Science.gov

Sample records for astrometric observations influence

  1. 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.

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

    NASA Technical Reports Server (NTRS)

    Marsden, B. G.

    1991-01-01

    The transformation of the Oak Ridge astrometry from a photographic program to a charge coupled device (CCD) program can now be considered complete, and the number of observations being made is now approaching an order of magnitude greater than in the old photographic program. Astrometric observations with the 1.5-m reflector were made at the Oak Ridge Observatory, and the progress, accomplishments, and projected accomplishments are presented.

  3. 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.

  4. 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.

  5. 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.

  6. An improved astrometric calibration technique for space debris observation

    NASA Astrophysics Data System (ADS)

    Sun, Rong-Yu; Zhao, Chang-Yin; Lu, Yao

    2016-02-01

    An optical survey is the main technique for detecting space debris. Due to the specific characteristics of observation, the pointing errors and tracking errors of the telescope as well as image degradation may be significant, which make it difficult for astrometric calibration. Here we present an improved method that corrects the pointing and tracking errors, and measures the image position precisely. The pipeline is tested on a number of CCD images obtained from a 1-m telescope administered by Xinjiang Astronomical Observatory while observing a GPS satellite. The results show that the position measurement error of the background stars is around 0.1 pixel, while the time cost for a single frame is about 7.5 s; hence the reliability and accuracy of our method are demonstrated. In addition, our method shows a versatile and feasible way to perform space debris observation utilizing non-dedicated telescopes, which means more sensors could be involved and the ability to perform surveys could be improved.

  7. 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

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

    NASA Technical Reports Server (NTRS)

    Mccrosky, Richard E.; Marsden, Brian G.

    1987-01-01

    The 155-cm reflector of the Smithsonian Astrophysical Observatory was used for observations of comets and minor planets on 35 nights during October l986- April l987. The distrubution was fairly uniform November-February, but poor weather permitted only 21 observations during March. Table I lists the 423 measurements published (in the MPCs) since the last report, two of them actually made at the very beginning of May l987. Forty-six of the observations refer to comets, 193 to numbered minor planets (numbered, that is, by the end of the semester; only 11 of them refer to minor planets already numbered at the time of the last report), and the remainder to unnumbered minor planets.

  9. 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).

  10. Astrometric results of observations of mutual occultations and eclipses of the Saturnian satellites in 2009

    NASA Astrophysics Data System (ADS)

    Arlot, J.-E.; Emelyanov, N. V.; Lainey, V.; Andreev, M.; Assafin, M.; Braga-Ribas, F.; Camargo, J. I. B.; Casas, R.; Christou, A.; Colas, F.; Da Silva Neto, D. N.; Dechambre, O.; Dias-Oliveira, A.; Dourneau, G.; Farmakopoulos, A.; Gault, D.; George, T.; Gorshanov, D. L.; Herald, D.; Kozlov, V.; Kurenya, A.; Le Campion, J. F.; Lecacheux, J.; Loader, B.; Massallé, A.; Mc Brien, M.; Murphy, A.; Parakhin, N.; Roman-Lopes, A.; Schnabel, C.; Sergeev, A.; Tsamis, V.; Valdés Sada, P.; Vieira-Martins, R.; Zhang, X.

    2012-08-01

    Context. The photometry of mutual occultations and eclipses of natural planetary satellites can be used to infer very accurate astrometric data. This can be achieved by processing the light curves of the satellites observed during international campaigns of photometric observations of these mutual events. Aims: This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Saturnian satellites made during the international campaign in 2009. The final goal is to derive new accurate astrometric data. Methods: We develop an accurate photometric model of mutual event observations of sufficiently high accuracy. Our original method is applied to derive astrometric data from photometric observations of the mutual occultations and eclipses of the Saturnian satellites. Results: We process the 26 light curves obtained during the international campaign of photometric observations of the Saturnian satellites in 2009. Compared with the theory TASS 1.7 by Vienne and Duriez, we find that the root mean square of the "O-C" residuals for the 23 highest quality observations are equal to 48.5 and 21.7 mas in right ascension and declination, respectively, we obtain 16.4 and 20.7 mas with the new theory by Lainey and collaborators and 17.3 and 21.6 mas with JPL SAT351 ephemerides. Topocentric or heliocentric angular differences for satellites pairs are obtained for 16 time instants during the time period from December 19, 2008 to July 16, 2009. Light curves are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A29

  11. Astrometric observations of the satellites of the outer planets. I - The Galilean satellites in 1977

    NASA Technical Reports Server (NTRS)

    Ianna, P. A.; Seitzer, P.; Levinson, F.

    1979-01-01

    Astrometric observations of the Galilean satellites of Jupiter performed around the opposition of 1977 with a 67-cm photovisual refractor are reported. The measurements are reduced to absolute and intersatellite positions by two different methods: a linear least-squares plate-constant solution to the AGK3 reference-star frame and the trail-scale method of Pascu (1977). Results of a plate-constant reduction are also presented for two observations of JV (Amalthea). Comparison of the data with Liske's (1978) theoretical predictions for the intersatellite positions indicates no systematic bias in the data; a probable scatter of about 15 arcsec in both right ascension and declination is estimated.

  12. 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.

  13. First astrometric observations of space debris with the MéO telescope

    NASA Astrophysics Data System (ADS)

    Laas-Bourez, Myrtille; Wailliez, Sébastien; Deleflie, Florent; Klotz, Alain; Albanese, Dominique; Saba, Nathalie

    2012-02-01

    The MéO (for Métrologie Optique) telescope is the Satellite and Lunar Laser Ranging (SLR) dedicated telescope of Observatoire de la Côte d'Azur (France) located at plateau de Calern. The telescope uses an altazimuth mount. The motorization of the mount has a capability of 6 deg/s allowing the follow up of Low Earth Orbits (LEO) satellites, as well as Medium Earth Orbits (MEO) and geostationary (GEO) satellites, and the Moon. The telescope has a primary mirror of 1.54 m. It uses a Nasmyth focus equipped with an EMCCD camera. The telescope field of view, defined by the equivalent focal length and the size of the camera, is currently 3.4 arcmin × 3.4 arcmin.Space debris observation with an optical telescope ideally requires a large field of view, accurate pointing, a fast slew rate, a high sensitivity, accurate astrometric positions, and a precise method for orbit propagation. The challenge is to obtain accurate orbits for all debris without compromising the field of view. The MéO telescope has a larger diameter than the ones habitually used for space debris tracking. It should improve the current accuracy of observations in the GEO region. For LEO, such sensitivity should allow observations of small pieces of debris at low altitudes.This paper presents the preliminary experiments carried out to benefit from the high astrometric quality of the instrument, namely the method developed to extract and to compute the astrometric positions of LEO and MEO satellites, as a test of the capabilities of such an instrument (very small field of view, but large aperture) for space debris tracking. Furthermore, we analyse the ability of MéO to keep track of an object for which only a preliminary orbit (computed by the Laplace method from previous observations) is known, so that high precision measurements can be obtained and the object can be catalogued with an updated orbit.The feasibility of our astrometric methods was tested throughout 2010. This paper presents the methods

  14. 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.

  15. 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

  16. Recent Results from Follow-up Astrometric Observations of KBOs and NEOs

    NASA Astrophysics Data System (ADS)

    Tholen, D. J.; Connelley, M. S.

    2001-11-01

    As of the abstract deadline, 481 Kuiper belt objects have been discovered, but only 50 have four-opposition or greater orbits. Historically, some of the three-opposition orbits still had assumed eccentricities, indicating the relative level of inaccuracy in the orbit determination. Meanwhile, several authors have published eccentricity versus semimajor axis plots for Kuiper belt objects without attaching error bars to the symbols. Caution should therefore be exercised when looking at the relative populations of resonant, classical, and scattered objects, or when reaching conclusions about mechanisms at work that shape the Kuiper belt. We have been working to ameliorate this situation by securing follow-up astrometric observations of Kuiper belt objects with shorter arc orbit solutions, thereby extending the arcs and improving the accuracy of their semimajor axis and eccentricity determinations. Approximately 30 objects have been recovered to date, including a serendipitous observation of the satellite of 1998 WW31. We will be presenting improved estimates of the relative populations of resonant, classical, and scattered objects at the DPS meeting. Emphasis has also been given to astrometric observations of faint near-Earth objects to prevent their ephemeris uncertainties from growing large enough to warrant being tagged as "lost". In some cases, arcs have been extended by a factor of more than sixty. Virtually all of our observations are the last available for these objects. The number one reason for failure to recover an object has been low galactic latitude, where the field star density is so high that after non-sidereal tracking is taken into account, the field of view is nearly completely covered by star trails. Notable recoveries include 2000 SG344 at magnitude 26 in 2001 August using the CFHT (this object had been identified as having a 1 in 1000 chance of colliding with the Earth in 2071), 2000 GD147 at magnitude 24.5 in 2001 September using the UH 2.24-m

  17. A Proposed Astrometric Observing Program for Densifying the ICRF in the Northern Hemisphere

    NASA Technical Reports Server (NTRS)

    Charlot, Patrick; Viateau, Bruno; Baudry, Alain; Ma, Chopo; Fey, Alan; Eubanks, Marshall; Jacobs, Christopher; Sovers, Ojars

    2000-01-01

    The International Celestial Reference Frame (ICRF) could be of significant importance to the astronomy community for observing weak objects angularly close to ICRF sources with the phase-referencing technique. However, the current distribution of the ICRF sources is found to be largely non-uniform, which precludes the wide use of the ICRF as a catalog of calibrators for phase-referencing observations. We show that adding 150 new sources at appropriate sky locations would reduce the distance to the nearest ICRF source for any randomly-chosen location in the northern sky from up to 13 deg to up to 6 deg, close to the requirement of the phase-referencing technique. Accordingly, a set of 150 such sources, selected from the Jodrell Bank-VLA Astrometric Survey and filtered out using the Very Long Baseline Array Calibrator Survey, has been proposed for observation to the European VLBI Network (EVN) extended with additional geodetic stations. The use of the EVN is essential to this project since most of the new sources will be weaker and thus difficult to observe with standard geodetic networks.

  18. 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.

  19. Range, Doppler and astrometric observables computed from Time Transfer Functions: a survey

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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 developed 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.

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. 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].

  6. 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.

  7. 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.

  8. 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.

  9. The Astrometric Telescope Facility

    NASA Technical Reports Server (NTRS)

    Black, David; Dyer, John; Nishioka, Kenji; Scargle, Jeffrey; Sobeck, Charlie

    1991-01-01

    The evolution of the Astrometric Telescope Facility (ATF) proposed for use on NASA's Space Station is traced and its design characteristics are presented. With a focal plane scale of 12.7 arcsec/mm, the strawman design has a field size of 10 sq arcmin and a limiting visual magnitude fainter than 16. Output from an observation includes the X and Y coordinates of each star and its relative brightness.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. New astrometric reduction of old photographic observations of Saturn's moons based on digitizing of astronegatives

    NASA Astrophysics Data System (ADS)

    Kiseleva, T. P.; Vasil'eva, T. A.; Izmailov, I. S.; Roshchina, E. A.

    2015-01-01

    The paper presents new results of the reduction of photographic observations made at the Pulkovo Observatory in 1972-1974 using digitized photographic plates of Saturn's moons obtained by the 26-inch refractor and normal astrograph. Lists of exact positions of 2-6th and 8th moons and Saturn itself are obtained. The results of the new reduction are stored in the Pulkovo database on the bodies of the solar system and are available online at www.puldb.ru. The comparison of the results of the old and new reductions with the latest ephemeris of Saturn's moons has shown that the positioning accuracy of the moons of Saturn has increased approximately twofold. A conclusion on the feasibility of reprocessing old observations using the new method is made.

  17. Ephemerides of the Uranian satellites determined from earth-based astrometric and Voyager imaging observations

    NASA Technical Reports Server (NTRS)

    Jacobson, R. A.; Lewis, G. D.; Riedel, J. E.; Roth, D. C.; Synnot, S. P.

    1986-01-01

    Uranian satellite ephemerides were needed by the Voyager project to support both navigation and acquisition of scientific data. This paper outlines the mathematical modeling approach taken to generate those ephemerides and discusses their pre-encounter development, real time updating, and post-encounter refinement. The results presented include the final set of model parameters which generate the ephemerides that best fit the Voyager optical data as well as the earth based observations of the satellites.

  18. 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/

  19. Ephemerides of the major Neptunian satellites determined from earth-based astrometric and Voyager imaging observations

    NASA Technical Reports Server (NTRS)

    Jacobson, R. A.; Lewis, G. D.; Owen, W. M.; Riedel, J. E.; Roth, D. C.; Synnott, S. P.; Taylor, A. H.

    1990-01-01

    The Voyager project used Neptunian satellite ephemerides to support both navigation and acquisition of scientific data. The development of postencounter ephemerides for the satellites Triton, Nereid, and 1989N1 is discussed. Primary results are the final set of model parameters which generate orbits that best fit both the earth-based satellite observations and data acquired by Voyager. The ephemerides are compared with those generated preencounter, and the accuracy of the final ephemerides is assessed. Mean orbital elements are also provided as a geometrical representation for the satellite orbits.

  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. 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.

  2. An astrometric analysis of eta Carinae's eruptive history using HST WF/PC2 and ACS observations

    NASA Astrophysics Data System (ADS)

    Dorland, Bryan N.

    eta Carinae is one of the most massive and engimatic stars in our galaxy. The star, estimated to be well over a hundred times more massive and millions of times brighter than our sun, is shrouded in an expanding cloud of gas and debris that was ejected around 1843 during it's so-called "Great Eruption" and surrounded by what appear to be fields of debris from previous eruptions. The fundamental nature of the star is not well understood. Quite basic questions remain, such as: is the star a binary? Various questions and disagreements are also present in the literature regarding the various debris features, their physical characteristics, and what they tell us about the star's history. In this dissertation, Hubble Space Telescope (HST) observations spanning nearly a decade and utilizing both the Wide Field/Planetary Camera 2 (WFPC2) and the Advanced Camera for Surveys (ACS) instruments--the most accurate visible imaging data yet taken of e Carinae--are used to address many of these fundamental issues. In the first section, HST/ACS data taken during 2003-2005 is used to address the question of binarity. Based on an astrometric analysis of the data, binary reflex motion is detected in the primary and, by combining these results with those of other authors, allows us to derive the physical parameters of the resultant system. In the second section, 1995 WFPC2 and 2003 ACS data are used to make the most precise measurements yet of the debris around the central star. A date of origin is derived for the Homunculus, and a new, much shorter interval for the duration of the Great Eruption. Certain equatorial features, previously associated with an 1890 eruptive event are instead shown to be coeval with the Homunculus features and are thus associated with the Great Eruption. New debris associations outside the Homunculus are identified and their dates of origin are determined, implying eruptive events that preceeded the Great Eruption. These results add both significant new

  3. The PRIMA Astrometric Planet Search project

    NASA Astrophysics Data System (ADS)

    Quirrenbach, Andreas; Henning, Thomas; Queloz, Didier; Albrecht, Simon; Bakker, Eric J.; Baumeister, Harald; Bizenberger, Peter; Bleuler, Hannes; Dandliker, Rene; de Jong, Jeroen A.; Fleury, Michel; Frink, Sabine; Gillet, Denis; Jaffe, Walter J.; Hiddo Hanenburg, S.; Hekker, Saskia; Launhardt, Ralf; Le Poole, Rudolf S.; Maire, Charles; Mathar, Richard; Mullhaupt, Philippe; Murakawa, Koji; Pepe, Francesco; Pragt, Johan H.; Sache, Laurent; Scherler, Olivier; Segransan, Damien; Setiawan, Johny; Sosnowska, Danuta; Tubbs, Robert N.; Venema, Lars B.; Wagner, Karl; Weber, Luc; Wuethrich, Rolf

    2004-10-01

    The PRIMA facility will implement dual-star astrometry at the VLTI. We have formed a consortium that will build the PRIMA differential delay lines, develop an astrometric operation and calibration plan, and deliver astrometric data reduction software. This will enable astrometric planet surveys with a target precision of 10μas. Our scientific goals include determining orbital inclinations and masses for planets already known from radial-velocity surveys, searches for planets around stars that are not amenable to high-precision radial-velocity observations, and a search for large rocky planets around nearby low-mass stars.

  4. Astrometric planet search around southern ultracool dwarfs. II. Astrometric reduction methods and a deep astrometric catalogue

    NASA Astrophysics Data System (ADS)

    Lazorenko, P. F.; Sahlmann, J.; Ségransan, D.; Martín, E. L.; Mayor, M.; Queloz, D.; Udry, S.

    2014-05-01

    Aims: We describe the astrometric reduction of images obtained with the FORS2/VLT camera in the framework of an astrometric planet search around 20 M/L-transition dwarfs. We present the correction of systematic errors, the achieved astrometric performance, and a new astrometric catalogue containing the faint reference stars in 20 fields located close to the Galactic plane. Methods: Remote reference stars were used both to determine the astrometric trajectories of the nearby planet search targets and to identify and correct systematic errors. Results: We detected three types of systematic errors in the FORS2 astrometry: the relative motion of the camera's two CCD chips, errors that are correlated in space, and an error contribution of as yet unexplained origin. The relative CCD motion probably has a thermal origin and typically is 0.001-0.010 px (~0.1-1 mas), but sometimes amounts to 0.02-0.05 px (3-6 mas). This instability and space-correlated errors are detected and mitigated using reference stars. The third component of unknown origin has an amplitude of 0.03-0.14 mas and is independent of the observing conditions. We find that a consecutive sequence of 32 images of a well-exposed star over 40 min at 0.6'' seeing results in a median rms of the epoch residuals of 0.126 mas. Overall, the epoch residuals are distributed according to a normal law with a χ2 value near unity. We compiled a catalogue of 12 000 stars with I-band magnitudes of 16-22 located in 20 fields, each covering ~ 2' × 2'. It contains I-band magnitudes, ICRF positions with 40-70 mas precision, and relative proper motions and absolute trigonometric parallaxes with a precision of 0.1 mas/yr and 0.1 mas at the bright end, respectively. Conclusions: This work shows that an astrometric accuracy of ~100 micro-arcseconds over two years can be achieved with a large optical telescope in a survey covering several targets and varying observing conditions. Based on observations made with ESO telescopes at the

  5. UCAC3: ASTROMETRIC REDUCTIONS

    SciTech Connect

    Finch, Charlie T.; Zacharias, Norbert; Wycoff, Gary L.

    2010-06-15

    Presented here are the details of the astrometric reductions from the x, y data to mean right ascension (R.A.), declination (decl.) coordinates of the third U.S. Naval Observatory CCD Astrograph Catalog (UCAC3). For these new reductions we used over 216,000 CCD exposures. The Two-Micron All-Sky Survey (2MASS) data are used extensively to probe for coordinate and coma-like systematic errors in UCAC data mainly caused by the poor charge transfer efficiency of the 4K CCD. Errors up to about 200 mas have been corrected using complex look-up tables handling multiple dependences derived from the residuals. Similarly, field distortions and sub-pixel phase errors have also been evaluated using the residuals with respect to 2MASS. The overall magnitude equation is derived from UCAC calibration field observations alone, independent of external catalogs. Systematic errors of positions at the UCAC observing epoch as presented in UCAC3 are better corrected than in the previous catalogs for most stars. The Tycho-2 catalog is used to obtain final positions on the International Celestial Reference Frame. Residuals of the Tycho-2 reference stars show a small magnitude equation (depending on declination zone) that might be inherent in the Tycho-2 catalog.

  6. ASTROMETRIC REVERBERATION MAPPING

    SciTech Connect

    Shen Yue

    2012-10-01

    Spatially extended emission regions of active galactic nuclei respond to continuum variations, if such emission regions are powered by energy reprocessing of the continuum. The response from different parts of the reverberating region arrives at different times lagging behind the continuum variation. The lags can be used to map the geometry and kinematics of the emission region (i.e., reverberation mapping, RM). If the extended emission region is not spherically symmetric in configuration and velocity space, reverberation may produce astrometric offsets in the emission region photocenter as a function of time delay and velocity, detectable with future {mu}as to tens of {mu}as astrometry. Such astrometric responses provide independent constraints on the geometric and kinematic structure of the extended emission region, complementary to traditional RM. In addition, astrometric RM is more sensitive to infer the inclination of a flattened geometry and the rotation angle of the extended emission region.

  7. Astrometric and Photometric Variability in Quasars

    NASA Astrophysics Data System (ADS)

    Andrei, A. H.; Bouquillon, S.; Penna, J. L.; Taris, F.; Anton, S.; Souchay, J.; Camargo, J. I. B.; da Silva Neto, D. N.; Vieira Martins, R.; Assafin, M.; Pinto, S. dos Reis Carvalho

    2010-05-01

    Quasars are the choicest objects to define a quasi-inertial reference frame. At the same time, they are active galactic nuclei powered by a massive black hole. As the astrometric precision of ground-based optical observations approaches the limit set by the forthcoming GAIA mission, astrometric stability can be investigated. Though the optical emission from the core region usually exceeds the other components by a factor of a hundred, the variability of those components must surely imply some measure of variability of the astrometric baricenter. Whether this is confirmed or not, it puts important constraints on the relationship of the quasar's central engine to the surrounding distribution of matter. To investigate the correlation between long-term optical variability and what is dubbed as the “random walk” of the astrometric center, a program is being pursued at the WFI/ESO 2.2m. The sample was selected from quasars known to undergo large-amplitude and long-term optical variations (Smith et al. 1993; Teerikorpi 2000). The observations are typically made every two months. The treatment is differential, comparing the quasar position and brightness against a sample of selected stars for which the average relative distances and magnitudes remain constant. The provisional results for four objects bring strong support to the hypothesis of a relationship between astrometric and photometric variability. A full account is provided by Andrei et al. (2009).

  8. Astrometric and photometric variability in quasars

    NASA Astrophysics Data System (ADS)

    Andrei, A. H.; Bouquillon, S.; de Camargo, J. I. B.; Penna, J. L.; Taris, F.; Souchay, J.; da Silva Neto, D. N.; Vieira Martins, R.; Assafin, M.

    2009-09-01

    Quasars are the choicest objects to define a quasi-inertial reference frame. At the same time they are active galactic nuclei powered by a massive black hole. As the astrometric precision approaches the limit set by the forthcoming GAIA mission, the astrometric stability can be investigated. Though the optical emission from the core region usually exceeds the other components by a factor of hundred, the variability of those components must surely imply in some measure of variability on the astrometric barycenter. To investigate the correlation between long term optical variability and what is dubbed as the random walk of the astrometric center, a program is being pursued at the WFI/ESO2.2m. A sample of quasars was selected by the large amplitude and long term optical variability. The observations are typically made every two months. The treatment is all differential, comparing the quasar position and brightness against a basket of selected stars for which the average relative distances and magnitudes remain constant. The provisional results for four objects bring strong support to the hypothesis of a degree of relationship between astrometric and photometric variability.

  9. NEAT: A Microarcsec Astrometric Telescope

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    NEAT, Nearby Exo-Earth Astrometric Telescope is a medium-small telescope (is) approximately 1m in diameter that is designed to make ultra precise (is) less than 1 uas (microarcsec) astrometric measurements of nearby stars in a (is) approximately 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 (is) approximately 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 (is) approximately 2000 arcsec field of view implies the focal plane is accurate or at least stable to 5 parts in 10(exp 10) over the lifetime of the mission ( (is) approximately 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 (is) greater than 2 pixels per lambda/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.

  10. NEAT: A Microarcsec Astrometric Telescope

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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 ?/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.

  11. Breakthrough in orbit determination of a binary. - In expectation of astrometric observations with high precision such as VERA and JASMINE -

    NASA Astrophysics Data System (ADS)

    Asada, Hideki

    2006-11-01

    There exists a very classical inverse problem regarding orbit determination of a binary system: "when an orbital plane of two bodies is inclined with respect to the line of sight, observables are their positions projected onto a celestial sphere. How do we determine the orbital elements from observations?" A "complete exact solution" has been found. It is reviewed with some related topics.

  12. Astrometric positions of minor planets in 1978

    NASA Astrophysics Data System (ADS)

    Debehogne, H.; Houziaux, L.

    1980-04-01

    Minor planets 6 Hebe, 7 Iris, 146 Lucina, 310 Margarita, 389 Industria, 407 Arachne, 582 Olympia, 608 Adolfina, 704 Interamnia, 1201 Strenua, 1257 Mora, 1649 = 1951 DE, and 1964 = 2007 P-L have been observed between 11 and 15 April 1978. 1950.0 astrometric positions are given.

  13. Aiming Schedule For Orbiting Astrometric Telescope

    NASA Technical Reports Server (NTRS)

    Mascy, Alfred C.; Sobeck, Charlie

    1991-01-01

    Report discusses schedule of observation times and aiming directions of proposed astrometric telescope facility mounted on Space Station in orbit around Earth. Primarily makes repeated observations of apparent positions of each of 127 selected stars with respect to distant reference stars in same field of view known to have unperturbed proper motions. Purpose of observations to detect motions of selected stars about centers of mass and to analyze harmonic content of motions to infer existence, number, masses, and orbital radii of planets.

  14. 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.

  15. COMPANIONS TO NEARBY STARS WITH ASTROMETRIC ACCELERATION. II

    SciTech Connect

    Tokovinin, Andrei; Hartung, Markus; Hayward, Thomas L. E-mail: mhartung@gemini.edu

    2013-07-01

    Hipparcos astrometric binaries were observed with the NICI adaptive optics system at Gemini-S, completing the work of Paper I. Among the 65 F, G, and K dwarfs within 67 pc of the Sun studied here, we resolve 18 new subarcsecond companions, remeasure 7 known astrometric pairs, and establish the physical nature of yet another 3 wider companions. The 107 astrometric binaries targeted at Gemini so far have 38 resolved companions with separations under 3''. Modeling shows that bright enough companions with separations on the order of an arcsecond can perturb the Hipparcos astrometry when they are not accounted for in the data reduction. However, the resulting bias of parallax and proper motion is generally below formal errors and such companions cannot produce fake acceleration. This work contributes to the multiplicity statistics of nearby dwarfs by bridging the gap between spectroscopic and visual binaries and by providing estimates of periods and mass ratios for many astrometric binaries.

  16. 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.

  17. 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.

  18. 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.

  19. Gravitation Astrometric Measurement Experiment (GAME)

    NASA Astrophysics Data System (ADS)

    Gai, M.; Vecchiato, A.; Ligori, S.; Riva, A.; Lattanzi, M. G.; Busonero, D.; Fienga, A.; Loreggia, D.; Crosta, M. T.

    2012-07-01

    GAME is a recent concept for a small/medium class mission aimed at Fundamental Physics tests in the Solar system, by means of an optimised instrument in the visible, based on smart combination of coronagraphy and Fizeau interferometry. The targeted precision on the γ and β parameters of the Parametrised Post-Newtonian formulation of General Relativity are respectively in the 10-7-10-8 and 10-5-10-6 range, improving by one or two orders of magnitude with respect to the expectations on current or near future experiments. Such precision is suitable to detect possible deviations 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 from a Solar system scale experiment. The measurement principle is based on the differential astrometric signature on the stellar positions, i.e. based on the spatial component of the effect rather than the temporal component as in the most recent experiments using radio link delay timing variation (Cassini). The instrument concept is based on multiple field, multiple aperture Fizeau interferometry, observing simultaneously regions close to the Solar limb (requiring the adoption of coronagraphic techniques), and others in opposition to the Sun. The diluted optics approach is selected for achieving an efficient rejection of the scattered solar radiation, while retaining an acceptable angular resolution on the science targets. The multiple field observation is aimed at cost-effective control of systematic effects through simultaneous calibration. We describe the science motivation, the proposed mission profile, the instrument concept and the expected performance.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. On the sources of astrometric anomalous refraction

    NASA Astrophysics Data System (ADS)

    Taylor, M. Suzanne

    2009-06-01

    Over 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, now known as "anomalous refraction," is again being observed. Anomalous refraction is described as a low frequency, large angular scale motion of the entire image plane with respect to the celestial coordinate system as observed and defined by previous astrometric catalogs. These motions of typically several tenths of an arcsecond with timescales on the order often minutes are ubiquitous to drift-scan ground-based 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 never 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 coherent dynamical structures in the boundary-layer below 60 meters.

  5. Astrometric microlensing with the GAIA satellite

    NASA Astrophysics Data System (ADS)

    Belokurov, V. A.; Evans, N. W.

    2002-04-01

    GAIA is the `super-Hipparcos ' survey satellite selected as a Cornerstone 6 mission by the European Space Agency. GAIA can measure microlensing by the brightening of source stars. For the broad G -band photometer, the all-sky source-averaged photometric optical depth is ~10-7 . There are ~1300 photometric microlensing events for which GAIA will measure at least one data point on the amplified light curve. GAIA can also measure microlensing by the small excursions of the light centroid that occur during events. The all-sky source-averaged astrometric microlensing optical depth is ~2.5×10-5 . Some ~25000 sources will have a significant variation of the centroid shift, together with a closest approach, during the lifetime of the mission. This is not the actual number of events that can be extracted from the GAIA data set, as the false detection rate has not been assessed. A covariance analysis is used to study the propagation of errors and the estimation of parameters from realistic sampling of the GAIA data stream of transits in the along-scan direction during microlensing events. The mass of the lens can be calculated to good accuracy if the lens is nearby so that the angular Einstein radius θ E is large; if the Einstein radius projected on to the observer plane r~ E is approximately an astronomical unit; or if the duration of the astrometric event is long (>~1yr) or the source star is bright . Monte Carlo simulations are used to study the ~2500 events for which the mass can be recovered with an error of <50 per cent. These high-quality events are dominated by disc lenses within a few tens of parsecs and source stars within a few hundred parsecs. We show that the local mass function can be recovered from the high-quality sample to good accuracy. GAIA is the first instrument with the capability of measuring the mass locally in very faint objects such as black holes and very cool white and brown dwarfs. For only ~5 per cent of all astrometric events will GAIA record

  6. IT challenges of Gaia's Astrometric Global Iterative Solution

    NASA Astrophysics Data System (ADS)

    Hernandez-Munoz, Jose Luis; O'Mullane, William

    2015-12-01

    The Astrometric Global Iterative Solution (AGIS) scheme is the key process in the astrometric reduction of the Gaia data. It's main purpose is to generate the astrometic part of the Gaia catalogue in a way that optimally combines all 10^12 available measurements in a globally, self-consistent manner.We will outline the technical design and chosen approaches for the distributed processing infrastructure of AGIS. An important aspect in this is the efficient reading and passing of observation data to the mathematical core algorithms.

