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Sample records for astrometric observations influence

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

    NASA Astrophysics Data System (ADS)

    Li, Z. X.

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

  2. Phobos and Deimos astrometric observations from Viking

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  3. Astrometric Observation of Delta Cepheus

    NASA Astrophysics Data System (ADS)

    Warren, Naomi; Wilson, Betsie; Estrada, Chris; Crisafi, Kim; King, Jackie; Jones, Stephany; Salam, Akash; Warren, Glenn; Collins, S. Jananne; Genet, Russell

    2012-04-01

    Members of a Cuesta College astronomy research seminar used a manually-controlled 10-inch Newtonian Reflector telescope to determine the separation and position angle of the binary star Delta Cepheus. It was observed on the night of Saturday, October 29, 2011, at Star Hill in Santa Margarita, California. Their values of 40.2 arc seconds and 192.4 degrees were similar to those reported in the WDS (1910).

  4. CCD astrometric observations of Amalthea and Thebe

    NASA Astrophysics Data System (ADS)

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

    2005-07-01

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

  5. Phobos and Deimos astrometric observations from the Phobos mission

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  6. Astrometric CCD Observations of Three Double Stars Measurements

    NASA Astrophysics Data System (ADS)

    Nand, Angela

    2017-04-01

    CCD astrometric observations of three double star groups from the Orion constellation were made. Position angles and separations of corresponding pairs were obtained from the data acquired and compared to previous observations listed in the Washington Double Star Catalog. Present data agrees with previous observational data.

  7. Astrometric and Space-Geodetic Observations of Polar Wander

    NASA Technical Reports Server (NTRS)

    Gross, R. S.; Vondrak, J.

    1998-01-01

    The terrestrial location of the Earth's rotation pole has been under continuous observation since 1899 when the International Latitude Service (ILS) began conducting optical astrometric measurements of star positions to determine variations in station latitude and hence variations in the location of the rotation pole.

  8. Phobos and Deimos astrometric observations from Mariner 9

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  9. 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.

  10. CCD astrometric observations of Phoebe in 2003-2004

    NASA Astrophysics Data System (ADS)

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

    2006-07-01

    In 2003-2004, we obtained 115 new observations of Phoebe, the 9th Saturnian faint satellite (visual magnitude of about 16.5). We used a large CCD detector (2048×2048 pixels) mounted on the 1.56 m astrometric reflector at the Sheshan Station, near Shanghai. In our reduction, an up-to-date catalogue of stars, UCAC2 (Zacharias et al. 2004), was chosen to ensure a proper astrometric calibration. A comparison of our observations to three recently available, high quality ephemerides, including the JPL SAT185 by Jacobson (2004b), has shown that most of our observed positions of Phoebe present an accuracy of some tens of mas, which appears to be a very high level for such a faint satellite.

  11. Astrometric observations of comets and minor planets

    NASA Technical Reports Server (NTRS)

    Williams, J. G.; Gibson, J.

    1991-01-01

    Comets and planet crossing asteroids are observed so that accurate positions can be determined. The observations are made with the Palomar 1.5 m telescope equipped with a CCD array. The combination of telescope and detector is quite effective at recording faint comets and minor planets. This proves useful for early acquisition of comets and asteroids returning for a new opposition. The resulting positions permit accurate orbits to be determined and allow the properties of the comets and asteroids to be measured by other observers using a variety of techniques. Recoveries and other notable observations of comets and planet crossing asteroids observed during the past years are discussed.

  12. Astrometric observations of comets and minor planets

    NASA Technical Reports Server (NTRS)

    Williams, J. G.; Gibson, J.

    1991-01-01

    Comets and planet crossings are observed so that accurate positions can be determined. The observations are made with the Palomar 1.5m telescope equipped with a charge coupled device (CCD) array. This combination is quite efficient at recording faint comets and minor planets. This proves quite useful for early acquisition of comets and asteroids returning for a new opposition. The resulting positions permit accurate orbits to be determined and allow the properties of the comets and asteroids to be measured by other observers using a variety of techniques. Recoveries and other notable observations of comets and planet crossing asteroids observed during the past year are discussed.

  13. Treatment of Star Catalog Biases in Asteroid Astrometric Observations

    DTIC Science & Technology

    2010-01-01

    Treatment of star catalog biases in asteroid astrometric observations Steven R. Chesley a, James Baer b,*, David G. Monet c a Jet Propulsion...2010 Accepted 2 June 2010 Available online 11 June 2010 Keywords: Asteroids Comets a b s t r a c t In this paper, we discuss the detection of systematic...biases in star positions of the USNO A1.0, A2.0, and B1.0 catalogs, as deduced from the residuals of numbered asteroid observations. We present a

  14. New astrometric observations of Triton in 2007-2009

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    SciTech Connect

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

    2011-05-15

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

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

    NASA Technical Reports Server (NTRS)

    Marsden, Brian G.; McCrosky, Richard E.

    1997-01-01

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

  17. Photometric, astrometric and polarimetric observations of gravitational microlensing events

    NASA Astrophysics Data System (ADS)

    Sajadian, Sedighe; Rahvar, Sohrab

    2015-09-01

    Gravitational microlensing can be used as a unique astrophysical tool to study the atmospheres of stars thousands of parsec away from us. This capability results from the bending of light rays in the gravitational field of a lens that can magnify the light of a background source star during the lensing. Moreover, one of the consequences of this light bending is that the circular symmetry of the source is broken because distorted images are produced at either side of the lens position. This property makes it possible to observe polarization, and also the light centroid shift of images. Assigning vectors for these two parameters, they are perpendicular to each other in simple and binary microlensing events, except in fold singularities. In this work, we investigate the advantages of polarimetric and astrometric observations during microlensing events (i) for studying the surface of the source star and spots on it and (ii) for obtaining extra information to determine the trajectory of source stars with respect to the lens. Finally, we analyse the largest sample of microlensing events from the Optical Gravitational Lensing Experiment (OGLE) catalogue and show that, for almost ˜4.3 per cent of events in the direction of the Galactic bulge, the polarization signals would be observable with large telescopes.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  20. Study of the impact of E-ELT and MICADO distortion and wavefront errors residuals on the MICADO astrometric observations

    NASA Astrophysics Data System (ADS)

    Rodeghiero, Gabriele; Pott, Jörg-Uwe; Bizenberger, Peter

    2016-08-01

    The paper describes the developments towards an end-to-end optical model based on a commercial ray tracing software for studying the effects of the telescope and instrumental instabilities on the Multi-AO Imaging Camera for Deep Observations (MICADO). The primary goal and observing mode of MICADO is imaging, with a focus on relative astrometry with an accuracy of about 50 μas. To achieve this ambitious goal a careful examination of the possible random and systematic effects that can influence the astrometric accuracy is required. Here we concentrate on the perturbations coming from the different telescope and instrumental instabilities, mainly related to the static and dynamical perturbations of the European-Extremely Large Telescope (E-ELT) optics, the cold optics tolerances of the instrument and the intrinsic geometric distortions of both the systems. ESO developed an extended dataset of the E-ELT perturbations that are integrated inside the optical model of the telescope and the instrument relay optics for gathering the aberrated wavefronts. The wavefront error residuals are then propagated inside the system to check the distortions and their effects on the astrometric measurement at the instrument focal plane. From our analysis the dominating instrumental errors are: (i) the telescope induced distortions, in the order of => 100μas, that originate from the optics misalignments and presumably vary over <= 1hr time-scales, and must be calibrated against sky measurements; (ii) the instrument optics induced distortions that can reach ˜ 1 arcsec levels, but are more stable than the telescope perturbations. They will be calibrated with the use of an astrometric calibration mask. We derived the order of magnitude of the astrometric distortions of E-ELT and MICADO. The results of our study will help to define an efficient instrumental calibration strategy against the astrometric error of the instrument.

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  2. Determination of the small Solar system bodies orbital elements from astrometric observations with OMT-800 telescope

    NASA Astrophysics Data System (ADS)

    Troianskyi, Volodymyr; Bazey, A. A.; Kashuba, V. I.; Zhukov, V. V.

    2014-11-01

    From the beginning of operation of the new OMT-800 telescope in late 2012 we were able to recieve the high-precision differential astrometrical observations of geostationary objects, asteroids and comets brighter than 21 mag. In this work, the technique of calculation of the orbital elements and prediction of the geostationary objects and asteroids trajectory are considered

  3. Simultaneous Position, Velocity, Attitude, Angular Rates, and Surface Parameter Estimation Using Astrometric and Photometric Observations

    DTIC Science & Technology

    2013-07-01

    Simultaneous Position, Velocity, Attitude, Angular Rates, and Surface Parameter Estimation Using Astrometric and Photometric Observations...estimation is extended to include the various surface parameters associated with the bidirectional reflectance distribution function (BRDF... parameters are estimated simultaneously Keywords—estimation; data fusion; BRDF I. INTRODUCTION Wetterer and Jah [1] first demonstrated how brightness

  4. Hubble Space Telescope Astrometric Observations and Orbital Mean Motion Corrections for the Inner Uranian Satellites

    NASA Astrophysics Data System (ADS)

    Pascu, Dan; Rohde, James R.; Seidelmann, P. Kenneth; Wells, Eddie N.; Kowal, Charles T.; Zellner, Ben H.; Storrs, Alex D.; Currie, Douglas G.; Dowling, Daniel M.

    1998-03-01

    The 10 small inner satellites of Uranus were discovered in 1986 with Voyager 2 and not seen again until 1994, when eight were recovered with the Hubble Space Telescope Wide Field Planetary Camera 2 for astrometric, dynamical, and photometric studies. Thirty-three exposures were taken on 1994 August 14 with the PC1 chip in the BVRI filters. Measurable images of Ariel and Miranda were also obtained on the same CCD frames with those of the faint satellites. We present here the astrometric observations of these eight satellites relative to Miranda, as well as corrected orbital mean motions for them. For the full-well images of Ariel and Miranda, the astrometric limitation was due to an inadequate geometric distortion correction and distance from center. For the faint inner satellites, the astrometric precision varied from 50 mas for Bianca (V = 23 mag) to 9 mas for Puck (V = 20 mag) and was due primarily to a centroiding error caused by a low signal-to-noise ratio. The orbits of Owen & Synnott for the inner satellites were compared with these observations and corrections derived to their mean daily motions. While the orbits of Owen & Synnott proved to be better than their errors indicated, the new mean motions are 2 orders of magnitude more precise.

  5. First astrometric observations with the MéO telescope in view of space debris observations

    NASA Astrophysics Data System (ADS)

    Laas-Bourez, Myrtille; Deleflie, Florent; Klotz, Alain; Albanese, Dominique; Samain, Etienne

    The MéO (for "Métrologie Optique") telescope is the Satellite and Lunar Laser Ranging dedicated telescope of Observatoire de la Côte d'Azur (France), and located at "plateau de Calern" (43,7546336886111 N 6,9215750911111 E 1323,3480 U). The telescope is pointed by an altazimu-tale mount. The motorization, with a typical velocity of 5 deg/s allows to follow LEO satellites (from an altitude of 400 kilometers), as well as MEO and GEO satellites, and the Moon. The telescope has an aperture of 1.54m. It has Nasmyth focus equipped with an EMCCD camera. The field of view, defined by the equivalent focal length and the size of the camera, is actually 3 arcmin x 3 arcmin. The paper aims at presenting two methods that we will be developing to observe LEO and MEO satellites, and give very precise astrometrical positions in view of testing the capabilities of such an instrument to track space debris. In particular, the greater diameter than the ones usually used for space debris tracking should improve the current accu-racy of the observations within in the GEO region. In the LEO region, such a diameter should allow to observe trailing satellites with a high magnitude (to be quantified). The first method is "stellar reference" -based. It consists in identifying stars on the images sky background and in using an astrometrical catalog to calibrate the passage relations between image coordinates and celestial coordinates. The main difficulty comes from the possible lack of catalogued stars on every image, to exactly identify, for each track, the original epoch and positions of stellar trails. The second method is "telescope referenced" -based. It consists in relying the opto-mechanical chain of the telescope to assign the theoretical value read in the ephemeris file as the center of the images. So, we can calibrate the field blind. The difficulty consists hence in estimating the accuracy of pointing of the telescope. The feasibility of these two methods was demonstrated in

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

    NASA Technical Reports Server (NTRS)

    Mccrosky, R. E.; Marsden, B. G.

    1986-01-01

    During the past year some 500 observations were made on 66 nights and published on the MPCs (Minor Planet Circulars/Minor Planets and Comets). In addition, a handful of measurements of earlier plates were completed and published. 121 of the observations published referred to comets. Of special importance were observations of comets (P/Giacobini-Zinner and P/Halley) in connection with the NASA ICE and ESA Giotto missions, but a special effort was made to get good coverage of almost all of the observable comets. Observations were also made of (2060) Chiron and of the earth-approaching objects (1627) Ivar, (1866) Sisyphys, (1943) Anteros, (3362) 1984 QA, 1985 JA, PA, TB and WA, and 1986 DA and EB. 46 minor planets were given permanent numbers entirely as a result of the observations.

  7. Astrometric observations of planetary satellites at the Abastumani Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Kiseleva, T. P.; Chanturiya, S. M.; Vasil'eva, T. A.; Kalinichenko, O. A.

    2012-11-01

    We present and discuss the results of the astrometry project during which we observed the satellites of Mars, Jupiter, Saturn, Uranus, and Neptune at the Abastumani Astrophysical Observatory (Georgia) between 1983 and 1994. Observations at the Abastumani Observatory were performed with the double Zeiss astrograph (DZA: D/ F = 400/3024 mm) and AZT-11 telescope ( F = 16 m). We processed a large array of observations and determined exact coordinates of the planets and their satellites in a system of reference stars of modern catalogues as well as relative coordinates of the satellites. The results were compared with modern ephemerides using the MULTI-SAT software. The comparison enabled us to estimate the accuracy of observations (their random and systematic uncertainties) and the accuracy of modern theories of the motion of planets and their satellites. Random uncertainties of observations are estimated to be 0.10″-0.40″ for various objects and observational conditions. Observational results obtained for Uranus, Neptune and the satellites Titania and Oberon were shown to deviate appreciably and systematically from theories of their motion. The results of observations are presented in the Pulkovo database for Solar System bodies that is available at the website http://www.puldb.ru.

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

    NASA Technical Reports Server (NTRS)

    Mccroskey, Richard E.; Marsden, Brian G.

    1988-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Mccrosky, Richard E.; Marsden, Brian G.

    1989-01-01

    Observations were made with the 155-cm reflector at the Oak Ridge Observatory. Since the last semiannual report (issued in November 1988) there have been 20 observations of comets, 146 of numbered minor planets and 135 of minor planets that were unnumbered at the time of observation. The orbit computations made during this period mainly applied to new discoveries, which have recently been exceptionally numerous. 1989 has already produced five new Apollo objects, and the new-moon period in early January produced a record six new comets.

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

    NASA Technical Reports Server (NTRS)

    Mccrosky, R. E.; Marsden, B. G.

    1986-01-01

    The 155-cm reflector was used for observations of comets and minor planets on 32 nights during April-October. The distribution was fairly uniform, ranging from 45 in June and September to 28 in July: on September 1 a total of 17 observations was made. A table is included which lists the 230 measurements published during the semester. These include six additional measurements going back to 1984 and the republication of a previously misidentified 1976 observation as a new discovery. Thirty-two of the observations refer to comets, 83 to numbered minor planets, and the remainder to unnumbered minor planets. Among the older-numbered minor planets observed were the Earth-approaching objects (3103) 1982 BB, (3199) 1982 RA (Nefertiti), (3361) 1982 HR and (3362) 1984 QA (Khufu), some of which were of interest for radar experiments. Unnumbered Earth-approaching objects observed were 1963 RH, 1983 RD, 1985 TB and 1986 DA, as well as the new discoveries 1986 JK, 1986 LA and 1986 PA.

  11. 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.

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

    PubMed

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

    2009-06-18

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

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

    NASA Astrophysics Data System (ADS)

    Lainey, Valéry; Arlot, Jean-Eudes; Karatekin, Özgür; van Hoolst, Tim

    2009-06-01

    Io is the volcanically most active body in the Solar System and has a large surface heat flux. The geological activity is thought to be the result of tides raised by Jupiter, but it is not known whether the current tidal heat production is sufficiently high to generate the observed surface heat flow. Io's tidal heat comes from the orbital energy of the Io-Jupiter system (resulting in orbital acceleration), whereas dissipation of energy in Jupiter causes Io's orbital motion to decelerate. Here we report a determination of the tidal dissipation in Io and Jupiter through its effect on the orbital motions of the Galilean moons. Our results show that the rate of internal energy dissipation in Io (k2/Q = 0.015+/-0.003, where k2 is the Love number and Q is the quality factor) is in good agreement with the observed surface heat flow, and suggest that Io is close to thermal equilibrium. Dissipation in Jupiter (k2/Q = (1.102+/-0.203)×10-5) is close to the upper bound of its average value expected from the long-term evolution of the system, and dissipation in extrasolar planets may be higher than presently assumed. The measured secular accelerations indicate that Io is evolving inwards, towards Jupiter, and that the three innermost Galilean moons (Io, Europa and Ganymede) are evolving out of the exact Laplace resonance.

  14. Strong Tidal Dissipation In Io And Jupiter From Astrometric Observations

    NASA Astrophysics Data System (ADS)

    Lainey, Valery; Arlot, J.; Karatekin, O.; Van Hoolst, T.

    2009-09-01

    Io is the volcanically most active body in the Solar System and has a large surface heat flux. The geological activity is thought to be the result of tides raised by Jupiter, but it is not known whether the current tidal heat production is sufficiently high to generate the observed surface heat flow. Io's tidal heat comes from the orbital energy of the Io-Jupiter system (resulting in orbital acceleration), whereas dissipation of energy in Jupiter causes Io's orbital motion to decelerate. Here we report a determination of the tidal dissipation in Io and Jupiter through its effect on the orbital motions of the Galilean moons. Our results show that the rate of internal energy dissipation in Io (k2/Q = 0.015+/-0.003, where k2 is the Love number and Q is the quality factor) is in good agreement with the observed surface heat flow, and suggest that Io is close to thermal equilibrium. Dissipation in Jupiter (k2/Q = (1.102+/-0.203) X 10-5) is close to the upper bound of its average value expected from the long-term evolution of the system, and dissipation in extrasolar planets may be higher than presently assumed. The measured secular accelerations indicate that Io is evolving inwards, towards Jupiter, and that the three innermost Galilean moons (Io, Europa and Ganymede) are evolving out of the exact Laplace resonance.

  15. 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).

  16. 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.

  17. Characterizing the astrometric precision limit for moving targets observed with digital-array detectors

    NASA Astrophysics Data System (ADS)

    Bouquillon, S.; Mendez, R. A.; Altmann, M.; Carlucci, T.; Barache, C.; Taris, F.; Andrei, A. H.; Smart, R.

    2017-10-01

    Aims: We investigate the maximum astrometric precision that can be reached on moving targets observed with digital-sensor arrays, and provide an estimate for its ultimate lower limit based on the Cramér-Rao bound. Methods: We extend previous work on one-dimensional Gaussian point-spread functions (PSFs) focusing on moving objects and extending the scope to two-dimensional array detectors. In this study the PSF of a stationary point-source celestial body is replaced by its convolution with a linear motion, thus effectively modeling the spread function of a moving target. Results: The expressions of the Cramér-Rao lower bound deduced by this method allow us to study in great detail the limit of astrometric precision that can be reached for moving celestial objects, and to compute an optimal exposure time according to different observational parameters such as seeing, detector pixel size, decentering, and elongation of the source caused by its drift. Comparison to simulated and real data shows that the predictions of our simple model are consistent with observations. Based on data taken with the VST of the European Southern Observatory, programme 092.B-0165 and 095.B-0046.

  18. 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

  19. Automated Astrometric Analysis of Satellite Observations using Wide-field Imaging

    NASA Astrophysics Data System (ADS)

    Skuljan, J.; Kay, J.

    2016-09-01

    An observational trial was conducted in the South Island of New Zealand from 24 to 28 February 2015, as a collaborative effort between the United Kingdom and New Zealand in the area of space situational awareness. The aim of the trial was to observe a number of satellites in low Earth orbit using wide-field imaging from two separate locations, in order to determine the space trajectory and compare the measurements with the predictions based on the standard two-line elements. This activity was an initial step in building a space situational awareness capability at the Defence Technology Agency of the New Zealand Defence Force. New Zealand has an important strategic position as the last land mass that many satellites selected for deorbiting pass before entering the Earth's atmosphere over the dedicated disposal area in the South Pacific. A preliminary analysis of the trial data has demonstrated that relatively inexpensive equipment can be used to successfully detect satellites at moderate altitudes. A total of 60 satellite passes were observed over the five nights of observation and about 2600 images were collected. A combination of cooled CCD and standard DSLR cameras were used, with a selection of lenses between 17 mm and 50 mm in focal length, covering a relatively wide field of view of 25 to 60 degrees. The CCD cameras were equipped with custom-made GPS modules to record the time of exposure with a high accuracy of one millisecond, or better. Specialised software has been developed for automated astrometric analysis of the trial data. The astrometric solution is obtained as a two-dimensional least-squares polynomial fit to the measured pixel positions of a large number of stars (typically 1000) detected across the image. The star identification is fully automated and works well for all camera-lens combinations used in the trial. A moderate polynomial degree of 3 to 5 is selected to take into account any image distortions introduced by the lens. A typical RMS

  20. A statistical study of radio-source structure effects on astrometric very long baseline interferometry observations

    NASA Technical Reports Server (NTRS)

    Ulvestad, J. S.

