WRF-CHEM model in data assimilation enabled/disabled configurations allowed the evaluation of satellite and ground data assimilation impact on the PM10 forecast performance for the Romanian territory. The model integration and evaluation were performed for two months, one in winter conditions (January 2013) and one in summer conditions (June 2013).

  2. In situ transmission electron microscopy observation of dislocation motion in 9Cr steel at elevated temperatures: influence of shear stress on dislocation behavior.

    PubMed

    Yamada, Susumu; Sakai, Takayuki

    2014-12-01

    To elucidate high-temperature plastic deformation (creep) mechanism in materials, it is essential to observe dislocation motion under tensile loading. There are many reports on in situ transmission electron microscopy (TEM) observations in the literature; however, the relationship between the dislocation motion and shear stress in 9Cr steel is still not clear. In this study, in order to evaluate this relationship quantitatively, in situ TEM observations were carried out in conjunction with finite element method (FEM) analysis. A tensile test sample was strained at an elevated temperature (903 K) inside a transmission electron microscope, and the stress distribution in the strained sample was analyzed by FEM. The dislocation behavior was clearly found to depend on the shear stress. At a shear stress of 66 MPa, both the dislocation velocity and mobile dislocation density were low. However, a high shear stress level of 95 MPa caused a noticeable increase in the dislocation velocity and mobile dislocation density. Furthermore, in this article, we discuss the dependence of the dislocation behavior on stress. The results presented here also indicate that the relationship between the microstructure and the strength of materials can be revealed by the methods used in this work. PMID:25298228

  3. Gross rainfall amount and maximum rainfall intensity in 60-minute influence on interception loss of shrubs: a 10-year observation in the Tengger Desert

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Shan; Zhao, Yang; Li, Xin-Rong; Huang, Lei; Tan, Hui-Juan

    2016-05-01

    In water-limited regions, rainfall interception is influenced by rainfall properties and crown characteristics. Rainfall properties, aside from gross rainfall amount and duration (GR and RD), maximum rainfall intensity and rainless gap (RG), within rain events may heavily affect throughfall and interception by plants. From 2004 to 2014 (except for 2007), individual shrubs of Caragana korshinskii and Artemisia ordosica were selected to measure throughfall during 210 rain events. Various rainfall properties were auto-measured and crown characteristics, i.e., height, branch and leaf area index, crown area and volume of two shrubs were also measured. The relative interceptions of C. korshinskii and A. ordosica were 29.1% and 17.1%, respectively. Rainfall properties have more contributions than crown characteristics to throughfall and interception of shrubs. Throughfall and interception of shrubs can be explained by GR, RI60 (maximum rainfall intensities during 60 min), RD and RG in deceasing importance. However, relative throughfall and interception of two shrubs have different responses to rainfall properties and crown characteristics, those of C. korshinskii were closely related to rainfall properties, while those of A. ordosica were more dependent on crown characteristics. We highlight long-term monitoring is very necessary to determine the relationships between throughfall and interception with crown characteristics.

  4. Gross rainfall amount and maximum rainfall intensity in 60-minute influence on interception loss of shrubs: a 10-year observation in the Tengger Desert

    PubMed Central

    Zhang, Zhi-Shan; Zhao, Yang; Li, Xin-Rong; Huang, Lei; Tan, Hui-Juan

    2016-01-01

    In water-limited regions, rainfall interception is influenced by rainfall properties and crown characteristics. Rainfall properties, aside from gross rainfall amount and duration (GR and RD), maximum rainfall intensity and rainless gap (RG), within rain events may