  7. Gamma Astrometric Measurement Experiment

    NASA Astrophysics Data System (ADS)

    Gai, M.; Lattanzi, M. G.; Ligori, S.; Loreggia, D.; Vecchiato, A.

    GAME aims at the measurement of gravitational deflection of the light by the Sun, by an optimised telescope on board a small class satellite. The targeted precision on the gamma parameter of the Parametrised Post-Newtonian formulation of General Relativity is below 10-6, i.e. one to two orders of magnitude better than the best current results. Such precision is suitable to detect possible deviations 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 differential astrometry. The observations also allow additional scientific objectives related to tests of General Relativity and to the study of exo-planetary systems. The instrument concept is based on a dual field, multiple aperture Fizeau interferometer, observing simultaneously two regions close to the Solar limb. The diluted optics achieves efficient rejection of the solar radiation, with good angular resolution on the science targets. We describe the science motivation, the proposed mission implementation and the expected performance.

  8. 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

  9. Astrometric Study of Lo 1339

    NASA Astrophysics Data System (ADS)

    Wiramihardja, S. D.; Arifyanto, M. I.; Sugianto, Y.; Kunjaya, C.

    2010-10-01

    We presented a preliminary result of astrometric study of galactic cluster Lo 1339 using proper motion data from UCAC2 catalog. We applied the maximum likelihood method to determine cluster membership by using the proper motion data. The Padova isochrones lines with solar metallicity were fitted upon the Color Magnitude Diagram in near-infrared to derive physical parameters of the cluster, where we obtained the age of cluster log t = 8.4+/-0.2, the distance of 1284+/-140 pc, and the absorption AJ = 0.26+/-0.13 mag with cluster diameter of 4.9+/-0.5 pc.

  10. Astrometric Discovery of GJ 164B

    NASA Technical Reports Server (NTRS)

    Pravdo, Steven H.; Shaklan, Stuart B.; Henry, Todd; Benedict, G. Fritz

    2004-01-01

    We discovered a low-mass companion to the M dwarf GJ 164 with the CCD-based imaging system of the Stellar Planet Survey astrometric program. The existence of GJ 164B was confirmed with Hubble Space Telescope NICMOS imaging observations. A high-dispersion spectral observation in V sets a lower limit of Deltam > 2.2 mag between the two components of the system. Based on our parallax value of 82 +/- 8 mas, we derive the following orbital parameters: P = 2.04 +/- 0.03 yr, a = 103 +/- 0.03, and M-total 0.265 +/- 0.020 M-circle dot. The component masses are M-A = 0.170 +/- 0.015 M-circle dot and M-B = 0.095 +/- 0/015 M-circle dot. Based on its mass, colors, and spectral properties, GJ 164B has spectral type M6-M8 V.

  11. 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.

  12. Astrometric Performance of STIS CCD CTI Corrections on Omega Cen Images

    NASA Astrophysics Data System (ADS)

    Biretta, John; Lockwood, Sean; Debes, John

    2015-09-01

    Here we examine the astrometric performance of these new pixel-based CTI corrections, and compare their performance to the already existing empirical CTI corrections. Tests are performed using imaging observations of the star cluster Omega Cen taken in 2012. The astrometric effects of CTI are evaluated by comparing the Y coordinates of the stars on images read out through the A and D amplifiers, which are located at opposite corners of the CCD detector.

  13. 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.

  14. 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.

  15. Metrology for AGP - Astrometric Gravitation Probe

    NASA Astrophysics Data System (ADS)

    Gai, Mario; et al.

    2015-08-01

    The Astrometric Gravitation Probe (AGP) is a concept of space mission aimed at tests of Fundamental Physics in the Solar system, using Fizeau interferometry and coronagraphy techniques to implement differential astrometry among superposed stellar fields. The main goal is verification of the General Relativity (GR) and competing gravitation theories in the weak field of the Solar System by high precision measurement of the light deflection in the vicinity of the Sun at < 10-7 and of the main and minor planet dynamics at the microarcsec/year level. The AGP payload concept is based on a single main telescope (1.15 m diameter) implementing a multi-aperture Fizeau interferometer, for simultaneous observation of four regions close to the Solar limb and in opposition; coronagraphic techniques are applied on the elementary sub-apertures. The star displacement due to light deflection is derived by differential astrometry on images taken in different deflection conditions (e.g. ON and OFF). The instrument design is focused on systematic error control through multiple field simultaneous observation and calibration. The metrology system requirements related to the science goals are discussed, and the technical aspects of possible implementations are investigated. The potential benefit of auto-collimation and cophasing techniques derives from monitoring comparably large sections of the optical system common to the stellar beams. The performance at microarcsec level is verified by simulation.

  16. 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).

  17. The Astrometric Model Implementation. Simulations and Data Reduction Compatibility Test

    NASA Astrophysics Data System (ADS)

    Anglada-Escudé, G.; Torra, J.; Masana, E.; Luri, X.

    2005-01-01

    The aim of this paper is to give a brief description of the astrometric model accuracy at the current stage of the implementation in GASS (simulator) and GDAAS2 (Data Reduction study). The astrometric model described is a set of algorithms which relate the astrometric parameters with the observed directions on the satellite quasi-intertial reference frame. This includes the kinematics of point sources, the relativistic light deflection due to Solar System gravitational field and the aberration. The description of this model was given by Klioner (2002), The form of these algorithms is slightly different in the telemetry simulations (S.A. Klioner, ANSI-C code) and in the data reduction scheme (Lindegren 2002, Fortran90). Both versions make use of the ephemeris for the Solar System by Observatoire de la Côte d'Azur (Mignard 2003, Fortran 90). All these algorithms have been wrapped or recoded since the simulations and data reduction both run in a Java environment. All these manipulations required a strict verification since these algorithms constitute the core of the GIS (Global Iterative Solution). We present the compatibility tests performed during last year that helped us to make fully compatible the simulated data with the data reduction scheme.

  18. Pluto-Charon: a test of the astrometric approach for finding asteroid satellites

    NASA Astrophysics Data System (ADS)

    Kikwaya, J.-B.; Thuillot, W.; Berthier, J.

    2003-05-01

    The astrometric method to find asteroid satellites is based on the search for the reflex effect on the primary object due to the orbital motion of a possible satellite (Monet & Monet 1998, Kikwaya et al. 2002). As reported by Kikwaya et al. (2003), the astrometric signature of a satellite of 146 Lucina may reach several mas. Spectral analysis might then detect the signal under good conditions of signal/noise ratio, with high quality astrometric measurements and large coverage by different sites of observation. However, the astrometric method cannot be applied to any binary system of asteroids. It depends strongly on the mass ratio of the two bodies and the distance between them (Kikwaya et al. 2002). Pluto-Charon provides a good test of this method. Previous works based on direct imaging of Charon show that its period is 6.357 days and the mass ratio is 0.122 (Wasserman et al. 2000), putting this system into the range that can be observed by our method. Using archived photographic observations (1914-1995) and CCD observations from US Naval Observatory, Flagstaff station (1995-1998), Bordeaux observatory (1996-1997) and Mc Donald Observatory (1997), we are analyzing the position of Pluto to see if its wobble effect due to Charon (amplitude around 95 mas) can be detected and if the orbital period of Charon can be recovered through a spectral analysis. If successful, this will reinforce the ability of our astrometric method to find asteroid satellites.

  19. 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

  20. 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

  1. A USNO Search for Astrometric Companions to Brown Dwarfs IV

    NASA Astrophysics Data System (ADS)

    Bartlett, Jennifer L.; Vrba, F. J.; Munn, J. A.; Luginbuhl, C. B.; Tilleman, T.; Henden, A. A.

    2014-01-01

    Preliminary analyses of ten brown dwarfs observed by the U.S. Naval Observatory infrared parallax program show no clear indication of astrometric perturbations due to low mass companions. The data were collected using ASTROCAM on the 1.55-m (61-in) Kaj Strand Astrometric Reflector from 2000 September through 2006 June over periods from 2.0 to 5.3 years. After our standard solution for parallax and proper motion, the residuals were subjected to a time-series analysis using the Lomb-Scargle periodogram method. The multiplicity fraction for brown dwarfs constrains theories of brown dwarf formation and evolution. Binary systems, especially those that straddle the transition between L and T spectral types, are also significant tests of atmospheric models. In addition, the identification of companions would have enabled the eventual measurement of the associated masses. This search for astrometric companions is an extension of the initial infrared parallax program. When finalized, the trigonometric parallaxes for these brown dwarfs will provide accurate distances for use in determining their luminosities and temperatures. The brown dwarfs in this subsample have spectral types that range from late M through mid-T. None of them are known binaries. Distance estimates place six of these objects within the 25-pc limit of the Solar Neighborhood, and preliminary parallaxes place another three between 25 and 35 pc. These substellar objects are located north of -15° Dec. The brown dwarfs evaluated are 2MASS J00325937+1410371, 2MASS J01514155+1244300 (BF Ari) 2MASS J02074284+0000564, 2MASS J03095345-0753156, SDSS J083717.21-000018.0, 2MASS J11101001+0116130, 2MASS J13262981-0038314 (2MUCD 11143), 2MASS J17502385+4222373, 2MASS J23391025+1352284, and 2MASS J23565477-1553111. Analyses of another 30 brown dwarfs were presented earlier and the analyses of 19 more brown dwarfs are planned.

  2. A USNO Search for Astrometric Companions to Brown Dwarfs III

    NASA Astrophysics Data System (ADS)

    Bartlett, Jennifer L.; Vrba, F. J.; Munn, J. A.; Luginbuhl, C. B.; Tillman, T.; Henden, A. A.

    2013-01-01

    Preliminary analyses of ten brown dwarfs observed by the U.S. Naval Observatory infrared parallax program show no clear indication of astrometric perturbations due to low mass companions. The data were collected using ASTROCAM on the 1.55-m Strand Astrometric Reflector from 2000 October through 2006 June over periods from 1.3 to 5.4 years. After our standard solution for parallax and proper motion, the residuals were subjected to a time-series analysis using the Lomb-Scargle periodogram method. The multiplicity fraction for brown dwarfs constrains theories of brown dwarf formation and evolution. Binary systems, especially those that straddle the transition between L and T spectral types, are also significant tests of atmospheric models. In addition, the identification of companions would have enabled the eventual measurement of the associated masses. This search for astrometric companions is an extension of the initial infrared parallax program. When finalized, the trigonometric parallaxes for these brown dwarfs will provide accurate distances for use in determining their luminosities and temperatures. The brown dwarfs in this subsample have spectral types that range from early L through mid-T. None are known binaries. Distance estimates place all but two within the 25-pc limit of the Solar Neighborhood; one outlier has a distance of approximately 62 pc based on its preliminary parallax. These substellar objects are located north of -25° Dec. and lie between 13h and 23h in R.A. The brown dwarfs evaluated are 2MASS J13464634-0031501, SDSS J144600.60+002452.0, 2MASS J16241436+0029158, 2MASS J17580545+4633099, 2MASS J19010601+4718136, 2MASS J21241387+0059599, 2MASS J22425317+2542573, 2MASS J22443167+2043433, 2MASS J22541892+3123498, and 2MASS J22552907-0034336. Analyses of another 20 brown dwarfs were presented earlier and the analyses of 19 more brown dwarfs are planned.

  3. An Optical/Infrared Astrometric Satellite Project LIGHT

    NASA Astrophysics Data System (ADS)

    Yoshizawa, M.; Sato, K.; Nishikawa, J.; Fukushima, T.; Miyamoto, M.

    1997-08-01

    LIGHT is the name of a scanning astrometric satellite for stellar and galactic astronomy planned to be launched between 2007 and 2010. Four sets of Fizeau-type interferometers with a beam combiner unit of 1m baseline are the basic structure of the satellite optics. LIGHT is expected to observe the parallaxes and proper motions of nearly a hundred million stars up to V=18 mag (K=15 mag) magnitude with the precision better than 0.1 milliarcsec (about 50 microarcsec in V-band and 90 microarcsec in K-band) in parallaxes and better than 0.1 milliarcsec per year in proper motions, as well as the precise photometric characteristics of the observed stars. Almost all of the giant and supergiant stars belonging to the disk and halo components of our Galaxy within 10 to 15kpc from the sun will be observed by LIGHT to study the most fundamental structure and evolution of the Galaxy. LIGHT will become a precursor of a more sophisticated future astrometric interferometer satellite like GAIA (Lindegren & Perryman 1996).

  4. FAME- Full-sky Astrometric Mapping Explorer

    NASA Astrophysics Data System (ADS)

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

    1999-09-01

    The Full-sky Astrometric Mapping Explorer (FAME) is a small satellite designed to perform an all-sky, astrometric survey with unprecedented accuracy. FAME will create an accurate astrometric catalog of \\ 40,000,000 stars with visual band magnitudes 5

  5. Correlated and Zonal Errors of Global Astrometric Missions: A Spherical Harmonic Solution

    NASA Astrophysics Data System (ADS)

    Makarov, V. V.; Dorland, B. N.; Gaume, R. A.; Hennessy, G. S.; Berghea, C. T.; Dudik, R. P.; Schmitt, H. R.

    2012-07-01

    We propose a computer-efficient and accurate method of estimating spatially correlated errors in astrometric positions, parallaxes, and proper motions obtained by space- and ground-based astrometry missions. In our method, the simulated observational equations are set up and solved for the coefficients of scalar and vector spherical harmonics representing the output errors rather than for individual objects in the output catalog. Both accidental and systematic correlated errors of astrometric parameters can be accurately estimated. The method is demonstrated on the example of the JMAPS mission, but can be used for other projects in space astrometry, such as SIM or JASMINE.

  6. CORRELATED AND ZONAL ERRORS OF GLOBAL ASTROMETRIC MISSIONS: A SPHERICAL HARMONIC SOLUTION

    SciTech Connect

    Makarov, V. V.; Dorland, B. N.; Gaume, R. A.; Hennessy, G. S.; Berghea, C. T.; Dudik, R. P.; Schmitt, H. R.

    2012-07-15

    We propose a computer-efficient and accurate method of estimating spatially correlated errors in astrometric positions, parallaxes, and proper motions obtained by space- and ground-based astrometry missions. In our method, the simulated observational equations are set up and solved for the coefficients of scalar and vector spherical harmonics representing the output errors rather than for individual objects in the output catalog. Both accidental and systematic correlated errors of astrometric parameters can be accurately estimated. The method is demonstrated on the example of the JMAPS mission, but can be used for other projects in space astrometry, such as SIM or JASMINE.

  7. Gaia relativistic astrometric models. I. Proper stellar direction and aberration

    NASA Astrophysics Data System (ADS)

    Crosta, M.; Vecchiato, A.

    2010-01-01

    The high accuracy achievable by modern space astrometry requires the use of General Relativity to model the stellar light propagation through the gravitational field encountered from a source to a given observer inside the Solar System. The general relativistic definition of an astrometric measurement needs an appropriate use of the concept of reference frame, which should then be linked to the conventions of the IAU resolutions. On the other hand, a definition of the astrometric observables in the context of General Relativity is also essential for finding the stellar coordinates and proper motion uniquely, this being the main physical task of the inverse ray-tracing problem. The aim of this work is to set the level of reciprocal consistency of two relativistic models, GREM and RAMOD (Gaia, ESA mission), in order to guarantee a physically correct definition of the light's local direction to a star and deduce the star coordinates and proper motions at the level of accuracy required by these models consistently with the IAU's adopted reference systems.

  8. 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.

  9. 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.

  10. Near-Term Prospects for Extra-Solar Planet Detection: The Astrometric Imaging Telescope

    NASA Astrophysics Data System (ADS)

    Terrile, Richard J.; Levy, Eugene H.; Gatewood, George D.

    The Astrometric Imaging Telescope (AIT) is a 1.5 to 2 meter diameter space-based telescope designed to carry out a comprehensive program of direct and indirect extra-solar planet detection. The telescope consists of two separate instruments, an astrometric experiment to measure the reflex motion of the parent stars and an imaging coronagraph to directly image planets and the circumstellar region. The astrometric technique utilizes the Multichannel Astrometric Photometer (MAP) which passes a Ronchi ruling over a field of stars and measures the centroid of the stars in two orthogonal observations. Used above the Earth's atmosphere this will be about two orders of magnitude more accurate than any existing astrometric instrument and will achieve an accuracy of about 10 microarcseconds. This will allow detection and study of Uranus-size or larger planets in Jovian orbits around several hundred nearby stars. The astrometric study of a parent star of a planetary system will lead to an accurate determination of its distance. The distance is inversely proportional to the magnitude of the annual parallactic motion. The same study yields the major characteristics of the individual bodies within the planetary system. The periods of the orbits are obtained from the analysis of the motions of the central star. Thy are directly related to the distances between the individual planets in the system and the system's sun. The distances in turn determine the thermal radiation level, or effective temperature, at the planet's orbit. With sufficient precision and time, the analysis of the apparent motion of the target star will also yield the eccentricities and the relative inclinations of the orbits of each of the planetary bodies. Assuming the mass of the primary star can be accurately estimated, the study will also yield the mass of each planet.

  11. New method for astrometric measurements in Space Mission, JASMINE

    NASA Astrophysics Data System (ADS)

    Yano, T.; Gouda, N.; Yamada, Y.

    We present a new method for measuring positions of stars in the Milky Way Galaxy by astrometric satellite, JASMINE, which is in progress at the National Astronomical Observatory of Japan. JASMINE is the acronym of the Japan Astrometry Satellite Mission for Infrared (z-band : 0.9 micron) Exploration, and is planned to be launched around 2015 The main objective of JASMINE is to study the fundamental structure and evolution of the bulge components of the Milky Way Galaxy. In order to accomplish these objectives, JASMINE will measure trigonometric parallaxes, positions and proper motions of about a few million stars during the observational program, with the precision of 10 microarcsec at z =14mag. The telescope of JASMINE has just one field of view, which is different from other astrometric satellites like Hipparcos and GAIA, that have two fields of view with large angle. These satellites, Hipparcos and GAIA, scan along the great circle with the spin axis perpendicular to both two fields of view to estimate the relative positions of stars on the great circle. They scan many different great circles to observe all the sky. On the other hand, JASMINE will take overlapping fields of view without any gaps to survey an area of about 20deg×10deg. Accordingly survey area covers the region of about 20deg×10deg in the bulge component. JASMINE will continue the above procedure for observing the area during the mission life. As a consequence, JASMINE will observe the restricted regions around the Galactic bulge and sweep repeatedly. The mission life is planned to be 5 years.

  12. New Method for Astrometric Measurements in Space Mission, JASMINE.

    NASA Astrophysics Data System (ADS)

    Yano, T.; Gouda, N.; Yamada, Y.

    2006-08-01

    We present a new method for measuring positions of stars in the Milky Way Galaxy by astrometric satellite, JASMINE, which is in progress at the National Astronomical Observatory of Japan. JASMINE is the acronym of the Japan Astrometry Satellite Mission for Infrared (z-band : 0.9 micron) Exploration, and is planned to be launched around 2015 The main objective of JASMINE is to study the fundamental structure and evolution of the bulge components of the Milky Way Galaxy. In order to accomplish these objectives, JASMINE will measure trigonometric parallaxes, positions and proper motions of about a few million stars during the observational program, with the precision of 10 microarcsec at z =14mag. The telescope of JASMINE has just one field of view, which is different from other astrometric satellites like Hipparcos and GAIA, that have two fields of view with large angle. These satellites, Hipparcos and GAIA, scan along the great circle with the spin axis perpendicular to both two fields of view to estimate the relative positions of stars on the great circle. They scan many different great circles to observe all the sky. On the other hand, JASMINE will take overlapping fields of view without any gaps to survey an area of about 20deg*10deg. Accordingly survey area covers the region of about 20deg*10deg in the bulge component. JASMINE will continue the above procedure for observing the area during the mission life. As a consequence, JASMINE will observe the restricted regions around the Galactic bulge and sweep repeatedly. The mission life is planned to be 5 years.

  13. SIM Lite Astrometric Observatory Progress Report

    NASA Technical Reports Server (NTRS)

    Marr, James C., IV; Shao, Michael; Goullioud, Renaud

    2010-01-01

    The SIM Lite Astrometric Observatory (aka SIM Lite), a micro-arcsecond astrometry space mission, has been developed in response to NASA's indefinite deferral of the SIM PlanetQuest mission. The SIM Lite mission, while significantly more affordable than the SIM PlanetQuest mission concept, still addresses the full breadth of SIM science envisioned by two previous National Research Council (NRC) Astrophysics Decadal Surveys at the most stringent 'Goal' level of astrometric measurement performance envisioned in those surveys. Over the past two years, the project has completed the conceptual design of the SIM Lite mission using only the completed SIM technology; published a 250 page book describing the science and mission design (available at the SIM website: http://sim.jpl.nasa.gov); been subject to an independent cost and technical readiness assessment by the Aerospace Corporation; and submitted a number of information responses to the NRC Astro2010 Decadal Survey. The project also conducted an exoplanet-finding capability double blind study that clearly demonstrated the ability of the mission to survey 60 to 100 nearby sun-like dwarf stars for terrestrial, habitable zone planets in complex planetary systems. Additionally, the project has continued Engineering Risk Reduction activities by building brassboard (form, fit and function to flight) version of key instrument elements and subjecting them to flight qualification environmental and performance testing. This paper summarizes the progress over the last two years and the current state of the SIM Lite project.

  14. Astrometric performance of the Gemini multiconjugate adaptive optics system in crowded fields

    NASA Astrophysics Data System (ADS)

    Neichel, Benoit; Lu, Jessica R.; Rigaut, François; Ammons, S. Mark; Carrasco, Eleazar R.; Lassalle, Emmanuel

    2014-11-01

    The Gemini multiconjugate adaptive optics system (GeMS) is a facility instrument for the Gemini South telescope. It delivers uniform, near-diffraction-limited image quality at near-infrared wavelengths over a 2 arcmin field of view. Together with the Gemini South Adaptive Optics Imager (GSAOI), a near-infrared wide-field camera, GeMS/GSAOI's combination of high spatial resolution and a large field of view will make it a premier facility for precision astrometry. Potential astrometric science cases cover a broad range of topics including exoplanets, star formation, stellar evolution, star clusters, nearby galaxies, black holes and neutron stars, and the Galactic Centre. In this paper, we assess the astrometric performance and limitations of GeMS/GSAOI. In particular, we analyse deep, mono-epoch images, multi-epoch data and distortion calibration. We find that for single-epoch, undithered data, an astrometric error below 0.2 mas can be achieved for exposure times exceeding 1 min, provided enough stars are available to remove high-order distortions. We show however that such performance is not reproducible for multi-epoch observations, and an additional systematic error of ˜0.4 mas is evidenced. This systematic multi-epoch error is the dominant error term in the GeMS/GSAOI astrometric error budget, and it is thought to be due to time-variable distortion induced by gravity flexure.

  15. The astrometric core solution for the Gaia mission. Overview of models, algorithms, and software implementation

    NASA Astrophysics Data System (ADS)

    Lindegren, L.; Lammers, U.; Hobbs, D.; O'Mullane, W.; Bastian, U.; Hernández, J.

    2012-02-01

    Context. The Gaia satellite will observe about one billion stars and other point-like sources. The astrometric core solution will determine the astrometric parameters (position, parallax, and proper motion) for a subset of these sources, using a global solution approach which must also include a large number of parameters for the satellite attitude and optical instrument. The accurate and efficient implementation of this solution is an extremely demanding task, but crucial for the outcome of the mission. Aims: We aim to provide a comprehensive overview of the mathematical and physical models applicable to this solution, as well as its numerical and algorithmic framework. Methods: The astrometric core solution is a simultaneous least-squares estimation of about half a billion parameters, including the astrometric parameters for some 100 million well-behaved so-called primary sources. The global nature of the solution requires an iterative approach, which can be broken down into a small number of distinct processing blocks (source, attitude, calibration and global updating) and auxiliary processes (including the frame rotator and selection of primary sources). We describe each of these processes in some detail, formulate the underlying models, from which the observation equations are derived, and outline the adopted numerical solution methods with due consideration of robustness and the structure of the resulting system of equations. Appendices provide brief introductions to some important mathematical tools (quaternions and B-splines for the attitude representation, and a modified Cholesky algorithm for positive semidefinite problems) and discuss some complications expected in the real mission data. Results: A complete software system called AGIS (Astrometric Global Iterative Solution) is being built according to the methods described in the paper. Based on simulated data for 2 million primary sources we present some initial results, demonstrating the basic

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. Design and construction of an astrometric astrograph

    NASA Astrophysics Data System (ADS)

    Vukobratovich, Daniel; Valente, Tina M.; Shannon, Robert R.; Hooker, Roger A.; Sumner, Richard E.

    1992-12-01

    The Optical Sciences Center, University of Arizona, has designed and constructed a unique 'red corrected' astrometric astrograph objective lens for the United States Naval Observatory. A five element design, with an integral Schott OG550 filter, was developed to meet the requirement for a 2060 mm focal length, f/10 system. The lens provides a nearly zero distortion flat field of 5 by 5 degrees in the sky. A weight limit of 55 kg led to the use of a titanium lens barrel. Assembly tolerances are satisfied through the use of elastomeric subcell mounting of the individual elements, and an adjustable final element. The lens is hermetically sealed and uses a filter/dessicator system to insure the long term cleanliness of the optics.

  2. Astrometrica: Astrometric data reduction of CCD images

    NASA Astrophysics Data System (ADS)

    Raab, Herbert

    2012-03-01

    Astrometrica is an interactive software tool for scientific grade astrometric data reduction of CCD images. The current version of the software is for the Windows 32bit operating system family. Astrometrica reads FITS (8, 16 and 32 bit integer files) and SBIG image files. The size of the images is limited only by available memory. It also offers automatic image calibration (Dark Frame and Flat Field correction), automatic reference star identification, automatic moving object detection and identification, and access to new-generation star catalogs (PPMXL, UCAC 3 and CMC-14), in addition to online help and other features. Astrometrica is shareware, available for use for a limited period of time (100 days) for free; special arrangements can be made for educational projects.

  3. Measurement of CFHT Images II. Astrometric Reduction

    NASA Astrophysics Data System (ADS)

    Bustos Fierro, I. H.; Calderón, J. H.

    2014-06-01

    In this paper we present the evaluations of the astrometric reduction of CFHT images that are intended to be used for the construction of a deep ecliptic catalogue, using UCAC3 as reference catalogue. We find that the average centering error for star-like objects is 0.012 pixel (2.2 mas), but for extended objects it is 0.037 pixel (6.9 mas). By comparing measurements with two different filters a strong chromatic aberration was detected, that was modeled and corrected. After that correction the differences between instrumental coordinates in both filters are (-7±11) mas in X and (-1±12) mas in Y and no systematic pattern is apparent. The differences between celestial coordinates obtained with the two filters are 15 mas in α cos(δ) and 26 mas in δ.

  4. The Low-mass Astrometric Binary LSR 1610-0040

    NASA Astrophysics Data System (ADS)

    Koren, Seth C.; Blake, Cullen H.; Dahn, Conard C.; Harris, Hugh C.

    2016-03-01

    Even though it was discovered more than a decade ago, LSR 1610-0040 remains an enigma. This object has a peculiar spectrum that exhibits some features typically found in L subdwarfs, and others common in the spectra of more massive M dwarf stars. It is also a binary system with a known astrometric orbital solution. Given the available data, it remains a challenge to reconcile the observed properties of the combined light of LSR 1610-0040AB with current theoretical models of low-mass stars and brown dwarfs. We present the results of a joint fit to both astrometric and radial velocity measurements of this unresolved, low-mass binary. We find that the photocentric orbit has a period P=633.0+/- 1.7 days, somewhat longer than previous results, eccentricity of e=0.42+/- 0.03, and we estimate that the semimajor axis of the orbit of the primary is {a}1≈ 0.32 {{AU}}, consistent with previous results. While a complete characterization of the system is limited by our small number of radial velocity measurements, we establish a likely primary mass range of 0.09-0.10 {M}⊙ from photometric and color-magnitude data. For a primary mass in this range, the secondary is constrained to be 0.06-0.075 {M}⊙ , making a negligible contribution to the total I-band luminosity. This effectively rules out the possibility of the secondary being a compact object such as an old, low-mass white dwarf. Based on our analysis, we predict a likely angular separation at apoapsis comparable to the resolution limits of current high-resolution imaging systems. Measuring the angular separation of the A and B components would finally enable a full, unambiguous solution for the masses of the components of this system.

  5. 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.

  6. 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.

  7. Astrometric investigations at the Vienna Observatory and astrometric plans for the 60 inch reflector of the L. Figl Observatory

    NASA Technical Reports Server (NTRS)

    Meurers, J.

    1971-01-01

    A short discussion of the astrometric instruments at the Vienna Observatory is given. The essential features of design and organization of the planned 60 inch telescope are described. Furthermore, several points of view concerning modern astrometry are discussed, especially the usefulness of comparing astrometric results based upon different instruments, for instance the comparison between mirrors and refractor based data. Some examples are given together with new immediate results. Lastly, as far as possible at this moment astrometric plans for the new telescope are formulated.

  8. Astrometric positioning and orbit determination of geostationary satellites

    NASA Astrophysics Data System (ADS)

    Montojo, F. J.; López Moratalla, T.; Abad, C.