    1989-01-01

    Errors from a number of sources in astrometric very long baseline interferometry (VLBI) have been reduced in recent years through a variety of methods of calibration and modeling. Such reductions have led to a situation in which the extended structure of the natural radio sources used in VLBI is a significant error source in the effort to improve the accuracy of the radio reference frame. In the past, work has been done on individual radio sources to establish the magnitude of the errors caused by their particular structures. The results of calculations on 26 radio sources are reported in which an effort is made to determine the typical delay and delay-rate errors for a number of sources having different types of structure. It is found that for single observations of the types of radio sources present in astrometric catalogs, group-delay and phase-delay scatter in the 50 to 100 psec range due to source structure can be expected at 8.4 GHz on the intercontinental baselines available in the Deep Space Network (DSN). Delay-rate scatter of approx. 5 x 10(exp -15) sec sec(exp -1) (or approx. 0.002 mm sec (exp -1) is also expected. If such errors mapped directly into source position errors, they would correspond to position uncertainties of approx. 2 to 5 nrad, similar to the best position determinations in the current JPL VLBI catalog. With the advent of wider bandwidth VLBI systems on the large DSN antennas, the system noise will be low enough so that the structure-induced errors will be a significant part of the error budget. Several possibilities for reducing the structure errors are discussed briefly, although it is likely that considerable effort will have to be devoted to the structure problem in order to reduce the typical error by a factor of two or more.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  2. 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.

  3. 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

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

    NASA Astrophysics Data System (ADS)

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

    1996-07-01

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

  5. 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.

  6. 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.

  7. Astrometric reduction of the Mars Exploration Rover night-time observations

    NASA Astrophysics Data System (ADS)

    Berthier, J.; Lainey, V.; Bell, J.; Dehant, V.

    2006-06-01

    In 2003 NASA launched toward Mars two robots, Spirit and Opportunity, in search of answers about the history of water on Mars. They landed on Mars on January 4 and January 24, 2004. Since this date, they have traversed around their landing site to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars. Among the science instruments carried by the rovers, the Panoramic Camera (Pancam) is used to determine the mineralogy, the texture, and the structure of the local terrain. The Pancam has also been used to take images of the Martian sky during the night. In particular, the Spirit rover has taken more than 500 night-time images showing Mars' moons Phobos and Deimos. We are performing the astrometric reduction of those images, with the goal of refining further the ephemerides of both satellites. Ephemeris improvements may help future targeting of high resolution images of the satellites from orbiters or other future missions. In addition, we hope to provide new constraints on the orbital evolution of the satellites through these observations and through other recent observations.

  8. 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

  9. 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.

  10. Astrometric Reduction of the Mars Exploration Rover Night-Time Observations of Phobos and Deimos

    NASA Astrophysics Data System (ADS)

    Dehant, Veronique; Berthier, J.; Bell, J., III; Lainey, V.; Million, C.

    2006-09-01

    In 2003 NASA launched toward Mars two robots, Spirit and Opportunity, in search of answers about the history of water on Mars. They landed on Mars on January 4 and January 24, 2004. Since this date, they have traversed around their landing site to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars. Among the science instruments carried by the rovers, the Panoramic Camera (Pancam) is used to determine the mineralogy, the texture, and the structure of the local terrain. The Pancam has also been used to take images of the martian sky during the night. In particular, the Spirit rover has taken more than 500 night-time images showing Mars's moons Phobos and Deimos. We are performing the astrometric reduction of those images, with the goal of refining further the ephemerides of both satellites. Ephemeris improvements may help future targeting of high resolution images of the satellites from orbiters or other future missions. In addition, we hope to provide new constraints on the orbital evolution of the satellites through these and other recent observations. In this presentation, we discuss in more detail the objectives of this campaign and our first preliminary results.

  11. 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.

  12. Speckle observations with PISCO in Merate: IV. Astrometric measurements of visual binaries in 2005

    NASA Astrophysics Data System (ADS)

    Scardia, M.; Prieur, J.-L.; Pansecchi, L.; Argyle, R. W.; Sala, M.; Basso, S.; Ghigo, M.; Koechlin, L.; Aristidi, E.

    2008-01-01

    We present relative astrometric measurements of visual binaries made during the second semester of 2005, with the speckle camera PISCO at the 102 cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long term program is to improve the accuracy of the orbits and determine the masses of the components.\\ We performed 130 new observations of 120 objects, with most of the angular separations in the range 0\\farcs1-4\\arcsec, and with an average accuracy of 0\\farcs01. Most of the position angles could be determined without the usual 180° ambiguity with the application of triple-correlation techniques, and their mean error is 0\\fdg8. We have found a possible new triple system: ADS 11077. škip0.15cm The measurements of the closest binaries were made with a new data reduction procedure, based on model fitting of the background of the auto-correlations. As this procedure proved to be very efficient, we have re-processed the old observations of close binaries made with PISCO in Merate since 2004. We thus improved 20 measurements already published and obtained 7 new measurements for observations that were previously reported as ``unresolved".\\ We finally present revised orbits for ADS 684, MCA 55Aac (in the Beta 1 Cyg-Albireo multiple system) and ADS 14783 for which the previously published orbits led to large residuals with our measurements and for which the new observations made since their computation allowed a significant improvement of those old orbits. The sum of the masses that we derived for those systems are consistent with the spectral type of the stars and the dynamic parallaxes are in good agreement with the parallaxes measured by Hipparcos.

  13. 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].

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  15. Astrometric cosmology .

    NASA Astrophysics Data System (ADS)

    Lattanzi, M. G.

    The accurate measurement of the motions of stars in our Galaxy can provide access to the cosmological signatures in the disk and halo, while astrometric experiments from within our Solar System can uniquely probe possible deviations from General Relativity. This article will introduce to the fact that astrometry has the potential, thanks also to impressive technological advancements, to become a key player in the field of local cosmology. For example, accurate absolute kinematics at the scale of the Milky Way can, for the first time in situ, account for the predictions made by the cold dark matter model for the Galactic halo, and eventually map out the distribution of dark matter, or other formation mechanisms, required to explain the signatures recently identified in the old component of the thick disk. Final notes dwell on to what extent Gaia can fulfill the expectations of astrometric cosmology and on what must instead be left to future, specifically designed, astrometric experiments.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. CCD astrometric observations of Amalthea and Thebe in the Gaia era

    NASA Astrophysics Data System (ADS)

    Robert, V.; Saquet, E.; Colas, F.; Arlot, J.-E.

    2017-05-01

    In the framework of the 2014-2015 campaign of mutual events, we observed Jupiter's inner satellites Amalthea (JV) and Thebe (JXIV). We focused on estimating whether the positioning accuracy determined from direct astrometry could compete with that derived from photometric observations of eclipses, for dynamical purposes. We present the analysis of 35 observations of Amalthea and 19 observations of Thebe realized with the 1-m telescope at the Pic du Midi observatory during three nights in 2015, January and April. The images were reduced through an optimal process that includes image and spherical corrections using the Gaia-DR1 catalogue to provide the most accurate equatorial (RA, Dec.) positions. We compared the observed positions of both satellites with the theoretical positions from JPL JUP310 satellite ephemerides and from the IMCCE INPOP13c planetary ephemeris. The values of rms (O-C) in equatorial positions are ±112 mas for the Amalthea observations, or 330 km at Jupiter, and ±90 mas for the Thebe observations, or 270 km at Jupiter. Using the Gaia-DR1 catalogue allowed us to eliminate systematic errors due to the star references up to 120 mas, or 350 km at Jupiter, by comparison with the UCAC4 catalogue.

  3. CCD astrometric observations of Amalthea and Thebe in the Gaia era

    NASA Astrophysics Data System (ADS)

    Robert, V.; Saquet, E.; Colas, F.; Arlot, J.-E.

    2017-01-01

    In the framework of the 2014-2015 campaign of mutual events, we observed Jupiter's inner satellites Amalthea (JV) and Thebe (JXIV). We focused on estimating whether the positioning accuracy determined from direct astrometry could compete with that derived from photometric observations of eclipses, for dynamical purposes. We present the analysis of 35 observations of Amalthea and 19 observations of Thebe realized with the 1-m telescope at Pic du Midi observatory during three nights in 2015, January and April. The images were reduced through an optimal process that includes image and spherical corrections using the Gaia-DR1 catalog to provide the most accurate equatorial (RA, Dec) positions. We compared the observed positions of both satellites with the theoretical positions from JPL JUP310 satellite ephemerides and from IMCCE INPOP13c planetary ephemeris. The rms (O-C) in equatorial positions are ±112 mas for the Amalthea observations, or 330 km at Jupiter, and ±90 mas for the Thebe observations, or 270 km at Jupiter. Using the Gaia-DR1 catalog allowed us to eliminate systematic errors due to the star references up to 120 mas, or 350 km at Jupiter, by comparison with the UCAC4 catalog.

  4. Astrometric observations of Phobos and Deimos during solar transits imaged by the Curiosity Mastcam

    NASA Astrophysics Data System (ADS)

    Lemmon, Mark; Bell, James; Malin, Michael; Bean, Keri; Wolff, Michael; Vasavada, Ashwin; Martin-Torres, F. Javier; Paz Zorzano-Mier, Maria; MSL Science Team

    2013-04-01

    Precise observations of the positions of the Martian moons can be used to refine knowledge of their orbits, allowing measurement of the rate at which their orbits evolve. Three transit events were targeted with the MSL Mastcam: sol (Martian day) 37 and 42 for Phobos, and 42 for Deimos. Observations were designed to take a large number of video frames with each camera. Observations were processed to determine the relative position of the satellite and the Sun through the transit. Comparison of the observations to the JPL Horizons ephemeris predictions results in Phobos arriving at the predicted time to within measurement precision, and Deimos arriving 3.0 sec early. Phobos was 3.3 km north of its predicted track, while Deimos was 1.7 km north. Uncertainties and possible systematic errors will be further refined and discussed.

  5. Astrometric observations of the Uranian satellites and a comparison with the theory.

    NASA Astrophysics Data System (ADS)

    Qiao, Rongchuan; Shen, Kaixian; Zhang, Xuefang

    1995-06-01

    The positions of the Uranian satellites from 7 photographic plates obtained with 1.0 m RCC telescope at the Yunnan Astronomical Observatory during the 1990 oppositions are given. These positions were compared with those calculated theoretically. The standard deviations of the observed-minus-calculated residuals referred to Titania are of the order of σα = 0″31, σδ = 0″33 and they are comparable with most of the precise observations found in the literature.

  6. 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.

  7. Use of long-term nongravitational force models for fitting astrometric observations of comet Encke

    NASA Astrophysics Data System (ADS)

    Usanin, V.; Nefedyev, Y.; Andreev, A.

    2017-09-01

    Based on the equations derived in (Usanin et al., 2016) a new solution combining the observations of 30 apparitions of the comet Encke from 1911 to 2010 is obtained. For the first time in the worldwide practice the solution is obtained by using converging differential correction of all 60 observed returns of the comet, however, the deviations are still unsatisfactory. The single solution has allowed to draw some preliminary conclusions. The contributions of planetary and nongravitational perturbations to the change of the elements of the orbit during the entire period of observation are determined. The extrapolation of the solution shows that for the past two thousand years the elements of the orbit orientation could change for a half of turnover, which should be taken into account when identifying the comet and associated meteor showers in ancient records. The predictions made by Z. Sekanina and I. Ferrín about oncoming termination of the comet activity are confirmed.

  8. 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.

  9. 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/

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

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

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

  12. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  14. Astrometric observations of Saturn's satellites from McDonald Observatory, 1972

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    Observations of Saturn's satellites have been reduced by means of secondary reference stars obtained by reduction of Palomar Sky Survey plates. This involved the use of 29 SAO stars and plate overlap technique to determine the coordinates of 59 fainter stars in the satellite field. Fourteen plate constants were determined for each of the two PSS plates. Comparison of two plate measurement and reduction techniques on the satellite measures appears to demonstrate the existence of a serious background gradient effect and the utility of microdensitometry to eliminate this error source in positional determinations of close satellites.

  15. 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.

  16. Astrometric observations of the main Uranian satellites at the Pulkovo Observatory in 2007-2016

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    In this paper we present the results of the observations of the Uranian satellites made with the 26-in. refractor at the Pulkovo Observatory in 2007-2016. Almost 7000 CCD frames were analyzed and reduced using the UCAC4 catalog. Coordinates of Uranus were determined indirectly using the satellite positions and their ephemeris relative to the planet. The (O-C) differences were calculated for each object using the INPOP13c planetary theory and Lainey's theory of the satellites' motion. The positioning accuracy is better than 0.5 arcsec. The mean values of (O-C) do not exceed 0 ″ .1 in RA and DEC correspondingly (Ariel: 0 ″ .043 and - 0 ″ .074 ; Umbriel: 0 . ″ 025 and - 0 . ″ 069 ; Titania: - 0 . ″ 009 and - 0 . ″ 014 ; Oberon: - 0 . ″ 001 and - 0 ″ .019 ; Uranus: 0 . ″ 002 and - 0 . ″ 016). They are in a good agreement with the ephemeris.

  17. The fields of reference stars for optical positional observations of astrometric extragalactic radio sources

    NASA Astrophysics Data System (ADS)

    Dement'eva, A. A.; Ryl'Kov, V. P.

    The Pulkovo programme (Pul ERS) and the techniques used to create a catalogue of coordinates and magnitudes for more than 7000 faint stars in 73 small fields around extragalactic radiosources (ERS) are described. Accurate positions of stars in the fields around ERS 2200+420 and ERS 2021+614 are given. The catalogue containing 223 stars is presented. The errors of coordinate reductions in the system of reference stars from the CMC catalogue are found to be 1.5-2.0 times smaller than for those in the system of the PPM catalogue. This programme (Pul ERS) is required for quick identification of the extragalactic radio sources and for obtaining their characteristics from observations with large telescopes and CCD detectors.

  18. BINARY ASTROMETRIC MICROLENSING WITH GAIA

    SciTech Connect

    Sajadian, Sedighe

    2015-04-15

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

  19. Astrometric Binaries: White Dwarfs?

    NASA Astrophysics Data System (ADS)

    Oliversen, Nancy A.

    We propose to observe a selection of astrometric or spectroscopicastrometric binaries nearer than about 20 pc with unseen low mass companions. Systems of this type are important for determining the luminosity function of low mass stars (white dwarfs and very late main sequence M stars), and their contribution to the total mass of the galaxy. Systems of this type are also important because the low mass, invisible companions are potential candidates in the search for planets. Our target list is selected primarily from the list of 31 astrometric binaries near the sun by Lippincott (1978, Space Sci. Rev., 22, 153), with additional candidates from recent observations by Kamper. The elimination of stars with previous IUE observations, red companions resolved by infrared speckle interferometry, or primaries later than M1 (because if white dwarf companions are present they should have been detected in the visible region) reduces the list to 5 targets which need further information. IUE SWP low dispersion observations of these targets will show clearly whether the remaining unseen companions are white dwarfs, thus eliminating very cool main sequence stars or planets. This is also important in providing complete statistical information about the nearest stars. The discovery of a white dwarf in such a nearby system would provide important additional information about the masses of white dwarfs. Recent results by Greenstein (1986, A. J., 92, 859) from binary systems containing white dwarfs imply that 80% of such systems are as yet undetected. The preference of binaries for companions of approximately equal mass makes the Lippincott-Kamper list of A through K primaries with unseen companions a good one to use to search for white dwarfs. The mass and light dominance of the current primary over the white dwarf in the visible makes ultraviolet observations essential to obtain an accurate census of white dwarf binaries.

  20. 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.

  1. 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.

  2. Influence of precision inertial systems on astronomical observations

    NASA Technical Reports Server (NTRS)

    Ouellette, G. A.; Gilmore, J. P.; Nurre, G. S.

    1974-01-01

    The incorporation of precision inertial control on LST could exert a strong influence on the philosophy of and techniques for carrying out astronomical observations. In conjunction with a fine guidance star sensor, the inertial reference unit (IRU) described herein could easily expand LST capability to include observations such as (1) tracking of solar system objects, including specific points of interest on the planets; (2) rapid repositioning of scanning sensors on distributed objects such as nebulae and galaxies; (3) carrying out unified star catalog measurements to eliminate the overlap problem which exists in all ground procedures; and (4) carrying out various astrometric measurements with 'real time' data reduction capability.

  3. Satellite Tracking Astrometric Network (STAN)

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Gai, Mario

    2015-08-01

    The possibility of precise orbit tracking and determination of different types of satellites has been explored for at least some 25 years (Arimoto et al., 1990). Proposals in this sense made use mainly of astrometric observations, but multiple tracking techniques combining transfer and laser ranging was also suggested (Guo et al., 2009; Montojo et al., 2011), with different requirements and performances ranging from $\\sim100$~m to tenths of meters.In this work we explore the possible improvements and a novel implementation of a technique relying on large angle, high precision astrometry from ground for the determination of satellite orbits. The concept is based on combined observation of geostationary satellites and other near-Earth space objects from two or more telescopes, applying the triangulation principle over widely separated regions of the sky. An accuracy of a few $10^{-2}$~m can be attained with 1-meter-class telescopes and a field of vied of some arcminutes.We discuss the feasibility of the technique, some of the implementation aspects, and the limitations imposed by atmospheric turbulence. The potential benefits for satellite orbit control and navigation systems are presented, depending on the number and position of the contributing telescopes.We also discuss the possibility that, by reversing the roles of stars and satellites, the same kind of observations can be used for verification and maintenance of astrometric catalogs.

  4. 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.

  5. Astrometric Telescope Facility - Status report

    NASA Astrophysics Data System (ADS)

    Nishioka, K.; Swenson, B. L.; Scargle, J. D.

    1986-01-01

    The advent of the Space Station Program has provided an unexpected opportunity for the Astrometric Telescope Facility (ATF) study program by providing a potential long-duration on-orbit serviceable platform. It required a concept change for ATF from a free-flyer observatory to a Space-Station-based Observatory. The program was sent in this new direction at the start of fiscal year 1985, and program plans including study schedules and science and technical requirements are being revised and defined. The facility is designed to be versatile and capable of fulfilling the primary goal of planet detection, and to be highly useful for other astrophysics observations. Basically the ATF observing program is a long-duration plan requiring repetitive observations of single stars over a one to two decade period. These repetitive observations are needed to provide data necessary to conclusively determine the existence (or nonexistence) of planets of the Uranus and Neptune class in extrasolar planetary systems.

  6. 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.

  7. New astrometric measurement and reduction of USNO photographic observations of the main Saturnian satellites: 1974-1998

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    Context. Accurate positional measurements of planets and satellites are used to improve our knowledge of their orbits and 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 Saturn and its main satellites taken with the US Naval Observatory 26-inch refractor from 1974 to 1998. Methods: We measured 526 astrophotographic plates with the digitizer of the Royal Observatory of Belgium and reduced them 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 satellites with the theoretical positions from INPOP13c and DE432 planetary ephemerides and from NOE-6-2015-SAT and SAT375 satellite ephemerides. The mean post-fit rms residuals in equatorial positions range from ±68 mas for the Titan observations or 400 km at Saturn, to ±100 mas for the Hyperion observations or 600 km at Saturn. The mean post-fit rms intersatellite residuals range from ±46 mas for the Rhea-Titan observations or 280 km at Saturn, to ±72 mas for the Hyperion-Titan observations or 430 km at Saturn. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A37 , at the Natural Satellites DataBase and Natural Satellites Data Center services of IMCCE via http://nsdb.imcce.fr/ or http://www.imcce.fr/nsdc/

  8. An Astrometric Analysis of eta Carinae’s Eruptive History Using HST WF/PC2 and ACS Observations

    DTIC Science & Technology

    2007-07-11

    2003, The Future of Small Telescopes In The New Millennium . Volume II - The Telescopes We Use, 67 [Zacharias et al.(2004)] Zacharias, N., Monet, D...tell us about the star’s history. In this dissertation, Hubble Space Telescope (HST) observations spanning nearly a decade and utilizing both the Wide...Homunculus, and a new , much shorter interval for the duration of the Great Eruption. Certain equatorial features, previously associated with an 1890

  9. White Dwarfs in Astrometric Binaries?

    NASA Astrophysics Data System (ADS)

    Oliversen, N. A.; Evans, N. R.; Feibelman, W. A.; Kamper, K. W.

    1993-12-01

    Lippincott (1978, Space Sci Rev, 22, 153) compiled a list of astrometric binaries with unseen companions typically within 20 pc of the sun. Red companions have been observed in a number of these systems (e.g. McCarthy, D. W. 1983, IAU Coll. # 76, p. 107). Unseen, low mass companions could also be white dwarfs. We have obtained IUE observations of stars on the list which have primaries with spectral types M1 or earlier (white dwarf companions of cooler primaries could be detected from the ground), and are brighter than 10 mag, which do not have known red companions. Preliminary reductions (comparison with standard stars of appropriate spectral types) indicate that there are no white dwarfs in the sample. Further processing is being done to determine limits on possible white dwarf temperatures.

  10. The SIM Lite Astrometric Observatory

    NASA Astrophysics Data System (ADS)

    Unwin, Stephen C.

    2009-05-01

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

  11. The Concept of a Stare-Mode Astrometric Space Mission

    DTIC Science & Technology

    2006-10-12

    observations, which is im- portant for some science goals, such as detecting extrasolar planets . The achievable astrometric mission precisions are...ing with instrumental effects, and attitude control). In addition, for many applications (parallaxes, planet detections), the one- dimensional

  12. Astrometric "Core-shifts" at the Highest Frequencies

    NASA Technical Reports Server (NTRS)

    Rioja, Maria; Dodson, Richard

    2010-01-01

    We discuss the application of a new VLBI astrometric method named "Source/Frequency Phase Referencing" to measurements of "core-shifts" in radio sources used for geodetic observations. We detail the reasons that astrometrical observations of 'core-shifts' have become critical in the era of VLBI2010. We detail how this new method allows the problem to be addressed at the highest frequencies and outline its superior compensation of tropospheric errors.

  13. Photometry of astrometric reference stars

    NASA Technical Reports Server (NTRS)

    Castelaz, Michael W.; Persinger, Tim; Stein, John W.; Prosser, James; Powell, Harry D.

    1991-01-01

    UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral types and luminosity classifications made from the colors are used to determine their spectroscopic parallaxes. In this paper, colors for 309 stars in 25 regions are given, and classifications for 210 stars have been made. These stars form reference frames in the Allegheny Observatory Multichannel Astrometric Photometer astrometric program, and in the Praesepe cluster reduced by Russell (1976). It is found that the present photometric spectral types are reliable to within 2.5 spectral subclasses.

  14. Optical Characteristics of Astrometric Radio Sources OCARS

    NASA Astrophysics Data System (ADS)

    Malkin, Z.

    2013-04-01

    In this paper, the current status of the catalog of Optical Characteristics of Astrometric Radio Sources OCARS is presented. The catalog includes radio sources observed in various astrometric and geodetic VLBI programs in 1979-2012. For these sources the physical object type, redshift and visual or infrared magnitude is given when available. Detailed comments are provided when some problems with published data were encountered. Since the first version created in December 2007, the catalog is continuously developed and expanded in respect to inclusion of new radio sources and addition of new or correction of old astrophysical data. Several sources of information are used for OCARS. The main of them are the NASA/IPAC Extragalactic Database (NED) and SIMBAD astronomical databases. Besides several astronomical journals and arXiv depository are regularly monitored, so that new data is included in OCARS just after publication. The redshift for about 150 sources have been determined from dedicated optical spectroscopic observations. As of October 2012, OCARS catalog includes 7173 radio sources. 3898 sources have known redshift, and 4860 sources have known magnitude. In 2009, it was used as a supplement material to the ICRF2. The list of radio sources with a good observational history but lacking astrophysical information is provide for planning of optical observations of the most important astrometric sources. The OCARS catalog is updated, in average every several weeks and is available at http://www.gao.spb.ru/english/as/ac_vlbi/ocars.txt.

  15. Astrometric exoplanet surveys in practice

    NASA Astrophysics Data System (ADS)

    Sahlmann, Johannes

    2016-10-01

    Conversely to the transit photometry and radial velocity methods, the astrometric discovery of exoplanets is still limited by the sensitivity of available instruments. Ground-based surveys are now sensitive to giant planets in orbit around nearby low-mass stars and brown dwarfs. In 2014, ESA's Gaia mission began its survey, which is expected to discover thousands of giant exoplanets by detecting the astrometric orbital motions of the host stars.

  16. 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.

  17. First Astrometric Results from the NPOI

    NASA Astrophysics Data System (ADS)

    Hutter, D. J.; Elias, N. M., II; Hummel, C. A.

    1997-12-01

    The Navy Prototype Optical Interferometer (NPOI), a joint project of the U.S. Naval Observatory, the Naval Research Laboratory, and Lowell Observatory has been in routine operation since 1996. Here, we present the first results of wide-angle astrometric observations made with the NPOI. The NPOI includes arrays for imaging and for astrometry. The imaging array consists of six movable siderostats, with baseline lengths from 2.0 m to 437 m. The astrometric array consists of four fixed siderostats, with baseline lengths from 18 m to 38 m. The astrometric array includes an extensive baseline metrology system to measure the motions of the siderostats with respect to the local bedrock to 100 nm accuracy. The arrays share vacuum feed and delay systems, active group-delay fringe tracking in 32 channels over a bandpass from 450 to 850 nm, and a high degree of automation. The goal of the astrometry program with the NPOI is an accuracy of 2 mas over large angles. This accuracy is comparable to that achieved by the Hipparcos satellite, and will be used to maintain the optical reference frame. (Positional accuracies in that frame would otherwise degrade to 10 mas by 2001.) In addition to maintaining accurate positions for several thousand Hipparcos stars, the NPOI will also greatly improve the proper motion accuracy by increasing the measurement time base. Astrometric observations of radio stars with the NPOI will maintain the link between the optical and radio reference frames, while imaging observations will improve the link by elucidating the relation between the radio and optical emission in these systems.

  18. AGP (Astrometric Gravitation Probe) optical design report

    NASA Astrophysics Data System (ADS)

    Riva, Alberto; Gai, Mario; Landini, Federico; Lazzarini, Paolo; Gallieni, Daniele; Tintori, Matteo; Anselmi, Alberto; Cesare, Stefano; Busonero, Deborah; Lattanzi, Mario Gilberto; Vecchiato, Alberto

    2016-08-01

    This paper describes the current opto-mechanical design of AGP, a mission designed for astrometric verification of General Relativity (GR) and competing gravitation theories by means of precise determination of light deflection on field stars, and of orbital parameters of selected Solar System objects. The optical concept includes a planar rear-view mirror for simultaneous imaging on the CCD mosaic detector of fields of view also from the direction opposite to the Sun, affected by negligible deflection, for the sake of real time calibration. The precision of astrometric measurements on individual stars will be of order of 1 mas, over two fields separated by few degrees around the Sun and observed simultaneously. We describe the optical design characteristics, with particular reference to manufacturing and tolerancing aspects, evidencing the preservation of very good imaging performance over the range of expected operating conditions.

  19. 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.

  20. GAME: Gamma Astrometric Measurement Experiment

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

    The GAME mission concept aims at the 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. The targeted precision on the γ parameter of the Parametrised Post-Newtonian formulation of General Relativity is 10-6 or better, i.e. one to two orders of magnitude better than the best currently available 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 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. The observation strategy also allows some additional scientific objectives related to other tests of General Relativity and to the study of exo-planetary field, multiple aperture Fizeau interferometer, observing simultaneously two regions close to the Solar limb. 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. We describe the science motivation, the proposed mission profile, the possible payload implementation and the expected performance.

  1. 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.

  2. Progress of astrometric research in Nikolaev Observatory

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  3. 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.

  4. Astrometric Exoplanet Detection with Gaia

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  5. 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.

  6. Gamma astrometric measurement experiment -science and implementation

    NASA Astrophysics Data System (ADS)

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

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

  7. 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.

  8. 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.

  9. 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.

  10. Exoplanet Detection by Astrometric Method

    NASA Astrophysics Data System (ADS)

    Xu, Wei-wei; Liao, Xin-hao; Zhou, Yong-hong; Xu, Xue-qing

    2017-07-01

    As we know, the exoplanets are mostly detected by the methods of radial velocity and transit, up to now only one is found by the astrometric method. As the data of the gaia will be soon released, astrometry will gradually become one of the most important methods for detecting exoplanets. Based on the sequence of star positions obtained by the astrometric method, the solution of the equations of dynamical conditions involving the calculations of planet's mass and orbital parameters is discussed in this paper. Due to the deficiency of the available theory (orbital element method), a new method (coordinate velocity method) is put forward. The differential correction formulae of the two methods, as well as the necessary simulation calculations are presented. In addition, the method established in this paper can be applied to the multi-planet system easily.

  11. 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.

  12. 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

  13. Astrometric aspects of 1980 Indian total solar eclipse.

    NASA Astrophysics Data System (ADS)

    Protitch-Benishek, V.; Arsenijević, J.; Vince, I.; Kubičela, A.; Lazendic, J.

    1997-05-01

    During the total solar eclipse of February 16, 1980, observable from India, besides many kinds of research programs, the sequence of eclipse phases was taken photographically for astrometric purposes. All relevant parameters of this eclipse are derived, including ΔT, Tmax, ΔRS etc.

  14. On the detection of other planetary systems by astrometric techniques

    NASA Technical Reports Server (NTRS)

    Black, D. C.; Scargle, J. D.

    1982-01-01

    A quantitative method for astrometrically detecting perturbations induced in a star's motion by the presence of a planetary object is described. A periodogram is defined, wherein signals observed from a star show exactly periodic variations, which can be extracted from observational data using purely statistical methods. A detection threshold is defined for the frequency of occurrence of some detectable signal, e.g., the Nyquist frequency. Possible effects of a stellar orbital eccentricity and multiple companions are discussed, noting that assumption of a circular orbit assures the spectral purity of the signal described. The periodogram technique was applied to 12 yr of astrometric data from the U.S. Naval Observatory for three stars with low mass stellar companions. Periodic perturbations were confirmed. A comparison of the accuracy of different astrometric systems shows that the detection accuracy of a system is determined by the measurement accuracy and the number of observations, although the detection efficiency can be maximized by minimizing the number of data points for the case when observational errors are proportional to the square root of the number of data points. It is suggested that a space-based astrometric telescope is best suited to take advantage of the method.

  15. Astrometric and Photometric Measurements of WDS 20210+1028

    NASA Astrophysics Data System (ADS)

    Cormier, Sebastien; Calanog, Jae; Stojimirovic, Irena; Hilburn, Jerry; Blanco, Philip; Fitzgerald, Brodney

    2017-07-01

    We report CCD astrometric and photometric measurements of the components of the double star system WDS20210+1028 (J 838) using the iTelescope network. Combined with historical observations, our measurements suggest that the existing fitted orbital solution may need to be modified.

  16. UCAC3: Astrometric Reductions

    DTIC Science & Technology

    2010-06-01

    side of the pier (east or west) then repeat with the telescope on the other side. Thus, two images of the same area in the sky are obtained which are...pixel phase errors were investigated further and found to also be a function of the FWHM of the stellar image profiles. The field distortion pattern...of high signal-to-noise ratio (S/N) stellar images , and mean image elongation. About 15% of the observations are qualified as “poor” (see also

  17. 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.

  18. 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

  19. Grasp observation influences speech production.

    PubMed

    Gentilucci, Maurizio

    2003-01-01

    Subjects pronounced either the syllable 'BA' or 'GA' while observing motor acts of hand grasp directed to objects of two sizes (experiment 1). Kinematics of lip aperture and amplitude spectrum of voice were influenced by the observation of the different grasp kinematics depending on the size of the target objects. Specifically, both lip aperture and voice peak amplitude were greater when the observed hand grasp was directed to the large object. Two control experiments ruled out that the different arm velocity when reaching objects varying in size (experiment 2), and overt visual analysis of the target-object (experiment 3), affected lip movement and voice emission. Results provide behavioural evidence in favour of the hypothesis that the system involved in observation (and preparation) of grasp movements partially shares the cortical areas involved in speech production.

  20. Utilizing Astrometric Orbits to Obtain Coronagraphic Images of Extrasolar Planets

    NASA Astrophysics Data System (ADS)

    Davidson, John M.

    2011-08-01

    We present an approach for utilizing astrometric orbit information to improve the yield of planetary images and spectra from a follow-on direct-detection mission. This approach is based on the notion—strictly hypothetical—that if a particular star could be observed continuously, the instrument would in time observe all portions of the habitable zone so that no planet residing therein could be missed. This strategy could not be implemented in any realistic mission scenario. But if an exoplanet’s orbit is known from astrometric observation, then it may be possible to plan and schedule a sequence of imaging observations that is the equivalent of continuous observation. A series of images—optimally spaced in time—could be recorded to examine contiguous segments of the orbit. In time, all segments would be examined, leading to the inevitable detection of the planet. In this article, we show how astrometric orbit information can be used to construct such a sequence. We apply this methodology to seven stars taken from the target lists of proposed astrometric and direct-detection missions. In addition, we construct this sequence for the Sun-Earth system as it would appear from a distance of 10 pc. In constructing these sequences, we have assumed that the imaging instrument has an inner working angle (IWA) of 75 mas and that the planets are visible whenever they are separated from their host stars by ≥IWA and are in quarter-phase or greater. In addition, we have assumed that the planets orbit at a distance of 1 AU scaled to luminosity and that the inclination of the orbit plane is 60°. For the individual stars in this target pool, we find that the number of observations in this sequence ranges from two to seven, representing the maximum number of observations required to find the planet. The probable number of observations ranges from 1.5 to 3.1. These results suggest that a direct-detection mission using astrometric orbits would find all eight exoplanets in

  1. An Updated 2017 Astrometric Solution for Betelgeuse

    NASA Astrophysics Data System (ADS)

    Harper, G. M.; Brown, A.; Guinan, E. F.; O'Gorman, E.; Richards, A. M. S.; Kervella, P.; Decin, L.

    2017-07-01

    We provide an update for the astrometric solution for the Type II supernova progenitor Betelgeuse using the revised Hipparcos Intermediate Astrometric Data (HIAD) of van Leeuwen, combined with existing VLA and new e-MERLIN and ALMA positions. The 2007 Hipparcos refined abscissa measurements required the addition of so-called Cosmic Noise of 2.4 mas to find an acceptable 5-parameter stochastic solution. We find that a measure of radio Cosmic Noise should also be included for the radio positions because surface inhomogeneities exist at a level significant enough to introduce additional intensity centroid uncertainty. Combining the 2007 HIAD with the proper motions based solely on the radio positions leads to a parallax of π =5.27+/- 0.78 mas ({190}-25+33 pc), smaller than the Hipparcos 2007 value of 6.56 ± 0.83 mas ({152}-17+22 pc). Furthermore, combining the VLA and new e-MERLIN and ALMA radio positions with the 2007 HIAD, and including radio Cosmic Noise of 2.4 mas, leads to a nominal parallax solution of 4.51 ± 0.80 mas ({222}-34+48 pc), which, while only 0.7σ different from the 2008 solution of Harper et al., is 2.6σ different from the solution of van Leeuwen. An accurate and precise parallax for Betelgeuse is always going to be difficult to obtain because it is small compared to the stellar angular diameter (θ =44 mas). We outline an observing strategy utilizing future mm and sub-mm high-spatial resolution interferometry that must be used if substantial improvements in the precision and accuracy of the parallax and distance are to be achieved.

  2. Finding Free-Floating Black Holes using Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Lu, Jessica R.; Ofek, Eran Oded; Sinukoff, Evan; Udalski, Andrzej; Kozlowski, Szymon

    2017-01-01

    Our Galaxy most likely hosts 10-100 million stellar mass black holes. The exact number and mass function of these black holes contains important information regarding our Galaxy's star formation history, stellar mass function, and the fate of very massive stars. However, isolated stellar black holes have yet to be detected. To date, stellar mass black holes have only been definitively detected in binary systems with accreting companions or merging to produce gravitational waves. In principle, the presence of isolated black holes can be inferred from astrometric and photometric signatures produced when they lens light from a background star. We attempt to detect the astrometric lensing signatures of several photometrically identified microlensing events, toward the Galactic Bulge. Long-duration events (t_Einstein > 100 days) were selected as the most likely black hole candidates and were observed using several years of laser-guided adaptive optics observations from the W. M. Keck telescopes. We present results from this search.

  3. Astrometric studies of the results of a new reduction of old photographic observations of the Saturnian System based on the comparison with the modern theories of satellite motion

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    The paper shows the possibility of increasing the accuracy of the results of photographic observations of Saturn and its moons made in the 1970s and reduced using the old reference star catalogues and semiautomatic measurements. New celestial coordinates of the moons (from the third to the eighth), "satellite minus satellite" relative moon coordinates, and Saturn coordinates by positions of satellites are obtained without measuring its images. The results are stored in the Pulkovo Observatory database on the Solar System bodies and are available online at www.puldb.ru. The efficiency of the reduction method based on digitizing of astronegatives using 21 Mpx Canon digital camera and IZMCCD software is shown. The comparison of new results of old observations with the latest theories of moon motion has revealed a significant increase in satellite positioning accuracy. The investigation of the differences (O-C) of celestial coordinates from satellite positions in their apparent Saturn-centric orbits has revealed a noticeable motion of the differences (O-C) in right ascension depending on their distances from Saturn for all moons.

  4. Establishing Alpha Oph as a Prototype Rotator: Improved Astrometric Orbit

    DTIC Science & Technology

    2011-01-10

    astrometric characterization of the companion orbit. We also use photometry from these observations to derive a model-based estimate of the companion mass. A...uncertainties. In addition to the dynamically derived masses, we use IJHK photometry to derive a model-based mass for α Oph B, of 0.77 ± 0.05 M...greater abundance of both stellar and planetary mass companions (Kratter et al. 2010, J. Crepp 2010, private communication). However, the multiplicity

  5. An operations concept for the Space Station based Astrometric Telescope Facility

    NASA Technical Reports Server (NTRS)

    Jackson, Robert W.; Smith, Martha A.

    1988-01-01

    The Astrometric Telescope Facility (AFT) will be an orbiting observatory which has been proposed to be attached to the NASA Space Station. The primary scientific objectives of the ATF will be to search for extrasolar planetary systems and to study their characteristics. In addition, the ATF will be able to perform other general astrometric observations of stars within the Milky Way Galaxy. Astrometric Telescope Facility operations from the Space Station will be simple and straightforward compared to other orbiting free-flying telescopes. The astrometric approach to planetary detection, which uses repeated measurements of the same set of target stars over many years, is compatible with simple, repetitive operations of the facility. The support provided by the Space Station and anomaly tolerance features of the ATF design also contribute to the simplicity of the operations concept.

  6. Astrometric Follow Up of Wide Planetary Candidates

    NASA Astrophysics Data System (ADS)

    Durkan, Stephen; Janson, Markus; Carson, Joseph

    2014-12-01

    The current population of known exoplanets is biased towards close in, short period planets due to the detection rate of transit and radial velocity techniques. However the advancement in direct imaging technologies and image reduction techniques has opened up sensitivity to massive planets at large separations, rapidly expanding the parameter space over which planetary existence and characteristics can be probed. The Spitzer space telescope is ideally suited for the direct imaging of such planets that have peak thermal emission at wavelengths around 4.5 microns. Previous Spitzer data collected under programs 34 and 48 has recently been the subject of a sophisticated principal components analysis reduction technique. This technique has removed stellar PSF to a much greater degree than preceding studies have achieved, the reduced archival Spitzer observations are sensitive to planetary mass companions at a much smaller separations than previously attainable. This reduction technique accompanied by stringent criteria, such as ≥5 sigma significance, realistic visual characteristics and taking into account the predicted spectral energy distribution of Jupiter mass planets, has identified a number of potential planetary companions. These targets must be observed in a 2nd epoch to test for common proper motion to offer a firm confirmation or refutation of the candidate's planetary nature. Here we propose to observe 12 of these targets for which data does not exist in a 2nd epoch to a sufficient degree of sensitivity to recover the potential planetary candidates for astrometric investigation.

  7. The Gamma Astrometric Measurement Experiment (GAME)

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

    The GAME mission concept is aimed at very precise measurement of the gravitational deflection of light by the Sun, by an optimized telescope in the visible and launched in orbit on a small class satellite. The targeted precision on the γ parameter of the Parametrized Post-Newtonian formulation of General Relativity is 10-6 or better, i.e. one to two orders of magnitude better than the best current results. Such precision is suitable to detect possible deviations from unity value, associated to generalized 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 astrometric signature on the stellar positions, i.e. on the spatial component of the effect rather than the temporal component as in recent experiments using radio link delay timing. Exploiting the observation strategy, it is also possible to target other interesting scientific goals both in the realm of General Relativity and in the observations of extrasolar systems. The instrument is a dual field, multiple aperture Fizeau interferometer, observing simultaneously two regions close to the Solar limb. The diluted optics approach is selected for efficient rejection of the solar radiation, while retaining an acceptable angular resolution on the science targets. We describe the science motivation, the proposed mission profile, the payload concept and the expected performance from recent results.

  8. Stray light evaluation for the astrometric gravitation probe mission

    NASA Astrophysics Data System (ADS)

    Landini, Federico; Riva, Alberto; Gai, Mario; Baccani, Cristian; Focardi, Mauro; Pancrazzi, Maurizio

    2016-08-01

    The main goal of the Astrometric Gravitation Probe mission is the verification of General Relativity and competing gravitation theories by precise astrometric determination of light deflection, and of orbital parameters of selected Solar System objects. The key element is the coherent combination of a set of 92 circular entrance apertures, each feeding an elementary inverted occulter similar to the one developed for Solar Orbiter/METIS.1 This provides coronagraphic functions over a relevant field of view, in which all stars are observed for astrometric purposes with the full resolution of a 1 m diameter telescope. The telescope primary mirror acts as a beam combiner, feeding the 92 pupils, through the internal optics, toward a single focal plane. The primary mirror is characterized by 92 output apertures, sized according to the entrance pupil and telescope geometry, in order to dump the solar disk light beyond the instrument. The astronomical objects are much fainter than the solar disk, which is angularly close to the inner field of view of the telescope. The stray light as generated by the diffraction of the solar disk at the edges of the 92 apertures defines the limiting magnitude of observable stars. In particular, the stray light due to the diffraction from the pupil apertures is scattered by the telescope optics and follows the same optical path of the astronomical objects; it is a contribution that cannot be eliminated and must therefore be carefully evaluated. This paper describes the preliminary evaluation of this stray light contribution.

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

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

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

  10. 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.

  11. 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.

  12. Precise astrometric positions of 40 minor planets obtained by GPO telescope of ESO - La Silla - in 1987 - 88.

    NASA Astrophysics Data System (ADS)

    Debehogne, H.; Protitch-Benishek, V.; Olevic, D.

    1996-11-01

    543 precise astrometric positions of 40 minor planets, observed during two missions (January 1987 and September - October 1988) at La Silla were obtained. 21 new minor planets were discovered during these observational periods.