    2011-03-01

    In the project titled “Astrometric Positioning of Geostationary Satellite” (PASAGE), carried out by the Real Instituto y Observatorio de la Armada (ROA), optical observation techniques were developed to allow satellites to be located in the geostationary ring with angular accuracies of up to a few tenths of an arcsec. These techniques do not necessarily require the use of large telescopes or especially dark areas, and furthermore, because optical observation is a passive method, they could be directly applicable to the detection and monitoring of passive objects such as space debris in the geostationary ring.By using single-station angular observations, geostationary satellite orbits with positional uncertainties below 350 m (2 sigma) were reconstructed using the Orbit Determination Tool Kit software, by Analytical Graphics, Inc. This software is used in collaboration with the Spanish Instituto Nacional de Técnica Aeroespacial.Orbit determination can be improved by taking into consideration the data from other stations, such as angular observations alone or together with ranging measurements to the satellite. Tests were carried out combining angular observations with the ranging measurements obtained from the Two-Way Satellite Time and Frequency Transfer technique that is used by ROA’s Time Section to carry out time transfer with other laboratories. Results show a reduction of the 2 sigma uncertainty to less than 100 m.

  9. A study of astrometric distortions due to "tree rings" in CCD sensors using LSST Photon Simulator

    NASA Astrophysics Data System (ADS)

    Beamer, B.; Nomerotski, A.; Tsybychev, D.

    2015-05-01

    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. Additionally, 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.

  10. Data reduction and astrometric calibration of a starshade test using real starlight

    NASA Astrophysics Data System (ADS)

    Jordan, Ian J. E.; Henze, Paul; Cash, Webster C.; Soummer, Remi; Regan, Michael W.; Westminster Astronomical Society, New Worlds

    2015-01-01

    Calibration of data obtained during 2011-2013 for a ground-based optically scaled starshade alignment sensing test is discussed. The equipment included a 3.7-cm starshade-occulter in front of a coelostat at separations of up to 90-metres from a small telescope. Various stellar and planetary sources were observed. Astrometric reduction of images was challenged by variable horizontal refraction and wavefront distortion during occultations and between images which introduced uncertainty in localizing the occulter. Guider software issues were an additional complication in the reduction process and are discussed. The changing conditions during each observing session necessitate careful tagging of different datasets for appropriate treatment in the reduction pipeline. The techniques for handling the data are described along with astrometric results.

  11. REVEALING COMPANIONS TO NEARBY STARS WITH ASTROMETRIC ACCELERATION

    SciTech Connect

    Tokovinin, Andrei; Hartung, Markus; Hayward, Thomas L.; Makarov, Valeri V. E-mail: mhartung@gemini.edu E-mail: valeri.makarov@usno.navy.mil

    2012-07-15

    A subset of 51 Hipparcos astrometric binaries among FG dwarfs within 67 pc has been surveyed with the Near-Infrared Coronagraphic Imager adaptive optics system at Gemini-S, directly resolving for the first time 17 subarcsecond companions and 7 wider ones. Using these data together with published speckle interferometry of 57 stars, we compare the statistics of resolved astrometric companions with those of a simulated binary population. The fraction of resolved companions is slightly lower than expected from binary statistics. About 10% of astrometric companions could be 'dark' (white dwarfs and close pairs of late M-dwarfs). To our surprise, several binaries are found with companions too wide to explain the acceleration. Re-analysis of selected intermediate astrometric data shows that some acceleration solutions in the original Hipparcos catalog are spurious.

  12. The comparison of the accuracy of asteroid orbit fitting with radar and astrometric observations. (Russian Title: Сравнение точности улучшения орбит астероидов по данным радарных и астрометрических наблюдений)

    NASA Astrophysics Data System (ADS)

    Baturin, A. P.

    2015-12-01

    The problem of asteroids' orbit fitting with their radar and astrometric observations has been considered. The problem has been solved in a standard way - by means of the weighted least-square fitting. The radar observations of both types (signal delays and Doppler) have been used. For several asteroids whose radar observations cover long time intervals the orbit fitting has been done with using both radar and astrometric observations. In all considered cases the astrometric observations covered the same time interval as the radar ones. The comparison of sizes of confidence regions of the obtained initial orbital parameters has been done.

  13. A Combined HIPPARCOS and Multichannel Astrometric Photometer Study of the Proposed Planetary System of Rho Coronae Borealis

    NASA Technical Reports Server (NTRS)

    Gatewood, George; Han, Inwoo; Black, David C.

    2001-01-01

    Hipparcos and Multichannel Astrometric Photometer (MAP) observations of rho Coronae Borealis independently display astrometric motion at the period of the proposed extrasolar planetary companion to the star. Individual least-squares fits to each astrometric data set yield independent estimates of the semimajor axis, inclination, and node angle that are in excellent agreement. A combined solution of the Hipparcos and MAP data yields an inclination of 0.5 deg, a node at 30.5 +/- 12.4, and a semimajor axis of 1.66 +/- 0.35 mas, indicating a companion mass of 0.14 +/- 0.05 solar masses over two orders of magnitude greater than the minimum mass for the companion as determined by radial velocity studies. This mass is approximately that of an M dwarf star, the companion cannot be a planetary object.

  14. Ground-based solar astrometric measurements during the PICARD mission

    NASA Astrophysics Data System (ADS)

    Irbah, A.; Meftah, M.; Corbard, T.; Ikhlef, R.; Morand, F.; Assus, P.; Fodil, M.; Lin, M.; Ducourt, E.; Lesueur, P.; Poiet, G.; Renaud, C.; Rouze, M.

    2011-11-01

    PICARD is a space mission developed mainly to study the geometry of the Sun. The satellite was launched in June 2010. The PICARD mission has a ground program which is based at the Calern Observatory (Observatoire de la C^ote d'Azur). It will allow recording simultaneous solar images from ground. Astrometric observations of the Sun using ground-based telescopes need however an accurate modelling of optical e®ects induced by atmospheric turbulence. Previous works have revealed a dependence of the Sun radius measurements with the observation conditions (Fried's parameter, atmospheric correlation time(s) ...). The ground instruments consist mainly in SODISM II, replica of the PICARD space instrument and MISOLFA, a generalized daytime seeing monitor. They are complemented by standard sun-photometers and a pyranometer for estimating a global sky quality index. MISOLFA is founded on the observation of Angle-of-Arrival (AA) °uctuations and allows us to analyze atmospheric turbulence optical e®ects on measurements performed by SODISM II. It gives estimations of the coherence parameters characterizing wave-fronts degraded by the atmospheric turbulence (Fried's parameter, size of the isoplanatic patch, the spatial coherence outer scale and atmospheric correlation times). This paper presents an overview of the ground based instruments of PICARD and some results obtained from observations performed at Calern observatory in 2011.

  15. 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.

  16. VLBI FOR GRAVITY PROBE B. IV. A NEW ASTROMETRIC ANALYSIS TECHNIQUE AND A COMPARISON WITH RESULTS FROM OTHER TECHNIQUES

    SciTech Connect

    Lebach, D. E.; Ratner, M. I.; Shapiro, I. I.; Bartel, N.; Bietenholz, M. F.; Lederman, J. I.; Ransom, R. R.; Campbell, R. M.; Gordon, D.

    2012-07-01

    When very long baseline interferometry (VLBI) observations are used to determine the position or motion of a radio source relative to reference sources nearby on the sky, the astrometric information is usually obtained via (1) phase-referenced maps or (2) parametric model fits to measured fringe phases or multiband delays. In this paper, we describe a 'merged' analysis technique which combines some of the most important advantages of these other two approaches. In particular, our merged technique combines the superior model-correction capabilities of parametric model fits with the ability of phase-referenced maps to yield astrometric measurements of sources that are too weak to be used in parametric model fits. We compare the results from this merged technique with the results from phase-referenced maps and from parametric model fits in the analysis of astrometric VLBI observations of the radio-bright star IM Pegasi (HR 8703) and the radio source B2252+172 nearby on the sky. In these studies we use central-core components of radio sources 3C 454.3 and B2250+194 as our positional references. We obtain astrometric results for IM Peg with our merged technique even when the source is too weak to be used in parametric model fits, and we find that our merged technique yields astrometric results superior to the phase-referenced mapping technique. We used our merged technique to estimate the proper motion and other astrometric parameters of IM Peg in support of the NASA/Stanford Gravity Probe B mission.

  17. Astrometric detection of gravitational effects of quantum vacuum

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Gai, Mario; Hajdukovic, Dragan

    2015-08-01

    In a series of recent papers it was suggested that the pairs of virtual particles-antiparticles composing the Quantum Vacuum (QV) can behave like gravitational dipoles with both attractive and repulsive interaction. If verified, this hypothesis would give raise to a series of gravitational effects at different scale length not yet considered in current gravity theories, and it may support galactic and cosmological models alternative to those involving Dark Matter and Dark Energy.Within the boundaries of the Solar System, the most promising targets for testing the gravitational QV conjecture are the binary trans-neptunian objects (TNOs). The gravitational action of the QV, in fact, would manifest itself as an external force inducing an anomalous precession, i.e. an excess shift of the longitude of the pericenter in the orbit of the TNO satellite which, e.g., for the UX25 candidate and under reasonable working hypothesis, was estimated to be about 0.23 arcsec per orbit.In this work we analyze in some detail the feasibility of testing the gravitational QV hypothesis estimating the above effect with ground-based and spaceborne astrometric observations. Several observing scenarios are explored here, including those using conventional and adaptive optics telescopes from ground, some spaceborne telescopes, and by exploring a list of possible candidates.

  18. 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

  19. Faster, Better, Cheaper: News on Seeking Gaia's Astrometric Solution with AGIS

    NASA Astrophysics Data System (ADS)

    Lammers, U.; Lindegren, L.; Bombrun, A.; O'Mullane, W.; Hobbs, D.

    2010-12-01

    Gaia is ESA’s ambitious space astrometry mission with a foreseen launch date in early 2012. Its main objective is to perform a stellar census of the 1000 Million brightest objects in our galaxy (completeness to V=20 mag) from which an astrometric catalog of micro-arcsec level accuracy will be constructed. A key element in this endeavor is the Astrometric Global Iterative Solution (AGIS) - the mathematical and numerical framework for combining the ≍80 available observations per star obtained during Gaia’s 5yr lifetime into a single global astrometric solution. At last year’s ADASS XVIII we presented (O4.1) in detail the fundamental working principles of AGIS, its development status, and selected results obtained by running the system on processing hardware at ESAC, Madrid with large-scale simulated data sets. We present here the latest developments around AGIS highlighting in particular a much improved algebraic solving method that has recently been implemented. This Conjugate Gradient scheme improves the convergence behavior in significant ways and leads to a solution of much higher scientific quality. We also report on a new collaboration aiming at processing the data from the future small Japanese astrometry mission Nano-Jasmine with AGIS.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Space Station Astrometric Telescope tracking for the detection of planetary systems

    NASA Technical Reports Server (NTRS)

    Mascy, Alfred C.; Sobeck, Charlie K.; Jorgensen, Helen

    1988-01-01

    The paper presents a comprehensive star observation and tracking strategy, which uses a computer simulation of the Space Station orbital mechanics, system constraints, and Astrometric Telescope Facility (ATF) tracking maneuvers over a long observational period. This approach may be used to obtain data which may assist in the preliminary systems definition of the ATF. Results are given for an analysis which uses a restricted target set in order to demonstrate the disproportionate effect of the galactic-photon-rate index on the observation times for each star.

  6. Multichannel astrometric photometer and photographic astrometric studies in the regions of Lalande 21185, BD 56 deg 2966, and HR 4784

    NASA Technical Reports Server (NTRS)

    Gatewood, George; Stein, John; De Jonge, Joost K.; Persinger, Timothy; Reiland, Thomas; Stephenson, Bruce

    1992-01-01

    The parallaxes of stars determined from the multichannel astrometric photometer (MAP) in the regions of Lalande 21185, BD 56 deg 2966, and from photographic plates in the region of BD 56 deg 2966 and the region of HR 4783 and HR 4784 are reported. The parallax determined for Lalande 21185, 395.1 +/-1.0 mas yields what is believed to be the most precise distance modulus (-2.984 +/-0.0055) known for a star other than the sun. The absolute magnitude of Lalande 21185 is found to be 10.474 +/-0.008. No significant evidence of unseen companions is detected. The photographic study of BD 56 deg 2966 indicates that the long-term (65 yr) motion of the star is linear to better than +/-16 mas, while the MAP study indicates that the motion is linear to better than +/-2.5 mas over a period of some 5 yr. The photographically determined parallaxes are compared with those observed with the MAP. The photographically calculated standard errors are found to be in agreement with the standard error of the differences.

  7. 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.

  8. 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 (.

  9. 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.

  10. 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.

  11. Ground Based Astrometric Search for Substellar Companions in Stellar Multiple Systems, The Case of the Exoplanet Host System HD 19994

    NASA Astrophysics Data System (ADS)

    Röll, T.; Seifahrt, A.; Neuhäuser, R.; Köhler, R.

    2010-12-01

    Due to the unknown inclination angle, radial velocity (RV) measurements only provide the minimum mass of companions. In combination with transit observations one can derive the true mass, but a transit is only observable for nearly edge-on systems. For all other systems, astrometry is the only method to get the true mass of an orbiting companion by measuring the reflex motion of the host star. In our ongoing astrometric search program we observe stellar multiple systems within a distance of 100 parsec in order to confirm RV exoplanet candidates and to search for unknown substellar companions. Here we present preliminary results of one of our targets, the binary HD 19994, which is known to harbour a RV planet candidate around the A component. From our astrometric observations over the last years, it seems that a high mass brown dwarf is orbiting the low-mass B component. Analysis of our data with speckle interferometry confirms the existence of an additional body.

  12. Little Stars Don't Like Big Planets: An Astrometric Search for Super-Jupiters Around Red Dwarfs

    NASA Astrophysics Data System (ADS)

    Lurie, John C.; Henry, T. J.; Jao, W.; Koerner, D. W.; Riedel, A. R.; Subasavage, J.; RECONS

    2013-01-01

    The astrometric detection and characterization of extrasolar planets presents considerable technical challenges, but also promises to greatly enhance our understanding of these systems. Nearly all currently confirmed exoplanets have been discovered using transit or radial velocity techniques. The former is geometrically biased towards planets with small orbits, while the latter is biased towards massive planets with short periods that exert large gravitational accelerations on their host stars. Astrometric techniques are limited by the minimum detectable perturbation of a star's position due to a planet, but allow for the determination of orbit inclination and an accurate planetary mass. Here we present astrometric solutions for five nearby stars with known planets: four M dwarfs (GJ 317, GJ 581, GJ 849, and GJ 1214) and one K dwarf (BD -10 3166). Observations have baselines of three to thirteen years, and were made using the 0.9 m telescope at CTIO as part of the RECONS long-term astrometry program. We provide improved parallaxes for the stars and find that there are no planets of several Jupiter masses or brown dwarfs orbiting these stars with periods up to twice the length of the astrometric coverage. In the broader context, these results are consistent with the paucity of super-Jupiter and brown dwarf companions we find among the roughly 200 red dwarfs searched in our astrometric program. This effort has been supported by the National Science Foundation via grant AST 09-08402 and the long-term cooperative efforts of the National Optical Astronomy Observatories and the members of the SMARTS Consortium.

  13. 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.

  14. Astrometric Correction for WFC3/UVIS Lithographic-Mask Pattern

    NASA Astrophysics Data System (ADS)

    Kozhurina-Platais, V.; Hammer, D.; Dencheva, N.; Hack, W.

    2013-07-01

    Observations of the central field in Cen taken with large dither patterns and over a large range of HST roll-angles exposed through F606W UVIS filter hav e been used to examine the lithographic-mask pattern imprinted on the WFC3/UVIS detec tor during the manufacturing process. This detector defect introduces fine-scale astrome tric errors at the level of about 0.2 pixel with a complicated spatial structure across the WFC3/ UVIS CCD chips. The fine-scale solution was utilized to construct a 2-D look-up table for co rrection of the WFC3/UVIS lithographic-mask pattern. The astrometric errors due to th is detector defect have been cor- rected down to the ~ 0.05 pixel level. The derived 2-D look-up table can be interpol ated at any point in the WFC3/UVIS image by ST software DrizzlePac / AstroDrizzle. The main results of these calibrations are: 1) new polynomial coefficien ts of geometric distortion for 14 calibrated UVIS filters in the form of Instrument Distortion Co rrection Table (IDCTAB file) were improved to account for the lithographic-mask pattern i n the WFC3/UVIS detector; 2) new derived look-up table in the form of a D2IMFILE, which sig nificantly improves (30-60%) the fine-scale structure in the WFC3/UVIS geometric distorti on; 3) geometric distortion cou- pled with the D2IMFILE and new improved IDCTAB can now be succ essfully corrected to the precision level of ~ 0.05 pixel (2 mas) for the UVIS detector.

  15. KLENOT Project 2002-2008 contribution to NEO astrometric follow-up

    NASA Astrophysics Data System (ADS)

    Ticha, J.; Tichy, M.; Kocer, M.; Honkova, M.

    2009-01-01

    Near-Earth object (NEO) research plays an increasingly important role not only in solar system science but also in protecting our planetary environment as well as human society from the asteroid and comet hazard. Consequently, interest in detecting, tracking, cataloguing, and the physical characterizing of these bodies has steadily grown. The discovery rate of current NEO surveys reflects progressive improvement in a number of technical areas. An integral part of NEO discovery is astrometric follow-up crucial for precise orbit computation and for the reasonable judging of future close encounters with the Earth, including possible impact solutions. The KLENOT Project of the Klet Observatory (South Bohemia, Czech Republic) is aimed especially at the confirmation, early follow-up, long-arc follow-up, and recovery of near-Earth objects. It ranks among the world’s most prolific professional NEO follow-up programs. The 1.06 m KLENOT telescope, put into regular operation in 2002, is the largest telescope in Europe used exclusively for observations of minor planets and comets, and full observing time is dedicated to the KLENOT team. In this paper, we present the equipment, technology, software, observing strategy, and results of the KLENOT Project obtained during its first phase from March 2002 to September 2008. The results consist of thousands of precise astrometric measurements of NEOs and also three newly discovered near-Earth asteroids. Finally, we also discuss future plans reflecting also the role of astrometric follow-up in connection with the modus operandi of the next generation surveys.

  16. Design of Astrometric Mission (JASMINE) by Applying Model Driven System Engineering

    NASA Astrophysics Data System (ADS)

    Yamada, Y.; Miyashita, H.; Nakamura, H.; Suenaga, K.; Kamiyoshi, S.; Tsuiki, A.

    2010-12-01

    We are planning space astrometric satellite mission named JASMINE. The target accuracy of parallaxes in JASMINE observation is 10 micro arc second, which corresponds to 1 nm scale on the focal plane. It is very hard to measure the 1 nm scale deformation of focal plane. Eventually, we need to add the deformation to the observation equations when estimating stellar astrometric parameters, which requires considering many factors such as instrument models and observation data analysis. In this situation, because the observation equations become more complex, we may reduce the stability of the hardware, nevertheless, we require more samplings due to the lack of rigidity of each estimation. This mission imposes a number of trades-offs in the engineering choices and then decide the optimal design from a number of candidates. In order to efficiently support such decisions, we apply Model Driven Systems Engineering (MDSE), which improves the efficiency of the engineering by revealing and formalizing requirements, specifications, and designs to find a good balance among various trade-offs.

  17. 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.

  18. 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.

  19. 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

  20. The Astrometric Imaging Telescope: Detection of planetary systems with imaging and astrometry

    NASA Technical Reports Server (NTRS)

    Pravdo, Steven H.; Terrile, Richard J.; Ftaclas, Christ; Gatewood, George D.; Levy, Eugene H.

    1994-01-01

    The Astrometric Imaging Telescope (AIT) is a proposed spaceborne observatory whose primary goal is the detecton and study of extra-solar planetary systems. It contains two instruments that use complementary techniques to address the goal. The first instrument, the Coronagraphic Imager, takes direct images of nearby stars and Jupiter-size planets. It uses a telescope with scattering-compensated optics and a high-efficiency coronagraph to separate reflected planet light from the central star light. Planet detections take hours; confirmations occur in months. With a program duration of about 2 years, about 50 stars are observed. The second instrument, the Astrometric Photometer, shares the same telescope and focal plane. It uses a Ronchi ruling that is translated across the focal plane to simultaneously measure the positions of each target star and about 25 reference stars with sufficient accuracy to detect Uranus-mass planets around hundreds of stars. Enough stars of several spectral types are observed to obtain a statistically significant measurement of the prevalence of planetary systems. This observing program takes about 10 years to complete. The combination of both instruments in a single telescope system results from a number of innovative solutions that are described in this paper.

  1. A spectro-astrometric measurement of Brackett gamma emission in Herbig Ae/Be stars

    NASA Astrophysics Data System (ADS)

    Rice, T. S.; Brittain, S.; Stevans, M.; Kurgatt, C.

    2012-07-01

    In T Tauri stars, the Brackett γ line strength is a reliable indicator of accretion luminosity. Among intermediate mass young stars, Herbig Ae stars also show this correlation, but in Herbig Be stars the Brγ line flux significantly overpredicts accretion luminosity. This Brγ excess in Herbig Be stars is thought to arise from a spatially extended outflow. Using commissioning data from the LUCIFER spectrograph on the 8.4-meter Large Binocular Telescope (LBT), we present a spectro-astrometric study of two Herbig Ae/Be stars, the HAe star MWC480 and the HBe star HD 259431. In both stars, an extended Brγ source can be ruled out down to 0.001 arcsec at the 1σ level. Using currently accepted parallax values of 137 ± 25 pc and 173 ± 37 pc, this implies a lack of spatially extended structure beyond 0.131 ± 0.024 AU for MWC 480 and 0.166 ± 0.036 AU for HD 259431. Spectro-astrometric precision depends on both the signal-to-noise and the angular resolution of an observation. To confidently rule out an extended Brγ source as the origin of the Brγ excess, either a repeat of these observations with the LBT's AO enabled, or an 81× increase in observing time, is needed.

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

    DOE PAGESBeta

    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

  3. 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.

  4. 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…

  5. Global Sphere Reconstruction in the Astrometric Verification Unit

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    The Gaia space satellite will perform absolute astrometry, aiming at the definition of a global astrometric reference frame at visual wavelengths. Within this reference system, it will be very difficult to identify possible errors in the measurements or in the data reduction process that brings about the definition of the final catalogue. The Gaia Data Processing and Analysis Consortium (DPAC) has established an Astrometric Verification Unit (AVU) to verify crucial steps in the baseline data processing chain and report on any significant difference. This process is essential in order to guarantee a high quality catalogue to the larger scientific community. We describe here the global sphere reconstruction (GSR) component of AVU hosted by the Italian data processing centre at Torino (DPCT).

  6. 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.

  7. 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.

  8. FAME - The Full-sky Astrometric Mapping Explorer

    NASA Astrophysics Data System (ADS)

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

    1998-12-01

    The Full-sky Astrometric Mapping Explorer (FAME) is a small satellite designed to perform an all-sky, astrometric survey with unprecedented accuracy. FAME will create an accurate 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. FAME will map our quadrant of the galaxy out to 2 kpc from the Sun providing the information needed to calibrate the standard candles that define the extragalactic distance scale, calibrate the absolute luminosities of stars of all spectral types for studies of stellar structure and evolution, and detect orbital motions caused by brown dwarfs and giant planets. FAME will not only improve on the accuracies of star positions determined by Hipparcos but also expand the volume of space for which accurate positions are known by a factor of 8,000. FAME is a joint development effort of the US Naval Observatory, the Smithsonian Astrophysical Observatory, the Infrared Processing and Analysis Center, Lockheed Martin Missiles and Space, the Naval Research Laboratory, and Omitron Incorporated.

  9. 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.

  10. The multichannel astrometric photometer and atmospheric limitations in the measurement of relative positions

    NASA Technical Reports Server (NTRS)

    Gatewood, George D.

    1987-01-01

    The operational Multichannel Astrometric Photometer (MAP) now in use in the Allegheny Observatory astrometric program is the culmination of a decade of design and development effort. A detailed description of the system and its related software is followed by analysis of data acquired in four stellar regions. The study indicates an accuracy (in the sense of conformity to the best model), per night, for stars of the eighth magnitude or brighter, of 0.003 arcsec or better. These data points each have approximately twice the precision of the annual normal points obtained in our photographic program. Accuracy is shown to depend on: (1) the photon-count rate of the target star (it follows that the number of photons from the reference frame is also in important factor), (2) the duration of the observation, (3) the angular size of the reference frame, and (4) the quality of the astronomical seeing. Since (4) and, to a lesser extent, (1) involve the atmospheric characteristics at the time of observation, the probable performance at more favorable sites is discussed briefly.

  11. 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.

  12. 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.

  13. 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.

  14. Mass Determination of the Nearby White Dwarf Stein 2051B through Astrometric Microlensing using HST

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash C.; Anderson, Jay; Casertano, Stefano; Bond, Howard E.; Nelan, Edmund P.; Calamida, Annalisa; Kains, Noe

    2016-06-01

    The nearby white dwarf (WD) Stein 2051B is one of the coolest and oldest known WDs. It passed very close to a 19.5-mag background star in 2014 March, with an impact parameter of only ~0.1 arcsec. This afforded us the opportunity to measure the mass of this WD through the deflection of the position of the background star -- the first application of this method to measure a stellar mass. We obtained HST/WFC3 images of the field at 7 epochs during the close passage to measure the deflection of the faint star. Since the background star is fainter than the WD by a factor of 400, it was a challenge to measure the astrometric deflection, but the deflection has been clearly measured. The gravitational deflection angle depends only on the distances and relative positions of the stars, and on the mass of the WD. Since the parallax distance and the positions of the WD could be determined precisely from the HST observations, the astrometric measurement offers a unique and direct method to measure the mass of the WD. One key astrophysical prediction for WDs is the existence of a mass-radius relation, which depends primarily on the core composition of the WD. Since the radius of Stein 2051B is known (from its distance, luminosity, and effective temperature), our mass measurement provides an important addition to the very small number of WDs with well-determined radii and masses.

  15. 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.

  16. Performance analysis of the multichannel astrometric photometer

    NASA Technical Reports Server (NTRS)

    Huang, Chunsheng; Lawrence, George N.; Levy, Eugene H.; Mcmillan, Robert S.

    1987-01-01

    It has been proposed that extrasolar planetary systems may be observed if perturbations in star position due to the orbit of Jupiter-type planets could be detected. To see this motion, high accuracy measurements of 0.01 milliarcsecond are required over a relatively large field of view. Techniques using a moving Ronchi grating have been proposed for this application and have been successful in ground-based lower resolution tests. The method may have application to other precision angular measurement problems. This paper explores the theoretical description of the method, considers certain of the error sources, and presents a preliminary calculation of the performance which may be achieved.

  17. 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).

  18. Coronal Hole Influence on the Observed Structure of Interplanetary CMEs

    NASA Astrophysics Data System (ADS)

    Mäkelä, P.; Gopalswamy, N.; Xie, H.; Mohamed, A. A.; Akiyama, S.; Yashiro, S.

    2013-05-01

    We report on the coronal hole (CH) influence on the 54 magnetic cloud (MC) and non-MC associated coronal mass ejections (CMEs) selected for studies during the Coordinated Data Analysis Workshops (CDAWs) focusing on the question if all CMEs are flux ropes. All selected CMEs originated from source regions located between longitudes 15E - 15W. Xie, Gopalswamy, and St. Cyr (2013, Solar Phys., doi:10.1007/s11207-012-0209-0) found that these MC and non-MC associated CMEs are on average deflected towards and away from the Sun-Earth line, respectively. We used a CH influence parameter (CHIP) that depends on the CH area, average magnetic field strength, and distance from the CME source region to describe the influence of all on-disk CHs on the erupting CME. We found that for CHIP values larger than 2.6 G the MC and non-MC events separate into two distinct groups where MCs (non-MCs) are deflected towards (away) from the disk center. Division into two groups was also observed when the distance to the nearest CH was less than 3.2×105 km. At CHIP values less than 2.6 G or at distances of the nearest CH larger than 3.2×105 km the deflection distributions of the MC and non-MCs started to overlap, indicating diminishing CH influence. These results give support to the idea that all CMEs are flux ropes, but those observed to be non-MCs at 1 AU could be deflected away from the Sun-Earth line by nearby CHs, making their flux rope structure unobservable at 1 AU.

  19. 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.

  20. 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

  1. 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

  2. ASTROMETRIC JITTER OF THE SUN AS A STAR

    SciTech Connect

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

    2010-07-10

    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 {mu}AU and 0.39 {mu}AU in the equatorial and the axial dimensions, respectively. The overall dispersion is strongly correlated with solar cycle, reaching 0.91 {mu}AU at maximum activity in 2000. The largest short-term deviations from the running average (up to 2.6 {mu}AU) 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 {mu}AU 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.

  3. 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.

  4. The global sphere reconstruction for the Gaia mission in the Astrometric Verification Unit

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Abbas, Ummi; Bandieramonte, Marilena; Becciani, Ugo; Bianchi, Luca; Bucciarelli, Beatrice; Busonero, Deborah; Lattanzi, Mario G.; Messineo, Rosario

    2012-09-01

    The core task of the Gaia mission is the solution of the Global Astrometric Sphere, which is providing the materialization of the astrometric reference frame for the catalog that will be the main outcome of the mission. Given the absolute character of the measurements, the Gaia Data Processing and Analysis Consortium (DPAC) has decided to replicate a dedicated version of this task, together with two other ones selected for their mission criticality, in an Astrometric Verification Unit (AVU). This task, named Global Sphere Reconstruction (GSR), focusses on the importance of having an implementation of the astrometric sphere solution from a well-defined subset of objects, based on an independent astrometric model as well as on a different solution algorithm. We analyze here these two aspects in the context of the GSR implementation at the Data Processing Center of Torino (DPCT) and the solution to implement the most computationally intensive part of the pipeline as a High-Performance Computing module.

  5. 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.

  6. Observations of swell influence on ocean surface roughness

    NASA Astrophysics Data System (ADS)

    Hwang, Paul A.