  13. A Model for Astrometric Detection and Characterization of Multi-Exoplanet Systems

    NASA Astrophysics Data System (ADS)

    April Thompson, Maggie; Spergel, David N.

    2017-01-01

    In this thesis, we develop an approximate linear model of stellar motion in multi- planet systems as an aid to observers using the astrometric method to detect and characterize exoplanets. Recent and near-term advances in satellite and ground-based instruments are on the threshold of achieving sufficient (~10 micro-arcsecond) angular accuracies to allow astronomers to measure and analyze the transverse mo- tion of stars about the common barycenter in single- and multi-planet systems due to the gravitational influence of companion planets. Given the emerging statistics of extrasolar planetary systems and the long observation periods required to assess exoplanet influences, astronomers should find an approximate technique for preliminary estimates of multiple planet numbers, masses and orbital parameters useful in determining the most likely stellar systems for follow-up studies. In this paper, we briefly review the history of astrometry and discuss its advantages and limitations in exoplanet research. In addition, we define the principal astrometric signature and describe the main variables affecting it, highlighting astrometry’s complementary role to radial velocity and photometric transit exoplanet detection techniques. We develop and test a Python computer code using actual data and projections of the Sun’s motion due to the influence of the four gas giants in the solar system. We then apply this model to over 50 hypothetical massive two- and three-exoplanet systems to discover useful general patterns by employing a heuristic examination of key aspects of the host star’s motion over long observation intervals. Finally, we modify the code by incorporating an inverse least-squares fit program to assess its efficiency in identifying the main characteristics of multi-planet systems based on observational records over 5-, 10- and 20-year periods for a variety of actual and hypothetical exoplanetary systems. We also explore the method’s sensitivity to

  14. Astrometric orbits of SB^9 stars

    NASA Astrophysics Data System (ADS)

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

    2005-10-01

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

  15. Astrometric Calibration of the Gemini Planet Imager

    NASA Astrophysics Data System (ADS)

    Tran, Debby; Konopacky, Quinn M.; GPIES Team

    2017-01-01

    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. We also examined the effects of the point spread function on the positions of the binaries as well as their separations, the results of which I will discuss.

  16. Possible Astrometric Perturbation of LHS 288

    NASA Astrophysics Data System (ADS)

    Bartlett, Jennifer L.; Ianna, P. A.; Begam, M. C.

    2007-05-01

    A sample of 13 stars from the University of Virginia southern hemisphere parallax program has been tested for possible astrometric perturbations due to low-mass companions. The selected objects are primarily early to mid-M dwarfs with large parallaxes, all are within 25 parsecs, that are not known to be binaries. The data were collected from CCD parallax observations made between 1991 and 2002 with the 1-meter reflector at the Siding Spring Observatory, Coonabarabran, Australia. Following our standard central overlap solution for parallax and proper motion, the residuals were subjected to a time-series analysis using the Lomb-Scargle normalized periodogram method (Press et al. 1992). Of these, LHS 288 displays a possible perturbation due to a very low mass companion; such a companion might be as small as 2.4 Jupiter masses. Because LHS 288 is a high proper-motion star in a rich field, the possibility that it passed over an undetected faint star during these observations cannot be eliminated; such a distorted point-spread function might mimic a perturbation. Additional observations from an independent data set could help determine whether the suggested perturbation is real. The remaining stars demonstrate no indication of any companions greater than about 17 Jupiter masses with orbits between 1.5 and 10 years. The single stars are LHS 34 (white dwarf), LHS 271, LHS 337, LHS 532, LHS 1134, LHS 1565, LHS 2310, LHS 2739, LHS 2813, LHS 3064, LHS 3242, and LHS 3418. We acknowledge support from NSF grants AST 98-20711 and 05-07711, Georgia State University, the Space Interferometry Mission (SIM), F. H. Levinson Fund of the Peninsula Community Foundation, UVa, and Hampden-Sydney College in addition to support and generous observing time allocations from the Research School of Astronomy and Astrophysics, Australian National University.

  17. Improvements in Ross type astrometric objectives

    NASA Technical Reports Server (NTRS)

    Baker, J.

    1971-01-01

    It is shown that aspheric deformations of the first and fourth elements of the four element Ross objective can be introduced to permit one to obtain improved color corrections for astrometric purposes. The usual monochromatic aberrations are as well corrected as for the standard Ross lens. In addition, one can eliminate or reduce additional aberrations, such as secondary spectrum, chromatic spherical aberration, chromatic coma and chromatic distortion. The resulting objectives are suitable for use as intermediate and long focus astrometric objectives covering large angle fields.

  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. Bias Properties of Extragalactic Distance Indicators. XI. Methods to Correct for Observational Selection Bias for RR Lyrae Absolute Magnitudes from Trigonometric Parallaxes Expected from the Full-Sky Astrometric Mapping Explorer Satellite

    NASA Astrophysics Data System (ADS)

    Sandage, Allan; Saha, A.

    2002-04-01

    A short history is given of the development of the correction for observation selection bias inherent in the calibration of absolute magnitudes using trigonometric parallaxes. The developments have been due to Eddington, Jeffreys, Trumpler & Weaver, Wallerstein, Ljunggren & Oja, West, Lutz & Kelker, after whom the bias is named, Turon Lacarrieu & Crézé, Hanson, Smith, and many others. As a tutorial to gain an intuitive understanding of several complicated trigonometric bias problems, we study a toy bias model of a parallax catalog that incorporates assumed parallax measuring errors of various severities. The two effects of bias errors on the derived absolute magnitudes are (1) the Lutz-Kelker correction itself, which depends on the relative parallax error δπ/π and the spatial distribution, and (2) a Malmquist-like ``incompleteness'' correction of opposite sign due to various apparent magnitude cutoffs as they are progressively imposed on the catalog. We calculate the bias properties using simulations involving 3×106 stars of fixed absolute magnitude using Mv=+0.6 to imitate RR Lyrae variables in the mean. These stars are spread over a spherical volume bounded by a radius 50,000 pc with different spatial density distributions. The bias is demonstrated by first using a fixed rms parallax uncertainty per star of 50 μas and then using a variable rms accuracy that ranges from 50 μas at apparent magnitude V=9 to 500 μas at V=15 according to the specifications for the Full-Sky Astrometric Mapping Explorer (FAME) satellite to be launched in 2004. The effects of imposing magnitude limits and limits on the ``observer's'' error, δπ/π, are displayed. We contrast the method of calculating mean absolute magnitude directly from the parallaxes where bias corrections are mandatory, with an inverse method using maximum likelihood that is free of the Lutz-Kelker bias, although a Malmquist bias is present. Simulations show the power of the inverse method. Nevertheless, we

  20. Continued Astrometric Follow-up Of Near-Earth Objects

    NASA Technical Reports Server (NTRS)

    Spahr, Timothy; Johnson, Lindley (Technical Monitor)

    2005-01-01

    As the grant periods overlapped, some of this information below will also be present on the previous final report. During the period May 1 2004 to April 30 2005, approximately 100 NEOs fainter than V = 20 were observed on separate nights from the 1.2-m telescope at Mt. Hopkins. Additionally, a few comets were targeted, including astrometric support of the Deep Impact mission by observing comet P/Tempel 1. Kyle Smalley was again employed as an independent contractor, and he was trained in use of the telescope, performed several remote observing runs on his own, and has now begun critical software support of the observing program. Code to automatically operate the telescope, given a target list, is approximately 90% done. During the first observing run scheduled in late September or early October, this code will be tested at on the telescope. It is probable that the 1.2m telescope will be run automatically all night without any interruption from the observer for anything during this time. Additional work on selecting which NEO targets to observe is progressing, with a beta-release of a simple target selection web page. Additionally, two-night objects with the potential of being NEOs have been extracted on a routine basis during this last grant cycle. These will also be added to a web page to facilitate additional astrometric follow-up.

  1. Global Astrometric Solutions with Sparse Matrix Techniques

    DTIC Science & Technology

    2000-03-01

    Global Astrometric Solutions with Sparse Matrix Techniques Richard L. Branham, Jr. Instituto Argentino de Nivologia y Glaciologia (IANIGLA), C.C...Physikalishen Teorien der hoheren Geodasie, 1 Teil, Leipzig: Teubner. Knuth, D., 1973, The Art of Computer Programming, Vol. 3, Sorting and Search- ing

  2. Developing Astrometric Drift Scans for the Spitzer Space Telescope

    NASA Astrophysics Data System (ADS)

    Carey, Sean J.; Ingalls, J.; Stauffer, J. R.; Grillmair, C. J.

    2014-01-01

    We are currently developing and optimizing a new observing mode using the IRAC instrument on-board the Spitzer Space Telescope. The new method which uses a constant rate drift scan while the instrument collects data is based on the successful HST drift scan method for producing high astrometric precision (20 micro-arcsecond) parallaxes to improve the cosmological distance scale. The HST experience indicates that a factor of 10 improvement in astrometric precision is possible. Currently Spitzer astrometric precision is of order 20-40 milli-arcseconds per epoch. Increasing the precision by even a factor of three greatly facilitates studies of nearby brown dwarfs and increases our ability to measure parallaxes to these intrinsically faint and cool sources out to ~30 parsecs. Initial tests of the method with observations of NGC 2516 at 3.6 and 4.5 microns have shown that useful data are taken in drift scan mode and the scans are in the specified direction and rate. We have developed a tool to measure source centroids in the stacks of images taken while scanning. The tool groups the centroids into tracklets which can then be simultaneously fit to remove telescope jitter and instrumental distortion. We present our latest results in the analysis of this mode and the prospects for the scientific exploitation of this method. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.

  3. The second version of the OCARS catalog of optical characteristics of astrometric radio sources

    NASA Astrophysics Data System (ADS)

    Malkin, Z. M.

    2016-11-01

    A new version of the Optical Characteristics of Astrometric Radio Sources (OCARS) catalog is presented. The catalog includes a list of radio sources observed in astrometric and geodetic VLBI programs since 1979, their redshifts, photometric data in 13 bands in the visible and near infrared, and a table indicating identifications btween the OCARS objects and objects in other catalogs. The main sources of information for the OCARS catalog are the NED and SIMBAD databases, as well as a variety of publications. Targeted observing programs designed to supplement the optical data for the astrometric radio sources have also been organized. The catalog currently contains 9956 sources, of which 5449 have redshifts and 7473 have photometric data. The catalog is updated, on average, once every several weeks, and is continuously augmented with new sources and new optical data.

  4. Microlensing Events in Gaia and other Astrometric Surveys

    NASA Astrophysics Data System (ADS)

    Baker, Claire; Di Stefano, Rosanne; Lepine, Sebastien

    2017-01-01

    The region within a kiloparsec of the Sun is a vast and mysterious place filled with uncharted planets, stars and compact objects, whose masses and properties are unknown. The Gaia space mission provides a unique opportunity to study of this region by measuring parallax distances and proper motions to millions of nearby stars, significantly advancing data available from previous astrometric surveys.We are putting this new astrometric information from the first Gaia data release to a novel use, by searching for matches between the positions of known microlensing events and the positions of stars observed by both the Gaia and the Tycho-2 missions, as listed in the Tycho-Gaia Astrometric Solution (TGAS) Catalogue.The existence of a gravitational microlensing event near a TGAS-listed star may provide information about the nature of either the source star lensed in the event, or the lens itself. For example, the source star lensed in the ‘TAGO’ event lies nearby, and is listed in the TGAS Catalogue. Other events may also have been caused by nearby TGAS-listed stars, or by their dim companions. In such cases, we can determine the lens mass and acquire information about any compact objects or planets which may exist around the lens.We report on the process of matching the positions of over 20,000 candidate microlensing events discovered by either OGLE and/or MOA, with the positions of 2 million stars from the TGAS Catalogue and stars from a range of other surveys, including Lepine's SUPERBLINK survey, and discuss the implications of the matches obtained.

  5. A Method for Rejection of Astrometric Outliers based on the Peirce Criterion

    NASA Astrophysics Data System (ADS)

    Micheli, Marco; Tholen, D. J.; Elliott, G. T.

    2012-10-01

    In the last decade the growing number of telescopes dedicated to NEO surveys, together with a rapid increase of the number of amateur-level observatories, resulted in a dramatic increase in the number of astrometric observations reported to the Minor Planet Center. The most accurate stations are now capable of obtaining astrometry of asteroids with random errors around 0.1”. On the other hand, the increase in the number of available data points is sometimes associated with an increasing occurrence of outliers, biases and erroneous observations, which may affect the correctness of scientific results obtained from those data, especially in cases of high-precision computations (impact monitoring, detection of non-gravitational effects, mission planning, ...). For well-calibrated professional settings, the dominant source of error is usually the astrometric catalog bias; debiasing methods have been developed (Chesley et al. 2010) based on the specific catalog used in the astrometric reduction. However, for astrometric positions coming from less-controlled sources, larger sources of error are often present (timing errors, improper handling of trailed sources, incorrect astrometric solutions, even misidentification of the target in some cases), and a complete but rigorous rejection of certain datapoints may become necessary. We recently developed a rejection method (Micheli et al. 2012) based on the little known Peirce criterion (Peirce 1852), that allows a mathematically founded approach to the rejection of observational data, specifically tailored for Rayleigh-distributed quantities (such as the optical astrometric residuals). We will present the basis of the method, together with its advantages over more common rejection algorithms, such as the ones based on the better known Chauvenet criterion. We will also present updated results on our application of this method to small-sized NEOs, that allows us to detect subtle non-gravitaional effects (such as radiation

  6. The astrometric lessons of Gaia-GBOT experiment

    NASA Astrophysics Data System (ADS)

    Bouquillon, S.; Mendez, R. A.; Altmann, M.

    2017-07-01

    To ensure the full capabilities of the Gaia's measurements, a programme of daily observations with Earth-based telescopes of the satellite itself - called Ground Based Optical Tracking (GBOT) - was implemented since the beginning of the Gaia mission (for more details concerning GBOT operating see Altmann et al. 2014 and concerning GBOT software facilities see Bouquillon et al. 2014). These observations are carried out mainly with two facilities: the 2.6m VLT Survey Telescope (ESO's VST) at the Cerro Paranal in Chile and the 2.0m Liverpool Telescope (LT) on the Canary Island of La Palma. The constraint of 20 mas on the tracking astrometric quality and the fact that Gaia is a faint and relatively fast moving target (its magnitude in a red passband is around 21 and its apparent speed around 0.04"/s), lead us to rigorously analyse the reachable astrometric precision for CCD observations of this kind of celestial objects. During LARIM 2016, we presented the main results of this study which uses the Cramér-Rao lower bound to characterize the precision limit for the PSF center when drifting in the CCD-frame. This work extends earlier studies dealing with one-dimensional detectors and stationary sources (Mendez et al. 2013 & 2014) firstly to the case of standard two-dimensional CCD sensors, and then, to moving sources. These new results have been submitted for a publication in A&A journal this year (Bouquillon et al. 2017).

  7. 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).

  8. 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

  9. First detection of the astrometric orbit of the single-lined spectroscopic binary epsilon Librae

    NASA Technical Reports Server (NTRS)

    Castelaz, Michael W.

    1989-01-01

    The Multichannel Astrometric Photometer of the University of Pittsburgh's Allegheny Observatory was used to successfully measure for the first time the astrometric orbit of the single-lined spectroscopic binary epsilon Lib. Solution of the orbit indicates that the secondary component is a 0.5-solar-mass star, assuming that the F5 IV primary is 1.3 solar mass. If the secondary is on the main sequence, then it is later than a K5 star, but earlier than an M2 star. In addition to detection of the astrometric orbit of epsilon Lib, two references stars used in the observations, AO 754 and AO 755, are found to be a common-proper-motion pair.

  10. First detection of the astrometric orbit of the single-lined spectroscopic binary epsilon Librae

    NASA Technical Reports Server (NTRS)

    Castelaz, Michael W.

    1989-01-01

    The Multichannel Astrometric Photometer of the University of Pittsburgh's Allegheny Observatory was used to successfully measure for the first time the astrometric orbit of the single-lined spectroscopic binary epsilon Lib. Solution of the orbit indicates that the secondary component is a 0.5-solar-mass star, assuming that the F5 IV primary is 1.3 solar mass. If the secondary is on the main sequence, then it is later than a K5 star, but earlier than an M2 star. In addition to detection of the astrometric orbit of epsilon Lib, two references stars used in the observations, AO 754 and AO 755, are found to be a common-proper-motion pair.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  12. 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.

  13. 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.

  14. An early TYCHO astrometric catalogue.

    NASA Astrophysics Data System (ADS)

    Høg, E.; Bässgen, G.; Bastian, U.; Egret, D.; Halbwachs, J. L.

    The TICR catalogue is a revision of the TYCHO Input Catalogue, TIC, containing positions derived from the first 12 months of TYCHO observations. Its properties, its role in TYCHO data analysis, and other possible uses are discussed.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  16. 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.

  17. 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.

  18. 546 precise astrometric positions of minor planets obtained at the GPO telescope of ESO - La Silla.

    NASA Astrophysics Data System (ADS)

    Debehogne, H.; Olević, D.; Protić-Benišek, V.

    1989-12-01

    Precise astrometric positions of minor planets: 383 Janina, 1111 Reinmuthia, 1586 Thiele, 1674 Groeneveld, 2682 Soromundi, 2911 1938 GJ, 3009 Coventry, 3032 Evans and 19 new ones, provisional designations 1986 QB1 - 1986 QC3 are presented. Photographic observations of minor planets were carried out in August and September 1986 with the Grand Prism Objective (GPO), 40/400 cm) at ESO.

  19. An early TYCHO astrometric catalogue

    NASA Astrophysics Data System (ADS)

    Hog, E.; Baessgen, G.; Bastian, U.; Egret, D.; Halbwachs, J. L.

    1991-03-01

    This paper describes the revised version of the Tycho Input Cagalog (TIC), TICR, which will contain positions derived from the first 12 months of the Tycho observations aboard the Hipparcos satellite, with special attention given to its proposed content, its use in the Tycho data analysis, and its other applications. The TICR will list about 500,000 stars with a positional precisions of 0.15 arcsec. Since TICR will contain ten times as many stars as does the IRS catalog and will have nearly the same accuracy, it will be a useful reference catalog for photographhic astrometry.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  1. Gamma Astrometric Measurement Experiment (GAME) - Science case

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Gai, Mario; Lattanzi, Mario G.; Crosta, Maria Teresa; Sozzetti, Alessandro

    GAME (Gamma Astrometric Measurement Experiment) is a concept for a small mission whose main goal is to measure from space the γ parameter of the Parameterized Post-Newtonian formalism. A satellite looking as close as possible to the Solar limb implements a technique similar to that used during the solar eclipse of 1919, when Dyson, Eddington and collaborators measured for the first time the gravitational bending of light. Preliminary simulations have shown that the expected final accuracy can reach the 10-7 level or better. This makes GAME a decisive experiment for the understanding of gravity physics, cosmology and the Universe evolution at a fundamental level. During the last decade, in fact, a strong experimental evidence of an acceleration of the expansion of the Universe at the present time has been provided by several observational data. This has been interpreted as the effect of a long range perturbation of the gravity field of the visible matter generated by the so-called Dark Energy. These data add to those available for long time at different scale length, which are explained with the existence of non-barionic Dark Matter (e.g. galaxy rotation curves) or with some kind of modification of the General Relativity theory (e.g. Pioneer anomalies). However, there are claims that these data can be explained with a modified version of General Relativity, in which the curvature invariant R is no longer constant in the Einstein equations (f (R) gravity theories). Present experimental data are not accurate enough to discriminate between these scenarios, but this could be done with a 10-7 -level measure of γ. Moreover, the limited fraction of time needed for the main experiment with respect to the overall mission duration opens interesting possibilities for other kinds of measurements. One is to measure the light deflection induced by the quadrupole moment of giant planets like Jupiter or Saturn, an effect predicted by General Relativity but never measured up to

  2. Resolved astrometric orbits of ten O-type binaries

    NASA Astrophysics Data System (ADS)

    Le Bouquin, J.-B.; Sana, H.; Gosset, E.; De Becker, M.; Duvert, G.; Absil, O.; Anthonioz, F.; Berger, J.-P.; Ertel, S.; Grellmann, R.; Guieu, S.; Kervella, P.; Rabus, M.; Willson, M.

    2017-05-01

    Aims: Our long-term aim is to derive model-independent stellar masses and distances for long period massive binaries by combining apparent astrometric orbit with double-lined radial velocity amplitudes (SB2). Methods: We followed-up ten O+O binaries with AMBER, PIONIER and GRAVITY at the VLTI. Here, we report on 130 astrometric observations over the last seven years. We combined this dataset with distance estimates to compute the total mass of the systems. We also computed preliminary individual component masses for the five systems with available SB2 radial velocities. Results: Nine of the ten binaries have their three-dimensional orbit well constrained. Four of them are known to be colliding wind, non-thermal radio emitters, and thus constitute valuable targets for future high angular resolution radio imaging. Two binaries break the correlation between period and eccentricity tentatively observed in previous studies. This suggests either that massive star formation produces a wide range of systems, or that several binary formation mechanisms are at play. Finally, we found that the use of existing SB2 radial velocity amplitudes can lead to unrealistic masses and distances. Conclusions: If not understood, the biases in radial velocity amplitudes will represent an intrinsic limitation for estimating dynamical masses from SB2+interferometry or SB2+Gaia. Nevertheless, our results can be combined with future Gaia astrometry to measure the dynamical masses and distances of the individual components with an accuracy of 5 to 15%, completely independently of the radial velocities. Based on observations collected with the PIONIER/VLTI, AMBER/VLTI and GRAVITY/VLTI instruments at the European Southern Observatory, Paranal, under programs 087.C-0458, 087.D-0150, 087.D-0264, 090.D-0036, 090.D-0291, 090.D-0600, 091.D-0087, 091.D-0334, 092.C-0243, 092.C-0542, 092.D-0015, 092.D-0366, 092.D-0590, 092.D-0647, 093.C-0503, 093.D-0039, 093.D-0040, 093.D-0673, 094.C-0397, 094.C-0884

  3. 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.

  4. 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.

  5. Astrophysical and Technical Aspects of Astrometric Methods on Hubble

    NASA Astrophysics Data System (ADS)

    Currie, D. G.

    2005-10-01

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

  6. 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.

  7. SIM Lite Astrometric Observatory progress report

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

    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 & 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.

  8. Astrometric techniques; Proceedings of the Symposium, Gainesville, FL, January 9-12, 1984

    NASA Astrophysics Data System (ADS)

    Eichhorn, H. K.; Leacock, R. J.

    The conference presents papers on the reduction technique, radio astrometry, photographic astrometry, interferometry, small field photoelectric astronomy, transit circles and astrolabes, space astronomy, objects, administration and distribution, and connections between the various techniques. Particular attention is given to the concepts of reference systems, the relativistic reduction of astrometric observations, computation of compilation catalogs, global reduction of fundamental astrometric data, the astrometric possibilities of very-long-base interferometry and the JPL/DSN J2000 radio reference frame. Papers are also presented on proper motions with respect to galaxies, plans for the second epoch of the southern proper motion program, trigonometric parallaxes obtained with the UK Schmidt telescope, astrometry with the Lowell PDS, speckle interferometry in astrometry, moving-image astrometry with the multianode microchannel array, timing and data acquisition for a field astrolabe, the use of photographic positions in determining the azimuth of a meridian circle, the Hipparcos satellite and the organization of the project, astrometric desiderata for nearby stars, astrometry in China, and the need for better cooperation and intercomparison in fundamental astrometry.

  9. A Search for Astrometric Companions to Southern Nearby Stars

    NASA Astrophysics Data System (ADS)

    Bartlett, J. L.; Ianna, P. A.; Begam, M. C.

    2002-05-01

    A sample of stars from the University of Virginia southern hemisphere parallax program has been tested for possible astrometric perturbations due to low-mass companions. The data were taken from CCD parallax observations with the one-meter reflector at the Siding Spring Observatory, Coonabarabran, Australia. Following our standard central overlap solution for parallax and proper motion, the residuals were subjected to a time-series analysis using the Lomb periodogram method (Press et al. 1992). The selected objects are late M-type stars with large parallaxes, mostly within 10 parsecs, not known to be binaries. They include LHS 288, LHS 337, LHS 532, LHS 1134, LHS 1565, LHS 2739, LHS 2813, and LHS 3064. We acknowledge support from NSF grant AST 98-20711 and from the Research School of Astronomy and Astrophysics, Australian National University.

  10. Improving the astrometric performance of VLTI-PRIMA

    NASA Astrophysics Data System (ADS)

    Woillez, J.; Abuter, R.; Andolfato, L.; Berger, J.-P.; Bonnet, H.; Delplancke, F.; Derie, F.; Di Lieto, N.; Guniat, S.; Mérand, A.; Duc, T. Phan; Schmid, C.; Schuhler, N.; Henning, T.; Launhardt, R.; Pepe, F.; Queloz, D.; Quirrenbach, A.; Reffert, S.; Sahlmann, J.; Segransan, D.

    2014-07-01

    In the summer of 2011, the first on-sky astrometric commissioning of PRIMA-Astrometry delivered a performance of 3 m″ for a 10 ″ separation on bright objects, orders of magnitude away from its exoplanet requirement of 50 μ″ ~ 20 μ″ on objects as faint as 11 mag ~ 13 mag in K band. This contribution focuses on upgrades and characterizations carried out since then. The astrometric metrology was extended from the Coudé focus of the Auxillary Telescopes to their secondary mirror, in order to reduce the baseline instabilities and improve the astrometric performance. While carrying out this extension, it was realized that the polarization retardance of the star separator derotator had a major impact on both the astrometric metrology and the fringe sensors. A local compensation of this retardance and the operation on a symmetric baseline allowed a new astrometric commissioning. In October 2013, an improved astrometric performance of 160 μ″ was demonstrated, still short of the requirements. Instabilities in the astrometric baseline still appear to be the dominating factor. In preparation to a review held in January 2014, a plan was developed to further improve the astrometric and faint target performance of PRIMA Astrometry. On the astrometric aspect, it involved the extension of the internal longitudinal metrology to primary space, the design and implementation of an external baseline metrology, and the development of an astrometric internal fringes mode. On the faint target aspect, investigations of the performance of the fringe sensor units and the development of an AO system (NAOMI) were in the plan. Following this review, ESO decided to take a proposal to the April 2014 STC that PRIMA be cancelled, and that ESO resources be concentrated on ensuring that Gravity and Matisse are a success. This proposal was recommended by the STC in May 2014, and endorsed by ESO.

  11. Modeling the Digital Output of the Multichannel Astrometric Photometer

    NASA Astrophysics Data System (ADS)

    de Jonge, Joost Kiewiet

    1995-05-01

    The periodic variation in the photon counts induced by the precision Ronchi ruling among the target and field stars imaged in the focal plane of the Thaw refractor has been and continues to be analyzed for phase differences in a purely numerical way. Efforts to develop a theoretical analytical output model for the MAP have so far been thwarted by the lack of an available, readily integrable mathematical function accurately representing the observed extended wing profiles of star images. However, it is shown that such a function exists in the form of a modified Bessel function. A complete theory of the instrument can therefore in principle be constructed. The derived time dependent output function has one given parameter (the ruling constant) and four adjustable parameters: FWHM image diameter (seeing diameter), semi-amplitude of the star's photon count, the cycle period and the time of zero phase. For each star first order approximations to these adjustable parameters (same for all cycles in a given run) are then improved by the method of differential corrections by solving the linearized equations of condition in a standard least square solution. The least square adjustments may extend over a few cycles or longer, yielding times of zero phase for each star and ultimately mean phase differences between all stars for a given run. Because the analytical model is capable of fitting the digital output of the MAP with great fidelity and is very flexible (it can accommodate a very wide variation in seeing and sky transparency) it is expected that its application to ongoing astrometric studies will bring about a further increase in the precision of astrometric observations at Allegheny Observatory.

  12. 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.

  13. 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.

  14. Verification of the Astrometric Performance of the Korean VLBI Network, Using Comparative SFPR Studies with the VLBA at 14/7 mm

    NASA Astrophysics Data System (ADS)

    Rioja, María J.; Dodson, Richard; Jung, TaeHyun; Sohn, Bong Won; Byun, Do-Young; Agudo, Iván; 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; Ryoung Kim, Hyo; Kim, Hyun-Goo; Lee, Chang-Hoon; Roh, Duk-Gyoo; Oh, Se-Jin; Yeom, Jae-Hwan; Song, Min-Gyu; Kang, Yong-Woo

    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.

  15. 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.

  16. 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.

  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. 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.

  20. Gaia astrometric instrument calibration and image processing

    NASA Astrophysics Data System (ADS)

    Castaneda, J.; Fabricius, C.; Portell, J.; Garralda, N.; González-Vidal, J. J.; Clotet, M.; Torra, J.

    2017-03-01

    The astrometric instrument calibration and image processing is an integral and critical part of the Gaia mission. The data processing starts with a preliminary treatment on daily basis of the most recent data received and continues with the execution of several processing chains included in a cyclic reduction system. The cyclic processing chains are reprocessing all the accumulated data again in each iteration, thus adding the latest measurements and recomputing the outputs to obtain better quality on their results. This cyclic processing lasts until the convergence of the results is achieved and the catalogue is consolidated and published periodically. In this paper we describe the core of the data processing which has made possible the first catalogue release from the Gaia mission.

  1. Astrometric studies in the region of Algol

    NASA Astrophysics Data System (ADS)

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

    1995-01-01

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

  2. Possible astrometric determination of tidal dissipation within Uranus from a future space mission

    NASA Astrophysics Data System (ADS)

    Lainey, Valery

    2014-11-01

    Tidal dissipation is the main actor of orbit migration among satellite systems. Recent work suggests possibly strong tidal dissipation within icy giant planets (Remus et al. 2013), with important consequences on satellite orbital evolution. Here we focus on the possible determination of tidal dissipation within Uranus using astrometric observations from ground and space. Besides regular observation campaigns from the Earth, simulations of observations from a future space probe around the Uranian system is considered. Constraints on the Uranian tidal ratio k2/Q as a function of astrometric accuracy and time span is assessed. This work is partly supported by EMERGENCE-UPMC grant (contract number: EME0911) and by the EC's 7th Framework Programme (FP7/2008-2017) under grant agreement n. 263466.

  3. Microlensing Constraints on the Mass of Single Stars from HST Astrometric Measurements

    NASA Astrophysics Data System (ADS)

    Kains, N.; Calamida, A.; Sahu, K. C.; Casertano, S.; Anderson, J.; Udalski, A.; Zoccali, M.; Bond, H.; Albrow, M.; Bond, I.; Brown, T.; Dominik, M.; Fryer, C.; Livio, M.; Mao, S.; Rejkuba, M.

    2017-07-01

    We report on the first results from a large-scale observing campaign aiming to use astrometric microlensing to detect and place limits on the mass of single objects, including stellar remnants. We used the Hubble Space Telescope to monitor stars near the Galactic Center for three years, and we measured the brightness and positions of ˜2 million stars at each observing epoch. In addition to this, we monitored the same pointings using the VIMOS imager on the Very Large Telescope. The stars we monitored include several bright microlensing events observed from the ground by the OGLE collaboration. In this paper, we present the analysis of our photometric and astrometric measurements for six of these events, and derive mass constraints for the lens in each of them. Although these constraints are limited by the photometric precision of ground-based data, and our ability to determine the lens distance, we were able to constrain the size of the Einstein ring radius thanks to our precise astrometric measurements—the first routine measurements of this type from a large-scale observing program. This demonstrates the power of astrometric microlensing as a tool to constrain the masses of stars, stellar remnants, and, in the future, extrasolar planets, using precise ground- and space-based observations. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained by the Space Telescope Science Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 091.D-0489(A) and 093.D-0522(A). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  4. Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties

    NASA Astrophysics Data System (ADS)

    Gaia Collaboration; Brown, A. G. A.; Vallenari, A.; Prusti, T.; de Bruijne, J. H. J.; Mignard, F.; Drimmel, R.; Babusiaux, C.; Bailer-Jones, C. A. L.; Bastian, U.; Biermann, M.; Evans, D. W.; Eyer, L.; Jansen, F.; Jordi, C.; Katz, D.; Klioner, S. A.; Lammers, U.; Lindegren, L.; Luri, X.; O'Mullane, W.; Panem, C.; Pourbaix, D.; Randich, S.; Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; Valette, V.; van Leeuwen, F.; Walton, N. A.; Aerts, C.; Arenou, F.; Cropper, M.; Høg, E.; Lattanzi, M. G.; Grebel, E. K.; Holland, A. D.; Huc, C.; Passot, X.; Perryman, M.; Bramante, L.; Cacciari, C.; Castañeda, J.; Chaoul, L.; Cheek, N.; De Angeli, F.; Fabricius, C.; Guerra, R.; Hernández, J.; Jean-Antoine-Piccolo, A.; Masana, E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Ordóñez-Blanco, D.; Panuzzo, P.; Portell, J.; Richards, P. J.; Riello, M.; Seabroke, G. M.; Tanga, P.; Thévenin, F.; Torra, J.; Els, S. G.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.; Lock, T.; Mercier, E.; Altmann, M.; Andrae, R.; Astraatmadja, T. L.; Bellas-Velidis, I.; Benson, K.; Berthier, J.; Blomme, R.; Busso, G.; Carry, B.; Cellino, A.; Clementini, G.; Cowell, S.; Creevey, O.; Cuypers, J.; Davidson, M.; De Ridder, J.; de Torres, A.; Delchambre, L.; Dell'Oro, A.; Ducourant, C.; Frémat, Y.; García-Torres, M.; Gosset, E.; Halbwachs, J.-L.; Hambly, N. C.; Harrison, D. L.; Hauser, M.; Hestroffer, D.; Hodgkin, S. T.; Huckle, H. E.; Hutton, A.; Jasniewicz, G.; Jordan, S.; Kontizas, M.; Korn, A. J.; Lanzafame, A. C.; Manteiga, M.; Moitinho, A.; Muinonen, K.; Osinde, J.; Pancino, E.; Pauwels, T.; Petit, J.-M.; Recio-Blanco, A.; Robin, A. C.; Sarro, L. M.; Siopis, C.; Smith, M.; Smith, K. W.; Sozzetti, A.; Thuillot, W.; van Reeven, W.; Viala, Y.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aguado, J. J.; Allan, P. M.; Allasia, W.; Altavilla, G.; Álvarez, M. A.; Alves, J.; Anderson, R. I.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.; Antoja, T.; Antón, S.; Arcay, B.; Bach, N.; Baker, S. G.; Balaguer-Núñez, L.; Barache, C.; Barata, C.; Barbier, A.; Barblan, F.; Barrado y Navascués, D.; Barros, M.; Barstow, M. A.; Becciani, U.; Bellazzini, M.; Bello García, A.; Belokurov, V.; Bendjoya, P.; Berihuete, A.; Bianchi, L.; Bienaymé, O.; Billebaud, F.; Blagorodnova, N.; Blanco-Cuaresma, S.; Boch, T.; Bombrun, A.; Borrachero, R.; Bouquillon, S.; Bourda, G.; Bouy, H.; Bragaglia, A.; Breddels, M. A.; Brouillet, N.; Brüsemeister, T.; Bucciarelli, B.; Burgess, P.; Burgon, R.; Burlacu, A.; Busonero, D.; Buzzi, R.; Caffau, E.; Cambras, J.; Campbell, H.; Cancelliere, R.; Cantat-Gaudin, T.; Carlucci, T.; Carrasco, J. M.; Castellani, M.; Charlot, P.; Charnas, J.; Chiavassa, A.; Clotet, M.; Cocozza, G.; Collins, R. S.; Costigan, G.; Crifo, F.; Cross, N. J. G.; Crosta, M.; Crowley, C.; Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; De Cat, P.; de Felice, F.; de Laverny, P.; De Luise, F.; De March, R.; de Martino, D.; de Souza, R.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.; Delgado, H. E.; Di Matteo, P.; Diakite, S.; Distefano, E.; Dolding, C.; Dos Anjos, S.; Drazinos, P.; Duran, J.; Dzigan, Y.; Edvardsson, B.; Enke, H.; Evans, N. W.; Eynard Bontemps, G.; Fabre, C.; Fabrizio, M.; Faigler, S.; Falcão, A. J.; Farràs Casas, M.; Federici, L.; Fedorets, G.; Fernández-Hernández, J.; Fernique, P.; Fienga, A.; Figueras, F.; Filippi, F.; Findeisen, K.; Fonti, A.; Fouesneau, M.; Fraile, E.; Fraser, M.; Fuchs, J.; Gai, M.; Galleti, S.; Galluccio, L.; Garabato, D.; García-Sedano, F.; Garofalo, A.; Garralda, N.; Gavras, P.; Gerssen, J.; Geyer, R.; Gilmore, G.; Girona, S.; Giuffrida, G.; Gomes, M.; González-Marcos, A.; González-Núñez, J.; González-Vidal, J. J.; Granvik, M.; Guerrier, A.; Guillout, P.; Guiraud, J.; Gúrpide, A.; Gutiérrez-Sánchez, R.; Guy, L. P.; Haigron, R.; Hatzidimitriou, D.; Haywood, M.; Heiter, U.; Helmi, A.; Hobbs, D.; Hofmann, W.; Holl, B.; Holland, G.; Hunt, J. A. S.; Hypki, A.; Icardi, V.; Irwin, M.; Jevardat de Fombelle, G.; Jofré, P.; Jonker, P. G.; Jorissen, A.; Julbe, F.; Karampelas, A.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, E.; Koposov, S. E.; Kordopatis, G.; Koubsky, P.; Krone-Martins, A.; Kudryashova, M.; Kull, I.; Bachchan, R. K.; Lacoste-Seris, F.; Lanza, A. F.; Lavigne, J.-B.; Le Poncin-Lafitte, C.; Lebreton, Y.; Lebzelter, T.; Leccia, S.; Leclerc, N.; Lecoeur-Taibi, I.; Lemaitre, V.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.; Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; Löffler, W.; López, M.; Lorenz, D.; MacDonald, I.; Magalhães Fernandes, T.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant, J. M.; Marconi, M.; Marinoni, S.; Marrese, P. M.; Marschalkó, G.; Marshall, D. J.; Martín-Fleitas, J. M.; Martino, M.; Mary, N.; Matijevič, G.; Mazeh, T.; McMillan, P. J.; Messina, S.; Michalik, D.; Millar, N. R.; Miranda, B. M. H.; Molina, D.; Molinaro, R.; Molinaro, M.; Molnár, L.; Moniez, M.; Montegriffo, P.; Mor, R.; Mora, A.; Morbidelli, R.; Morel, T.; Morgenthaler, S.; Morris, D.; Mulone, A. F.; Muraveva, T.; Musella, I.; Narbonne, J.; Nelemans, G.; Nicastro, L.; Noval, L.; Ordénovic, C.; Ordieres-Meré, J.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler, F.; Palacin, H.; Palaversa, L.; Parsons, P.; Pecoraro, M.; Pedrosa, R.; Pentikäinen, H.; Pichon, B.; Piersimoni, A. M.; Pineau, F.-X.; Plachy, E.; Plum, G.; Poujoulet, E.; Prša, A.; Pulone, L.; Ragaini, S.; Rago, S.; Rambaux, N.; Ramos-Lerate, M.; Ranalli, P.; Rauw, G.; Read, A.; Regibo, S.; Reylé, C.; Ribeiro, R. A.; Rimoldini, L.; Ripepi, V.; Riva, A.; Rixon, G.; Roelens, M.; Romero-Gómez, M.; Rowell, N.; Royer, F.; Ruiz-Dern, L.; Sadowski, G.; Sagristà Sellés, T.; Sahlmann, J.; Salgado, J.; Salguero, E.; Sarasso, M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol, M.; Segovia, J. C.; Segransan, D.; Shih, I.-C.; Smareglia, R.; Smart, R. L.; Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.; Steidelmüller, H.; Stephenson, C. A.; Stoev, H.; Suess, F. F.; Süveges, M.; Surdej, J.; Szabados, L.; Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira, R.; Terrett, D.; Tingley, B.; Trager, S. C.; Turon, C.; Ulla, A.; Utrilla, E.; Valentini, G.; van Elteren, A.; Van Hemelryck, E.; van Leeuwen, M.; Varadi, M.; Vecchiato, A.; Veljanoski, J.; Via, T.; Vicente, D.; Vogt, S.; Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Weingrill, K.; Wevers, T.; Wyrzykowski, Ł.; Yoldas, A.; Žerjal, M.; Zucker, S.; Zurbach, C.; Zwitter, T.; Alecu, A.; Allen, M.; Allende Prieto, C.; Amorim, A.; Anglada-Escudé, G.; Arsenijevic, V.; Azaz, S.; Balm, P.; Beck, M.; Bernstein, H.-H.; Bigot, L.; Bijaoui, A.; Blasco, C.; Bonfigli, M.; Bono, G.; Boudreault, S.; Bressan, A.; Brown, S.; Brunet, P.-M.; Bunclark, P.; Buonanno, R.; Butkevich, A. G.; Carret, C.; Carrion, C.; Chemin, L.; Chéreau, F.; Corcione, L.; Darmigny, E.; de Boer, K. S.; de Teodoro, P.; de Zeeuw, P. T.; Delle Luche, C.; Domingues, C. D.; Dubath, P.; Fodor, F.; Frézouls, B.; Fries, A.; Fustes, D.; Fyfe, D.; Gallardo, E.; Gallegos, J.; Gardiol, D.; Gebran, M.; Gomboc, A.; Gómez, A.; Grux, E.; Gueguen, A.; Heyrovsky, A.; Hoar, J.; Iannicola, G.; Isasi Parache, Y.; Janotto, A.-M.; Joliet, E.; Jonckheere, A.; Keil, R.; Kim, D.-W.; Klagyivik, P.; Klar, J.; Knude, J.; Kochukhov, O.; Kolka, I.; Kos, J.; Kutka, A.; Lainey, V.; LeBouquin, D.; Liu, C.; Loreggia, D.; Makarov, V. V.; Marseille, M. G.; Martayan, C.; Martinez-Rubi, O.; Massart, B.; Meynadier, F.; Mignot, S.; Munari, U.; Nguyen, A.-T.; Nordlander, T.; Ocvirk, P.; O'Flaherty, K. S.; Olias Sanz, A.; Ortiz, P.; Osorio, J.; Oszkiewicz, D.; Ouzounis, A.; Palmer, M.; Park, P.; Pasquato, E.; Peltzer, C.; Peralta, J.; Péturaud, F.; Pieniluoma, T.; Pigozzi, E.; Poels, J.; Prat, G.; Prod'homme, T.; Raison, F.; Rebordao, J. M.; Risquez, D.; Rocca-Volmerange, B.; Rosen, S.; Ruiz-Fuertes, M. I.; Russo, F.; Sembay, S.; Serraller Vizcaino, I.; Short, A.; Siebert, A.; Silva, H.; Sinachopoulos, D.; Slezak, E.; Soffel, M.; Sosnowska, D.; Straižys, V.; ter Linden, M.; Terrell, D.; Theil, S.; Tiede, C.; Troisi, L.; Tsalmantza, P.; Tur, D.; Vaccari, M.; Vachier, F.; Valles, P.; Van Hamme, W.; Veltz, L.; Virtanen, J.; Wallut, J.-M.; Wichmann, R.; Wilkinson, M. I.; Ziaeepour, H.; Zschocke, S.