    2008-12-01

    Field measurements of the ocean surface wave spectrum focusing on the slope-contributing components are used to construct a spectral model of the ocean surface roughness. The spectral parameterization is established with the observed empirical power law relation between the dimensionless wave spectral density and wind speed. The power law parameters (proportionality coefficient and exponent) are shown to be modified by swell. Discussions are presented on the swell effects of spectral properties, including their wind speed dependence and swell modification of roughness components characterizing Bragg resonance and surface tilting in radar application. Several notable results include the following: (1) With increasing swell intensity, the spectral density increases in the long-wave portion and decreases in the short-wave portion of the intermediate-scale waves. (2) There is a nodal point with respect to swell impact in the wave number dependence of the coefficient and exponent of the spectral parameterization function in the vicinity of wave number near 3 rad/m, suggesting that waves about a couple of meters long are insensitive to swell influence. (3) Spectral density in the decimeter length scale becomes less sensitive to wind speed variation as swell intensity increases. (4) Increasing swell influence shifts wave breaking toward shorter and broader scales.

  7. Full-sky Astrometric Mapping Explorer (FAME) Rescope Activities

    NASA Astrophysics Data System (ADS)

    Johnston, K.; Dorland, B.; Gaume, R.; Hajian, A.; Harris, F.; Harris, H.; Hennessy, G.; Kaplan, G.; Levine, S.; Monet, D.; Munn, J.; Murison, M.; Pier, J.; Urban, S.; Zacharias, N.; Seidelmann, P. K.; Lee, J.; Makarov, V.; Olling, R.; Codella, T.; Geary, J.; Latham, D.; Phillips, J.; Johnson, M.; Vassar, R.; Horner, S.

    2001-12-01

    The Full-sky Astrometric Mapping Explorer (FAME) will measure the positions, proper motions, parallaxes, and photometry for 40 million stars between 5 and 15 magnitude, with accuracies of 50 microarcseconds at 9th magnitude and degraded accuracy for fainter stars as faint as 15 magnitude. The mission is planned for an October 2004 launch and a five-year duration. The FAME mission has progressed in its development. Due to budget, weight, and power limitations, the FAME architecture has been rescoped so that it will satisfy the budget limitations and retain the basic science objectives of the mission. The new design and characteristics, the status of developments and tests, and the scientific baseline and minimum mission requirements are presented.

  8. Full-sky Astrometric Mapping Explorer (FAME) CCD centroiding experiment

    NASA Astrophysics Data System (ADS)

    Triebes, Kenneth J.; Gilliam, Larry; Hilby, Timothy; Horner, Scott D.; Perkins, Patrick; Vassar, Richard H.; Harris, Frederick H.; Monet, David G.

    2000-07-01

    FAME is a MIDEX astrometry mission designed to map the position of 40,000,000 stars to an accuracy of 50 micro-arc seconds. Optimized between mission requirements, size, weight, and cost, the FAME instrument consists of a 0.6 X 0.5 m2 aperture whose point spread function central peak is linearly sampled by two pixels. To achieve its astrometric mapping mission requirements, this instrument must achieve a single look centroiding accuracy on a visual magnitude 9.0 (or brighter) star of < 0.003 pixels while operating the focal plane in a time domain integration, TDI, mode. As this performance requirement represents a significant improvement over the current state of the art of 0.02 to 0.01 pixel resolution, a risk reduction experiment was conducted to determine our centroiding ability using a flight traceable CCD operated in TDI mode.

  9. An astrometric facility for planetary detection on the Space Station

    NASA Astrophysics Data System (ADS)

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

    1987-03-01

    The preliminary system definition study for an Astrometric Telescope Facility (ATF) designed for the Space Station IOC is discussed, and a strawman system is designed which is found to meet the requirements for extrasolar planetary systems search and study. The strawman facility design, with a prime-focus 1.25-m aperture telescope and an f ratio of 13, was selected to minimize random and systematic errors. A basic operations approach is identified, including the approach to launch, initial on-orbit assembly and checkout, normal operations, and the response to anomolous conditions or failures. The preliminary system is designed to be fail-safe and single-fault tolerant. Mission analysis indicates that the basic viewing required for planetary detection can be accomplished in about 2/3 of the total viewing time.

  10. 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

    The preliminary system definition study for an Astrometric Telescope Facility (ATF) designed for the Space Station IOC is discussed, and a strawman system is designed which is found to meet the requirements for extrasolar planetary systems search and study. The strawman facility design, with a prime-focus 1.25-m aperture telescope and an f ratio of 13, was selected to minimize random and systematic errors. A basic operations approach is identified, including the approach to launch, initial on-orbit assembly and checkout, normal operations, and the response to anomolous conditions or failures. The preliminary system is designed to be fail-safe and single-fault tolerant. Mission analysis indicates that the basic viewing required for planetary detection can be accomplished in about 2/3 of the total viewing time.

  11. Analysis of astrometric catalogues with vector spherical harmonics

    NASA Astrophysics Data System (ADS)

    Mignard, F.; Klioner, S.

    2012-11-01

    Aims: We compare stellar catalogues with position and proper motion components using a decomposition on a set of orthogonal vector spherical harmonics. We aim to show the theoretical and practical advantages of this technique as a result of invariance properties and the independence of the decomposition from a prior model. Methods: We describe the mathematical principles used to perform the spectral decomposition, evaluate the level of significance of the multipolar components, and examine the transformation properties under space rotation. Results: The principles are illustrated with a characterisation of systematic effects in the FK5 catalogue compared to Hipparcos and with an application to extraction of the rotation and dipole acceleration in the astrometric solution of QSOs expected from Gaia.

  12. Full-sky Astrometric Mapping Explorer (FAME): Instrument Status

    NASA Astrophysics Data System (ADS)

    Horner, S.; Aamodt, E.; Ambrose, J.; Baraze, R.; Barrett, S.; Dineen, P.; Garabedian, P.; Gilliam, L.; Huff, L.; Lanham, L.; Mason, D.; Nordt, A.; Perkins, P.; Read, D.; Seidel, D.; Sokolsky, L.; Van Bezooijen, R.; Vassar, R.; Harris, F.; Monet, D.

    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 instrument design, integration, and testing is the responsibility of the Lockheed Martin Advanced Technology Center in Palo Alto. Here we present the updated instrument design and discuss some of the trade studies that have been completed or are in progress. CCD tests are being made to investigate (1) the use of start-stop technique for bright stars with the time delay integration (TDI), (2) techniques for fitting point spread functions under conditons of noise and smearing, (3) the use of charge injection preceding stars to mitigate the effects of traps, and (4) the effects of radiation over the lifetime of the mission. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Automated Astrometric and Photometric TASS Data Reduction Techniques

    NASA Astrophysics Data System (ADS)

    Gombert, G.

    1997-05-01

    Since the fall of 1996 I have operated TASS Camera No. 1 in Dayton, Ohio, collecting data every clear night and also developing data analysis techniques to make automated astrometric and photometric measurements. I have often had the opportunity to compare results and refine my measurement techniques through frequent e-mail with Michael Richmond at Princeton University and Arne Henden at the U.S. Naval Observatory. Henden has contributed to the analysis by making measurements of several fields from data he has collected at USNO, to serve as a reference for measurements taken by various TASS cameras. To compare results obtained at various TASS camera sites two specific fields were chosen for study: Field A: RA = 12:30 - 12:45 Dec = 0 degrees Field B: RA = 08:45 - 09:00 Dec = 0 degrees Field "A" is sparse at high galactic latitude; Field "B" is at a fairly low galactic latitude, is more crowded, much more of a challenge for automated data reduction methods. To analyze the data from the Dayton TASS camera I used Emanual Burton's "SExtracotr" (or Source- Extractor) program to generate catalogs of detected objects. Burton, a PhD student at the Paris Observatory, developed Source-Extractor as a part of his thesis. Source-Extractor has been used reduce data from several astronomical survey projects, including data taken with the Hubble Space Telescope. (See "Deep Optical Galaxy Counts," ApJ, 20 August, 1995; "Lensing by Distant Clusters," ApJ, 20 December, 1995 My paper will focus will on the calibration method's used to make precise astrometric and photometric measurements from TASS images. Also, a comparison of the results achieved using the above technique with results obtained by Richmond and Henden using different methods to generate catalogs of objects from TASS images for the above mentioned "A" and "B" fields will be discussed.

  17. Quasars can be used to verify the parallax zero-point of the Tycho-Gaia Astrometric Solution

    NASA Astrophysics Data System (ADS)

    Michalik, Daniel; Lindegren, Lennart

    2016-02-01

    Context. The Gaia project will determine positions, proper motions, and parallaxes for more than one billion stars in our Galaxy. It is known that Gaia's two telescopes are affected by a small but significant variation of the basic angle between them. Unless this variation is taken into account during data processing, e.g. using on-board metrology, it causes systematic errors in the astrometric parameters, in particular a shift in the parallax zero-point. Previously, we suggested an early reduction of Gaia data for the subset of Tycho-2 stars (Tycho-Gaia Astrometric Solution; TGAS). Aims: We investigate whether quasars can be used to independently verify the parallax zero-point in early data reductions. This is not trivially possible as the observation interval is too short to disentangle parallax and proper motion for the quasar subset. Methods: We repeat TGAS simulations but additionally include simulated Gaia observations of quasars from ground-based surveys. All observations are simulated with basic angle variations. To obtain a full astrometric solution for the quasars in TGAS we explore the use of prior information for their proper motions. Results: It is possible to determine the parallax zero-point for the quasars with a few μas uncertainty, and it agrees to a similar precision with the zero-point for the Tycho-2 stars. The proposed strategy is robust even for quasars exhibiting significant spurious proper motion due to a variable source structure, or when the quasar subset is contaminated with stars misidentified as quasars. Conclusions: Using prior information about quasar proper motions we could provide an independent verification of the parallax zero-point in early solutions based on less than one year of Gaia data.

  18. Astrometric planet search around southern ultracool dwarfs. I. First results, including parallaxes of 20 M8-L2 dwarfs

    NASA Astrophysics Data System (ADS)

    Sahlmann, J.; Lazorenko, P. F.; Ségransan, D.; Martín, E. L.; Mayor, M.; Queloz, D.; Udry, S.

    2014-05-01

    Context. Extrasolar-planet searches that target very low-mass stars and brown dwarfs are hampered by intrinsic or instrumental limitations. Time series of astrometric measurements with precisions better than one milli-arcsecond can yield new evidence on the planet occurrence around these objects. Aims: We present first results of an astrometric search for planets around 20 nearby dwarf stars with spectral types M8-L2. Methods: Over a time-span of two years, we obtained I-band images of the target fields with the FORS2 camera at the Very Large Telescope. Using background stars as references, we monitored the targets' astrometric trajectories, which allowed us to measure parallax and proper motions, set limits on the presence of planets, and to discover the orbital motions of two binary systems. Results: We determined trigonometric parallaxes with an average accuracy of 0.09 mas (≃0.2%), which resulted in a reference sample for the study of ultracool dwarfs at the M/L transition, whose members are located at distances of 9.5-40 pc. This sample contains two newly discovered tight binaries (DE0630-18 and DE0823-49) and one previously known wide binary (DE1520-44). Only one target shows I-band variability >5 mmag rms. We derived planet exclusion limits that set an upper limit of 9% on the occurrence of giant planets with masses ≳5 MJ in intermediate-separation (0.01-0.8 AU) orbits around M8-L2 dwarfs. Conclusions: We demonstrate that astrometric observations with an accuracy of 120 μas over two years are feasible from the ground and can be used for a planet-search survey. The detection of two tight very low-mass binaries shows that our search strategy is efficient and may lead to the detection of planetary-mass companions through follow-up observations. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme IDs 086.C-0680, 087.C-0567, 088.C-0679, and 089.C-0397.Figures 5-7 and Appendices are available in electronic form

  19. Improving distance estimates to nearby bright stars: Combining astrometric data from Hipparcos, Nano-JASMINE and Gaia

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    Starting in 2013, Gaia will deliver highly accurate astrometric data, which eventually will supersede most other stellar catalogues in accuracy and completeness. It is, however, limited to observations from magnitude 6 to 20 and will therefore not include the brightest stars. Nano-JASMINE, an ultrasmall Japanese astrometry satellite, will observe these bright stars, but with much lower accuracy. Hence, the Hipparcos catalogue from 1997 will likely remain the main source of accurate distances to bright nearby stars. We are investigating how this might be improved by optimally combining data from all three missions through a joint astrometric solution. This would take advantage of the unique features of each mission: the historic bright-star measurements of Hipparcos, the updated bright-star observations of Nano-JASMINE, and the very accurate reference frame of Gaia. The long temporal baseline between the missions provides additional benefits for the determination of proper motions and binary detection, which indirectly improve the parallax determination further. We present a quantitative analysis of the expected gains based on simulated data for all three missions.

  20. 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.

  1. 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.

  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. Astrometric Masses of 21 Asteroids, and an Integrated Asteroid Ephemeris

    NASA Astrophysics Data System (ADS)

    Baer, James J.; Chesley, S. R.

    2007-07-01

    We apply the technique of astrometric mass determination to measure the masses of 21 main-belt asteroids; the masses of 6 Hebe (7.59 +/- 1.42 x 10-12 SM), 9 Metis (1.03 +/- 0.24 x 10-11 SM), 17 Thetis (6.17 +/- 0.64 x 10-13 SM), 19 Fortuna (5.41 +/- 0.76 x 10-12 SM), and 189 Phthia (1.87 +/- 0.64 x 10-14 SM) appear to be new. The resulting bulk porosities of 11 Parthenope (12%) and 16 Psyche (45%) are smaller than previous values; while the bulk porosities of 52 Europa (41%) and 189 Phthia (64%) are significant. The variations in density within the C- and S-classes are consistent with either heteorogenous mineralogical compositions within each class, significant variations in porosity, or both. To accurately model the forces on these asteroids during the mass determination process, we created an integrated ephemeris of the 300 large asteroids used in preparing the DE-405 planetary ephemeris; this new BC-405 integrated asteroid ephemeris also appears useful in other high-accuracy applications.

  4. 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.

  5. Mass constraints on substellar companion candidates from the re-reduced Hipparcos intermediate astrometric data: nine confirmed planets and two confirmed brown dwarfs

    NASA Astrophysics Data System (ADS)

    Reffert, S.; Quirrenbach, A.

    2011-03-01

    Context. The recently completed re-reduction of the Hipparcos data by van Leeuwen (2007a, Astrophysics and Space Science Library, 350) makes it possible to search for the astrometric signatures of planets and brown dwarfs known from radial velocity surveys in the improved Hipparcos intermediate astrometric data. Aims: Our aim is to put more significant constraints on the orbital parameters which cannot be derived from radial velocities alone, i.e. the inclination and the longitude of the ascending node, than was possible before. The determination of the inclination in particular allows to calculate an unambiguous companion mass, rather than the lower mass limit which can be obtained from radial velocity measurements. Methods: We fitted the astrometric orbits of 310 substellar companions around 258 stars, which were all discovered via the radial velocity method, to the Hipparcos intermediate astrometric data provided by van Leeuwen. Results: Even though the astrometric signatures of the companions cannot be detected in most cases, the Hipparcos data still provide lower limits on the inclination for all but 67 of the investigated companions, which translates into upper limits on the masses of the unseen companions. For nine companions the derived upper mass limit lies in the planetary and for 75 companions in the brown dwarf mass regime, proving the substellar nature of those objects. Two of those objects have minimum masses also in the brown dwarf regime and are thus proven to be brown dwarfs. The confirmed planets are the ones around Pollux (β Gem b), ɛ Eri b, ɛ Ret b, μ Ara b, υ And c and d, 47 UMa b, HD 10647 b and HD 147513 b. The confirmed brown dwarfs are HD 137510 b and HD 168443 c. In 20 cases, the astrometric signature of the substellar companion was detected in the Hipparcos data, resulting in reasonable constraints on inclination and ascending node. Of these 20 companions, three are confirmed as planets or lightweight brown dwarfs (HD 87833 b, ι Dra

  6. 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…

  7. 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.

  8. 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.

  9. Full Sky Astrometric Mapping Explorer, FAME, CCD Centroiding Experiment

    NASA Astrophysics Data System (ADS)

    Triebes, K.; Gilliam, L.; Harris, F.; Hilby, T.; Horner, S.; Monet, D.; Perkins, P.; Vassar, R.

    1999-12-01

    FAME is a MIDEX astrometry experiment designed to map the positions of 40,000,000 stars to an accuracy of 50 micro-arc seconds. Optimized between mission requirements, size, weight, and cost, the FAME instrument consists of a 0.6 x 0.25 m2 aperture whose point spread function central peak is linearly sampled by two pixels. In order to achieve its astrometric mapping mission requirements, this instrument must achieve a single look centroiding accuracy on a visual magnitude 9.0 star of <0.003 pixels while operating the focal plane in a time domain integration, TDI, mode. As this performance requirement represents a significant improvement over the current state of the art of 0.02 to 0.01 pixel resolution, a risk reduction experiment was conducted to determine our centroiding ability using a flight traceable CCD operated in TDI mode. An ultra-stable optical system was configured to project a simulated starfield onto the CCD which was mounted on a high precision moveable stage. Moving the stage across the projected starfield in synchronization with the TDI rate simulated the sensing environment expected in the final instrument, and intensities were adjusted to simulate 9th visual magnitude stars. Experimental results demonstrated single look centroiding accuracy of <0.002 pixels in addition to yielding unexpected dividends in refining CCD operations and centroid data analysis. This poster paper describes the experiment design, centroiding results, CCD operating techniques and data analysis methods. This work was jointly sponsored by Lockheed Martin and the U.S. Naval Observatory.

  10. Astrometric Calibration of Digitized Wide-Field Photographic Plates

    NASA Astrophysics Data System (ADS)

    Boyce, Peter B.; Truong, P. N.

    2006-12-01

    8000 photographic plates originally taken at Maria Mitchell Observatory from 1913 to 1996 were scanned and digitized in 2002-2003. The resulting scans are stored in TIFF format. We have investigated the use of currently existing tools to convert plate coordinates to RA and Dec to ready the scans for inclusion in the National Virtual Observatory. This involves converting the scans to FITS format and adding WCS headers. Five of the digitized images, with slightly different centers, covering 13° x 16° in Cygnus, were calibrated using the CDS Aladin program version 3.6. An initial Tangent Plane fit was produced by entering parameters applicable for the MMO plates. The images were first calibrated by parameters. The calibration was refined by matching stars images with their positions by overlaying the positions from the Bright Star Catalog. Once a reasonably accurate calibration has been determined, additional star catalogs can be used to refine the calibration. We find that the accuracy of the calibration for a Tangent Plane is not heavily dependent upon the number of stars used. Using a simple Tangent Plane model on these wide-field plates, the coordinates of objects near the edges of the plate often differ from coordinates of objects in the catalog by up to an arcminute. As a check, we also used the WCS Tools programs written by Doug Mink at the Harvard-Smithsonian CfA, and they yield the same results. A satisfactory astrometric calibration which covers the whole field will require the use of higher order polynomials. This project was supported by the NSF/REU grant AST-0354056, the NASA/AAS Small Research Grant Program and the Nantucket Maria Mitchell Association.

  11. 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

  12. 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.

  13. Action Experience, More than Observation, Influences Mu Rhythm Desynchronization

    PubMed Central

    Cannon, Erin N.; Yoo, Kathryn H.; Vanderwert, Ross E.; Ferrari, Pier F.; Woodward, Amanda L.; Fox, Nathan A.

    2014-01-01

    Since the discovery of mirror neurons in premotor and parietal areas of the macaque monkey, the idea that action and perception may share the same neural code has been of central interest in social, developmental, and cognitive neurosciences. A fundamental question concerns how a putative human mirror neuron system may be tuned to the motor experiences of the individual. The current study tested the hypothesis that prior motor experience modulated the sensorimotor mu and beta rhythms. Specifically, we hypothesized that these sensorimotor rhythms would be more desynchronized after active motor experience compared to passive observation experience. To test our hypothesis, we collected EEG from adult participants during the observation of a relatively novel action: an experimenter used a claw-like tool to pick up a toy. Prior to EEG collection, we trained one group of adults to perform this action with the tool (performers). A second group comprised trained video coders, who only had experience observing the action (observers). Both the performers and the observers had no prior motor and visual experience with the action. A third group of novices was also tested. Performers exhibited the greatest mu rhythm desynchronization in the 8–13 Hz band, particularly in the right hemisphere compared to observers and novices. This study is the first to contrast active tool-use experience and observation experience in the mu rhythm and to show modulation with relatively shorter amounts of experience than prior mirror neuron expertise studies. These findings are discussed with respect to its broader implication as a neural signature for a mechanism of early social learning. PMID:24663967

  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 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.

  17. Photometric and Astrometric Characterization of the La Silla QUEST AGN Variability Survey

    NASA Astrophysics Data System (ADS)

    Coppi, Paolo S.; Cartier, R. A.; QUEST Team

    2014-01-01

    We study the photometric and astrometric properties of the La Silla QUEST AGN Variability Survey and present preliminary results. This wide-field survey is designed to collect well-sampled AGN light curves, on day to year timescales, in order to better characterize the variability properties of a large sample of AGN selected by a variety of other techniques. These properties can then be used to test and improve AGN variability selection techniques, e.g., to better prepare for the arrival of LSST. Additionally, we hope to connect these variability properties to the fundamental physical parameters of AGN such as black hole mass. To achieve this goal, we carry out nightly observations of a set of extragalactic fields with good multiwavelength coverage such as COSMOS. The survey uses the QUEST camera (with ~7.5 square degree field-of-view) operating on the 1m ESO Schmidt located in La Silla, Chile. The survey began in March 2010 and will likely continue for at least two more years. We review our progress and present sample AGN light curves from the first two years of the survey. We use the two-year data to test for possible biases in current selection variability techniques by looking at the known AGN in the COSMOS field. The larger QUEST variabiliity survey, which is now being used to find supernova, will eventually provide high-quality AGN variability data over ~15,000 square degrees of sky.

  18. Global Lidar Observations of Aerosol Distribution and Radiative Influence

    NASA Technical Reports Server (NTRS)

    Spinhirne, James; Starr, David OC. (Technical Monitor)

    2001-01-01

    A very visible impact of human activities is the brownish aerosol haze that pervades many industrialized regions as well as areas in the subtropics and tropics where biomass burning occurs. Well known examples are the Asian Brown Cloud, Arctic Haze and East Coast Haze. Atmospheric transport transforms this haze into regional and hemispheric aerosol layers of significant concentrations. The overall impact on the radiation balance of the atmosphere, surface solar irradiance and other meteorology factors is recognized as a major uncertainty for climate change. In order to understand the impact, the global distribution of aerosol and their properties must be known. . A missing element of observations, but critical for understanding transport has been the height distribution of aerosol. Lidar measurements of aerosol height distribution have been important in GLOBE, ACE, INDOEX and other field studies A network of continuously operating eye safe lidar ground sites has now been established for baseline aerosol profiling. In 2002 NASA will launch the Geoscience Laser Altimeter System (GLAS) mission which will provide for the first time global observations of the height distribution of aerosol. The combination of these and other modem satellite observations, field experiments and models of global aerosol composition and transport should begin to unravel the impacts of particles in the atmosphere.

  19. The scientific goal of the Japanese small astrometric satellite, Small-JASMINE

    NASA Astrophysics Data System (ADS)

    Yano, Taihei; Gouda, Naoteru; Kobayashi, Yukiyasu; Tsujimoto, Takuji; Niwa, Yoshito; Yamada, Yoshiyuki

    2013-02-01

    Small-JASMINE is a small Japanese astrometric satellite, developed mainly at the National Astronomical Observatory of Japan. The target launch date of Small-JASMINE is around 2017. The satellite will be equipped with a telescope with an aperture size of 30 cm and a focal length of approximately 3.9 m. The operational wavelength will be centered on the infrared Hw band, between 1.1 and 1.7 μm, using a HgCdTe detector with 4k × 4k pixels. This will enable us to observe the central regions of our Galaxy and clarify the dynamical structure of the bulge region. A restricted region of the Galactic bulge will be observed using a frame-linking method, which is different from the approach taken by both Hipparcos and Gaia, both developed at ESA. The target accuracy of the annual parallax and proper motion is approximately 10 μas and 10 μas yr-1, respectively, in the central region of the survey area of 0.3 × 0.3 deg2. The target accuracy of the annual parallax, ~ 50 μas, and that of the proper motion, ~ 50 μas yr-1, will be obtained within a region of 2 × 2 deg2. The observing region covers a field of approximately 3 × 3 deg2. The mission is required to continue for around three years to obtain reliable measurements. In the winter season, the angular distance between the Sun and the Galactic bulge region is small. Accordingly, we may have the chance to observe different regions which contain scientifically interesting targets, such as Cygnus X-1. If we are successful in observing the object over the course of a few weeks, the orbital elements of the star accompanying Cygnus X-1 can be resolved by Small-JASMINE.

  20. Extending the ICRF to higher radio frequencies: Initial global astrometric results

    NASA Astrophysics Data System (ADS)

    Jacobs, C. S.; Charlot, P.; Gordon, D.; Lanyi, G. E.; Ma, C.; Naudet, C. J.; Sovers, O. J.; Zhang, L. D.; K-Q VLBI Survey Collaboration

    2002-12-01

    Astrometric observations of distant active galactic nuclei (AGN) have been used to construct quasi-inertial global reference frames, most notably the International Celestial Reference Frame (ICRF) which now forms the basis for all astrometry including deep space navigation. The ICRF frame was defined using X- (8.4 GHz) and S-band (2.3 GHz) observations over the past 20+ years. There are several motivations for extending this work to higher radio frequencies, namely, to construct a more stable frame based on more compact sources, to provide calibrators for phase referencing, and to support spacecraft navigation at higher frequencies. As a first step toward these goals, in 2002 we began a series of survey observations using the Very Long Baseline Array (VLBA) of ten radio telescopes at K-band (24 GHz) and Q-band (43 GHz). Each session covers the full 24 hours of right ascension and covers declinations down to the VLBA's southern limit (approx. -30 deg). Preliminary analysis of the first session produced a full sky catalog of 65 sources with formal position uncertainties of about 0.5 mas. Group delay residuals were an excellent 15-20 psec WRMS. We will present evidence from an external comparison to the S/X-band ICRF that shows zonal errors at several times the level of the formal precision. We expect these errors to be reduced as futher sessions are added to the analysis thereby strengthening the observation geometry. --- The research described in this paper was in part performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration, Goddard Space Flight Center, U.S. Naval Observatory, National Radio Astronomical Observatory, and Bordeaux Observatory.

  1. 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.

  2. 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

  3. Astrometric light-travel time signature of sources in nonlinear motion. I. Derivation of the effect and radial motion

    NASA Astrophysics Data System (ADS)

    Anglada-Escudé, G.; Torra, J.

    2006-04-01

    Context: .Very precise planned space astrometric missions and recent improvements in imaging capabilities require a detailed review of the assumptions of classical astrometric modeling.Aims.We show that Light-Travel Time must be taken into account in modeling the kinematics of astronomical objects in nonlinear motion, even at stellar distances.Methods.A closed expression to include Light-Travel Time in the current astrometric models with nonlinear motion is provided. Using a perturbative approach the expression of the Light-Travel Time signature is derived. We propose a practical form of the astrometric modelling to be applied in astrometric data reduction of sources at stellar distances(d>1 pc).Results.We show that the Light-Travel Time signature is relevant at μ as accuracy (or even at mas) depending on the time span of the astrometric measurements. We explain how information on the radial motion of a source can be obtained. Some estimates are provided for known nearby binary systemsConclusions.Given the obtained results, it is clear that this effect must be taken into account in interpreting precise astrometric measurements. The effect is particularly relevant in measurements performed by the planned astrometric space missions (GAIA, SIM, JASMINE, TPF/DARWIN). An objective criterion is provided to quickly evaluate whether the Light-Travel Time modeling is required for a given source or system.

  4. VLBI astrometric identification of the radio emitting region in Algol and determination of the orientation of the close binary

    NASA Technical Reports Server (NTRS)

    Lestrade, Jean-Francois; Phillips, Robert B.; Hodges, Mark W.; Preston, Robert A.

    1993-01-01

    A minute displacement of the radio source in Algol was measured by VLBI during two consecutive orbital revolutions of the close binary. The magnitude of the displacement unambiguously indicates that the less massive star of the close binary, a K subgiant, is the star responsible for the nonthermal radio emission of the system. This is consistent with the idea that the radio emission in Algol is related to the strong magnetic activity of the subgiant. The orientation and sense of the displacement on the sky that are directly deduced from our astrometric VLBI observations imply: (1) that the orbital plane of the close binary is at P.A. = +52 deg +/- 5 deg; and (2) that the sense of circulation of the close binary is clockwise, as seen on the sky. Thus, the long-period and close binary orbital motions are almost orthogonal and counterrevolving and this is relevant for evolution and dynamical studies.

  5. 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

  6. 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.

  7. The Gaia Astrometric Survey of Nearby M Dwarfs: A Treasure Trove for Exoplanet Astrophysics

    NASA Astrophysics Data System (ADS)

    Sozzetti, Alessandro; Giacobbe, P.; Lattanzi, M. G.; Micela, G.; Tinetti, G.