    2016-11-01

    Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims: A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Methods: The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results: Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues - a realisation of the Tycho-Gaia Astrometric Solution (TGAS) - and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of 3000 Cepheid and RR Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr-1 for the proper motions. A systematic component of 0.3 mas should be added to the parallax uncertainties. For the subset of 94 000 Hipparcos stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr-1. For the secondary astrometric data set, the typical uncertainty of the positions is 10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to 0.03 mag over the magnitude range 5 to 20.7. Conclusions: Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five

  5. 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.

  6. Using HST to Detect Isolated Black Holes and Neutron Stars through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash C.; Albrow, M.; Anderson, J.; Bond, H. E.; Bond, I.; Brown, T. M.; Casertano, S.; Dominik, M.; Ferguson, H. C.; Fryer, C.; Livio, M.; Mao, S.; Perrott, Y.; Udalski, A.; Yock, P.

    2012-05-01

    To date, Black Hole (BH) and Neutron Star (NS) masses have been directly measured only in binaries; no isolated stellar-mass BH has been detected unambiguously within our Galaxy. We have underway a large, 3-year HST program (192 orbits) designed to detect microlensing events caused by non-luminous isolated BHs and NSs in the direction of the Galactic bulge. Our program consists of monitoring of 12 fields in the Sagittarius window of the Galactic bulge, containing a total of 1.5 million stars down to V=28. Our observations have a typical cadence of one observation every two weeks, and are primarily targeted towards detecting microlensing events caused by non-luminous isolated BHs and NSs in the Galactic disk and bulge. The unique capability of HST imaging for microlensing observations is the addition of high-precision astrometry, allowing detection of the astrometric shift of the source during the event. Combined with the lens parallax, which can be determined from the light curve as measured by HST (and supplemented by GEMINI) observations, the astrometric shift provides a direct measurement of the lens mass. Our program is optimized to detect long-duration events, which are more likely to be caused by massive lenses. We expect to detect a few dozen long-duration microlensing events, of which 45% will show astrometric deflections, leading to direct determinations of the lens masses.

  7. Impact of basic angle variations on the parallax zero point for a scanning astrometric satellite

    NASA Astrophysics Data System (ADS)

    Butkevich, Alexey G.; Klioner, Sergei A.; Lindegren, Lennart; Hobbs, David; van Leeuwen, Floor

    2017-07-01

    Context. Determination of absolute parallaxes by means of a scanning astrometric satellite such as Hipparcos or Gaia relies on the short-term stability of the so-called basic angle between the two viewing directions. Uncalibrated variations of the basic angle may produce systematic errors in the computed parallaxes. Aims: We examine the coupling between a global parallax shift and specific variations of the basic angle, namely those related to the satellite attitude with respect to the Sun. Methods: The changes in observables produced by small perturbations of the basic angle, attitude, and parallaxes were calculated analytically. We then looked for a combination of perturbations that had no net effect on the observables. Results: In the approximation of infinitely small fields of view, it is shown that certain perturbations of the basic angle are observationally indistinguishable from a global shift of the parallaxes. If these kinds of perturbations exist, they cannot be calibrated from the astrometric observations but will produce a global parallax bias. Numerical simulations of the astrometric solution, using both direct and iterative methods, confirm this theoretical result. For a given amplitude of the basic angle perturbation, the parallax bias is smaller for a larger basic angle and a larger solar aspect angle. In both these respects Gaia has a more favourable geometry than Hipparcos. In the case of Gaia, internal metrology is used to monitor basic angle variations. Additionally, Gaia has the advantage of detecting numerous quasars, which can be used to verify the parallax zero point.

  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. Astrometric Detection of Binary Companions and Planets: Acceleration of Proper Motion

    DTIC Science & Technology

    2003-07-14

    the ESO Symp. From Extrasolar Planets to Cosmology: The VLT Opening Symposium, Springer-Verlag, Berlin, p. 492 Appendix A: Simplified development of...Astron. Nachr./AN 324, No. 5, 419–424 (2003) / DOI 10.1002/asna.200310159 Astrometric detection of binary companions and planets : Acceleration of...period is at least several times the span of observations. We estimate orbit dimensions and distances at which low-mass companions and planets may be

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

    NASA Astrophysics Data System (ADS)

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

    2003-02-01

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

  11. Astrometric Telescope Facility isolation and pointing study

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  12. A measurement of the systematic astrometric error in GeMS and the short-term astrometric precision in ShaneAO

    NASA Astrophysics Data System (ADS)

    Ammons, S. M.; Neichel, Benoit; Lu, Jessica; Gavel, Donald T.; Srinath, Srikar; McGurk, Rosalie; Rudy, Alex; Rockosi, Connie; Marois, Christian; Macintosh, Bruce; Savransky, Dmitry; Galicher, Raphael; Bendek, Eduardo; Guyon, Olivier; Marin, Eduardo; Garrel, Vincent; Sivo, Gaetano

    2014-08-01

    We measure the long-term systematic component of the astrometric error in the GeMS MCAO system as a function of field radius and Ks magnitude. The experiment uses two epochs of observations of NGC 1851 separated by one month. The systematic component is estimated for each of three field of view cases (15'' radius, 30'' radius, and full field) and each of three distortion correction schemes: 8 DOF/chip + local distortion correction (LDC), 8 DOF/chip with no LDC, and 4 DOF/chip with no LDC. For bright, unsaturated stars with 13 < Ks < 16, the systematic component is < 0.2, 0.3, and 0.4 mas, respectively, for the 15'' radius, 30'' radius, and full field cases, provided that an 8 DOF/chip distortion correction with LDC (for the full-field case) is used to correct distortions. An 8 DOF/chip distortion-correction model always outperforms a 4 DOF/chip model, at all field positions and magnitudes and for all field-of-view cases, indicating the presence of high-order distortion changes. Given the order of the models needed to correct these distortions (~8 DOF/chip or 32 degrees of freedom total), it is expected that at least 25 stars per square arcminute would be needed to keep systematic errors at less than 0.3 milliarcseconds for multi-year programs. We also estimate the short-term astrometric precision of the newly upgraded Shane AO system with undithered M92 observations. Using a 6-parameter linear transformation to register images, the system delivers ~0.3 mas astrometric error over short-term observations of 2-3 minutes.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  15. 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

  16. 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.

  17. The Carlsberg Meridian Telescope: an astrometric robotic telescope

    NASA Astrophysics Data System (ADS)

    Evans, D. W.

    2001-12-01

    An overview is given of the Carlsberg Meridian Telescope on La Palma, which is one of the oldest robotic telescopes, having started observing on La Palma in 1984. In the spring of 1997, a further stage of automation was made when we converted the telescope to remote operation. Since then, the telescope has been operated over the Internet from Britain, Denmark or Spain. In 1997, a CCD camera, operating in a drift-scan mode, was installed. A year later the telescope underwent a major upgrade and a larger 2k×2k CCD camera was installed, with a Sloan r' filter. With the new system, the magnitude limit is r'=17 and the positional accuracy is in the range 0.03'' to 0.05''. The main task of the project is to map the sky in the declination range -3o to +50o, with the aim of providing an astrometric and photometric catalogue that can accurately transfer the Hipparcos/Tycho reference frame to Schmidt plates. We will release the first data by the end of 2001. Using the photometric information, extinction data for La Palma is also provided.

  18. The Carlsberg Meridian Telescope: An Astrometric Robotic Telescope

    NASA Astrophysics Data System (ADS)

    Evans, Dafydd Wyn

    An overview is given of the Carlsberg Meridian Telescope on La Palma, which is one of the oldest robotic telescopes, having started observing in 1984. In the spring of 1997, a further stage of automation was made when we converted the telescope to remote operation. Since then, the telescope has been operated over the Internet from Britain, Denmark or Spain. Two years ago, the telescope underwent a major upgrade and a 2k×2k CCD camera was installed, with a Sloan r' filter, operating in a drift scan mode. With the new system, the magnitude limit is r'=17 and the positional accuracy is in the range 0.03'' to 0.05''. The main task of the project is to map the sky in the declination range -3o to +50o, with the aim of providing an astrometric and photometric catalogue that can accurately transfer the Hipparcos/Tycho reference frame to Schmidt plates. We will release the first data by the end of the year.

  19. 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.

  20. 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.

  1. 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 $\\approx$ 20 mas across multi-year 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 $\\lesssim 7$ 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.

  2. Analogue Simulation and Orbital Solving Algorithm of Astrometric Exoplanet Detection

    NASA Astrophysics Data System (ADS)

    Huang, P. H.; Ji, J. H.

    2016-09-01

    Astrometry is an effective method to detect exoplanets. It has many advantages that other detection methods do not bear, such as providing three dimensional planetary orbit and determining the planetary mass. Astrometry will enrich the sample of exoplanets. As the high-precision astrometric satellite Gaia (Global Astrometry interferometer for Astrophysics) was launched in 2013, there will be abundant long-period Jupiter-size planets to be discovered by Gaia. In this paper, we specify the α Centauri A, HD 62509, and GJ 876 systems, and generate the synthetic astrometric data with the single astrometric precision of Gaia. Then we use the Lomb-Scargle periodogram to analyse the signature of planets and the Markov Chain Monte Carlo (MCMC) algorithm to fit the orbit of planets. The simulation results are well coincide with the initial solutions.

  3. Analogue Simulation and Orbit Solution Algorithm of Astrometric Exoplanet Detection

    NASA Astrophysics Data System (ADS)

    Huang, Ping-hui; Ji, Jiang-hui

    2017-07-01

    Astrometry is an effective measure to detect exoplanets. It has many advantages that other detection methods do not bear, such as providing three dimensional planetary orbit, and determining planetary mass, etc. Astrometry will enrich the sample of exoplanets. As the high-precision astrometric satellite Gaia (Global Astrometry Interferometer for Astrophysics) was launched in 2013, it is predictable that there will be abundant long-period Jupiter-size planets to be discovered by Gaia. In this paper, we specify the α Centauri A, HD 62509, and GJ 876 systems, and generate the synthetic astrometric data with the single-time astrometric precision of Gaia. Then we use the Lomb-Scargle periodogram to analyze the periodical signal of planetary orbit, and use the Markov Chain Monte Carlo (MCMC) algorithm to make the orbit inversion of the planetary system, the obtained result is well coincident with the initial parameters of the planet.

  4. Observation of static gestures influences speech production.

    PubMed

    Jarick, Michelle; Jones, Jeffery A

    2008-08-01

    Research investigating 'mirror neurons' has demonstrated the presence of an observation-execution matching system in humans. One hypothesized role for this system might be to aid in action understanding by encoding the underlying intentions of the actor. To investigate this hypothesis, we asked participants to observe photographs of an actor making orofacial gestures (implying verbal or non-verbal acts), and to produce syllables that were compatible or incompatible with the gesture they observed. We predicted that if mirror neurons encode the intentions of an actor, then the pictures implying verbal gestures would affect speech production, whereas the non-verbal gestures would not. Our results showed that the observation of compatible verbal gestures facilitated verbal responses, while incompatible verbal gestures caused interference. Although this compatibility effect did not reach statistical significance when the photographs implied a non-verbal act, responses were faster on average when the gesture implied the use of similar articulators as those involved with the production of the target syllable. Altogether, these behavioral findings compliment previous neuroimaging studies indicating that static pictures portraying gestures activate brain regions associated with an observation-execution matching system.

  5. Revisiting TW Hydrae in light of new astrometric data

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  6. Toward astrometric tracking with the infrared spatial interferometer

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  7. New constraints on Saturn's interior from Cassini astrometric data

    NASA Astrophysics Data System (ADS)

    Lainey, Valéry; Jacobson, Robert A.; Tajeddine, Radwan; Cooper, Nicholas J.; Murray, Carl; Robert, Vincent; Tobie, Gabriel; Guillot, Tristan; Mathis, Stéphane; Remus, Françoise; Desmars, Josselin; Arlot, Jean-Eudes; De Cuyper, Jean-Pierre; Dehant, Véronique; Pascu, Dan; Thuillot, William; Le Poncin-Lafitte, Christophe; Zahn, Jean-Paul

    2017-01-01

    Using astrometric observations spanning more than a century and including a large set of Cassini data, we determine Saturn's tidal parameters through their current effects on the orbits of the eight main and four coorbital Moons. We have used the latter to make the first determination of Saturn's Love number from observations, k2=0.390 ± 0.024, a value larger than the commonly used theoretical value of 0.341 (Gavrilov & Zharkov, 1977), but compatible with more recent models (Helled & Guillot, 2013) for which the static k2 ranges from 0.355 to 0.382. Depending on the assumed spin for Saturn's interior, the new constraint can lead to a significant reduction in the number of potential models, offering great opportunities to probe the planet's interior. In addition, significant tidal dissipation within Saturn is confirmed (Lainey et al., 2012) corresponding to a high present-day tidal ratio k2/Q=(1.59 ± 0.74) × 10-4 and implying fast orbital expansions of the Moons. This high dissipation, with no obvious variations for tidal frequencies corresponding to those of Enceladus and Dione, may be explained by viscous friction in a solid core, implying a core viscosity typically ranging between 1014 and 1016 Pa.s (Remus et al., 2012). However, a dissipation increase by one order of magnitude at Rhea's frequency could suggest the existence of an additional, frequency-dependent, dissipation process, possibly from turbulent friction acting on tidal waves in the fluid envelope of Saturn (Ogilvie & Lin, 2004; Fuller et al. 2016).

  8. 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.

  9. Astrometric Models of the Phobos Orbiter TV Cameras

    NASA Technical Reports Server (NTRS)

    Duxbury, T. C.

    1993-01-01

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

  10. 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. CCD Astrometric Measurements of WDS 05247+3723

    NASA Astrophysics Data System (ADS)

    Chasin, Mike; Adas, Matthew; Tanon, Naylynn; Boyce, Grady; Boyce, Pat

    2017-07-01

    Theta and rho astrometric measurements were made of the double star system WDS 05247+3723 pairs AB, AC, and CD. These measurements compared favorably with the historic data from the Washington Double Star Catalog (WDS). We also measured the AD, BC, & BD pair relative astrometry.

  12. UCAC and URAT: Optical Astrometric Catalog Observing Programs

    DTIC Science & Technology

    2010-09-21

    photometry (1 band) Zacharias & Gaume: UCAC and URAT; Journees, Paris2010 Sep 21 12 Norbert Zacharias StarScan plate measure machine Washington, DC Zacharias...10 mas per image (well exposed star) multiple sky overlaps / year, 7 - 18 mag clocked anti-blooming: extend dynamic range neutral density spots...Zacharias & Gaume: UCAC and URAT; Journees, Paris2010 Sep 21 33 2010, June 29: successful image backside, thinned 10k detector in lab at STA, 16

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

    SciTech Connect

    Rioja, M.; Dodson, R.

    2011-04-15

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

  14. 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.

  15. Photometric and Astrometric Vagaries of the Enigma Star KIC 8462852

    NASA Astrophysics Data System (ADS)

    Makarov, Valeri V.; Goldin, Alexey

    2016-12-01

    We apply a principal component analysis (PCA)-based pre-whitening method to the entire collection of main Kepler mission long-cadence data for KIC 8462852 spanning four years. This technique removes the correlated variations of instrumental origin in both the detected light curves and astrometry, resolving intrinsic changes in flux and image position of less than 100 ppm and 1 mas, respectively. Beside the major dips in the light curve during mission quarters 8 and 16, when the flux dropped by up to 20%, we confirm multiple smaller dips across the time span of observation with amplitudes ranging from 0.1% to 7%. A variation of flux with a period of 0.88 day and a half-amplitude of approximately 90 ppm is confirmed in the PCA-cleaned data. We find that the phase of the wave is steady over a 15 month interval. We confidently detect a weak variability-induced motion (VIM) effect in the cleaned astrometric trajectories, when the moment-based centroids shift synchronously with the flux dips by up to 0.0008 pixels on the detector. The inconsistent magnitude and direction of VIM effects within the same quarter point at more than one source of photometric variability in the blended image. The 0.88 day periodicity comes from a different source, not from the target star KIC 8462852. We discuss a possible interpretation of the bizarre properties of the source as a swarm of interstellar junk (comets and planetoids) crossing the line of sight to the star and its optical companions at approximately 7 mas yr-1.

  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. Detecting and Measuring the Masses of Isolated Black Holes and Neutron Stars through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2011-10-01

    We propose a 3-year program of monitoring of 12 fields in the Galactic bulge, containing a total of 1.5 million stars down to V=28. Our primary aim is to detect microlensing events caused by non-luminous isolated black holes {BHs} and neutron stars {NSs} in the Galactic disk and bulge.The unique capability of HST imaging for microlensing observations is the addition of high-precision astrometry, allowing detection of the astrometric shift of the source during the event. Combined with the lens parallax, provided by the HST event light curve, the astrometric shift provides a direct measurement of the lens mass. We will detect 120 microlensing events, of which 45% will show astrometric deflections, leading to direct determinations of the lens masses. Of these, about 18 lenses are expected to be BHs and 14 of them NSs, along with about 22 events due to main-sequence stars.To date, BH and NS masses have been directly measured only in binaries; no isolated BH has been detected unambiguously within our Galaxy. A survey of the scope proposed here is the only means available at present for measuring the mass function of isolated BHs and NSs, and moreover one that is normalized to that of luminous stars. The results will provide a quantitative estimate of the mass content in the form of stellar remnants in the young Galactic disk and old bulge, and important constraints on SN/GRB explosion mechanisms that produce NSs and BHs.Our data will also be useful for other investigations, including a more accurate determination of the microlensing optical depth, faint variable stars, bulge proper motions and kinematics, and a deep luminosity function of the disk and bulge stars.

  19. Detecting and Measuring the Masses of Isolated Black Holes and Neutron Stars through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2012-10-01

    We propose a 3-year program of monitoring of 12 fields in the Galactic bulge, containing a total of 1.5 million stars down to V=28. Our primary aim is to detect microlensing events caused by non-luminous isolated black holes {BHs} and neutron stars {NSs} in the Galactic disk and bulge.The unique capability of HST imaging for microlensing observations is the addition of high-precision astrometry, allowing detection of the astrometric shift of the source during the event. Combined with the lens parallax, provided by the HST event light curve, the astrometric shift provides a direct measurement of the lens mass. We will detect 120 microlensing events, of which 45% will show astrometric deflections, leading to direct determinations of the lens masses. Of these, about 18 lenses are expected to be BHs and 14 of them NSs, along with about 22 events due to main-sequence stars.To date, BH and NS masses have been directly measured only in binaries; no isolated BH has been detected unambiguously within our Galaxy. A survey of the scope proposed here is the only means available at present for measuring the mass function of isolated BHs and NSs, and moreover one that is normalized to that of luminous stars. The results will provide a quantitative estimate of the mass content in the form of stellar remnants in the young Galactic disk and old bulge, and important constraints on SN/GRB explosion mechanisms that produce NSs and BHs.Our data will also be useful for other investigations, including a more accurate determination of the microlensing optical depth, faint variable stars, bulge proper motions and kinematics, and a deep luminosity function of the disk and bulge stars.

  20. Detecting and Measuring the Masses of Isolated Black Holes and Neutron Stars through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2013-10-01

    We propose a 3-year program of monitoring of 12 fields in the Galactic bulge, containing a total of 1.5 million stars down to V=28. Our primary aim is to detect microlensing events caused by non-luminous isolated black holes {BHs} and neutron stars {NSs} in the Galactic disk and bulge.The unique capability of HST imaging for microlensing observations is the addition of high-precision astrometry, allowing detection of the astrometric shift of the source during the event. Combined with the lens parallax, provided by the HST event light curve, the astrometric shift provides a direct measurement of the lens mass. We will detect 120 microlensing events, of which 45% will show astrometric deflections, leading to direct determinations of the lens masses. Of these, about 18 lenses are expected to be BHs and 14 of them NSs, along with about 22 events due to main-sequence stars.To date, BH and NS masses have been directly measured only in binaries; no isolated BH has been detected unambiguously within our Galaxy. A survey of the scope proposed here is the only means available at present for measuring the mass function of isolated BHs and NSs, and moreover one that is normalized to that of luminous stars. The results will provide a quantitative estimate of the mass content in the form of stellar remnants in the young Galactic disk and old bulge, and important constraints on SN/GRB explosion mechanisms that produce NSs and BHs.Our data will also be useful for other investigations, including a more accurate determination of the microlensing optical depth, faint variable stars, bulge proper motions and kinematics, and a deep luminosity function of the disk and bulge stars.

  1. 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

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

    DOE PAGES

    Beamer, Benjamin; Nomerotski, Andrei; Tsybychev, Dmitri

    2015-05-22

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

  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. 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.

  5. 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.

  6. Precise astrometric positions of 36 minor planets obtained by GPO telescope of ESO -La Silla in 1988.

    NASA Astrophysics Data System (ADS)

    Debehogne, H.; Protitch-Benishek, V.; Olević, D.

    1995-04-01

    During September 1988 at La Silla 396 precise astrometric positions of 36 minor planets were obtained. The objects were observed with the Grand Prism Objective (GPO) of La Silla Observatory by H. Debehogne. 25 new minor planets were discovered during this campaign. The measurements were made with Ascorecord of the Observatoire Royal de Belgique. The reductions were performed using the dependence method by means of five reference stars.

  7. Precise astrometric positions of 16 minor planets obtained by GPO telescope of ESO - La Silla in 1988.

    NASA Astrophysics Data System (ADS)

    Debehogne, H.; Protitch-Benishek, V.

    1992-03-01

    During the mission in January 1988 at La Silla 252 precise astrometric positions of 16 minor planets were obtained. The objects were observed with the Grand Prism Objective (GPO) of La Silla Observatory by H. Debehogne. Ten new asteroids were discovered during this mission. The measurements were done with Ascorecord of the Observatoire Royal de Belgique. The reductions were performed using the dependance method by means of five reference stars.

  8. Astrometric telescope of ten microarcsecond accuracy on the Space Station

    NASA Technical Reports Server (NTRS)

    Levy, E. H.; Mcmillan, R. S.; Gatewood, G. D.; Stein, J. W.

    1986-01-01

    The Astrometric Telescope Facility (ATF) will be operated in the NASA Space Station in the 1990s, furnishing long term, highly accurate relative astrometry of nearby stars in order to detect gravitational perturbations by companion stars with masses as small as that of Neptune. An accuracy of 10 microarcsec is required; this is 100 times better than ground observatory performance. In the Gatewood et al. (1980) astrometric technique used, the relative positions of star images in the telescope focal plane are indicated by the relative phases of the modulations of star brightnesses introduced by translating a Ronchi ruling across the focal plane at uniform speed. Space Station vibration damping, fine guiding accuracy, optical configuration, Ronchi ruling metric accuracy, and the choice of detectors, are discussed.

  9. Astrometric Jitter of the Sun as a Star

    DTIC Science & Technology

    2010-05-01

    1NASA Exoplanet Science Institute, Caltech, Pasadena, CA 91125 2Department of Physics and Astronomy, University of California, Los Angeles, CA 90095...nearby dwarfs should be as amenable to exoplanet detection as the Sun. The aim of this paper is to determine the solar astrometric jitter directly...axis. Planets in eccentric orbits also produce higher-order harmonics (overtones) of smaller amplitudes. The spectroscopic method of exoplanet

  10. Astrometric Calibration and Performance of the Dark Energy Camera

    DOE PAGES

    Bernstein, G. M.; Armstrong, R.; Plazas, A. A.; ...

    2017-05-30

    We characterize the ability of the Dark Energy Camera (DECam) to perform relative astrometry across its 500 Mpix, 3more » $deg^2$ science field of view, and across 4 years of operation. This is done using internal comparisons of $~ 4 x 10^7$ measurements of high-S/N stellar images obtained in repeat visits to fields of moderate stellar density, with the telescope dithered to move the sources around the array. An empirical astrometric model includes terms for: optical distortions; stray electric fields in the CCD detectors; chromatic terms in the instrumental and atmospheric optics; shifts in CCD relative positions of up to $$\\approx 10 \\mu m$$ when the DECam temperature cycles; and low-order distortions to each exposure from changes in atmospheric refraction and telescope alignment. Errors in this astrometric model are dominated by stochastic variations with typical amplitudes of 10-30 mas (in a 30 s exposure) and $$5^{\\prime}-10^{\\prime}$$ arcmin coherence length, plausibly attributed to Kolmogorov-spectrum atmospheric turbulence. The size of these atmospheric distortions is not closely related to the seeing. Given an astrometric reference catalog at density $$\\approx 0.7$$ $$arcmin^{-2}$$, e.g. from Gaia, the typical atmospheric distortions can be interpolated to $$\\approx$$ 7 mas RMS accuracy (for 30 s exposures) with $$1^{\\prime}$$ arcmin coherence length for residual errors. Remaining detectable error contributors are 2-4 mas RMS from unmodelled stray electric fields in the devices, and another 2-4 mas RMS from focal plane shifts between camera thermal cycles. Thus the astrometric solution for a single DECam exposure is accurate to 3-6 mas ( $$\\approx$$ 0.02 pixels, or $$\\approx$$ 300 nm) on the focal plane, plus the stochastic atmospheric distortion.« less

  11. Astrometric Measurement of WDS 03117+8128 STF 327 AB

    NASA Astrophysics Data System (ADS)

    van den Bergh, Hilde; Olivas, Chris; Hilburn, Jerry; Pat, Boyce; Boyce, Grady

    2017-07-01

    We report CCD astrometric measurements of the double star system WDS 03117+8128 STF327AB using the iTelescope network. We found the relative position to be r = 20.26 ± 0.12 arc-sec and q = 289.1 ± 0.39 degrees at epoch 2016.84. When combined with the historical data over the last 114 years the trend suggests the decreasing of the distance between the AB pair.

  12. Astrometric Calibration and Performance of the Dark Energy Camera

    NASA Astrophysics Data System (ADS)

    Bernstein, G. M.; Armstrong, R.; Plazas, A. A.; Walker, A. R.; Abbott, T. M. C.; Allam, S.; Bechtol, K.; Benoit-Lévy, A.; Brooks, D.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Eifler, T. F.; Fernandez, E.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kent, S.; Krause, E.; Kuehn, K.; Kuropatkin, N.; Li, T. S.; Maia, M. A. G.; March, M.; Marshall, J. L.; Menanteau, F.; Miquel, R.; Ogando, R. L. C.; Reil, K.; Roodman, A.; Rykoff, E. S.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; DES Collaboration

    2017-07-01

    We characterize the ability of the Dark Energy Camera (DECam) to perform relative astrometry across its 500 Mpix, 3-deg2 science field of view and across four years of operation. This is done using internal comparisons of ˜4 × 107 measurements of high signal-to-noise ratio stellar images obtained in repeat visits to fields of moderate stellar density, with the telescope dithered to move the sources around the array. An empirical astrometric model includes terms for optical distortions; stray electric fields in the CCD detectors; chromatic terms in the instrumental and atmospheric optics; shifts in CCD relative positions of up to ≈10 μm when the DECam temperature cycles; and low-order distortions to each exposure from changes in atmospheric refraction and telescope alignment. Errors in this astrometric model are dominated by stochastic variations with typical amplitudes of 10-30 mas (in a 30 s exposure) and 5‧-10‧ coherence length, plausibly attributed to Kolmogorov-spectrum atmospheric turbulence. The size of these atmospheric distortions is not closely related to the seeing. Given an astrometric reference catalog at density ≈ 0.7 {{arcmin}}-2, e.g., from Gaia, the typical atmospheric distortions can be interpolated to ≈7 mas rms accuracy (for 30 s exposures) with 1\\prime coherence length in residual errors. Remaining detectable error contributors are 2-4 mas rms from unmodelled stray electric fields in the devices, and another 2-4 mas rms from focal plane shifts between camera thermal cycles. Thus the astrometric solution for a single DECam exposure is accurate to 3-6 mas (≈0.02 pixels, or ≈300 nm) on the focal plane, plus the stochastic atmospheric distortion.

  13. Space Station utilization for the Astrometric Telescope Facility

    NASA Technical Reports Server (NTRS)

    Nishioka, Kenji; Black, David C.; Gatewood, George D.; Levy, Eugene H.

    1989-01-01

    It is shown how it is possible for the Astrometric Telescope Facility (ATF) to utilize the Space Station Freedom as an attached payload by complying with changes in the Station concept and schedule. The ability of the station to accommodate ATF's firm requirements is also addressed. The main factors that led the ATF to utilize the Space Station Freedom are the Station's relative orbital stability and longevity, the availability of maintenance and repair services, and the provision of utilities.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. SPHERE IRDIS and IFS astrometric strategy and calibration

    NASA Astrophysics Data System (ADS)

    Maire, Anne-Lise; Langlois, Maud; Dohlen, Kjetil; Lagrange, Anne-Marie; Gratton, Raffaele; Chauvin, Gaël.; Desidera, Silvano; Girard, Julien H.; Milli, Julien; Vigan, Arthur; Zins, Gerard; Delorme, Philippe; Beuzit, Jean-Luc; Claudi, Riccardo U.; Feldt, Markus; Mouillet, David; Puget, Pascal; Turatto, Massimo; Wildi, François

    2016-08-01

    We present the current results of the astrometric characterization of the VLT planet finder SPHERE over 2 years of on-sky operations. We first describe the criteria for the selection of the astrometric fields used for calibrating the science data: binaries, multiple systems, and stellar clusters. The analysis includes measurements of the pixel scale and the position angle with respect to the North for both near-infrared subsystems, the camera IRDIS and the integral field spectrometer IFS, as well as the distortion for the IRDIS camera. The IRDIS distortion is shown to be dominated by an anamorphism of 0.60+/-0.02% between the horizontal and vertical directions of the detector, i.e. 6 mas at 1 arcsec. The anamorphism is produced by the cylindrical mirrors in the common path structure hence common to all three SPHERE science subsystems (IRDIS, IFS, and ZIMPOL), except for the relative orientation of their field of view. The current estimates of the pixel scale and North angle for IRDIS are 12.255+/-0.009 milliarcseconds/pixel for H2 coronagraphic images and -1.70+/-0.08°. Analyses of the IFS data indicate a pixel scale of 7.46+/-0.02 milliarcseconds/pixel and a North angle of -102.18+/-0.13°. We finally discuss plans for providing astrometric calibration to the SPHERE users outside the instrument consortium.

  20. 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.

  1. Astrometric Determination of VSOP-2 Orbital Parameters

    NASA Astrophysics Data System (ADS)

    Fomalont, E.; Moellenbrock, G.; Claussen, M.

    2009-08-01

    VSOP-2 phase referencing, needed to image faint sources and to determine accurate positions, will require an orbit accuracy of about 2 cm at 23 GHz. This accuracy, however, may not be obtainable by direct orbital measurements. We propose an observation scheme, similar to that used at the VLBA, to be included during a phase referencing observation of about one orbit in order to determine a more accurate orbit determination. We show the effects of orbit errors, explain the suggested observations and reduction methods, and discuss the potential problems that might impede the use of this technique.

  2. Astrometric Detection of Terrestrial Planets in the Habitable Zones of Nearby Stars with SIM PlanetQuest

    NASA Astrophysics Data System (ADS)

    Catanzarite, Joseph; Shao, Michael; Tanner, Angelle; Unwin, Stephen; Yu, Jeffrey

    2006-09-01

    SIM PlanetQuest (formerly the Space Interferometry Mission) is a space-borne Michelson interferometer for precision stellar astrometry, with a 9 m baseline, currently slated for launch in 2016. One of the principal science goals is the astrometric detection and orbital characterization of terrestrial planets in the habitable zones of nearby stars. Differential astrometry of the target star against a set of reference stars lying within 1° will allow measurement of the target star's reflex motion with astrometric accuracy of 1 μas in a single measurement. The purpose of the present paper is to quantitatively assess SIM's capability for detection (as opposed to characterization by orbital determination) of terrestrial planets in the habitable zones of nearby stars. Note that the orbital periods of these planets are generally shorter than the 5 year SIM mission. We formulate a ``joint periodogram'' as a tool for planet detection from astrometric data. For adequately sampled orbits (i.e., five or more observations per period over a sampling time span longer than the orbital period), we find that the joint periodogram is more sensitive than the χ2 test for the null hypothesis. In our analysis of the problem, we use Monte Carlo simulations of orbit detection, together with realistic observing scenarios, actual target and reference star lists, realistic estimates of SIM instrument performance, and plausible distributions of planetary system parameters.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  4. A Search for Astrometric Companions to Stars in the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Bartlett, Jennifer L.; Ianna, Philip A.; Begam, Michael C.

    2009-04-01

    Thirteen nearby stars from the former University of Virginia Southern Parallax Program were tested for possible astrometric perturbations that might indicate very low mass companions. For 12 of these stars—LHS 34, 271, 337, 532, 1134, 1565, 2310, 2739, 2813, 3064, 3242, and 3418—no clear indication of any unseen companion was detected. One star, LHS 288, however, may have a perturbation meriting further investigation. These high proper motion stars are all members of the solar neighborhood, lying within 25 pc. Other than the white dwarf LHS 34, these stars are early M dwarfs (M0.5-M5.5 V). After a minimum of 50 observations spread over at least three years, the relative parallax solutions for these stars have errors less than 3 mas. Following the calculation of relative parallaxes and proper motions, time-series analyses using Lomb-Scargle periodograms tested the astrometric residuals for any additional periodic signals. An upper limit to the mass of companions that could remain undetected was estimated for each star individually.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  6. A Test of GEMS Astrometric Precision for Exoplanet Detection and Mass Measurement

    NASA Astrophysics Data System (ADS)

    Ammons, S. Mark; Marois, Christian; Macintosh, Bruce; Konopacky, Quinn; Neichel, Benoit; Galicher, Raphael; Bendek, Eduardo; Guyon, Olivier

    2014-08-01

    Precision astrometry is so far the only mainstream exoplanet detection technique that has yet to find a new planet. The unique capabilities of GeMS and GSAOI may finally be what we have been waiting for: the combination of a large aperture and wide-field AO correction for stable high-resolution wide-field diffraction-limited imaging. As part of this program, we have observed the astrometric calibrator star TYC 7122-00041-1 to demonstrate GeMS' long-term astrometric precision of < 0.4 mas in sparse fields (Ammons et al. 2013). Here, we propose two more epochs on the closest brown dwarf pair at 2 pc, WISE J1049-53 (Luhman 2013), newly discovered with Gemini in 2013 to be the third closest system known. GEMS will in one year obtain the best available projected relative orbits and a < 1% trigonometric distance, enabling precision masses and luminosity measurements for both L/T transition components of WISE 1049-53.

  7. Evaluation of the Astrometric Potential of NIR Focal Plane Arrays for Determination of Parallaxes and Proper Motions of L and T Dwarfs

    NASA Astrophysics Data System (ADS)

    Vrba, F. J.; Henden, A. A.; Luginbuhl, C. B.; Guetter, H. H.; Monet, D. G.

    2000-05-01

    The capability of carrying out astrometric observations at near-infrared wavelengths has been long sought, as the region between 1.2-2.2 microns offers smaller atmospheric refractive distortions and measurement of objects which are not easily detectable at optical wavelengths. The recent discoveries by 2MASS, DENIS, and SDSS of numerous nearby L- and T-dwarfs whose SEDs peak in the near-infrared makes the capability of determining parallaxes and proper motions at these wavelengths especially attractive. We have carried out astrometric test observations using a Rockwell 256x256 HgCdTe (NICMOS 3) array at the USNO 1.55-m telescope to gain understanding of the prospects and problems inherent in a long-term near-infrared astrometric program. We routinely obtain accuracies of about 10 mas for a single measurement for well-exposed stars between 1.2 and 2.2 microns. We expect this accuracy to allow distance determinations to 2% or better for the majority of known L and T dwarfs within a two to three year observation series. These tests were carried out in anticipation of the use of an ALADDIN 1024x1024 InSb array, which will provide a larger FOV and increased sensitivity at 2.2 microns, for routine near-infrared parallax observations at USNO beginning in summer 2000. We report preliminary astrometric results obtained with engineering-grade ALADDIN arrays employed in NOAO instrumentation.

  8. Performance considerations for the astrometric Telescope Facility on the Phase I Space Station

    NASA Technical Reports Server (NTRS)

    Nishioka, Kenji; Mascy, Alfred C.; Sobeck, Charles K.; Sperans, Joel; Gatewood, George D.

    1988-01-01

    The Astrometric Telescope Facility (ATF) is an optical telescope facility of extreme astrometric precision whose principal scientific purpose is the detection and study of planetary systems about nearby stars. With the recent change in the space station program to two phases, the suitability of initial operations from the phase 1 station need to be evaluated. This paper presents the results of such an evaluation for the Astrometric Telescope Facility.

  9. Performance considerations for the astrometric telescope facility on the phase 1 space station

    NASA Technical Reports Server (NTRS)

    Nishioka, Kenji; Gatewood, George D.; Macsy, Alfred C.; Sobeck, Charles K.; Sperans, Joel

    1987-01-01

    The Astrometric Telescope Facility (ATF) is an optical telescope facility of extreme astrometric precision whose principle scientific purpose is the detection and study of planetary systems about nearby stars. With the recent change in the space station program to two phases, the suitability of initial operations from the phase 1 station need to be evaluated. This paper presents the results of such an evaluation for the Astrometric Telescope Facility.

  10. VSOP-2 Astrometric Accuracy with Phase Referencing

    NASA Astrophysics Data System (ADS)

    Asaki, Y.; Kono, Y.

    2009-08-01

    The VSOP-2 mission is expected to conduct phase referencing observations with the unprecedented spatial resolutions at 8.4, 22, and 43 GHz together with the ASTRO-G satellite. In this report, VSOP-2 astrometry with phase referencing is examined in detail based on a simulation tool, ARIS.

  11. Astrometric Measurements of Selected Visual Double Stars

    NASA Astrophysics Data System (ADS)

    Boyd, J.; Brokaw, A.; Deventer, J.; Garcia, M.; Gastelum, M.; Guerrero, Y.; Hallett, J.; Heape, K.; Ibarra, M.; Langston, R.; Maddux, D.; Moreland, J.; Mozzillo, R.; Overholts, J.; Perez, K.; Randle, V.; Savard, S.; Stewart, M.; West, L.; McClure, A.; Walker, D.

    2012-04-01

    The observations and measurements for a selected set of 13 double stars are reported. These tasks comprised the activities in a special course designated as a Learning Community which combines a standard astronomy course with a mathematics course devoted to research techniques. This class was taught at the Estrella Mountain Community College in Avondale, Arizona during the fall semester 2011. This course is a result of expanding the special research mathematics courses offered during the fall 2010 and spring 2011 semesters. Observations and measurements were taken with a Meade 12" Schmidt Cassegrain Telescope (SCT) using the Celestron MicroGuideTM and supplemented with imagery acquired with the Tzec Maun Foundation remote telescope system located in New Mexico.

  12. Astrometric calibration of the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center (XSTPS-GAC)

    NASA Astrophysics Data System (ADS)

    Zhang, Hui-Hua; Liu, Xiao-Wei; Yuan, Hai-Bo; Zhao, Hai-Bin; Yao, Jin-Sheng; Zhang, Hua-Wei; Xiang, Mao-Sheng; Huang, Yang

    2014-04-01

    We present astrometric calibration of the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center (XSTPS-GAC). XSTPS-GAC is the photometric part of the Digital Sky Survey of the Galactic Anti-center (DSS-GAC), which is a photometric and spectroscopic sky survey, in combination with LAMOST. In order to select an astrometric reference catalog, we made comparisons between the four widely used astrometric catalogs, GSC2.3, USNO-B1.0, UCAC3 and PPMXL. PPMXL shows relatively small systematic errors in positions and more homogeneous proper motion distributions toward the Galactic Anti-center (GAC), and was selected as the reference catalog. Based on the high quality and bright reference stars that were picked out from PPMXL, we performed a 4th-order polynomial fitting in image units, to construct the transformation relation between coordinates used by XSTPS-GAC and standard coordinates, and to simultaneously correct the image distortions in the CCD. Then we applied the derived relation to all sources to obtain their mean celestial coordinates based on the International Celestial Reference System. For bright point sources with r < 17.0 mag, the accuracy of astrometric calibration could reach about 80 mas for each of the g, r, i bands, with systematic errors being less than 10 mas. But for the faint sources at the brightness limit of the survey, which was r ~ 19.0 mag, the accuracy can still reach 200 mas. After combining all observations, the final weighted average coordinates could reach an accuracy of less than 70 mas for bright stars. For faint stars, the rms residuals of weighted coordinates decrease to ~ 110 mas. The final combined XSTPS-GAC coordinates show a good consistency with the Sloan Digital Sky Survey.

  13. The influence of environmental context in interpersonal observation-execution.

    PubMed

    Roberts, James W; Bennett, Simon J; Welsh, Timothy N; Elliott, Digby; Lyons, Jim L; Hayes, Spencer J

    2016-03-16

    Cyclical upper-limb movements involuntarily deviate from a primary movement direction when the actor concurrently observes incongruent biological motion. We examined whether environmental context influences such motor interference during interpersonal observation-execution. Participants executed continuous horizontal arm movements while observing congruent horizontal or incongruent curvilinear biological movements with or without the presence of an object positioned as an obstacle or distractor. When participants were observing a curvilinear movement, an object located within the movement space became an obstacle, and, thus, the curvilinear trajectory was essential to reach into horizontal space. When acting as a distractor, or with no object, the curvilinear trajectory was no longer essential. For observing horizontal movements, objects were located at the same relative locations as in the curvilinear movement condition. We found greater involuntary movement deviation when observing curvilinear than horizontal movements. Also, there was an influence of context only when observing horizontal movements, with greater deviation exhibited in the presence of a large obstacle. These findings suggest that the influence of environmental context is underpinned by the (mis-)matching of observed and executed actions as incongruent biological motion is primarily coded via bottom-up sensorimotor processes, whilst the congruent condition incorporates surrounding environmental features to modulate the bottom-up sensorimotor processes.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  15. 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).

  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. CCD Astrometric Measurements of WDS 00023-7238 HJ5439

    NASA Astrophysics Data System (ADS)

    Nguyen, Kelvin; Radhakrishnan, Sibi; Schoenbrunner, Max; Nazemi, Ariane; Calanog, Jae; Boyce, Pat; Boyce, Grady

    2017-07-01

    We obtained astrometric measurements of the double star system 00023-7238 (HJ 5439) using the iTelescope network and MaximDL v6 software. We measured a mean position angle of 79.2 deg ± 0.2 deg and an average separation distance of 9.53" ± 0.04"; these measurements show a decrease of 0.4 deg and 0.23" from the last measurement in epoch 1998.50. Historical and current data show no obvious signs of orbital motion, which suggests that HJ 5439 may be a visual double.