    2011-09-01

    Cool, nearby M dwarfs within a few tens of parsecs from the Sun are becoming the focus of dedicated experiments in the realm of exoplanets astrophysics. This is due to the shift in theoretical paradigms in light of new observations, and to the improved understanding of the observational opportunities for planet detection and characterization provided by this sample. Gaia, in its all-sky survey, will deliver precision astrometry for a magnitude-limited (V=20) sample of M dwarfs, providing an inventory of cool nearby stars with a much higher degree of completeness (particularly for late sub-types) with respect to currently available catalogs. We gauge the Gaia potential for precision astrometry of exoplanets orbiting a sample of already known dM stars within 30 pc from the Sun, carefully selected based on cross-correlation among catalogs in the literature (e.g., Lepine, PMSU). We express Gaia sensitivity thresholds as a function of system parameters and in view of the latest mission profile, including the most up-to-date astrometric error model. The simulations also provide insight on the capability of high-precision astrometry to reconstruct the underlying orbital elements and mass distributions of the generated companions. These results will help in evaluating the complete expected Gaia planet population around late-type stars. We investigate the synergy between the Gaia data on nearby M dwarfs and other ground-based and space-borne programs for planet detection and characterization, with a particular focus on: a) the improvements in the determination of transiting planet parameters thanks to the exquisitely precise stellar distances determined by Gaia; b) the betterment in orbit modeling when Gaia astrometry and precision radial-velocities are available for the same targets; and c) the ability of Gaia to carefully predict the ephemerides of (transiting and non-transiting) planets around M stars, for spectroscopic characterization of their atmospheres with

  8. An Astrometric Companion to the Nearby Metal-Poor, Low-Mass Star LHS 1589

    NASA Astrophysics Data System (ADS)

    Lépine, Sébastien; Rich, R. Michael; Shara, Michael M.; Cruz, Kelle L.; Skemer, Andrew

    2007-10-01

    We report the discovery of a companion to the high proper motion star LHS 1589, a nearby high-velocity, low-mass subdwarf. The companion (LHS 1589B) is located 0.224''+/-0.004'' to the southwest of the primary (LHS 1589A), and is 0.5 mag fainter than the primary in the Ks band. The pair was resolved with the IRCAL infrared camera at Lick Observatory, operating with the Laser Guide Star Adaptive Optics system. A low-resolution spectrum of the unresolved pair obtained at the MDM observatory shows the source to be consistent with a cool subdwarf of spectral subtype sdK7.5. A photometric distance estimate places the metal-poor system at a distance d=81+/-18 pc from the Sun. We also measure a radial velocity Vrad=67+/-8 km s-1, which, together with the proper motion and estimated distance, suggests that the pair is roaming the inner Galactic halo on a highly eccentric orbit. With a projected orbital separation s=18.1+/-4.8 AU, and a crude estimate of the system's total mass, we estimate the orbital period of the system to be in the range 75 yr astrometrically, after monitoring the orbital motion over a decade or so. The LHS 1589AB system could thus provide a much needed constraint to the mass-luminosity relationship of metal-poor, low-mass stars. Based on observations performed with the Laser Guide Star Adaptive Optics system at the Lick Observatory, operated by the University of California system. Based on observations conducted at the MDM observatory, operated jointly by the University of Michigan, Dartmouth College, the Ohio State University, Columbia University, and the University of Ohio.

  9. Upper mass limits for known radial velocity planets from Hipparcos Intermediate Astrometric Data

    NASA Astrophysics Data System (ADS)

    Frink, Sabine

    2003-10-01

    For all 104 extrasolar planetary candidates known today, we calculate the expected peak-to-peak astrometric signatures, using the spectroscopic elements, primary star masses and the Hipparcos parallaxes. For those eight stars with expected astrometric signatures larger than 1 mas, we fit an orbital model to the Hipparcos Intermediate Astrometric Data, using again the spectroscopic elements; the only two free parameters in the fit are thus the inclination and the ascending node. In no case the astrometric signature of the companion is detected in the Hipparcos Data. However, the non-detection of these astrometric signatures places stringent constraints on the upper mass limits of the companions; in all eight investigated cases the substellar nature of the companion could be established. The derived 3 upper mass limits are: 15MJ for υ And d, 16MJ for 14 Her, 44MJ for HD 38529 c, 20MJ for HD 33636, 2.5MJ for ɛ Eri, 43MJ for HD 168443 c, 31MJ for HD 39091, and 6.3MJ for 55 Cnc d. Three of those systems have been investigated before by Zucker & Mazeh (2001), and our results for υ And d and 14 Her are in excellent agreement. The results for ɛ Eri differ by about an order of magnitude. Zucker & Mazeh (2001) used somewhat different orbital elements for ɛ Eri, but the effect is too large to be caused by differences in the orbital elements. We caution however that our results for ɛ Eri and especially 55 Cnc d are less reliable because their orbital periods exceed the time baseline covered by the Hipparcos measurements.

  10. The Astrometric-Spectroscopic Binary System HIP 50796: An Overmassive Companion

    NASA Astrophysics Data System (ADS)

    Torres, Guillermo

    2006-02-01

    We report spectroscopic observations of the star HIP 50796, previously considered (but later rejected) as a candidate member of the TW Hya association. Our measurements reveal it to be a single-lined binary with an orbital period of 570 days and an eccentricity of e=0.61. The astrometric signature of this orbit was previously detected by Hipparcos in the form of curvature in the proper-motion components, although the period was unknown at the time. By combining our radial velocity measurements with the Hipparcos intermediate data (abscissa residuals) we are able to derive the full three-dimensional orbit and determine the dynamical mass of the unseen companion, as well as a revised trigonometric parallax that accounts for the orbital motion. Given our primary mass estimate of 0.73 Msolar (mid-K dwarf), the companion mass is determined to be 0.89 Msolar, or ~20% larger than the primary. The likely explanation for the larger mass without any apparent contribution to the light is that the companion is itself a closer binary composed of M dwarfs. The near-infrared excess and X-ray emission displayed by HIP 50796 support this. Our photometric modeling of the excess leads to a lower limit to the mass ratio of the close binary of q~0.8 and individual masses of 0.44-0.48 and 0.41-0.44 Msolar. The new parallax (π=20.6+/-1.9 mas) is significantly smaller than the original Hipparcos value and more precise.

  11. 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.

  12. 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

  13. 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

  14. On the use of long series of ground-based astrometric data at post-Hipparcos era.

    NASA Astrophysics Data System (ADS)

    Yatskiv, Ya. S.

    With the compilation of the Hipparcos catalogue, astrometric data of unprecedented quality and quantity has become available. However, the Hipparcos mission does not make the ground-based astrometry obsolete. On the contrary, it shows the importance of long series of ground-based astrometric data for densification and improvement of the Hipparcos Reference Frame and it indicates the ways of future developments of astrometry. Some application examples concerning the use of ground-based astrometric data at post-Hipparcos era are discussed.

  15. 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

  16. A conjugate gradient algorithm for the astrometric core solution of Gaia

    NASA Astrophysics Data System (ADS)

    Bombrun, A.; Lindegren, L.; Hobbs, D.; Holl, B.; Lammers, U.; Bastian, U.

    2012-02-01

    Context. The ESA space astrometry mission Gaia, planned to be launched in 2013, has been designed to make angular measurements on a global scale with micro-arcsecond accuracy. A key component of the data processing for Gaia is the astrometric core solution, which must implement an efficient and accurate numerical algorithm to solve the resulting, extremely large least-squares problem. The Astrometric Global Iterative Solution (AGIS) is a framework that allows to implement a range of different iterative solution schemes suitable for a scanning astrometric satellite. Aims: Our aim is to find a computationally efficient and numerically accurate iteration scheme for the astrometric solution, compatible with the AGIS framework, and a convergence criterion for deciding when to stop the iterations. Methods: We study an adaptation of the classical conjugate gradient (CG) algorithm, and compare it to the so-called simple iteration (SI) scheme that was previously known to converge for this problem, although very slowly. The different schemes are implemented within a software test bed for AGIS known as AGISLab. This allows to define, simulate and study scaled astrometric core solutions with a much smaller number of unknowns than in AGIS, and therefore to perform a large number of numerical experiments in a reasonable time. After successful testing in AGISLab, the CG scheme has been implemented also in AGIS. Results: The two algorithms CG and SI eventually converge to identical solutions, to within the numerical noise (of the order of 0.00001 micro-arcsec). These solutions are moreover independent of the starting values (initial star catalogue), and we conclude that they are equivalent to a rigorous least-squares estimation of the astrometric parameters. The CG scheme converges up to a factor four faster than SI in the tested cases, and in particular spatially correlated truncation errors are much more efficiently damped out with the CG scheme. While it appears to be difficult

  17. 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.

  18. A New Astrometric Technique Applied to the Likely Tidal Disruption Event, Swift J166+57

    NASA Astrophysics Data System (ADS)

    Alianora Hounsell, Rebekah; Fruchter, Andrew S.; Levan, Andrew J.

    2015-01-01

    We have developed a new technique to align Hubble Space Telescope (HST) data using background galaxies as astrometric markers. This technique involves the cross correlation of cutouts of regions about individual galaxies from different epochs, enabling the determination of an astrometric solution. The method avoids errors introduced by proper motion when the locations of stars are used to transform the images. We have used this approach to investigate the nature of the unusual gamma-ray source Sw J1644+57, which was initially classified as a long gamma ray burst (LGRB). However, due to the object's atypical behavior in the X-ray and optical, along with its location within the host (150 ± 150 pc, see Levan et al. 2011) it has been suggested that the transient may be caused by a tidal disruption event (TDE). Additional theories have also been suggested for its origin which remain based on the collapsar model for a long burst, such as the collapse of a red giant, rather than a stripped star as is typical in LGRBs, or the creation of a magnetar.Precise astrometry of the transient with respect to the galaxy can potentially distinguish between these scenarios. Here we show that our method of alignment dramatically reduces the astrometric error of the position of the transient with respect to the nucleus of the host. We therefore discuss the implication of our result on the astrophysical nature of the object.

  19. 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.

  20. 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

  1. 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,…

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Influence of Madden-Julian Oscillation on Southeast Asia rainfall extremes: Observations and predictability

    NASA Astrophysics Data System (ADS)

    Xavier, Prince; Rahmat, Raizan; Cheong, Wee Kiong; Wallace, Emily

    2014-06-01

    The influence of Madden-Julian Oscillation (MJO) on the rainfall distribution of Southeast Asia is studied using TRMM satellite-derived rainfall and rain gauge data. It is shown that convectively active (suppressed) phases of MJO can increase (decrease) the probability of extreme rain events over the land regions by about 30-50% (20-25%) during November-March season. The influence of MJO on localized rainfall extremes are also observed both in rainfall intensity and duration. The Met Office Global Seasonal forecasting system seasonal forecasting system is shown to reproduce the MJO influence on rainfall distribution well despite the model biases over land. Skills scores for forecasting 90th percentile extreme rainfall shows significant skills for convective phases. This study demonstrates the feasibility of deriving probabilistic forecasts of extreme rainfall at medium range.

  7. 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.

  8. Astrometría de pequeño campo con CCD: Evaluación de la aplicabilidad del método de ajuste en bloque

    NASA Astrophysics Data System (ADS)

    Bustos Fierro, I. H.; Calderón, J. H.

    The measuring of astrometric positions from a mosaic of direct CCD images with partial overlap taken with the Telescope Jorge Sahade is proposed. The influence of the errors introduced by the method itself, the instrumental errors, the measuring errors and the errors in the reference positions is analyzed in numerical simulations. The achievable accuracy in a square field 25'sided mapped with sixteen frames 10' sided in a center-edge arrangement is determined. It is found that the errors of the method itself and the reference catalog lead to positions with the same order accuracy than the reference catalog. In a measurement of second epoch positions for the determination of proper motions from Carte du Ciel plates, such errors are not significant if the ACT Reference Catalog is the source of the reference positions. It is also found that the errors of the measured positions are dominated by the aberrations of the optical system and the centering error of the stellar images.

  9. 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

  10. The GAIA astrometric survey of the solar neighborhood and its contribution to the target database for DARWIN/TPF

    NASA Astrophysics Data System (ADS)

    Sozzetti, A.; Casertano, S.; Lattanzi, M. G.; Spagna, A.

    2003-10-01

    We evaluate the potential of the ESA Cornerstone Mission GAIA in helping populate the database of nearby stars (d < 25 pc) for subsequent target selection for DARWIN/TPF. The GAIA high-precision astrometric measurements will make it an ideal tool for a complete screening of the expected several thousands stars within 25 pc in order to identify and characterize (or rule out the presence of) Jupiter signposts. GAIA astrometry will be instrumental in complementing radial velocity surveys of F-G-K stars, and will more effectively search for massive planets the large database of nearby M dwarfs, which are less easily accessible with precision spectroscopy. The ability to determine the actual planet masses and inclination angles for detected systems, especially those with low-mass primaries (M < 0.6 Msun), stems as a fundamental contribution GAIA will make toward the final target selection for DARWIN/TPF, thus complementing exo-zodiacal dust emission observations from ground-based observatories such as Keck, LBTI, and VLTI.

  11. 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.

  12. 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.

  13. A Combined Astrometric and Spectroscopic Study of Metal-Poor Binaries

    NASA Astrophysics Data System (ADS)

    Benamati, L.; Sozzetti, A.; Santos, N. C.; Latham, D. W.

    2013-11-01

    In this work we present a study of binary systems in a metal-poor sample of solar type stars. The stars analyzed were rejected from two planet search samples because they were found to be binaries. Using available radial velocity and Hipparcos astrometric data, we apply different methods to find, for every binary system, a possible range of solutions for the mass of the companion and its orbital period. In one case we find that the solution depends on the Hipparcos data used: the old and new reductions give different results. Some candidate low-mass companions are found, including some close to the brown dwarf regime.

  14. Application of the "scanner + MIDAS" complex for processing astrometric photographic plates

    NASA Astrophysics Data System (ADS)

    Pogoreltsev, Yu.; Babenko, Yu.; Vertypolokh, Yu.

    Researches of an opportunity of use in the astrometric purposes of the photographic plates digital images received by the scanner ScanMaker-4 manufactured by Microtec were carried out by the authors. Photographic plates with the images of star fields received with different telescopes were used for researches. The processing of digital images of photoplates was made with the ESO-MIDAS and with the programs developed by one of the authors. The researches have shown, that this technology provides results with acceptable quality level. That makes possible use of the given scanner for mass processing of the stored photographic material.

  15. 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.

  16. 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.

  17. Astrometric Microlensing Constraints on a Massive Body in the Outer Solar System with Gaia

    NASA Astrophysics Data System (ADS)

    Gaudi, B. Scott; Bloom, Joshua S.

    2005-12-01

    A body in solar orbit beyond the Kuiper Belt exhibits an annual parallax that exceeds its apparent proper motion by up to many orders of magnitude. Apparent motion of this body along the parallactic ellipse will deflect the angular position of background stars due to astrometric microlensing (``induced parallax''). By synoptically sampling the astrometric position of background stars over the entire sky, constraints on the existence (and basic properties) of a massive nearby body may be inferred. With a simple simulation, we estimate the signal-to-noise ratio for detecting such a body-as a function of mass, heliocentric distance, and ecliptic latitude-using the anticipated sensitivity and temporal cadences from Gaia (launch date 2011). A Jupiter-mass (MJ) object at 2000 AU is detectable by Gaia over the whole sky above 5 σ, with even stronger constraints if it lies near the ecliptic plane. Hypotheses for the mass (~3MJ), distance (~20,000 AU), and location of the proposed perturber (``Planet X''), which gives rise to long-period comets, may be testable.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. 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

  4. 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.

  5. 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…

  6. The influence of social and symbolic cues on observers' gaze behaviour.

    PubMed

    Hermens, Frouke; Walker, Robin

    2016-08-01

    Research has shown that social and symbolic cues presented in isolation and at fixation have strong effects on observers, but it is unclear how cues compare when they are presented away from fixation and embedded in natural scenes. We here compare the effects of two types of social cue (gaze and pointing gestures) and one type of symbolic cue (arrow signs) on eye movements of observers under two viewing conditions (free viewing vs. a memory task). The results suggest that social cues are looked at more quickly, for longer and more frequently than the symbolic arrow cues. An analysis of saccades initiated from the cue suggests that the pointing cue leads to stronger cueing than the gaze and the arrow cue. While the task had only a weak influence on gaze orienting to the cues, stronger cue following was found for free viewing compared to the memory task. PMID:26582135

  7. 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

  8. 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

  9. Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

    NASA Astrophysics Data System (ADS)

    Vogt, N.; Schmidt, T. O. B.; Neuhäuser, R.; Bedalov, A.; Roell, T.; Seifahrt, A.; Mugrauer, M.

    2012-10-01

    Context. The star-forming regions in Chamaeleon (Cha) are one of the nearest (distance ~ 165 pc) and youngest (age ~ 2 Myr) conglomerates of recently formed stars and the ideal target for population studies of star formation. Aims: We investigate a total of 16 Cha targets that have been suggested, but not confirmed, to be binaries or multiple systems in previous literature. Methods: We used the adaptive optics instrument Naos-Conica (NACO) at the Very Large Telescope Unit Telescope (UT) 4 / YEPUN of the Paranal Observatory, at 2-5 different epochs, in order to obtain relative and absolute astrometric measurements, as well as differential photometry in the J, H, and K band. On the basis of known proper motions and these observations, we analyse the astrometric results in our proper motion diagram (PMD: angular separation / position angle versus time), to eliminate possible (non-moving) background stars, establish co-moving binaries and multiples, and search for curvature as indications for orbital motion. Results: All previously suggested close components are co-moving and no background stars are found. The angular separations range between 0.07 and 9 arcsec, corresponding to projected distances between the components of 6-845 AU. Thirteen stars are at least binaries and the remaining three (RX J0919.4-7738, RX J0952.7-7933, VW Cha) are confirmed high-order multiple systems with up to four components. In 13 cases, we found significant slopes in the PMDs, which are compatible with orbital motion whose periods (estimated from the observed gradients in the position angles) range from 60 to 550 years. However, in only four cases there are indications of a curved orbit, the ultimate proof of a gravitational bond. Conclusions: A statistical study based on the 2MASS catalogue confirms the high probability of all 16 stellar systems being gravitationally bound. Most of the secondary components are well above the mass limit of hydrogen burning stars (0.08 M⊙), and have

  10. 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.

  11. 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.

  12. Multichannel astrometric photometer-based parallaxes of evolved stars - Chi Cygni, 51 Andromedae, and OP Andromedae

    NASA Technical Reports Server (NTRS)

    Stein, John W.

    1991-01-01

    Using data from Allegheny Observatory's Thaw/MAP astrometric system, absolute parallaxes are presented for Chi Cygni, 51 Andromedae, the newly discovered RS CVn variable OP Andromedae, and selected stars in these fields. Using existing angular diameter measures and the new parallaxes, linear diameters for Chi Cygni and 51 And are given. Chi Cygni has a perturbation in declination having a period of 0.75 yr and an amplitude of +/- 5 mas. Owing to the extreme variability of Chi Cygni, no further characterization of the system is possible at this time. Other results of spectral interest include the detection of a perturbation in the motion of BD +47 deg 466. This system was found to have a parallax of 14.4 +/- 1.2 mas.

  13. 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.

  14. 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.

  15. Nano-JASMINE: use of AGIS for the next astrometric satellite

    NASA Astrophysics Data System (ADS)

    Yamada, Y.; Gouda, N.; Lammers, U.

    2011-02-01

    The core data reduction for the Nano-JASMINE mission is planned to be done with Gaia's Astrometric Global Iterative Solution (AGIS). The collaboration started at 2007 prompted by Uwe Lammers' proposal. In addition to similar design and operating principles of the two missions, this is possible thanks to the encapsulation of all Gaia-specific aspects of AGIS in a Parameter Database. Nano-JASMINE will be the test bench for Gaia AGIS software. We present this idea in detail and the necessary practical steps to make AGIS work with Nano-JASMINE data. We also show the key mission parameters, goals, and status of the data reduction for the Nano-JASMINE.

  16. A Spectro-Astrometric Measurement of Brackett Gamma Emission in Herbig Ae/Be Stars

    NASA Astrophysics Data System (ADS)

    Rice, Thomas; Brittain, S.

    2012-01-01

    In T Tauri stars, the Brackett-gamma line strength is a reliable indicator of accretion luminosity. Among intermediate mass young stars, Herbig Ae stars also show this correlation, but in Herbig Be stars the Br-gamma line flux significantly overpredicts accretion luminosity. This Br-gamma excess in Herbig Be stars is thought to arise from a spatially extended outflow. Using commissioning data from the LUCIFER spectrograph on the 8.4-meter Large Binocular Telescope (LBT), we present a spectro-astrometric study of two Herbig Ae/Be stars, the HAe star MWC480 and the HBe star HD 259431. In both stars, an extended Br-gamma source can be ruled out down to 0.001'' at the 1σ level. We discuss the implication of our limits on the extension of the Br-gamma emission and possible ways forward.

  17. Dark companions of stars - Astrometric commentary on the lower end of the Main Sequence

    NASA Astrophysics Data System (ADS)

    van de Kamp, P.

    1986-04-01

    The smaller the mass of a star, the lower its central temperature and the lower its luminosity. The zero-age Main Sequence is thus explained down to its lower, red dwarf section; there is, however, a critical mass value below which the central temperature is too low to permit conventional nuclear energy production, and the resulting objects are designated substellar, black, brown, or even 'dark red' stars. The present consideration of the dark companions of stars gives attention to visible and invisible dark dwarfs, as well as to the stars Sirius and Procyon, the planets Neptune and Pluto, spectroscopic, photometric, and eclipsing companion stars, the serendipitously discovered cases of Ross 614 and VW Cephei C, and astrometric study results for Barnard's star.

  18. 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.

  19. 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.

  20. Influence of solar-probe inherent atmosphere on in-situ observations

    SciTech Connect

    Hassanein, A.; Konkashbaev, A.I.; Konkashbaev, I.K.; Nikandrov, L.B.

    1998-08-01

    The solar corona is the source of the solar wind, which is responsible for the heliosphere and plays a crucial role in solar/terrestrial phenomena. A comprehensive understanding of these phenomena can be established only by directly measuring ion and electron velocity distributions, plasma waves, and fluxes of energetic particles near the sun. The problem resulting from the inherent atmosphere of a spacecraft moving in the vicinity of the sun and the influence of this atmosphere on in-situ measurements of the solar corona plasma is key to the realization and success of any solar probe mission. To evaluate the influence of the probe-inherent atmosphere on in-situ observations, the authors have developed comprehensive radiation hydrodynamic models. The physics of plasma/probe/vapor interaction are also being developed in a self-consistent model to predict the effect of probe inherent atmosphere on in-situ measurements of corona parameters during solar flares. Interaction of the ionized atmosphere with the ambient natural plasma will create a turbulent shock wave that can affect in-situ measurements and must be taken into account in designing the spacecraft and its scientific components.

  1. 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

  2. High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)

    NASA Astrophysics Data System (ADS)

    Malbet, Fabien; Léger, Alain; Shao, Michael; Goullioud, Renaud; Lagage, Pierre-Olivier; Brown, Anthony G. A.; Cara, Christophe; Durand, Gilles; Eiroa, Carlos; Feautrier, Philippe; Jakobsson, Björn; Hinglais, Emmanuel; Kaltenegger, Lisa; Labadie, Lucas; Lagrange, Anne-Marie; Laskar, Jacques; Liseau, René; Lunine, Jonathan; Maldonado, Jesús; Mercier, Manuel; Mordasini, Christoph; Queloz, Didier; Quirrenbach, Andreas; Sozzetti, Alessandro; Traub, Wesley; Absil, Olivier; Alibert, Yann; Andrei, Alexandre Humberto; Arenou, Frédéric; Beichman, Charles; Chelli, Alain; Cockell, Charles S.; Duvert, Gilles; Forveille, Thierry; Garcia, Paulo J. V.; Hobbs, David; Krone-Martins, Alberto; Lammer, Helmut; Meunier, Nadège; Minardi, Stefano; Moitinho de Almeida, André; Rambaux, Nicolas; Raymond, Sean; Röttgering, Huub J. A.; Sahlmann, Johannes; Schuller, Peter A.; Ségransan, Damien; Selsis, Franck; Surdej, Jean; Villaver, Eva; White, Glenn J.; Zinnecker, Hans

    2012-10-01

    science program will encompass an astrometric survey of our 200 closest F-, G- and K-type stellar neighbors, with an average of 50 visits each distributed over the nominal mission duration. The main survey operation will use approximately 70% of the mission lifetime. The remaining 30% of NEAT observing time might be allocated, for example, to improve the characterization of the architecture of selected planetary systems around nearby targets of specific interest (low-mass stars, young stars, etc.) discovered by Gaia, ground-based high-precision radial-velocity surveys, and other programs. With its exquisite, surgical astrometric precision, NEAT holds the promise to provide the first thorough census for Earth-mass planets around stars in the immediate vicinity of our Sun.

  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. 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

  5. The influence of polarization on box air mass factors for UV/vis nadir satellite observations

    NASA Astrophysics Data System (ADS)

    Hilboll, Andreas; Richter, Andreas; Rozanov, Vladimir V.; Burrows, John P.

    2015-04-01

    Tropospheric abundances of pollutant trace gases like, e.g., NO2, are often derived by applying the differential optical absorption spectroscopy (DOAS) method to space-borne measurements of back-scattered and reflected solar radiation. The resulting quantity, the slant column density (SCD), subsequently has to be converted to more easily interpretable vertical column densities by means of the so-called box air mass factor (BAMF). The BAMF describes the ratio of SCD and VCD within one atmospheric layer and is calculated by a radiative transfer model. Current operational and scientific data products of satellite-derived trace gas VCDs do not include the effect of polarization in their radiative transfer models. However, the various scattering processes in the atmosphere do lead to a distinctive polarization pattern of the observed Earthshine spectra. This study investigates the influence of these polarization patterns on box air mass factors for satellite nadir DOAS measurements of NO2 in the UV/vis wavelength region. NO2 BAMFs have been simulated for a multitude of viewing geometries, surface albedos, and surface altitudes, using the radiative transfer model SCIATRAN. The results show a potentially large influence of polarization on the BAMF, which can reach 10% and more close to the surface. A simple correction for this effect seems not to be feasible, as it strongly depends on the specific measurement scenario and can lead to both high and low biases of the resulting NO2 VCD. We therefore conclude that all data products of NO2 VCDs derived from space-borne DOAS measurements should include polarization effects in their radiative transfer model calculations, or at least include the errors introduced by using linear models in their uncertainty estimates.

  6. Influence of in-medium NN cross sections, symmetry potential, and impact parameter on isospin observables

    NASA Astrophysics Data System (ADS)

    Zhang, Yingxun; Coupland, D. D. S.; Danielewicz, P.; Li, Zhuxia; Liu, Hang; Lu, Fei; Lynch, W. G.; Tsang, M. B.

    2012-02-01

    We explore the influence of the in-medium nucleon-nucleon cross section, symmetry potential, and impact parameter on isospin sensitive observables in intermediate-energy heavy-ion collisions with the ImQMD05 code, a modified version of the quantum molecular dynamics model. At incident velocities above the Fermi velocity, we find that the density dependence of the symmetry potential plays a more important role on the double neutron-to-proton ratio DR(n/p) and the isospin transport ratio Ri than the in-medium nucleon-nucleon cross sections, provided that the latter are constrained to a fixed total NN collision rate. We also explore both DR(n/p) and Ri as a function of the impact parameter. Since the copious production of intermediate mass fragments is a distinguishing feature of intermediate-energy heavy-ion collisions, we examine the isospin transport ratios constructed from different groups of fragments. We find that the values of the isospin transport ratios for projectile rapidity fragments with Z⩾20 are greater than those constructed from the entire projectile rapidity source. We believe experimental investigations of this phenomenon can be performed. These may provide significant tests of fragmentation time scales predicted by ImQMD calculations.

  7. Observation of influences of mental health promotion and mental intervention on mental health status of professionals

    PubMed Central

    Jiang, Shu-Qiang; Zhang, Jian-Ling

    2015-01-01

    Objective: To observe the influences of mental health promotion and mental intervention on mental health status of professionals. Method: 2878 professionals for physical examination were selected and randomly divided into treatment group and control group, with 1443 professionals and 1435 professionals, respectively. Then, the difference of mental health status before and after mental intervention between two groups was compared. Results: In treatment group, the proportion of people with healthy mental and modest pressure after mental intervention was higher than that before mental intervention and that in control group after mental intervention (P<0.01); the proportion of people with psychological sub-heath and moderate pressure after mental intervention was significantly lower than that before mental intervention and that in control group after mental intervention (P<0.05). There was no significant difference in mental health status in control group before and after mental intervention (P>0.05). Mental health consciousness, health status, self pressure-relief capability, job satisfaction, and happiness index of professionals were up to 63.3%~78.8%. Conclusions: Mental health promotion and mental intervention may significantly improve mental health status of professionals. PMID:26221385

  8. 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

  9. Emotional signals from faces, bodies and scenes influence observers' face expressions, fixations and pupil-size

    PubMed Central

    Kret, Mariska E.; Roelofs, Karin; Stekelenburg, Jeroen J.; de Gelder, Beatrice

    2013-01-01

    We receive emotional signals from different sources, including the face, the whole body, and the natural scene. Previous research has shown the importance of context provided by the whole body and the scene on the recognition of facial expressions. This study measured physiological responses to face-body-scene combinations. Participants freely viewed emotionally congruent and incongruent face-body and body-scene pairs whilst eye fixations, pupil-size, and electromyography (EMG) responses were recorded. Participants attended more to angry and fearful vs. happy or neutral cues, independent of the source and relatively independent from whether the face body and body scene combinations were emotionally congruent or not. Moreover, angry faces combined with angry bodies and angry bodies viewed in aggressive social scenes elicited greatest pupil dilation. Participants' face expressions matched the valence of the stimuli but when face-body compounds were shown, the observed facial expression influenced EMG responses more than the posture. Together, our results show that the perception of emotional signals from faces, bodies and scenes depends on the natural context, but when threatening cues are presented, these threats attract attention, induce arousal, and evoke congruent facial reactions. PMID:24391567

  10. 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

  11. 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.

  12. Observations of artificial satellites of Earth and natural satellites of Jupiter in Crimean Laboratory of SAI

    NASA Astrophysics Data System (ADS)

    Irsmambetova, T. R.; Borisova, N. N.; Borisov, G. V.; Bagaev, L. A.; Agapov, V. M.; Molotov, I. E.

    2014-03-01

    In the report possibilities of the telescope RST-220 (diameter of the mirror 22cm) for the solution of various observation tasks are shown. Since 2008 this tool has been used for regular high-precision astrometric observations of geostationary satellites within cooperation of observations according to the ISON program. In addition to astrometric observations photometric observations have been made as well. In 2009 the worldwide campaign on photometric observations of mutual occultations and eclipses of Galilean satellites of Jupiter was founded. Using RST-220 it was managed to obtain some light curves. The light curve of the unique double event - an occultation and an eclipse - is given for satellites Io and Europe.

  13. Conditions of possible programs using small and medium size ground-based astrometric instruments

    NASA Astrophysics Data System (ADS)

    Kovalevsky, J.

    The post-HIPPARCOS era has brought some uncertainty on the future of ground-based astrometry. However, the discussions that were initiated by the IAU Working Group on future development of ground-based astrometry, showed that there are a number of fields that will not be satisfactorily covered by space astrometry. The instruments that could be used are shortly described. Then the complementarity of ground-based and space astrometry is discussed. The papers presented at this very session confirm the point of view that, with minor modifications and improvement of existing instruments, many sound scientific programs can be undertaken. The principal domains in which major scientific inputs are expected from ground-based astrometry concern the dynamics of minor planets and satellites, the shape of the Sun, double stars, kinematics within stellar clusters and radiosource optical counterparts. In addition, the use of some small telescopes for monitoring long period irregular variable stars could be a useful reconversion of astrometric activity. Some possible projects in these fields will be presented, but the Working Group cannot manage such programs. Its objective is to help organizing them and to encourage people to join them. An important point concerning these programs is that all the participants should have a reward in their work in terms of publications.

  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. 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.

  16. Local stellar kinematics from large astrometric surveys: mapping the Galactic phase-space substructure

    NASA Astrophysics Data System (ADS)

    Lepine, Sebastien

    2016-05-01

    The potential of future large astrometric catalogs for mapping the velocity-space distribution of local stars in the Galaxy is illustrated with a kinematic study of K and M dwarfs in the SUPERBLINK catalog of 2.5 million stars with large proper motions (mu>40 mas/yr). Low mass K and M dwarfs, found in abundance thanks to the faint magnitude limit of the catalog (V<20) provide the densest possible sampling of the [(X,Y,Z),(U,V,W)] phase-space, making them well-suited to map out substructure (so-called "streams") in the velocity-space distributions, as well as variations in said distribution over >100 parsec scale distances. The SUPERBLINK proper motion catalog thus provides kinematic data for ~1.5 million M dwarfs from the Galactic disk population, located within 200 parsecs of the Sun, and for ~180,000 K and M (sub)dwarfs from the Galactic halo population, all within 500 parsecs of the Sun. While the disk dwarfs show clear signs of velocity-space substructure, the distribution of halo subdwarf does appear to be relatively smooth ("streamless") in contrast. Evidence for spatial variations at the few hundred parsec scale is also discussed. The current and unfortunately "blurry" view of the local velocity-space distribution promises to be set in much sharper focus with the upcoming availability of data from the GAIA mission.

  17. 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.

  18. 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.

  19. The Influence of First-Language Bidialectism in Foreign-Language Classrooms: Observations from Cyprus

    ERIC Educational Resources Information Center

    Yiakoumetti, Androula; Mina, Marina

    2011-01-01

    The sociolinguistic phenomenon of bidialectism can significantly influence foreign-language learning. This study provides empirical evidence (drawn from the Greek Cypriot bidialectal community) for this influence and it supports the recommendation that foreign-language educators be trained in language-variation issues. The study's methodological…

  20. 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

  1. 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)

  2. Influence of inhomogeneous cloud fields on optical properties retrieved from satellite observations

    NASA Astrophysics Data System (ADS)

    Dim, Jules R.; Takamura, Tamio; Okada, Itaru; Nakajima, Takashi Y.; Takenaka, Hideaki

    2007-07-01

    Analyses of solar radiation exchanges between the atmosphere and clouds are vital for the understanding of climate processes and cycles. Comparisons of satellite-to-satellite or satellite-to-ground-truth observations aiming at, elucidating the radiative behavior of atmospheric components (clouds, aerosols, gas, etc.), or validating data of a particular satellite are a common practice in global radiation investigations. In order to assess the quality of cloud optical properties derived from Geostationary Meteorological Satellite-5/Stretched Visible Infrared Spin Scan Radiometer (GMS-5/SVISSR), the former procedure (satellite-to-satellite comparison) was used. Data derived from GMS-5/SVISSR satellite were compared with those from the polar-orbiting Terra-Moderate Resolution Imaging Spectroradiometer (Terra-MODIS) satellite. This comparison showed serious discrepancies between cloud optical depth (COD) data retrieved from the two satellites' observations. GMS-5/SVISSR-retrieved COD appeared mostly lower than that of Terra-MODIS. To understand the origin of such differences, an identification procedure of the major factors likely to affect these data is conducted. Some of these factors were the satellite viewing and solar conditions, the cloud thermodynamic phase differentiation and particle effective radius, and the cloud inhomogeneity. Then emphasis was put on the examination of the latter effect (i.e., the cloud inhomogeneity). The analysis procedure was as follows: First, data having close-viewing geometries between both satellites were selected and used to understand the effects of the remaining factors. Among these, the cloud thermodynamic phase appeared to play the major role as analyses showed that most of the COD differences between both satellites were confined within ice clouds while warm clouds had the least discrepancies. This would suggest that the choice of a water cloud particle radiative transfer model to analyze a 2-phase cloud radiation data, as used

  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. 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…

  5. 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…

  6. ORBIT DETERMINATION OF DOUBLE-LINED SPECTROSCOPIC BINARIES BY FITTING THE REVISED HIPPARCOS INTERMEDIATE ASTROMETRIC DATA

    SciTech Connect

    Ren Shulin; Fu Yanning E-mail: fyn@pmo.ac.c

    2010-05-15

    Untill now, the Hipparcos intermediate astrometric data (HIAD) have contributed little to the full orbit determination of double-lined spectroscopic binaries (SB2s). This is because the photocenter of such a binary system is usually not far from the system mass center, and its orbital wobble is generally weak with respect to the accuracy of the HIAD. However, the HIAD have been recently revised and the accuracy is increased by a factor of 2.2 in the total weight. Therefore, it is interesting to see if the revised HIAD can be used in the orbit determination at least for some SB2s. In this paper, we first search the 9th Catalogue of Orbits of Spectroscopic Binaries (S{sub B{sup 9}}) for SB2s with reliable spectroscopic orbital solutions and with periods between 50 days and 3.2 years. This leaves us with 56 systems. The full orbital solutions of these systems are then determined from the HIAD by a highly efficient grid search method developed in this paper. The high efficiency is achieved by reducing the number of nonlinear model parameters to one, and by allowing all parameters to be adjustable within a region centered at each grid point. After a variety of tests, we finally accept orbital solutions of 13 systems. Among these systems, six (HIP 677, 20894, 87895, 95995, 101382, and 111170) are well resolved with reliable interferometric data. Orbital solutions from these data are consistent with our results. The full orbital solutions of the other seven systems (HIP 9121, 17732, 32040, 57029, 76006, 102431, and 116360) are determined for the first time.

  7. 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…

  8. Influence of Previous Knowledge, Language Skills and Domain-Specific Interest on Observation Competency

    ERIC Educational Resources Information Center

    Kohlhauf, Lucia; Rutke, Ulrike; Neuhaus, Birgit

    2011-01-01

    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…

  9. The functional equivalence between movement imagery, observation, and execution influences imagery ability.

    PubMed

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

    2011-09-01

    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 internal visual-imagery perspective, and kinesthetic modality, 36 participants (M age = 20.58; SD = 3.11; 18 women and 18 men) completed an adapted version of the Movement Imagery Questionnaire-Revised under four modes of delivery (movement prime, external observation prime, internal observation prime, and image-only). The results revealed that ease of imaging was significantly greater during the movement and observation prime conditions compared to the image-only condition (p < .05). Specifically when priming external visual imagery and internal visual imagery, observation facilitated ease of imaging only when the perspective was congruent with the imagery perspective. The results support the use of movement and observation to facilitate ease of imaging, but highlight the importance of considering the visual perspective when using observation. PMID:21957714

  10. 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

  11. The Influence of Same Day or Separate Day Observations on the Reliability of Assessment Data.

    ERIC Educational Resources Information Center

    Yap, Kueh Chin; Capie, William

    The purpose of this study was to compare the relative magnitude of the variance components and generalizability coefficients derived from the Teacher Performance Assessment Instruments (TPAI) data using two different methods of data collection: (1) occasions when observers were in the classroom for simultaneous observation and (2) occasions when…

  12. The Influence of Teacher Experience on the Elementary Classroom System: An Observational Study

    ERIC Educational Resources Information Center

    O'Connor, Evelyn A.; Fish, Marion C.; Yasik, Anastasia E.

    2004-01-01

    This study used a systems perspective to determine whether differences exist between classrooms of expert (n=35) and novice (n=35) teachers on the cohesion, communication, and flexibility dimensions of the Classroom Systems Observation Scale (CSOS). A 50-minute observation using the CSOS was conducted in elementary school classrooms in New York…

  13. 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.…

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. The influence of instructional interactions on students’ mental models about the quantization of physical observables: a modern physics course case

    NASA Astrophysics Data System (ADS)

    Didiş Körhasan, Nilüfer; Eryılmaz, Ali; Erkoç, Şakir

    2016-01-01

    Mental models are coherently organized knowledge structures used to explain phenomena. They interact with social environments and evolve with the interaction. Lacking daily experience with phenomena, the social interaction gains much more importance. In this part of our multiphase study, we investigate how instructional interactions influenced students’ mental models about the quantization of physical observables. Class observations and interviews were analysed by studying students’ mental models constructed in a modern physics course during an academic semester. The research revealed that students’ mental models were influenced by (1) the manner of teaching, including instructional methodologies and content specific techniques used by the instructor, (2) order of the topics and familiarity with concepts, and (3) peers.

  19. 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

  20. The Relative Influence of Goal and Kinematics on Corticospinal Excitability Depends on the Information Provided to the Observer.

    PubMed

    Mc Cabe, Sofía I; Villalta, Jorge Ignacio; Saunier, Ghislain; Grafton, Scott T; Della-Maggiore, Valeria

    2015-08-01

    Viewing a person perform an action activates the observer's motor system. Whether this phenomenon reflects the action's kinematics or its final goal remains a matter of debate. One alternative to this apparent controversy is that the relative influence of goal and kinematics depends on the information available to the observer. Here, we addressed this possibility. For this purpose, we measured corticospinal excitability (CSE) while subjects viewed 3 different grasping actions with 2 goals: a large and a small object. Actions were directed to the large object, the small object, or corrected online in which case the goal switched during the movement. We first determined the kinematics and dynamics of the 3 actions during execution. This information was used in 2 other experiments to measure CSE while observers viewed videos of the same actions. CSE was recorded prior to movement onset and at 3 time points during the observed action. To discern between goal and kinematics, information about the goal was manipulated across experiments. We found that the goal influenced CSE only when its identity was known before movement onset. In contrast, a kinematic modulation of CSE was observed whether or not information regarding the goal was provided. PMID:24591524

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. The observational influence of the North Atlantic SST tripole on the early spring atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Han, Zhe; Luo, Feifei; Wan, Jianghua

    2016-03-01

    This study investigated the forcing of the North Atlantic sea surface temperature (SST) tripole on the North Atlantic Oscillation (NAO)-like circulation in early spring (February-April) in observations. Corresponding to an SST tripole forcing in early spring, the atmospheric circulation is very weak and insignificant. However, further analyses indicate that the observational effect of the SST anomalies on the NAO-like circulation is disturbed by the concomitant sea ice anomalies. With the linear effects of sea ice anomalies removed, there is an equivalent barotropic NAO-like circulation in early spring related to a North Atlantic SST tripole.

  7. Combining and Comparing Astrometric Data from Different Epochs: A Case Study with Hipparcos and Nano-JASMINE

    NASA Astrophysics Data System (ADS)

    Michalik, D.; Lindegren, L.; Hobbs, D.; Lammers, U.; Yamada, Y.

    2012-09-01

    The Hipparcos mission (1989-1993) resulted in the first space-based stellar catalogue including measurements of positions, parallaxes and annual proper motions accurate to about one milli-arcsecond. More space astrometry missions will follow in the near future. The ultra-small Japanese mission Nano-JASMINE (launch in late 2013) will determine positions and annual proper motions with some milli-arcsecond accuracy. In mid 2013 the next-generation ESA mission Gaia will deliver some tens of micro-arcsecond accurate astrometric parameters. Until the final Gaia catalogue is published in early 2020 the best way of improving proper motion values is the combination of positions from different missions separated by long time intervals. Rather than comparing positions from separately reduced catalogues, we propose an optimal method to combine the information from the different data sets by making a joint astrometric solution. This allows to obtain good results even when each data set alone is insufficient for an accurate reduction. We demonstrate our method by combining Hipparcos and simulated Nano-JASMINE data in a joint solution. We show a significant improvement over the conventional catalogue combination.

  8. 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…

  9. Mineral dust influence on West-African Sahel rainrates as observed by MODIS and TRMM

    NASA Astrophysics Data System (ADS)

    Klüser, L.; Holzer-Popp, T.

    2009-04-01

    Mineral Dust in the West-African Sahel, either advected from source regions in the Sahara or mobilised by local sources, interacts with the local climate system by modulating the radiation balance and also by changing cloud properties and rainfall. Mineral dust affects rain rates and precipitation amounts of clouds subject to the dust entrainment mainly by the increased number of available cloud condensation nuclei leading to a larger number of cloud droplets with overall smaller droplet sizes. Aerosol observations from the MODerate resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite and rainfall data from the Tropical Rainfall measuring Mission (TRMM) are used to examine the interactions of mineral dust and rainfall in the West-African Sahel. Five years of daily TRMM rainrates and droplet sizes are analysed with respect to atmospheric dust loadings in the West-African Sahel as inferred from MODIS AOD observations (only AOD observations showing mineral dust aerosol as inferred from MODIS aerosol type classification and Ångstrom exponents are used). The ratio of observed precipitation event numbers and total cloud observation numbers in the Sahel is significantly reduced in the presence of mineral dust, reaching up to rainfall reduction by more than 50% in scenes with high dust loading. Not only the number of precipitation events but also the rain rates and raindrop sizes for precipitating clouds are found to be generally reduced under dusty conditions. As well median rain rates as also the spread of the 25%- and 75%-quantiles of the observed rain rate distribution are significantly lower under dusty conditions. From these results it can be concluded that also year-to-year variations of monsoon onset and overall precipitation amount of the summer monsoon, an important factor for both, vegetation and human life in the region, are sensitive to mineral dust export from the Sahara towards the Sahel and to the amount of locally mobilised mineral dust

  10. 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.

  11. 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. PMID:2086629

  12. 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

  13. Io's volcanic influence on the Io plasma torus: HISAKI observation in 2015

    NASA Astrophysics Data System (ADS)

    Tsuchiya, F.; Yoshioka, K.; Kimura, T.; Murakami, G.; Yoneda, M.; Koga, R.; Kagitani, M.; Sakanoi, T.; Kasaba, Y.; Yamazaki, A.; Yoshikawa, I.

    2015-12-01

    The satellite Io which has many active volcanos supplies volcanic gases to the Jovian magnetosphere with typical rate of 1 ton/sec and has been known be a primary source of plasmas in the magnetosphere. Change in the volcanic activity on Io should cause change of the supply rate and could affect structure of the magnetosphere and dynamics occurs in it. However, responses of the magnetosphere to the volcanic activity is still not fully understood; one of the reasons is lack of continuous and long term observations of Io' volcanic gas extended around Io, plasmas in the Io torus, and activity of the magnetosphere. The extreme ultraviolet (EUV) spectroscope, EXCEED, onboard the HISAKI satellite has capability to measure ion and atomic emission lines in EUV range (55-145nm) and is dedicated to observing solar system planets. The satellite has been successfully launched on Sep. 2013 and 2nd campaign of Io plasma torus and Jovian northern EUV aurora observation has been done from the end of Nov. 2014 to middle of May 2015. On middle of Jan. 2015, HISAKI detected gradual increase in intensity of S+ emission lines and decrease of S3+ ones in the plasma torus. The S+ intensity showed a maximum around the end of Feb. and S++ and S3+ intensities also showed maxima subsequently. Simultaneous ground based observation of the sodium nebula showed increase of the emission intensity from the middle of Jan. to the beginning of Mar. These observations suggest that the volcanic activity began at the middle of Jan. and increase neutral atom and ion densities in the Io torus. The intensities of S+ and S2+ ions returned to the pre-increase level by the middle of May 2015. S3+ had still been in the decay phase at the end of the observation. Change in radial structure of the plasma torus was also found during the volcanic event. The intensity of S+ ion began to increase around the orbit of Io (6 Jovian radii). The brightened region propagated outward and reached at 8.5 Jovian radii from

  14. 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.

  15. 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.

  16. 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

  17. An observational analysis: Tropical relative to Arctic influence on midlatitude weather in the era of Arctic amplification

    NASA Astrophysics Data System (ADS)

    Cohen, Judah

    2016-05-01

    The tropics, in general, and El Niño/Southern Oscillation (ENSO) in particular are almost exclusively relied upon for seasonal forecasting. Much less considered and certainly more controversial is the idea that Arctic variability is influencing midlatitude weather. However, since the late 1980s and early 1990s, the Arctic has undergone the most rapid warming observed globally, referred to as Arctic amplification (AA), which has coincided with an observed increase in extreme weather. Analysis of observed trends in hemispheric circulation over the period of AA more closely resembles variability associated with Arctic boundary forcings than with tropical forcing. Furthermore, analysis of intraseasonal temperature variability shows that the cooling in midlatitude winter temperatures has been accompanied by an increase in temperature variability and not a decrease, popularly referred to as "weather whiplash."

  18. Observational signatures of the influence of the interplanetary shocks on the associated low-energy particle events

    NASA Astrophysics Data System (ADS)

    Heras, A. M.; Sanahuja, B.; Sanderson, T. R.; Marsden, R. G.; Wenzel, K.-P.

    1994-01-01

    We have analyzed the temporal evolution of the upstream particle fluxes and anisotropies in a set of particle events associated with interplanetary shocks, detected by International Sun-Earth Explorer (ISEE) 3 during the period 1978-1980 in the 147-238 and 620-1000 keV energy ranges. In particular, we have studied those features that can perhaps be used as signatures of the history of the influence of the shock on the particle event. We have paid special attention to the evolution of the flux anisotropy that can carry relevant information on the contribution of shock accelerated particles to the total observed flux. Our analysis shows that during most events, long-lasting (between 5 and 36 hours) large anisotropies are observed upstream of the shock, supporting the hypothesis of continuous injection of shock accelerated paricles in the interplanetary medium while the shock is propagating outward from the Sun. The evolution of the anisotropy throughout each event shows a dependence on the longitude of the parent solar source. We have interpreted the observations considering that shock accelerated particles contribute significantly to the total observed flux from the time when the shock intersects the magnetic field line that connects with the observer. The heliocentric distance of this initial intersection point has been derived from the flux anisotropy observations for each event. The values obtained show a distribution with respect to the longitude of the solar source that can be reproduced with a simple model, which assumes a spherical shock with an angular extension approximately equals 100 deg and an archimedian spiral structure for the interplanetary magnetic field. The results of this work provide a further insight into both the importance of shock acceleration, as well as the influence of the large-scale shock structure in low-energy particle events.

  19. 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.

  20. 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.

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

    DOE PAGESBeta

    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

  2. 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

  3. 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

  4. Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations

    PubMed Central

    Álvarez-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. PMID:22389611

  5. Democratic parenting beliefs and observed parental sensitivity: Reciprocal influences between coparents.

    PubMed

    Schofield, Thomas J; Weaver, Jennifer M

    2016-06-01

    Three hundred sixty-five 2-parent families from the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development were rated by trained observers on their parenting behavior at 6 assessments ranging from 6 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. (PsycINFO Database Record PMID:26551656

  6. 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.

  7. 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.

  8. Observed Influence of Riming, Temperature, and Turbulence on the Fallspeed of Solid Precipitation

    NASA Astrophysics Data System (ADS)

    Garrett, T. J.; Yuter, S. E.

    2014-12-01

    Forecasts of the amount and geographic distribution of snow are highly sensitive to a model's parameterization of hydrometeor fallspeed. Riming is generally thought to lead to larger, heavier particles with higher terminal velocities. Yet models commonly assume that heavily rimed particles such as graupel have a fixed density and that their settling speed is unaffected by turbulence in storms. Here we show automated measurements of photographed hydrometeor shape and fallspeed using a Multi Angle Snowflake Camera placed in Utah's Wasatch Mountain Range. The data show that graupel in low turbulence conditions has a size-dependent fallspeed distribution with a mode near 1 m/s, a result that is generally consistent with prior observations. However, the distributions are broadened by turbulence and a correspondence between particle density and air temperature. In high turbulence and at low temperatures, any sensitivity of fallspeed to particle size disappears.

  9. Observed influence of riming, temperature, and turbulence on the fallspeed of solid precipitation

    NASA Astrophysics Data System (ADS)

    Garrett, Timothy J.; Yuter, Sandra E.

    2014-09-01

    Forecasts of the amount and geographic distribution of snow are highly sensitive to a model's parameterization of hydrometeor fallspeed. Riming is generally thought to lead to particles with a higher mass and terminal velocity. Yet models commonly assume that heavily rimed particles such as graupel have a fixed density and that their settling speed is unaffected by turbulence in storms. Here we show automated measurements of photographed hydrometeor shape and fallspeed using a new instrument placed in Utah's Wasatch Mountain Range. The data show that graupel in low-turbulence conditions has a size-dependent fallspeed distribution with a mode near 1 m s-1, a result that is generally consistent with prior observations. However, the distributions are broadened by turbulence and there is a correspondence between particle density and air temperature. In high turbulence and at low temperatures, any sensitivity of fallspeed to particle size disappears.

  10. 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.

  11. Direct Observation of Transient Surface Species during Ge Nanowire Growth and Their Influence on Growth Stability.

    PubMed

    Sivaram, Saujan V; Shin, Naechul; Chou, Li-Wei; Filler, Michael A

    2015-08-12

    Surface adsorbates are well-established choreographers of material synthesis, but the presence and impact of these short-lived species on semiconductor nanowire growth are largely unknown. Here, we use infrared spectroscopy to directly observe surface adsorbates, hydrogen atoms and methyl groups, chemisorbed to the nanowire sidewall and show they are essential for the stable growth of Ge nanowires via the vapor-liquid-solid mechanism. We quantitatively determine the surface coverage of hydrogen atoms during nanowire growth by comparing ν(Ge-H) absorption bands from operando measurements (i.e., during growth) to those after saturating the nanowire sidewall with hydrogen atoms. This method provides sub-monolayer chemical information at relevant reaction conditions while accounting for the heterogeneity of sidewall surface sites and their evolution during elongation. Our findings demonstrate that changes to surface bonding are critical to understand Ge nanowire synthesis and provide new guidelines for rationally selecting catalysts, forming heterostructures, and controlling dopant profiles. PMID:26147949

  12. Influence of LCD color reproduction accuracy on observer performance using virtual pathology slides

    NASA Astrophysics Data System (ADS)

    Krupinski, Elizabeth A.; Silverstein, Louis D.; Hashmi, Syed F.; Graham, Anna R.; Weinstein, Ronald S.; Roehrig, Hans

    2012-02-01

    The use of color LCDs in medical imaging is growing as more clinical specialties use digital images as a resource in diagnosis and treatment decisions. Telemedicine applications such as telepathology, teledermatology and teleophthalmology rely heavily on color images. However, standard methods for calibrating, characterizing and profiling color displays do not exist, resulting in inconsistent presentation. To address this, we developed a calibration, characterization and profiling protocol for color-critical medical imaging applications. Physical characterization of displays calibrated with and without the protocol revealed high color reproduction accuracy with the protocol. The present study assessed the impact of this protocol on observer performance. A set of 250 breast biopsy virtual slide regions of interest (half malignant, half benign) were shown to 6 pathologists, once using the calibration protocol and once using the same display in its "native" off-the-shelf uncalibrated state. Diagnostic accuracy and time to render a decision were measured. In terms of ROC performance, Az (area under the curve) calibrated = 0.8640; uncalibrated = 0.8558. No statistically significant difference (p = 0.2719) was observed. In terms of interpretation speed, mean calibrated = 4.895 sec, mean uncalibrated = 6.304 sec which is statistically significant (p = 0.0460). Early results suggest a slight advantage diagnostically for a properly calibrated and color-managed display and a significant potential advantage in terms of improved workflow. Future work should be conducted using different types of color images that may be more dependent on accurate color rendering and a wider range of LCDs with varying characteristics.

  13. 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

  14. 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.

  15. 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

  16. The Influence of Solar Extreme Ultraviolet Radiation on Ring Current Ion Composition: Polar and CRRES Observations

    NASA Astrophysics Data System (ADS)

    Roeder, J. L.; Fennell, J. F.; Pulkkinen, T. I.; Turner, N. E.; Grande, M.

    2001-05-01

    The ion composition observations by the Polar spacecraft from the last solar minimum to the present are compared to similar observations by CRRES in the previous cycle. The Magnetospheric Ion Composition Spectrometer (MICS) was onboard CRRES and is part of the Polar CAMMICE experiment. The MICS sensor provided mass and charge state composition data for the energetic (1-425 keV/q) ions including H+, He+, He++, and O+. The 5-minute average number densities for each species are computed by mapping the MICS fluxes down to the magnetic equator using the measured pitch angle distributions and integrating the equatorial spectrum over the energy range 1-200 keV/q. Approximately 3.5 years of the Polar mission in the rising part of the solar cycle are used for the database. The densities are analyzed statistically with the solar EUV index F10.7 and various geomagnetic indices such as Kp and Dst. The results are compared with a similar study of the ion composition in the energy range 0.9-15.9 keV/q measured by the GEOS 2 satellite during geomagnetically quiet periods [Young et al., 1982], and with the recent survey of the relative composition measured by Polar averaged over all times [Pulkkinen et al., 2000]. It is found that ion densities at L ~ 6-7 during relatively quiet intervals show correlations to the EUV and geomagnetic activity similar to the results of Young et al. [1992]. At lower L the correlation of the ion density with the EUV and activity levels increases substantially, due in part to the extremely low energetic ion densities during the quiet intervals of solar minimum. This may be interpreted as a combination of the solar cycle effects on 1) the ring current source population; and 2) the processes which transport the ions to lower L. The behavior of the ion composition during geomagnetic stormtime is also investigated by restricting the density database to those intervals with the Dst index below a threshold value. Paradoxically, the Polar data shows that the

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

    PubMed Central

    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

  18. 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.

  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. An analysis of observations of mutual events of the Galilean satellites made in 1985 in Brazil

    NASA Astrophysics Data System (ADS)

    Arlot, J.-E.; Barroso, J.; Jablonsky, F. J.; Quast, G. R.; Thuillot, W.

    1990-03-01

    Mutual phenomena of the Galilean satellites occur every six years. These eclipses and occultations of a satellite by another lead to very accurate astrometric observations. During the last period in 1985 the Bureau des Longitudes organized a campaign of observation, and the Laboratorio Nacional de Astrofisica in Brazil joined it. This paper gives an analysis of the results obtained.

  1. 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

  2. Posture influences patient cough rate, sedative requirement and comfort during bronchoscopy: An observational cohort study

    PubMed Central

    2011-01-01

    Objectives To investigate differences between semi-recumbent and supine postures in terms of cough rate, oxygen desaturation, sedative use, and patient comfort during the initial phase of bronchoscopy. Methods Consecutive bronchoscopy patients (n = 69) participated in this observational cohort study. Posture was determined by the bronchoscopist's usual practice. Patient demographics, spirometry, pulse, and SpO2 were recorded. The initial phase was defined as the time from bronchoscopy insertion to visualisation of both distal main bronchi. Cough rate, peak pulse, nadir SpO2, oxygen supplementation, and sedative use during the initial phase were recorded. A post-procedure questionnaire was administered to the patient and the attending nurse. Results 36 patients had bronchoscopy in the semi-recumbent posture, 33 in the supine posture. 3 of 5 bronchoscopists performed in both postures. There were no differences in baseline parameters between the groups. The semi-recumbent posture resulted in significantly less cough (mean (SD) 3.6 (2.3) vs. 6.1 (4.5) coughs/min, p = 0.007) and less fentanyl use (70 (29) vs. 88 (28) mcg, p = 0.011) in the initial phase. There were no significant differences in the nadir SpO2, fall in SpO2, oxygen supplementation, or increase in pulse rate between the groups. On 100 mm visual analogue scale, nurse perception of patient discomfort was lower in the semi-recumbent position (23 (21) vs. 39 (28) mm, p = 0.01), and there was a trend towards less patient perceived cough in the semi-recumbent group (28 (25) vs. 40 (28) mm, p = 0.06). Conclusions Bronchoscopy performed in the semi-recumbent posture results in less cough and sedative requirement, and may improve patient comfort. PMID:22074355

  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. Observational Model for Precision Astrometry with the Space Interferometry Mission

    NASA Technical Reports Server (NTRS)

    Turyshev, Slava G.; Milman, Mark H.

    2000-01-01

    The Space Interferometry Mission (SIM) is a space-based 10-m baseline Michelson optical interferometer operating in the visible waveband that is designed to achieve astrometric accuracy in the single digits of the microarcsecond domain. Over a narrow field of view SIM is expected to achieve a mission accuracy of 1 microarcsecond. In this mode SIM will search for planetary companions to nearby stars by detecting the astrometric "wobble" relative to a nearby reference star. In its wide-angle mode, SIM will provide 4 microarcsecond precision absolute position measurements of stars, with parallaxes to comparable accuracy, at the end of its 5-year mission. The expected proper motion accuracy is around 3 microarcsecond/year, corresponding to a transverse velocity of 10 m/ s at a distance of 1 kpc. The basic astrometric observable of the SIM instrument is the pathlength delay. This measurement is made by a combination of internal metrology measurements that determine the distance the starlight travels through the two arms of the interferometer, and a measurement of the white light stellar fringe to find the point of equal pathlength. Because this operation requires a non-negligible integration time, the interferometer baseline vector is not stationary over this time period, as its absolute length and orientation are time varying. This paper addresses how the time varying baseline can be "regularized" so that it may act as a single baseline vector for multiple stars, as required for the solution of the astrometric equations.

  5. The influence of the Indian Ocean Dipole on interannual variations in phytoplankton size structure as revealed by Earth Observation

    NASA Astrophysics Data System (ADS)

    Brewin, Robert J. W.; Hirata, Takafumi; Hardman-Mountford, Nick J.; Lavender, Samantha J.; Sathyendranath, Shubha; Barlow, Ray

    2012-11-01

    Using a decade of satellite ocean-colour observations and a model that links chlorophyll-a to the size of the phytoplankton cells, parameterised using pigment data from the Indian Ocean, we examine the implications of the Indian Ocean Dipole (IOD) for phytoplankton size structure. The inferred interannual anomalies in phytoplankton size structure are related to those in sea-surface temperature (SST) and sea-surface height (SSH), derived using satellite radiometry and altimetry, and stratification, derived using the Simple Ocean Data Assimilation (SODA) database. In regions influenced by the Indian Ocean Dipole, we observe a tight correlation between phytoplankton size structure and the physical variables, such that interannual variations in the physical variables accounts for up to 70% of the total variance in phytoplankton size structure. For much of the Indian Ocean, low temperature, low SSH and low stratification (indicative of a turbulent environment) are correlated with larger size classes, consistent with theories on coupling between physical-chemical processes and ecosystem structure. To the extent that phytoplankton function is related to its size structure, changes in physical forcing are likely to influence biogeochemical cycles in the region and the pelagic food web. The limitations of our approach are discussed and we highlight future challenges in satellite ocean-colour monitoring, should climate change lead to any modification in our marine ecosystem.

  6. 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).

  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. 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

  9. 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.

    2015-05-01

    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.

  10. Investigating the Influence of Anthropogenic Forcing on Observed Mean and Extreme Sea Level Pressure Trends over the Mediterranean Region

    DOE PAGESBeta

    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

  11. Investigating the Influence of Anthropogenic Forcing on Observed Mean and Extreme Sea Level Pressure Trends over the Mediterranean Region

    PubMed Central

    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-scale 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. PMID:22654622

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. Patterns of flow and sedimentation in channels with variable tidal and fluvial influence: observations from coastal Georgia.

    NASA Astrophysics Data System (ADS)

    Hughes, Z. J.; Howes, N. C.; Georgiou, I. Y.; FitzGerald, D.

    2014-12-01

    Significant differences exist between the sedimentology of fluvial and tidal channels. This is primarily the result of differences in the temporal and spatial patterns of the hydrodynamics, and, where the regimes overlap, complex interactions between the two. In this detailed study, we investigate flow and resulting sedimentation in six tidal meander bends with varying levels of fluvial influence. Tidal currents were recorded using a combination of continuous deployments and vessel-based synoptic measurements. Residual circulation patterns and estimates of tidal asymmetry were determined. A series of cores, taken along transects both parallel and perpendicular to the channel, were used to examine the spatial variation of mud and sand deposits. We observed a separation of flow into ebb and flood pathways, creating a residual circulation and encouraging the growth of point bars. At our study sites, the majority of the channels were found to be ebb dominant. At several tidal sites, we identified regions of the channel where the flow remained close to zero throughout much of the tidal cycle. This occurred in sections of the channel that were primarily active during the flood tide. In these areas, settling of fine sediment was not limited to slack water periods as is common to most systems and, instead, could occur over longer periods. This translated to sandier sediments being observed in parts of the channel that were primarily active during the ebb tide, compared to muddier sediments where the channel only was active during flood tides. In regions where there was a greater fluvial influence, flow reversal during flood tides was reduced, and the timing of slack water was altered. At the upstream limit of our observations, minimal flow reversal was observed during the tide and the current slowed to zero (slack) only once per tidal cycle (during the flood). Although water levels at this site indicated that the tidal wave was strongly flood dominated due to shallow water

  17. Stratospheric influence on the seasonal cycle of nitrous oxide in the troposphere as deduced from aircraft observations and model simulations

    NASA Astrophysics Data System (ADS)

    Ishijima, Kentaro; Patra, Prabir K.; Takigawa, Masayuki; Machida, Toshinobu; Matsueda, Hidekazu; Sawa, Yosuke; Steele, L. Paul; Krummel, Paul B.; Langenfelds, Ray L.; Aoki, Shuji; Nakazawa, Takakiyo

    2010-10-01

    The atmospheric N2O variations between the Earth's surface and the lower stratosphere, simulated by an atmospheric general circulation model-based chemistry transport model (ACTM), are compared with aircraft and satellite observations. We validate the newly developed ACTM simulations of N2O for loss rate and transport in the stratosphere using satellite observations from the Aura Microwave Limb Sounder (Aura-MLS), with optimized surface fluxes for reproducing N2O trends observed at the surface stations. Observations in the upper troposphere/lower stratosphere (UT/LS) obtained by the Japan AirLines commercial flights commuting between Narita (36°N), Japan, and Sydney (34°S), Australia, have been used to study the role of stratosphere-troposphere exchange (STE) on N2O variability near the tropopause. Low N2O concentration events in the UT region are shown to be captured statistically significantly by the ACTM simulation. This is attributed to successful reproduction of stratospheric air intrusion events and N2O vertical/horizontal gradients in the lower stratosphere. The meteorological fields and N2O concentrations reproduced in the ACTM are used to illustrate the mechanisms of STE and subsequent downward propagation of N2O-depleted stratospheric air in the troposphere. Aircraft observations of N2O vertical profile over Surgut (West Siberia, Russia; 61°N), Sendai-Fukuoka (Japan; 34°N-38°N), and Cape Grim (Tasmania, Australia; 41°S) have been used to estimate the relative contribution of surface fluxes, transport seasonality in the troposphere, and STE to N2O seasonal cycles at different altitude levels. Stratospheric N2O tracers are incorporated in the ACTM for quantitative estimation of the stratospheric influence on tropospheric N2O. The results suggest strong latitude dependency of the stratospheric contribution to the tropospheric N2O seasonal cycle. The periods of seasonal minimum in the upper troposphere, which are spring over Japan and summer over Surgut

  18. 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

  19. 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

  20. 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.

  1. An Observational Case Study on the Influence of Atmospheric Boundary-Layer Dynamics on New Particle Formation

    NASA Astrophysics Data System (ADS)

    Platis, Andreas; Altstädter, Barbara; Wehner, Birgit; Wildmann, Norman; Lampert, Astrid; Hermann, Markus; Birmili, Wolfram; Bange, Jens

    2016-01-01

    We analyze the influence of atmospheric boundary-layer development on new particle formation (NPF) during the morning transition. Continuous in-situ measurements of vertical profiles of temperature, humidity and aerosol number concentrations were quasi-continously measured near Melpitz, Germany, by unmanned aerial systems to investigate the potential connection between NPF and boundary-layer dynamics in the context of turbulence, temperature and humidity fluctuations. On 3 April 2014 high number concentrations of nucleation mode particles up to 6.0 × 10^4 cm^{-3} were observed in an inversion layer located about 450 m above ground level. The inversion layer exhibited a spatial temperature structure parameter C_T^2 15 times higher and a spatial humidity structure parameter C_q^2 5 times higher than in the remaining part of the vertical profile. The study provides hints that the inversion layer is responsible for creating favorable thermodynamic conditions for a NPF event. In addition, this layer showed a strong anti-correlation of humidity and temperature fluctuations. Using estimates of the turbulent mixing and dissipation rates, it is concluded that the downward transport of particles by convective mixing was also the reason of the sudden increase of nucleation mode particles measured on ground. This work supports the hypothesis that many of the NPF events that are frequently observed near the ground may, in fact, originate at elevated altitude, with newly formed particles subsequently being mixed down to the ground.

  2. 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

  3. 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

  4. Astrometric positions of Jupiter VI, Jupiter VII, and minor planet (2153) Akiyama from Table Mountain Observatory, with remarks on decimalization in astronomy

    NASA Astrophysics Data System (ADS)

    Mulholland, J. Derral

    1990-11-01

    Astrometric positions of satellites VI and VII of Jupiter were obtained on plates taken at the 60-cm reflector at Table Mountain Observatory on one night in February 1968. Prediscovery images of minor planet (2153) Akiyama were found on two of the plates. The presentation of numerical results is bolstered with remarks on the four-century history of use of decimal fractions in astronomy.

  5. Tropical Atlantic influence on Pacific variability and mean state in the twentieth century in observations and CMIP5

    NASA Astrophysics Data System (ADS)

    Kucharski, F.; Syed, F. S.; Burhan, A.; Farah, I.; Gohar, A.

    2015-02-01

    This paper investigates the influence of the tropical Atlantic on the tropical Pacific interannual variability and mean state in the twentieth century. It is demonstrated that observational datasets show a significant time-delayed impact of the tropical Atlantic on tropical Pacific sea surface temperatures, leading to an anticorrelation between the tropical Atlantic and the eastern Pacific if the Atlantic is leading by about 10 months. This result is robust across different sea surface temperature reconstructions. There is no robust correlation between the tropical Atlantic and the eastern Pacific when the Pacific is leading, although in recent decades a positive correlation between the two basins is more dominant. An analysis of the surface pressure response to the tropical Atlantic indicates an atmospheric bridge and a modification of the Walker circulation as the likely trigger for the teleconnection, and this result is consistent with recent observational and modelling results for the recent decades. 30 out of the analyzed 45 World Climate Research Program's Coupled Model Intercomparison Project Phase 5 (CMIP5) models show statistically significant anticorrelations between individual tropical Atantic warm and cold events and the time-lagged eastern Pacific sea surface temperatues. 16 out of the 45 analyzed models fulfill the more stringent criterion of lead-lag correlations between the tropical Atlantic and Pacific similar to the observations. The atmospheric bridge mechanism seems also valid in the selected CMIP5 models. We have identified the tropical Atlantic warm bias present in nearly all models as one potential candidate for the overall weak time-delayed teleconnection between the tropical Atlantic and the Pacific, but also other mean state biases are important. In the selected models a stronger warming of the tropical Atlantic Ocean compared to the global sea surface temperature mean is associated with a La Nina-like mean state change in the tropical

  6. 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

  7. 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

  8. 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

  9. Uncertainties of astrometric catalogues SPM_{MC}, XPM and UCAC4 in the Magellanic Clouds using the Wielen method

    NASA Astrophysics Data System (ADS)

    Dávila, E.; Vieira, K.

    2015-10-01

    The individual uncertainties of the proper motion catalogues SPM_{MC}, XPM and UCAC4 are determined using the method of Wielen, in an area of the sky containing the Magellanic Clouds. These uncertainties are a measure of the quality and the reliability of these catalogs for kinematical studies. The data preparation begins by cross identifying stars common to the catalogs, and on this sample, systematic differences are detected, modeled and corrected. After applying the Wielen method and evaluating the results, it follows that the catalog of best astrometric quality is UCAC4, with an uncertainty of (epsilon _{mu _{alpha } cos(delta )},epsilon _{mu _{delta }})=(2.92,1.90) mas/yr. The SPM_{MC} has a quality similar to the previous catalogue, expressed as (epsilon _{mu _{alpha } cos(delta )},epsilon _{mu _{delta }})_{frac {SPM_{MC}}{UCAC4}}=(1.11,1.53) times the UCAC4. Finally the quality for the XPM differs significantly from the other two catalogues, its errors are (epsilon _{mu _{alpha } cos(delta )},epsilon _{mu _{delta }})_{(XPM)/(UCAC4)}=(6.32,8.87) times the UCAC4.

  10. Study of key factors influencing dust emission: An assessment of GEOS-Chem and DEAD simulations with observations

    NASA Astrophysics Data System (ADS)

    Bartlett, Kevin S.

    Mineral dust aerosols can impact air quality, climate change, biological cycles, tropical cyclone development and flight operations due to reduced visibility. Dust emissions are primarily limited to the extensive arid regions of the world, yet can negatively impact local to global scales, and are extremely complex to model accurately. Within this dissertation, the Dust Entrainment And Deposition (DEAD) model was adapted to run, for the first known time, using high temporal (hourly) and spatial (0.3°x0.3°) resolution data to methodically interrogate the key parameters and factors influencing global dust emissions. The dependence of dust emissions on key parameters under various conditions has been quantified and it has been shown that dust emissions within DEAD are largely determined by wind speeds, vegetation extent, soil moisture and topographic depressions. Important findings were that grid degradation from 0.3ºx0.3º to 1ºx1º, 2ºx2.5º, and 4°x5° of key meteorological, soil, and surface input parameters greatly reduced emissions approximately 13% and 29% and 64% respectively, as a result of the loss of sub grid detail within these key parameters at coarse grids. After running high resolution DEAD emissions globally for 2 years, two severe dust emission cases were chosen for an in-depth investigation of the root causes of the events and evaluation of the 2°x2.5° Goddard Earth Observing System (GEOS)-Chem and 0.3°x0.3° DEAD model capabilities to simulate the events: one over South West Asia (SWA) in June 2008 and the other over the Middle East in July 2009. The 2 year lack of rain over SWA preceding June 2008 with a 43% decrease in mean rainfall, yielded less than normal plant growth, a 28% increase in Aerosol Optical Depth (AOD), and a 24% decrease in Meteorological Aerodrome Report (METAR) observed visibility (VSBY) compared to average years. GEOS-Chem captured the observed higher AOD over SWA in June 2008. More detailed comparisons of GEOS

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. The influence of body composition on therapeutic hypothermia: a prospective observational study of patients after cardiac arrest

    PubMed Central

    Jimmink, Joost J; Binnekade, Jan M; Paulus, Frederique; Mathus-Vliegen, Elisebeth MH; Schultz, Marcus J; Vroom, Margreeth B

    2008-01-01

    Introduction Patients after out-of-hospital cardiac arrest (OHCA) benefit from therapeutic hypothermia for 24 hours. The time needed to reach hypothermia (target temperature of 32°C to 34°C) varies widely. In this study, we explore the relation between measures of body composition and the time needed to reach target temperature with hypothermia. Method We conducted a prospective observational study in patients treated with hypothermia after OHCA. Data collected included weight and height, body composition by anthropometric measures and by single-frequency body impedance, and waist-to-hip ratio. Analysis of concordance between impedance and anthropometric measures and hazard ratios of achieving target temperature (event) corrected for different body composition measures. Results Twenty-seven patients were included. The median (interquartile range) time to reach target temperature after admission to the intensive care unit was 191 (105 to 382) minutes. Intraclass correlation for total body fat (TBF) measures was 0.94 (95% confidence interval [CI] 0.89 to 0.97). Only TBF percentage (anthropometrics by the Durnin's table) appeared to be associated with time to reach target temperature: 0.93 (95% CI 0.87 to 0.99; P = 0.03). Conclusion The body composition measures from single-frequency impedance and anthropometrics appear to be very concordant. Only TBF percentage (anthropometrics) showed a significant but clinically irrelevant influence on time needed to achieve target temperature with hypothermia. We conclude that there are no indications to adjust current cooling practice toward the body composition of patients. PMID:18616810

  17. 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

  18. 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.

  19. 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.

  20. Measuring and scanning methods in astrometric processing of the photographic plates

    NASA Astrophysics Data System (ADS)

    Bocsa, Gheorghe; Tsvetkov, Milcho

    2008-09-01

    This paper is dedicated to the first comparative study concerning position determinations of selected small bodies in the solar system observed with the Bucharest Observatory equatorial PRIN-MERTZ refractor (d = 0.38m, f = 6.0m) by means of the Carl-Zeiss ASCORECORD measurements and the processing of 5 photographic plates dating from 1971, digitized with the EPSON 1640XL flatbed scanner of the Sofia. The calculations were done with PC computer, with the same program for both cases using a double precision accuracy on the way to compare manual measurements and data processing using the digitized plates. The scan resolution used was 1600 dpi-14 bit grayscale up to 3.6 densities. With this scale 1 pix = 15.875 microns we had the extended field of 15184×15219 pix. The format of the scans was FITS using the standard twain driver for EPSON 1640XL and software developed by S. Mottola.

  1. 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.

  2. 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

  3. Evaluation of a numerical observer to determine the influence of JPEG data compression on the diagnostic quality of computed tomography images

    NASA Astrophysics Data System (ADS)

    Uys, Nico J.; Herbst, Charles P.; Lotter, Mattheus G.; De Villiers, Johannes F. K.; van Zyl, Martin

    1997-05-01

    A numerical observer (JPEGNO) to evaluate the influence of JPEG compression on the diagnostic quality of CT image is proposed. JPEGNO is based on the grey scale histogram of the image and is defined as the inverse of the sum of the difference between successive grey levels in the histogram of the image.

  4. Full-sky Astrometric Mapping Explorer (FAME): CCD Tests and Optical Requirements

    NASA Astrophysics Data System (ADS)

    Johnston, K. J.

    2002-12-01

    The FAME project team has pursued several studies in order to resolve technical, schedule, and mission cost concerns and to investigate requirements for future space astrometry missions. Two CCD fabrication runs have been completed with good yields of operating CCDs. The first fabrication run, using a mixture of 37 and 100 ohm cm substrate, produced 100 ohm cm devices with a reduced CTE. Thus, only 37 ohm cm substrate was used in the second run. To mitigate the effects of on-orbit radiation damage, FAME CCDs are designed with charge injection capabilities. The current FAME CCDs have a reduced yield of devices with good operating charge injection. The CCDs are currently being tested for image centroiding accuracy and operating characteristics, both before and after laboratory irradiation. The intent is to learn more about the radiation effects on the CCDs and the methods of mitigating the effects of charge transfer inefficiency. Results of these tests will be given. The requirements for very accurate centroiding of images places strict requirements on the optical design, distortions, and the tolerances on the alignment and thermal variations of the optical components of the instrument. The exact requirements necessary to reach the measurement accuracy have a large effect on the schedule and cost of manufacturing and installing the optics. Therefore, special studies have been conducted to determine the exact requirements for the optical design. The science that would result from the FAME observations remains compelling, which is the reason for the efforts to continue to develop the project. The latest status and future plans for FAME will be included.

  5. 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

  6. 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)…

  7. 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.

  8. Estimation of the influence of cloudiness on the Earth observation from space through a gap in a cloudy field

    NASA Astrophysics Data System (ADS)

    Belov, V. V.; Kirnos, I. V.; Tarasenkov, M. V.

    2015-11-01

    For atmospheric correction of satellite images, the problem is formulated to estimate the distance from a cloud at which its influence on the satellite image of the Earth surface can be neglected. The Monte Carlo method of conjugate trajectories is used. The gap radius in the field of continuous cloudiness at which the influence of the cloudy medium on the received signal intensity does not exceed 10 % is obtained. It is revealed that for the Lambert law of radiation reflection from the Earth surface, the curve of the dependence of the received signal intensity on the gap radius has a maximum caused by the opposite influence of light scattering by the cloudy medium and radiation reflection by the surface (adjacency effect). To further generalize the examined problem to a stochastic cloud field, the method of direct simulation of photon trajectories in a stochastic medium is compared with G. A. Titov's method of closed equations in the gap vicinity. A comparison is carried out with the model of the stochastic medium in the form of a cloud field of constant geometric thickness consisting of rectangular clouds whose boundaries are determined by the stationary Poisson flow of points. It is demonstrated that results of calculations can differ at most by 20‒30 %; however, in some cases (for some sets of initial data), the difference for the entire region of cloud cover indices is within 7 %.

  9. Influence of end-to-end diffusion on intramolecular energy transfer as observed by frequency-domain fluorometry

    NASA Astrophysics Data System (ADS)

    Lakowicz, Joseph R.; Wiczk, Wieslaw M.; Gryczynski, Ignacy; Szmacinski, Henryk; Johnson, Michael L.

    1990-05-01

    We investigated the influence of end-to-end diffusion on intramolecular energy transfer between a naphthalene donor and dansyl acceptor linked by polymethylene chain. A range of viscosities of 0.6 - 200cP were obtained using propylene glycol at different temperatures (0-80°C) and methanol at 20°C. The intensity decays of naphthalene were measured in frequency-domain. Several theoretical models, including distance distributions were used to fit the data. The results indicate that end-to-end diffusion of flexible donor - acceptor pairs can be readily detected and quantified using frequency-domain fluorometry.

  10. 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.

  11. 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

  12. 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…

  13. 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.

  14. 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

  15. 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. PMID:26842827

  16. 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.

  17. To blame or not to blame: influences of target race and observer sex on rape blame attribution.

    PubMed

    Donovan, Roxanne A

    2007-06-01

    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) and strength and/or toughness (matriarch stereotype). The myth of the Black male sexual predator of White women is also investigated. Data provided partial support for the jezebel stereotype. There were also contradictory findings supporting and challenging the acceptance of the Black rapist of White women stereotype. No significant differences were found for the matriarch stereotype. Reasons for and implications of findings are explored. PMID:17515432

  18. Influence of polymer network in polymer-stabilized ferroelectric liquid crystals and its direct observation using a confocal microscope

    NASA Astrophysics Data System (ADS)

    Petkovšek, R.; Pirš, J.; Kralj, S.; Čopič, M.; Šuput, D.

    2006-01-01

    The paper presents the analysis of the three-dimensional polymer network distribution inside the polymer-stabilized ferroelectric liquid-crystal layer based on the laser scanning fluorescence confocal microscopy and a fluorescent dye tagging of the polymer. The studies of polymer-stabilized ferroelectric liquid-crystal structures described in this paper are focused on the comparison of the influence of polymer network in case that the polymerization is initiated in the chevron as well as in the quasibookshelf liquid-crystal molecular orientation. In the case of the chevron structure the regular distribution of the polymer network within the layer leads to the monostability of the chevron state. On the other hand the specific distribution of the polymer in the polymer-stabilized quasibookshelf stripe textures leads to the perfect bistability, improved multiplex driving, and analog gray scale capability.

  19. 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.

  20. Does type of hospital ownership influence physicians' daily work schedules? An observational real-time study in German hospital departments

    PubMed Central

    Mache, Stefanie; Scutaru, Cristian; Vitzthum, Karin; Quarcoo, David; Schöffel, Norman; Welte, Tobias; Klapp, Burghard F; Groneberg, David A

    2009-01-01

    Background During the last two decades the German hospital sector has been engaged in a constant process of transformation. One obvious sign of this is the growing amount of hospital privatization. To date, most research studies have focused on the effects of privatization regarding financial outcomes and quality of care, leaving important organizational issues unexplored. Yet little attention has been devoted to the effects of privatization on physicians' working routines. The aim of this observational real-time study is to deliver exact data about physicians' work at hospitals of different ownership. By analysing working hours, further impacts of hospital privatization can be assessed and areas of improvement identified. Methods Observations were made by shadowing 100 physicians working in private, for-profit or non-profit as well as public hospital departments individually during whole weekday shifts in urban German settings. A total of 300 days of observations were conducted. All working activities were recorded, accurate to the second, by using a mobile personal computer. Results Results have shown significant differences in physicians' working activities, depending on hospital ownership, concerning working hours and time spent on direct and indirect patient care. Conclusion This is the first real-time analysis on differences in work activities depending on hospital ownership. The study provides an objective insight into physicians' daily work routines at hospitals of different ownership, with additional information on effects of hospital privatization. PMID:19473487

  1. Detecting anthropogenic influences on climate with an atmospheric model forced with observed variations in sea surface temperature

    SciTech Connect

    Folland, C.K.; Sexton, D.; Karoly, D.

    1997-11-01

    Six ensembles of four simulations with the Hadley Centre atmospheric general circulation model (HADAM2a) have been carried out for late 1948 to the end of 1994 with different specified atmospheric forcing distributions. These simulations are being used to understand the role of different forcing processes in determining the observed climate variations during the second half of the twentieth century. All ensembles started from different initial conditions and were forced with specified global observed monthly sea ice and sea surface temperature distributions using the GISST1.1 data set. The approach used deterministic sampling of observed variations in climate rather than a coupled model. The technique was also different in that it looked at the smaller residual climate signal due to direct anthropogenic over and above those captured in ocean surface temperatures. The results indicate that this method is a useful complement to approaches based on coupled models, aided by the fact that some of the residual climate signals are almost as large as the full signals seen in coupled models, particularly in the stratosphere. 9 refs., 4 figs.

  2. The influence of variations of the Earth' magnetic field on the elaboration of geomagnetic observations in Poland

    NASA Astrophysics Data System (ADS)

    Welker, E.

    2012-06-01

    The increase of accuracy of magnetic measurements generated the need of testing of the influence of variations of the geomagnetic field on their elaboration. On the basis of the magnetic data obtained from European observatories and from magnetic stations operating in 2010 and 2011, the chart of amplitude changes of Y magnetic field component (magnetic declination too) in Poland and the chart of time shift between the records of Belsk Observatory - considered as central observatory - as well as the records from other measurement points were processed. Data from some geomagnetic stations operating in the 1960. (with records of D, H and Z components) stored in the database at the Institute of Geodesy and Cartography, Warsaw, were re used to analyse geomagnetic field intensity changes (Uhrynowski, 1962, 1964). The error of transforming analogue data from paper records to the digital form is bigger than amplitude changes of declination D and H component. The results of Fourier transformation of millions of data from magnetic observatories allowed for mapping the distribution of amplitude changes of Y component and time shift of records from chosen European observatories with respect to Belsk Observatory. The range of amplitude changes of the X, Y and Z components of the geomagnetic field intensity in Poland is exceptionally small. It reaches only ±2-3 nT which is at the level of the error of geomagnetic data elaboration. The range of time shift of the record from points by eastern border of Poland with respect to those by western border of Poland vary from -6 to +15 minutes for Y component. The test made with data from secular point (repeat station) measurements from 2009-2011 shows that the differences between results obtained without and with time corrections reach only 10-302 for declination and inclination, and 5 nT for total intensity vector length. The use of the magnetograms from Belsk Observatory for the geomagnetic measurement reduction without any time

  3. Uncertainties in global trends in observational soil moisture data and their impact on the detectability of human influence

    NASA Astrophysics Data System (ADS)

    Mueller, B.; Wen, Q. H.; Zhang, X.

    2013-12-01

    Global trends in soil moisture are difficult to determine due to the lack of global reference datasets and discrepancies between drought indices based on different formulations. Nevertheless, soil moisture changes are among the most relevant impacts of climate change due to their importance for agriculture, water and food security as well as due to possible devastating consequences of floods. What effect increasing temperatures and greenhouse gas concentrations have on the global hydrological cycle is still not well understood. Using global climate models allows disentangling the effects of natural and anthropogenic forcings on variables of interest. We here present an analysis of soil moisture in CMIP5 climate model simulations and perform a formal detection and attribution. We have chosen one set of CMIP5 simulations driven with historical natural forcing (NAT, solar irradiance and volcanic activity) and one driven with all forcing (ALL, both natural and anthropogenic forcing). Due to the lack of global, direct observations of soil moisture, we consider output from four different land-surface models (LSMs) as pseudo-observations. Land-surface models are similar to land-surface schemes employed in global climate models or atmospheric reanalyses, but run in an offline mode and forced with observational data. The LSMs considered here are driven with CRU and NCEP historical forcing. A comparison of past soil moisture trends (1950-2007) shows large spatial discrepancies between the four different LSMs. Each of the LSMs is, however, more consistent with CMIP5 simulations driven with ALL forcing then driven with natural forcing only. NAT simulations display positive trends in most regions of the globe, while ALL exhibit strong negative trends in, e.g., most parts of the Americas and Europe. These trends are consistent among individual CMIP5 models. We show that despite clear differences between CMIP5 simulations driven with natural forcing only and driven with

  4. 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.

  5. Influence of stress-induced deformations on observed water flow in fractures at the Climax granitic stock

    SciTech Connect

    Wilder, D.G.

    1987-06-01

    Three examples of stress-induced displacement influence on fracture-dominated hydrology were noted in drifts 1400 ft below surface in granite. Seepage into drifts was limited to portions of shears near a fault zone. No water entered the drifts from the fault itself, although its orientation relative to Basin and Range extension is favorable for fracture opening. Localization of seepage appears to result from excavation block motion that increased apertures of the shear zones in contrast to the fault where asperities had been destroyed by earlier shearing thus minimizing aperture increases. Seepage was also noted, in an adjoining drift, from a set of shallow-dip healed fractures that intersected the rib, and from vertical fractures that increased the crown. The restricted location of this seepage apparently was a result of shear opening of the joints that occurred because of cantilevered support of tabular rock between joints. Interpretation of paleostresses based on joint chronologies and orientations indicates that sets subjected to shear stresses at a time when normal stresses were low contained mineral infilling. Sets subjected to shear stresses at a time when the normal stresses were significant had minimal mineral infilling. 8 refs., 7 figs.

  6. 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.

  7. 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.

  8. 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.

  9. Influence of semidiurnal and semimonthly lunar tides on the mesopause as observed in hydroxyl layer and noctilucent clouds characteristics

    NASA Astrophysics Data System (ADS)

    Pertsev, N. N.; Dalin, P. A.; Perminov, V. I.

    2015-11-01

    New results of research on lunar tides in the midlatitude mesopause region are presented. According to observational data on noctilucent clouds and spectrophotometric measurements of hydroxyl radiation, among the semimonthly and semidiurnal lunar tidal harmonics under consideration, the semimonthly zonal tide (13.66 days), semimonthly synodic tide (14.77 days), and semidiurnal tide (12 h 25 min) were proven to be statistically significant. The temperature oscillations in the summer hydroxyl layer and the brightness of noctilucent clouds turned out to be nearly out of phase. For the first time, we considered two possible mechanisms of the generation of the synodic semimonthly harmonic. Here, statistical analysis of the hydroxyl data shows that the nonlinear demodulation of the superposition of solar and lunar semidiurnal tidal harmonics is the most probable process.

  10. Chemical and physical influences on aerosol activation in liquid clouds: a study based on observations from the Jungfraujoch, Switzerland

    SciTech Connect

    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

    2016-01-01

    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.

  11. 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.

  12. Chemical and physical influences on aerosol activation in liquid clouds: a study based on observations from the Jungfraujoch, Switzerland

    DOE PAGESBeta

    Hoyle, Christopher R.; Webster, Clare S.; Rieder, Harald E.; Nenes, Athanasios; Hammer, Emanuel; Herrmann, Erik; Gysel, Martin; Bukowiecki, Nicolas; Weingartner, Ernest; Steinbacher, Martin; et al

    2016-03-29

    In this study, 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 additionmore » 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). Finally, 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.« less

  13. 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.

  14. Hubble Space Telescope faint object spectrograph Quasar Absorption System Snapshot Survey (AbSnap). 1: Astrometric optical positions and finding charts of 269 bright QSO

    NASA Technical Reports Server (NTRS)

    Bowen, David V.; Osmer, Samantha J.; Blades, J. Chris; Tytler, David; Cottrell, Lance; Fan, Xiao-Ming; Lanzetta, Kenneth M.

    1994-01-01

    We present finding charts and optical positions accurate to less than 1 arcsec for 269 bright (V less than or = 18.5) Quasi-Stellar Objects (QSOs). These objects were selected as candidates for the Hubble Space Telescope (HST) Quasar Absorption System Snapshot Survey (AbSnap), a program designed to use the Faint Object Spectrograph (FOS) to obtain short exposure ultraviolet (UV) spectra of bright QSOs. Many quasars were included because of their proximity to bright, low redshift galaxies and positions of these QSOs are measured accurately for the first time. Data were obtained using the digitized sky survey produced by the Space Telescope Science Institute's Guide Stars Selection System Astrometric Support Program.

  15. 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.

  16. 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.

  17. Influence of observable and unobservable exposure on the patient's risk of acquiring influenza-like illness at hospital.

    PubMed

    Payet, C; Voirin, N; Ecochard, R; Vanhems, P

    2016-07-01

    During outbreaks of hospital-acquired influenza-like illness (HA-ILI) healthcare workers (HCWs), patients, and visitors are each a source of infection for the other. Quantifying the effects of these various exposures will help improve prevention and control of HA-ILI outbreaks. We estimated the attributability of HA-ILI to: (1) exposure to recorded or unrecorded sources; (2) exposure to contagious patient or contagious HCW; (3) exposure during observable or unobservable contagious period of the recorded sources; and, (4) the moment of exposure. Among recorded sources, 59% [95% credible interval (CrI) 34-83] of HA-ILI of patients was associated with exposure to contagious patients and 41% (95% CrI 17-66) with exposure to contagious HCWs. Exposure during the unobservable contagiousness period of source patients accounted for 49% (95% CrI 19-75) of HA-ILI, while exposure during the unobservable contagiousness period of source HCWs accounted for 82% (95% CrI 51-99) of HA-ILI. About 80% of HA-ILIs were associated with exposure 1 day earlier. Secondary cases of HA-ILI might appear as soon as the day after the detection of a primary case highlighting the explosive nature of HA-ILI spread. Unobservable transmission was the main cause of HA-ILI transmission suggesting that symptom-based control measures alone might not prevent hospital outbreaks. The results support the rapid implementation of interventions to control influenza transmission. PMID:26846882

  18. 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.

  19. Spectroscopic parallaxes of MAP region stars from UBVRI, DDO, and uvbyH-beta photometry. [Multichannel Astrometric Photometer for astronomical observation

    NASA Technical Reports Server (NTRS)

    Persinger, Tim; Castelaz, Michael W.

    1990-01-01

    This paper presents the results of spectral type and luminosity classification of reference stars in the Allegheny Observatory MAP parallax program, using broadband and intermediate-band photometry. In addition to the use of UBVRI and DDO photometric systems, the uvbyH-beta photometric system was included for classification of blue (B - V less than 0.6) reference stars. The stellar classifications made from the photometry are used to determine spectroscopic parallaxes. The spectroscopic parallaxes are used in turn to adjust the relative parallaxes measured with the MAP to absolute parallaxes. A new method for dereddening stars using more than one photometric system is presented. In the process of dereddening, visual extinctions, spectral types, and luminosity classes are determined, as well as a measure of the goodness of fit. The measure of goodness of fit quantifies confidence in the stellar classifications. It is found that the spectral types are reliable to within 2.5 spectral subclasses.

  20. 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

  1. 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.

  2. 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

  3. 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 ?

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. Comparison of Modeled and Observed Environmental Influences on the Stable Oxygen and Hydrogen Isotope Composition of Leaf Water in Phaseolus vulgaris L. 1

    PubMed Central

    Flanagan, Lawrence B.; Comstock, Jonathan P.; Ehleringer, James R.

    1991-01-01

    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

  9. 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

  10. 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

  11. Hubble Space Telescope observations of the very low mass companion to Gliese 105A

    NASA Technical Reports Server (NTRS)

    Golimowski, David A.; Fastie, William G.; Uomoto, Alan; Schroeder, Daniel J.

    1995-01-01

    Hubble Space Telescope images of the astrometric binary GI 105A confirm the previous ground-based detection of a faint, very red companion (GI 105C) located 3.39 sec from GI 105A at P.A. 290 deg. The instrumental magnitudes of GI 105C are (visual magnitude) V(sub 555) = 16.86 and I(sub 814) = 13.54. The observed position of GI 105C differs significantly from the positions expected from current astrometric solutions. No other companions brighter than I(sub 814) = 20.3 are seen between 1 sec and 13.5 sec from GI 105A. Using the M dwarf model atmospheres of Allard and Hauschildt, we obtain for GI 105C a standard color of V - I = 4.6, which suggests a spectral type of M7 V.

  12. 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

  13. In-situ observations on the influence of wood moisture content and temperature on spore germination and wood colonization by Poria carbonica

    SciTech Connect

    Przybylowicz, P.R.; Corden, M.E.

    1986-01-01

    A method for observing germinating fungal spores on wood was developed in which temperature and wood moisture content could be easily controlled and subsequent wood colonization could be determined. Thin radial sections of Douglas fir (Pseudotsuga menziesii) heartwood (8 mm x 8 mm x 60 mu m) were inoculated with a spore suspension and a similar wood section was placed over the inoculated section forming a ''spore sandwich''. The ''spore sandwiches'' were incubated between larger blocks of Douglas fir heartwood to maintain control of the wood moisture content during incubation in controlled temperature-humidity chambers. Spore germination was observed by opening the ''spore sandwiches'' and staining the spores in situ for microscopic observation. Wood colonization was determined by isolations from the surrounding wood blocks. The ''spore sandwich'' method was used to study the influences of temperature and wood moisture content on spore germination of Poria carbonica. Basidiospores and asexual spores germinated and colonized wood at and above the fibre saturation point (c 30% moisture content), but not below. Both spore types germinated and colonized wood at 22 and 30 degrees Centigrade, but basidiospores failed to germinate at 5 and 35 degrees, whereas asexual spores germinated at 5 and 35 degrees, but were unable to colonize the wood. The ''spore sandwich'' method provides a means for assessing spore germination and wood colonization by wood decaying fungi under conditions simulating those occurring naturally in wood in service. (Refs. 21).

  14. Observations and Modelling of Hillslope Throughflow Temperature and Its Influence on Headwater Stream Thermal Regimes in the Rain-on-Snow Zone

    NASA Astrophysics Data System (ADS)

    Leach, J. A.; Moore, R. D.

    2014-12-01

    Stream temperature controls a variety of biological, chemical and physical in-stream processes. A growing body of research has highlighted the importance of advection associated with surface water and groundwater interactions on stream thermal regimes, and considerable effort has focused on the thermal role of hyporheic exchange and groundwater discharge. However, few studies have focused on advection associated with hillslope throughflow inputs. Current catchment-scale coupled hydrology and stream temperature models (DHSVM, SWAT, HSPF, CEQUEAU, MIKE SHE) use a variety of approaches to estimate throughflow temperatures, but none of these approaches has been evaluated against field measurements of throughflow temperature. We monitored throughflow temperature at fifty locations along a headwater stream located in the rain-on-snow zone of the Pacific Northwest. Current approaches to estimate throughflow temperature were evaluated against field observations and were found to under- or over-predict throughflow temperatures by up to 8 °C, or not be able to represent the influence of transient snow cover. Therefore, we developed a conceptual-parametric hydrology and stream temperature model that simulates hillslope throughflow temperatures. The model successfully predicts throughflow temperatures and highlights the dominant role of throughflow advection and the influence of snow cover on stream thermal regimes during high flow periods and rain-on-snow events.

  15. 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

  16. The Power of Simultaneous Multifrequency Observations for mm-VLBI: Astrometry up to 130 GHz with the KVN

    NASA Astrophysics Data System (ADS)

    Rioja, María J.; Dodson, Richard; Jung, Taehyun; Sohn, Bong Won

    2015-12-01

    Simultaneous observations at multiple frequency bands have the potential to overcome the fundamental limitation imposed by the atmospheric propagation in (sub)millimeter very long baseline interferometry (mm-VLBI) observations. The propagation effects place a severe limit on the sensitivity achievable in mm-VLBI, reducing the time over which the signals can be coherently combined, and preventing the use of phase referencing and astrometric measurements. We carried out simultaneous observations at 22, 43, 87, and 130 GHz of a group of five active galactic nuclei, the weakest of which is ∼200 mJy at 130 GHz, with angular separations ranging from 3.°6 to 11°, using the Korean VLBI Network. We analyzed these data using the frequency phase transfer (FPT) and the source frequency phase referencing (SFPR) techniques, which use the observations at a lower frequency to correct those at a higher frequency. The results of the analysis provide an empirical demonstration of the increase in the coherence times at 130 GHz from a few tens of seconds to about 20 minutes, with FPT, and up to many hours with SFPR. Moreover, the astrometric analysis provides high-precision relative position measurements between two frequencies, including, for the first time, astrometry at 130 GHz. Finally, we demonstrate a method for the generalized decomposition of the relative position measurements into absolute position shifts for bona fide astrometric registration of the maps of the individual sources at multiple frequencies, up to 130 GHz.

  17. 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

  18. 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. PMID:26449712

  19. 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.

  20. Observing Gravitational Lensing Effects by Sgr A* with GRAVITY

    NASA Astrophysics Data System (ADS)

    Bozza, V.; Mancini, L.

    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 LS, γ, K], where D LS is the distance between the lens and the source, γ 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.

  1. Influences of visual pitch and visual yaw on visually perceived eye level (VPEL) and straight ahead (VPSA) for erect and rolled-to-horizontal observers.

    PubMed

    Li, W; Dallal, N; Matin, L

    2001-10-01

    Localization within the space in front of an observer can be specified along two orthogonal physical dimensions: elevation ('up', 'down') and horizontal ('left','right'). For the erect observer, these correspond to egocentric dimensions along the long and short axes of the body, respectively. However, when subjects are rolled-to-horizontal (lying on their sides), the correspondence between the physical and egocentric dimensions is reversed. Employing egocentric coordinates, localization can be referred to a central perceptual point-visually perceived eye level (VPEL) along the long axis of the body, and visually perceived straight ahead (VPSA) along the short axis of the body. In the present experiment, measurements of VPEL and of VPSA were made on each of eight subjects who were either erect or rolled-to-horizontal while monocularly viewing a long 2-line stimulus (two parallel, 64 degrees -long lines separated by 50 degrees ) in otherwise complete darkness that was centered on the eye of the observer and was tilted out of the frontoparallel plane by a variable amount and direction (from -30 degrees to +30 degrees in 10 degrees steps). The stimulus tilt was either around an axis through the center of the two eyes (pitch; VPEL was measured) or around the long axis of the body that passed through the center of the viewing eye (yaw; VPSA was measured). Large variations in the localization settings were measured that were systematic with stimulus tilt. The slopes of the functions plouing the deviations from veridicality against the orientation of the 2-line stimulus ('induction functions') were larger for the rolled-to-horizontal observer than for the erect observer for both VPEL and VPSA, and for a given body orientation were larger for the VPEL discrimination than for the VPSA discrimination; the influences of body orientation in physical space and the direction of the discrimination relative to the body were lineraly additive. Both the y-intercepts of the induction

  2. Mass Spectral Observations of Submicron Aerosol Particles and Production of Secondary Organic Aerosol at an Anthropogenically Influenced Site during the Wet Season of GoAmazon2014

    NASA Astrophysics Data System (ADS)

    de Sá, S. S.; Palm, B. B.; Campuzano Jost, P.; Day, D. A.; Hu, W.; Newburn, M. K.; Ferreira De Brito, J.; Artaxo, P.; Shilling, J. E.; Souza, R. A. F. D.; Manzi, A. O.; Alexander, M. L.; Jimenez, J. L.; Martin, S. T.

    2014-12-01

    As part of GoAmazon2014, a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed to characterize the composition, size, and spectral markers present in submicron atmospheric aerosol particles at a site downwind of Manaus, Brazil, in the central Amazon basin. The focus was on the influence of biogenic-anthropogenic interactions on the measured aerosol particles, especially as related to the formation of secondary organic aerosol (SOA). Through a combination of meteorology, emissions, and chemistry, the research site was affected by biogenic emissions from the tropical rainforest that were periodically mixed with urban outflow from the Manaus metropolitan area. Results from the first intensive operation period, from 1 February to 31 March 2014, show that for the wet season the PM1 mass concentration had typical values on order of 1 to 2 μg/m3. The organic species were dominant, followed by sulfate. The mass-diameter distribution of the particle population had a prevailing mode between 300 and 400 nm (vacuum aerodynamic diameter, dva), and at times a smaller mode at finer size was also present. Highly oxidized organic material was frequently observed, characterized by a dominant peak at m/z 44. There was a diel trend in the elemental oxygen-to-carbon (O:C) ratio peaking in the afternoon. The analysis of the results aims at delineating the anthropogenic impact on the measurements. Multivariate statistical analysis by positive-matrix factorization (PMF) is applied to the time series of organic particle mass spectra. The factors and their loadings provide information on the relative and time-varying contributions of different sources and processes affecting the organic component of the aerosol particle phase. Relationships between AMS results and measurements from co-located instruments that provide information on anthropogenic and biogenic gas and particle tracers are investigated, toward the goal of improving the understanding of

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Age, body weight and backfat thickness at first observed oestrus in crossbred Landrace x Yorkshire gilts, seasonal variations and their influence on subsequence reproductive performance.

    PubMed

    Tummaruk, P; Tantasuparuk, W; Techakumphu, M; Kunavongkrit, A

    2007-05-01

    The objective of the present study was to investigate puberty attainment in crossbred Landrace x Yorkshire (LY) gilts reared under tropical conditions and their subsequent reproductive performance. This study was carried out in a 2400-sow herd over a 1-year period. A total of 696 crossbred LY replacement gilts were included. Faecal samples from 214 gilts were collected to determine the faecal progesterone profiles around the time of first oestrus. Solid-phase 125I-radioimmunoassay was used to determine the progesterone concentrations in the faecal extract. The gilts entered the herd at an average age of 177.5 +/- 12.6 days, 95.7 +/- 10.2 kg body weight (BW) and a backfat thickness (BF) of 12.0 +/- 2.9 mm. On average, the gilts expressed first standing oestrus at 195 days of age, 106 kg of BW and a BF of 13.0 mm. The interval from entry to the gilt pool to the first observed oestrus (EOI) was 24.4 +/- 18.0 days (range 0-88 days). The hormonal profile indicated that the gilts that actually ovulated during the first observed oestrus was 34% (group A), the gilts that had ovulated before the first observed oestrus was 21% (group B) and the gilts that did not ovulate during the first observed oestrus was 45% (group C). During summer the proportion of group A gilts was significantly lower than during the winter and the rainy seasons (P < 0.05). The BW of gilts at entry significantly correlated with the BF at entry (r = 0.31, P < 0.001), the age at entry (r = 0.47, P < 0.001), the BW at first oestrus (r = 0.65, P < 0.001) and the BF at first oestrus (r = 0.33, P < 0.001). An increase of BW at entry of 1 kg resulted in a decrease of EOI of 0.28 days. The age, BW and BF of gilts at the first observed oestrus significantly influenced the total number of piglets born per litter (TB) and the number of piglets born alive per litter (BA) in the first three parities. Gilts expressing their first oestrus between 181 and 200 days had a significantly larger TB than gilts that

  10. 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

  11. 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.

  12. Two abyssal sites in the Southern Ocean influenced by different organic matter inputs: Environmental characterization and preliminary observations on the benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Hughes, J. A.; Smith, T.; Chaillan, F.; Bett, B. J.; Billett, D. S. M.; Boorman, B.; Fisher, E. H.; Frenz, M.; Wolff, G. A.

    2007-09-01

    The abundance and diversity of the deep-sea benthos are intimately linked to inputs of organic matter from the euphotic zone. However, it is often difficult to isolate the influence of surface productivity on benthic ecosystems from other environmental factors. To this end, two abyssal sites (˜4200 m water depth) located under contrasting productivity regimes around the Crozet Plateau, in the Indian Ocean sector of the Southern Ocean, were sampled during the austral summer of 2004/2005. One site (M5), east of the Crozet Isles, was located beneath an area where there was an enduring seasonal phytoplankton bloom. The second site (M6) was located in an oligotrophic high-nutrient low-chlorophyll (HNLC) region to the south of the islands. Organic fluxes to the seafloor at these sites are thought to reflect the overlying productivities, so that the benthic environment to the east of the islands was more eutrophic than at the southerly station. All other environmental variables were similar at the two sites, which are located just 460 km apart. The concentrations of chlorophyll- a and total organic carbon in the surficial sediments were significantly greater at the relatively eutrophic site, east of the islands (M5), than at the southerly site (M6). Total nitrogen, however, was similar at both sites. Significantly higher phytopigment concentrations were observed in the surficial sediments at the eutrophic site; in particular, the concentration of chlorophyll- a was 3 times greater than at the southern site, although the freshness of the labile component, as measured by chlorophyll- a to pheophorbide ratio, was not different between sites. These results confirm that fluxes of organic matter to the seafloor were higher at the site located beneath the bloom region. This was reflected in the abundance and diversity of live (stained) and dead benthic foraminifera (>125 μm), which were greater at the eutrophic site. The species composition of the dead foraminiferal

  13. 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.

  14. Observations on dietary aluminum level, time duration exposure to dietary aluminum, and the influence of specific dietary blocking agents on tissue aluminum accumulation in the rat

    SciTech Connect

    Kettleson, K.C.A.

    1986-01-01

    Two experiments were conducted to observe the association of dietary aluminum (Al) with tissue Al accumulation. Other objectives included: to determine if alginic acid (AA) and pectin (P) in the diet could inhibit Al accumulation in tissues, and to relate time of exposure of dietary Al to Al tissue accumulation. The first experiment was conducted with a test diet feeding period of 35 days in a factorial arrangement of treatments with 24 rats, six rats per treatment. The dietary treatments were: groups 0 and 1, no added dietary Al (Al < 20 ppm) with or without 5% AA; groups 2 and 3, 400 ppm additional dietary Al with or without 5% AA. Kidney tissue analyzed by neutron activation showed no significant Al accumulation, or influence of the blocking agent. The second experiment was conducted over two time intervals (phase I with 24 rats for 28 days, and phase II with 26 rats for 56 days) and was done with 7 different diets. The diets included a control (basal with no added Al or blocking agent), the basal with 425 or 640 ppm Al added, with 5% AA or 5% P added to each Al test level. The Al source for both experiments was aluminum dibasic acetate. Tissues collected and pooled for analyses by inductively coupled plasma atomic emission spectroscopy included bone, brain, and kidney. The addition of 425 ppm Al to the diets stimulated body weight gain by about 10% relative to the controls. The blocking agents suppressed Al-induced weight gain, although AA stimulated feed intake (P < 0.05). Trends in Al accumulation appeared to occur in bone and brain tissues associated with dietary Al; but independent of blocking agents and independent of time exposure to the dietary Al.

  15. Regional seismic observations of the 9 October 2006 underground nuclear explosion in North Korea and the influence of crustal structure on regional phases

    NASA Astrophysics Data System (ADS)

    Hong, Tae-Kyung; Baag, Chang-Eob; Choi, Hoseon; Sheen, Dong-Hoon

    2008-03-01

    The crustally guided shear wave, Lg, is typically the most prominent phase of a nuclear explosion at regional distance. This Lg phase is analyzed often to discriminate a nuclear explosion from a natural earthquake. In addition, the Lg phase allows us to determine the size of the detonation. A nuclear explosion test in North Korea was conducted on 9 October 2006. The epicenter was located close to the eastern shore of the Korean Peninsula, resulting in raypaths that vary significantly according to the azimuths. In particular, rays radiated in the southern direction experience lateral variation of crustal structures at the continental margin. We examine the influence of raypaths on regional seismic phases by comparing the spectra and waveforms from different raypaths. Three natural earthquakes in North Korea are also examined to determine the raypath effect. We find that the Lg from the nuclear explosion dissipated significantly as result of energy leakage into the mantle resulting from variations in crustal thickness along the portion of the raypath traversing the western tip of the Sea of Japan (East Sea). Some of the leaked energy develops into mantle lid waves (Sn), causing a large energy increase to Sn. A similar feature is observed in the records of natural earthquakes. This feature is confirmed by seismic waveform modeling. The raypath effect also causes underestimation of magnitude. The Lg body wave magnitude, mb(Lg), is estimated to be 3.8-4.2 for records from pure continental paths and 2.6-3.4 for records from paths crossing continental margins. This result illustrates the need to consider raypath effects for the correct estimation of magnitudes of regional events, including a nuclear explosion.

  16. 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

  17. 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.

  18. 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

  19. The COLON study: Colorectal cancer: Longitudinal, Observational study on Nutritional and lifestyle factors that may influence colorectal tumour recurrence, survival and quality of life

    PubMed Central

    2014-01-01

    Background There is clear evidence that nutrition and lifestyle can modify colorectal cancer risk. However, it is not clear if those factors can affect colorectal cancer treatment, recurrence, survival and quality of life. This paper describes the background and design of the “COlorectal cancer: Longitudinal, Observational study on Nutritional and lifestyle factors that may influence colorectal tumour recurrence, survival and quality of life” – COLON – study. The main aim of this study is to assess associations of diet and other lifestyle factors, with colorectal cancer recurrence, survival and quality of life. We extensively investigate diet and lifestyle of colorectal cancer patients at diagnosis and during the following years; this design paper focusses on the initial exposures of interest: diet and dietary supplement use, body composition, nutrient status (e.g. vitamin D), and composition of the gut microbiota. Methods/Design The COLON study is a multi-centre prospective cohort study among at least 1,000 incident colorectal cancer patients recruited from 11 hospitals in the Netherlands. Patients with colorectal cancer are invited upon diagnosis. Upon recruitment, after 6 months, 2 years and 5 years, patients fill out food-frequency questionnaires; questionnaires about dietary supplement use, physical activity, weight, height, and quality of life; and donate blood samples. Diagnostic CT-scans are collected to assess cross-sectional areas of skeletal muscle, subcutaneous fat, visceral fat and intermuscular fat, and to assess muscle attenuation. Blood samples are biobanked to facilitate future analyse of biomarkers, nutrients, DNA etc. Analysis of serum 25-hydroxy vitamin D levels, and analysis of metabolomic profiles are scheduled. A subgroup of patients with colon cancer is asked to provide faecal samples before and at several time points after colon resection to study changes in gut microbiota during treatment. For all patients, information on vital

  20. Flow of a reactive fluid through partially saturated fractures: Experimental observations of the influence of entrapped phase geometry on evolving flow channels

    NASA Astrophysics Data System (ADS)

    Detwiler, R. L.; Fisher, S.

    2008-12-01

    Reactive fluids cause dissolution and precipitation along mineral surfaces that can lead to the development of flow channels in porous and fractured media. In fully saturated fractures, dissolution of fracture surfaces leads to different behaviors depending on the relative magnitudes of advective and diffusive transport of dissolved minerals and surface reaction rates. The resulting alterations of the fracture pore space (apertures) range from relatively uniform dissolution of the fracture surfaces to the formation of distinct dissolution channels that dominate flow through the fracture. These processes are further complicated in many subsurface systems, where multiple fluids/phases interact within pore spaces (e.g., CO2 sequestration, groundwater contamination by organic solvents, oil and gas production). We present experimental results that explore the additional influence of an entrapped nonwetting phase on the formation of dissolution channels in fractures. We fabricated analog fractures by mating a 10x15-cm, smooth, reactive surface (KH2PO4) with a rough, non-reactive surface (glass). The resulting fractures were transparent allowing direct measurement of evolving fracture apertures and fluid phase distribution using established quantitative visualization techniques. Experiments were initiated by slowly injecting (negligible viscous forces) air into a fully saturated fracture followed by slow reinvasion of water. The resulting initial condition for the fracture dissolution experiments was a complex distribution of immobile air bubbles entrapped predominantly within large aperture regions. These bubbles were completely surrounded by flowing water (under-saturated with respect to KH2PO4) within smaller aperture regions. During experiments, mineral dissolution led to localized fracture aperture growth, which in turn caused gradual redistribution of the entrapped air within the fracture. The resulting evolution of dissolution channels differed significantly from

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Practice Pattern of Gastroenterologists for the Management of GERD Under the Minimal Influence of the Insurance Reimbursement Guideline: A Multicenter Prospective Observational Study

    PubMed Central

    Lee, Kwang Jae; Kim, Jin Il; Park, Ju Sang; Moon, Byung Sik; Kim, Sang-Gyun; Chun, Jae Hee; Jung, Hoon-Yong; Choi, Chang Hwan; Chun, Seong Woo; Song, Geun Am; Choi, Myung Gyu

    2011-01-01

    The objective of the study was to document practice pattern of gastroenterologists for the management of gastroesophageal reflux disease (GERD) under the minimal influence of the insurance reimbursement guideline. Data on management for 1,197 consecutive patients with typical GERD symptoms were prospectively collected during 16 weeks. In order to minimize the influence of reimbursement guideline on the use of proton pump inhibitors (PPIs), rabeprazole was used for the PPI treatment. A total of 861 patients (72%) underwent endoscopy before the start of treatment. PPIs were most commonly prescribed (87%). At the start of treatment, rabeprazole 20 mg daily was prescribed to 94% of the patients who received PPI treatment and 10 mg daily to the remaining 6%. At the third visits, rabeprazole 20 mg daily was prescribed to 70% of those who were followed and 10 mg daily for the remaining 30%. Continuous PPI treatment during the 16-week period was performed in 63% of the study patients. In conclusion, a full-dose PPI is preferred for the initial and maintenance treatment of GERD under the minimal influence of the insurance reimbursement guideline, which may reflect a high proportion of GERD patients requiring a long-term treatment of a full-dose PPI. PMID:22147999

  11. 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

  12. 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

  13. Observations of Hierarchical Solar-type Multiple Star Systems

    NASA Astrophysics Data System (ADS)

    Roberts, Lewis C., Jr.; Tokovinin, Andrei; Mason, Brian D.; Hartkopf, William I.; Riddle, Reed L.

    2015-10-01

    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.

  14. 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

  15. 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.

  16. 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

  17. 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

  18. An Increase in Forearm Cortical Bone Size After Menopause May Influence the Estimated Bone Mineral Loss--A 28-Year Prospective Observational Study.

    PubMed

    Karlsson, Magnus K; Ahlborg, Henrik G; Svejme, Ola; Nilsson, Jan-Åke; Rosengren, Björn E

    2016-01-01

    Areal bone mineral density (aBMD) is the most common estimate of bone mass, incorporated in the World Health Organization definition of osteoporosis. However, aBMD depends on not only the amount of mineral but also the bone size. The estimated postmenopausal decline in aBMD could because of this be influenced by changes in bone size.We measured bone mineral content (BMC; mg), aBMD (mg/cm2), and bone width (mm) by single-photon absorptiometry at the cortical site of the forearm in a population-based sample of 105 Caucasian women. We conducted 12 measurements during a 28-yr period from mean 5 yr (range: 2-9) before menopause to mean 24 yr (range: 18-28) after menopause. We calculated individual slopes for changes in the periods before menopause, 0-<8, 8-<16, and 16-28 yr after menopause. Data are presented as means with 95% confidence intervals. The annual BMC changes in the 4 periods were -1.4% (-0.1, -2.6), -1.1% (-0.9, -1.4), -1.2% (-0.9, -1.6), and -1.1% (-0.8, -1.4) and the annual increase in bone width 0.4% (-1.2, 1.9), 0.7% (0.5, 0.9), 0.1% (-0.2, 0.4), and 0.1% (-0.2, 0.4). BMC loss was similar in all periods, whereas the increase in bone width was higher in the first postmenopausal period than in the second (p=0.003) and the third (p=0.01) postmenopausal periods. Menopause is followed by a transient increase in forearm bone size that will influence the by aBMD estimated cortical loss in bone minerals. PMID:25708121

  19. 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

  20. 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.

  1. 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.

  2. An observational study of the influence of solar zenith angle on properties of the M1 layer of the Mars ionosphere

    NASA Astrophysics Data System (ADS)

    Fallows, K.; Withers, P.; Matta, M.

    2015-02-01

    The variations in peak properties of the M1 layer (the lower photochemical plasma layer) with solar zenith angle (SZA) are important relationships for understanding the physical processes which control this region of the Mars ionosphere. The behavior of the M1 layer has been poorly characterized to date. Here we introduce an automated and repeatable method for determining properties of the M1 and M2 layers simultaneously in 5600 Mars Global Surveyor radio occultation profiles of dayside electron density. The results support previous findings for M1 and M2 subsolar peak densities and the dependence of peak densities on solar zenith angle. The ratio of M1 peak density to M2 peak density remains constant at 0.4 for 70° observations. These findings provide meaningful observational constraints for numerical models, which are known to have trouble reproducing observations and observed trends associated with the M1 layer.

  3. 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.

  4. 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

  5. Modelling VOC source impacts on high ozone episode days observed at a mountain summit in Hong Kong under the influence of mountain-valley breezes

    NASA Astrophysics Data System (ADS)

    Lam, S. H. M.; Saunders, S. M.; Guo, H.; Ling, Z. H.; Jiang, F.; Wang, X. M.; Wang, T. J.

    2013-12-01

    A top-down approach to evaluate high ozone (O3) formation, attributed to different emission sources, is developed for anti-cyclonic conditions in a region of Hong Kong influenced by meso-scale circulations. A near-explicit photochemical model coupled with the Master Chemical Mechanism (MCMv3.2) is used to investigate the chemical characteristics in the region. Important features have been enhanced in this model including the photolysis rates, simulated by the National Center for Atmospheric Research (NCAR) Tropospheric Ultraviolet and Visible (TUV) Radiation Model, as well as hourly variation of Volatile Organic Compound (VOC) concentration input from on-site sampling. In general, the combined