  18. 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…

  19. The First U.S. Naval Observatory Robotic Astrometric Telescope Catalog

    NASA Astrophysics Data System (ADS)

    Zacharias, N.; Finch, C.; Subasavage, J.; Bredthauer, G.; Crockett, C.; Divittorio, M.; Ferguson, E.; Harris, F.; Harris, H.; Henden, A.; Kilian, C.; Munn, J.; Rafferty, T.; Rhodes, A.; Schultheiss, M.; Tilleman, T.; Wieder, G.

    2015-10-01

    URAT1 is an observational, astrometric catalog covering most of the δ ≥slant -15° area and a magnitude range of about R = 3-18.5. Accurate positions (typically 10-30 mas standard error) are given for over 228 million objects at a mean epoch around 2013.5. For the over 188 million objects matched with the Two Micron All Sky Survey (2MASS) point-source catalog proper motions (typically 5-7 mas yr-1 standard errors) are provided. These data are supplemented by 2MASS and AAVSO Photometric All-Sky Survey (APASS) photometry. Observations, reductions, and catalog construction are described, together with results from external data verifications. The catalog data are served by CDS, Starsbourg (I/329).

  20. 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.

  1. 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

  2. Astrometric Detection of a Low Mass Companion Orbiting the Star AB Doradus

    NASA Technical Reports Server (NTRS)

    Guirado, J. C.; Soderhjelm, S.; Reynolds, J. E.

    1997-01-01

    We report submilliarcsecond--precise astrometric measurements for the late-type star AB Doradus via a combination of VLBI(very long baseline interferometry) and Hipparcos satellite data. Our astrometric analysis results in the precise determination of the kinematics of this star, that reveals an orbital motion readily explained as caused by the gravitational interaction with a low-mass companion.

  3. Astrometric Detection of a Low Mass Companion Orbiting the Star AB Doradus

    NASA Technical Reports Server (NTRS)

    Soderhjelm, S.; Guirado, J. C.; Reynolds, J. E.; Lestrade, J. F.; Preston, R. A.; Jauncey, D. L.; Jones, D. L.; Tzioumis, A. K.; Ferris, R. H.; King, E. A.; hide

    1997-01-01

    We report submilliarsecond-precise astrometric measurement for the late-type star AB Doradus via a combination of VLBI (very long baseline interferometry) and Hipparos satellite data. Our astrometric analysis results in the precise determination of the kinematics of this star, that reveals an orbital motion readily explained as caused by the gravitational interaction with a low-mass companion.

  4. 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.

  5. Astrometric and Photometric Study of the Open Cluster NGC 2323

    NASA Astrophysics Data System (ADS)

    Amin, M. Y.; Elsanhoury, W. H.

    2017-06-01

    We present a study of the open cluster NGC 2323 using astrometric and photometric data. In our study we used two methods that are able to separate open cluster's stars from those that belong to the stellar background. Our results of calculations by these two methods indicate that: 1) according to the membership probability, NGC 2323 should contain 497 stars, 2) the cluster center should be at 07h 02m 48.02s and -08° 20' 17" 74, 3) the limiting radius of NGC 2323 is 2.31 ± 0.04 pc, the surface number density at this radius is 98.16 stars pc^{-2}, 4) the magnitude function has a maximum at about m_{v} = 14 mag, 5) the total mass of NGC 2323 is estimated dynamically by using astrometric data to be 890 M_{⊙}, and statistically by using photometric data to be 900 M_{⊙}, and 6) the distance and age of the cluster are found to be equal to 900 ± 100 pc, and 140 ± 20 Myr, respectively. Finally the dynamical evolution parameter τ of the cluster is about 436.2.

  6. The SIM Lite Astrometric Observatory: engineering risk reduction activity

    NASA Astrophysics Data System (ADS)

    Goullioud, Renaud; Dekens, Frank; Nemati, Bijan; An, Xin; Hovland, Larry

    2010-07-01

    The SIM Lite Astrometric Observatory is a mission concept for a space-borne instrument to perform micro-arcsecond 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 main enabling technology development for the mission was completed during phases A & B. While the project is waiting for the results of the ASTRO2010 Decadal Survey to proceed into flight implementation, the instrument team is currently converting 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 (ABC), the fine steering mechanism (FSM), the path-length control and modulation optical mechanisms (POM & MOM), focal plane camera electronics (ATC & FTC), camera cooling cryo-heat pipe, and the siderostat mechanism are currently under development. Main assemblies are built to meet flight requirements and have been or will be subjected to flight qualification level environmental testing (random vibration and thermal cycling) and performance testing. The Spectral Calibration Development Unit (SCDU), a white light interferometer testbed has recently demonstrated how to perform the spectral calibration of the instrument. The Guide 2 Telescope testbed (G2T) has demonstrated the 50 micro-arcsecond angle monitoring capability required by SIM Lite to perform astrometry. This paper summarizes recent progress in engineering risk reduction activities.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  8. 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.

  9. Current results and developments in astrometric VLBI at the Jet Propulsion Laboratory

    NASA Technical Reports Server (NTRS)

    Purcell, G. H., Jr.; Cohen, E. J.; Fanselow, J. L.; Rogstad, D. H.; Skjerve, L. J.; Spitzmesser, D. J.; Thomas, J. B.

    1979-01-01

    The Jet Propulsion Laboratory's program of astrometric VLBI as one element of a navigation system for interplanetary spacecraft includes developing a radioastrometric source catalog, and a catalog of positions of compact extragalactic radio sources correct to about 0.01 arc sec. The three (64 m) antenna complexes of the Deep Space Network in Spain, Australia, and the U.S. are involved, each equipped to receive simultaneously at wavelengths of 13 and 3.6 cm with total system temperatures of about 20-25 K at both wavelengths. The program is to provide precise values of parameters used in navigational computations, including UT1 accurate to about 0.001s, and current values of polar motion to 30 cm. Bandwidth synthesis methods were applied to measure delays as well as rates regarding source positions derived from observations using the Mark II VLBI recording system which has a sampling rate of four million bits per second.

  10. Advanced Undergraduate Computer Based Astronomy Lab. The Astrometric Binary Kruger 60.

    NASA Astrophysics Data System (ADS)

    Slovak, M. H.

    2002-12-01

    A challenging computer based lab for astronomy undergraduate students has been developed to determine the masses of the components of the visual binary system Kruger 60 = HD 239960 = BD+56 2783 using archival astrometric observations. The data consist of separations and position angles from 1898 to 1949 (Lippincott 1953; Van de Kamp 1967) of Kruger 60B relative to Kruger 60A covering a complete orbit. After reviewing Kepler's 3rd or Harmonic Law and Newton's revision, they analyze the data using Microsoft Excel to calculate a best fitting elliptical orbit to the relative orbit of Kruger 60B. The importance of deriving stellar masses from such binaries is emphasized by discussing the significance of mass in the role of stellar evolution. This lab is one in a series being designed to provide astronomy majors practical experience in mathematically modeling astronomical data.This research was supported in part by NASA LaSPACE LURA Grant LSU 3115-30-5199.

  11. 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.

  12. The investigation of determination asteroids positions errors by observations of telescope SBG AO UFU

    NASA Astrophysics Data System (ADS)

    Kaizer, G. T.; Skripnichenko, P. V.

    2013-07-01

    The article is about investigation of influence astrometric CCD image processing conditions on the accuracy of determining the positions of asteroids. The main this research's problem is dependence of calculatedasteroids coordinates error from used in the processing mathematical model that approximated the image of the objects on the CCD image. In thearticle described of the effect of Lorentz and Moffatt profiles on the accuracy ofasteroids positions determining by the observation from SBG AO UFU.

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

    NASA Astrophysics Data System (ADS)

    Bedin, Luigi

    2014-10-01

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

  14. VizieR Online Data Catalog: HD 128311 radial velocity and astrometric data (McArthur+, 2014)

    NASA Astrophysics Data System (ADS)

    McArthur, B. E.; Benedict, G. F.; Henry, G. W.; Hatzes, A.; Cochran, W. D.; Harrison, T. E.; Johns-Krull, C.; Nelan, E.

    2017-05-01

    The High Resolution Spectrograph (HRS; Tull, 1998SPIE.3355..387T) at the HET at McDonald Observatory was used to make the spectroscopic observations using the iodine absorption cell method (Butler et al. 1996PASP..108..500B). Our reduction of HET HRS data is given in Bean et al. (2007AJ....134..749B), which uses the REDUCE package (Piskunov & Valenti, 2002A&A...385.1095P). Our observations include a total of 355 high-resolution spectra which were obtained between 2005 April and 2011 January. Because typically two or more observations were made in less than 1 hr per night, we observed at 161 epochs with the HET HRS. The astrometric observations were made with the Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) 1r, a two-axis interferometer, in position (POS) "fringe-tracking" mode. Twenty-nine orbits of HST astrometric observations were made between 2007 December and 2009 August. (2 data files).

  15. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  18. Astrometric Constraints on the Masses of Long-period Gas Giant Planets in the TRAPPIST-1 Planetary System

    NASA Astrophysics Data System (ADS)

    Boss, Alan P.; Weinberger, Alycia J.; Keiser, Sandra A.; Astraatmadja, Tri L.; Anglada-Escude, Guillem; Thompson, Ian B.

    2017-09-01

    Transit photometry of the M8V dwarf star TRAPPIST-1 (2MASS J23062928-0502285) has revealed the presence of at least seven planets with masses and radii similar to that of Earth, orbiting at distances that might allow liquid water to be present on their surfaces. We have been following TRAPPIST-1 since 2011 with the CAPSCam astrometric camera on the 2.5 m du Pont telescope at the Las Campanas Observatory in Chile. In 2016, we noted that TRAPPIST-1 lies slightly farther away than previously thought, at 12.49 pc, rather than 12.1 pc. Here, we examine 15 epochs of CAPSCam observations of TRAPPIST-1, spanning the five years from 2011 to 2016, and obtain a revised trigonometric distance of 12.56 ± 0.12 pc. The astrometric data analysis pipeline shows no evidence for a long-period astrometric wobble of TRAPPIST-1. After proper motion and parallax are removed, residuals at the level of ±1.3 mas remain. The amplitude of these residuals constrains the masses of any long-period gas giant planets in the TRAPPIST-1 system: no planet more massive than ∼4.6 M Jup orbits with a 1 year period, and no planet more massive than ∼1.6 M Jup orbits with a 5 year period. Further refinement of the CAPSCam data analysis pipeline, combined with continued CAPSCam observations, should either detect any long-period planets, or put an even tighter constraint on these mass upper limits.

  19. 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

  20. Estimation of position and velocity for a low dynamic vehicle in near space using nonresolved photometric and astrometric data.

    PubMed

    Jing, Nan; Li, Chuang; Chong, Yaqin

    2017-01-20

    An estimation method for indirectly observable parameters for a typical low dynamic vehicle (LDV) is presented. The estimation method utilizes apparent magnitude, azimuth angle, and elevation angle to estimate the position and velocity of a typical LDV, such as a high altitude balloon (HAB). In order to validate the accuracy of the estimated parameters gained from an unscented Kalman filter, two sets of experiments are carried out to obtain the nonresolved photometric and astrometric data. In the experiments, a HAB launch is planned; models of the HAB dynamics and kinematics and observation models are built to use as time update and measurement update functions, respectively. When the HAB is launched, a ground-based optoelectronic detector is used to capture the object images, which are processed using aperture photometry technology to obtain the time-varying apparent magnitude of the HAB. Two sets of actual and estimated parameters are given to clearly indicate the parameter differences. Two sets of errors between the actual and estimated parameters are also given to show how the estimated position and velocity differ with respect to the observation time. The similar distribution curve results from the two scenarios, which agree within 3σ, verify that nonresolved photometric and astrometric data can be used to estimate the indirectly observable state parameters (position and velocity) for a typical LDV. This technique can be applied to small and dim space objects in the future.

  1. High-precision Astrometric Millimeter Very Long Baseline Interferometry Using a New Method for Multi-frequency Calibration

    NASA Astrophysics Data System (ADS)

    Dodson, Richard; Rioja, María J.; Molina, Sol N.; Gómez, José L.

    2017-01-01

    In this paper we describe a new approach for millimeter Very Long Baseline Interferometry (mm-VLBI) calibration that provides bona-fide astrometric alignment of the millimeter-wavelength images from a single source, for the measurement of frequency-dependent effects, such as “core-shifts” near the black hole of active galactic nucleus jets. We achieve our astrometric alignment by solving first for the ionospheric (dispersive) contributions using wide-band centimeter-wavelength observations. Second, we solve for the tropospheric (non-dispersive) contributions by using fast frequency-switching at the target millimeter-wavelengths. These solutions can be scaled and transferred from low frequency to the high frequency. To complete the calibration chain an additional step is required to remove a residual constant phase offset on each antenna. The result is an astrometric calibration and the measurement of the core-shift between 22 and 43 GHz for the jet in BL Lacertae to be ‑8 ± 5, 20 ± 6 μas, in R.A. and decl., respectively. By comparison to conventional phase referencing at centimeter-wavelengths we are able to show that this core shift at millimeter-wavelengths is significantly less than what would be predicted by extrapolating the low-frequency result, which closely followed the predictions of the Blandford & Königl conical jet model. As such it would be the first demonstration for the association of the VLBI core with a recollimation shock, normally hidden at low frequencies due to the optical depth, which could be responsible for the γ-ray production in blazar jets.

  2. An astrometric and spectroscopic study of the δ Scuti variable HD 21190 and its wide companion CPD -83° 64B

    NASA Astrophysics Data System (ADS)

    Niemczura, E.; Scholz, R.-D.; Hubrig, S.; Järvinen, S. P.; Schöller, M.; Ilyin, I.; Kahraman Aliçavuş, F.

    2017-10-01

    Although pulsations of δ Scuti type are not expected among Ap stars from a theoretical point of view, previous observations of the known δ Scuti star HD 21190 indicated a spectral classification F2 III SrEuSi:, making it the most evolved Ap star known. Our atmospheric chemical analysis based on recent High Accuracy Radial velocity Planet Searcher observations confirms the presence of chemical peculiarities in HD 21190. This star is also the only target known to host a magnetic field along with its δ Scuti pulsation properties. Using an astrometric analysis, we show that HD 21190 forms a physical binary system with the companion CPD -83° 64B. The presented astrometric and spectroscopic study of the binary components is important to understand the complex interplay between stellar pulsations, magnetic fields and chemical composition.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Influence of the lower boundary in lysimeter observations

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  9. Experimental Tests of the Astrometric Precision Obtainable with a Ten Micron Interferometer.

    DTIC Science & Technology

    1982-01-18

    declination-dependent phase offset is caused by the failure of the axes of rotation of the heliostat mirrors to intersect precisely . The source...A-Ji>L __ _ _ _ _ _ 4. TITLE (and Subtitle) S. TYPE Of REPORT & PERIOD COVERED EXPERIMENTAL TESTS OF THE ASTROMETRIC PRECISION Final Contract...of tests successfully achieved its objective and demonstrated the usefulness of infrared spatial interferometry for very precise astrometric

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

    PubMed

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

    2007-10-11

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-07-01

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

  12. GeMS/GSAOI Photometric and Astrometric Performance in Dense Stellar Fields

    NASA Astrophysics Data System (ADS)

    Dalessandro, E.; Saracino, S.; Origlia, L.; Marchetti, E.; Ferraro, F. R.; Lanzoni, B.; Geisler, D.; Cohen, R. E.; Mauro, F.; Villanova, S.

    2016-12-01

    Ground-based imagers at 8 m class telescopes assisted by multi-conjugate adaptive optics are primary facilities with which to obtain accurate photometry and proper motions in dense stellar fields. We observed the central region of the globular clusters Liller 1 and NGC 6624 with the Gemini Multi-conjugate Adaptive Optics System (GeMS) feeding the Gemini South Adaptive Optics Imager (GSAOI) currently available at the Gemini South telescope, under different observing conditions. We characterized the stellar point-spread function (PSF) in terms of FWHM, Strehl ratio (SR), and encircled energy (EE), over the field of view (FOV). We found that, for sub-arcsecond seeing at the observed airmass, we can obtain the diffraction-limited PSF (FWHM ≈ 80 mas), SR ∼ 40%, and EE ≥ 50% with a dispersion around 10% over the FOV of 85″ × 85″, in the K s band. In the J band the best images provide FWHMs between 60 and 80 mas, SR \\gt 10 % , and {EE}\\gt 40 % . For seeing at the observed airmass exceeding 1″, the performance worsens but it is still possible to perform PSF fitting photometry with 25% EE in J and 40% in K s . We also computed the geometric distortions of GeMS/GSAOI and we obtained corrected images with an astrometric accuracy of ∼1 mas in a stellar field with high crowding.

  13. The SOPHIE search for northern extrasolar planets. XII. Three giant planets suitable for astrometric mass determination with Gaia

    NASA Astrophysics Data System (ADS)

    Rey, J.; Hébrard, G.; Bouchy, F.; Bourrier, V.; Boisse, I.; Santos, N. C.; Arnold, L.; Astudillo-Defru, N.; Bonfils, X.; Borgniet, S.; Courcol, B.; Deleuil, M.; Delfosse, X.; Demangeon, O.; Díaz, R. F.; Ehrenreich, D.; Forveille, T.; Marmier, M.; Moutou, C.; Pepe, F.; Santerne, A.; Sahlmann, J.; Ségransan, D.; Udry, S.; Wilson, P. A.

    2017-05-01

    We present new radial velocity measurements for three low-metallicity solar-like stars observed with the SOPHIE spectrograph and its predecessor ELODIE, both installed at the 193 cm telescope of the Haute-Provence Observatory, allowing the detection and characterization of three new giant extrasolar planets in intermediate periods of 1.7 to 3.7 yr. All three stars, HD 17674, HD 42012 and HD 29021 present single giant planetary companions with minimum masses between 0.9 and 2.5 MJup. The range of periods and masses of these companions, along with the distance of their host stars, make them good targets to look for astrometric signals over the lifetime of the new astrometry satellite Gaia. We discuss the preliminary astrometric solutions obtained from the first Gaia data release. Based on observations collected with the SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France by the SOPHIE Consortium.Tables 5-7 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A9

  14. 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

  15. 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.

  16. 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.

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

    SciTech Connect

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

    2015-11-13

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

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

    DOE PAGES

    De Rosa, Robert J.; Nielsen, Eric L.; Blunt, Sarah C.; ...

    2015-11-13

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

  19. Astrometric Confirmation and Preliminary Orbital Parameters of the Young Exoplanet 51 Eridani b with the Gemini Planet Imager

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  2. 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.

  3. A Test of GEMS Astrometric Precision for Exoplanet Detection and Mass Measurement

    NASA Astrophysics Data System (ADS)

    Ammons, S. Mark; Marois, Christian; Macintosh, Bruce; Konopacky, Quinn; Neichel, Benoit; Galicher, Raphael; Bendek, Eduardo; Guyon, Olivier

    2013-08-01

    Precision astrometry is so far the only mainstream exoplanet detection technique that has yet to find a new planet. The unique capabilities of GeMS and GSAOI may finally be what we have been waiting for: the combination of a large aperture and wide-field AO correction for stable high-resolution wide-field diffraction-limited imaging. As part of a multi-year program starting in 2013A, we are observing SCR 1845 and Mu Arae in 2013A to (1) astrometrically verify the presence and measure the dynamical mass of the nearby brown dwarf companion orbiting SCR 1845 (Biller et al. 2006) and (2) measure the dynamical mass of mu Arae e, an RV discovery of 1.9 MJUP with a signal of approximately 0.5 mas (Pepe et al. 2008). Here, due to visibility constraints on SCR 1845 and Mu Arae, we propose four new epochs on the closest brown dwarf pair at 2 pc, WISE J1049-53 (Luhman 2013), newly discovered with Gemini in 2013 to be the third closest system known. GEMS will in one year obtain the best available projected relative orbits and a < 1% trigonometric distance, enabling precision masses and luminosity measurements for both L/T transition components.

  4. 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.

  5. 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.

  6. Spectro-astrometric Study of HI emission lines from Herbig Ae/Be Stars

    NASA Astrophysics Data System (ADS)

    Cade Adams, Steven; Brittain, Sean D.; Dougados, Catherine; Benisty, Myriam; Podio, Linda; Whelan, Emma

    2015-01-01

    We present a spectro-astrometric study of the Pa β and Br γ lines from six Herbig Ae/Be stars using NIFS on Gemini North. The goal of this study is to determine the origin of the HI emission lines. By combining the high angular resolution ( 0.1") and intermediate spectral resolution (R~5000) of GEMINI/NIFS we measured the spectro-astrometric signal of the Pa β and Br γ emission lines at the 0.1 mas level. The HAe stars showed no significant spectro-astrometric signal, while the HBe stars did show significant detections. We compare our results to models and discuss the implications for understanding the origin of the HI lines in Herbig Ae/Be stars and their utility for measuring the accretion rate. We also discuss various artifacts in the data and prospects for more sensitive measurements in the future.

  7. 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…

  8. 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.

  9. Astrometric Companions Detected at Visible Wavelengths with the Hubble Space Telescope Fine Guidance Sensors

    NASA Astrophysics Data System (ADS)

    Franz, O. G.; Wasserman, L. H.; Bradley, A. J.; Benedict, G. F.; Duncombe, R. L.; Hemenway, P. D.; Jefferys, W. H.; McArthur, B.; Nelan, E.; Shelus, P. J.; Story, D.; Whipple, A. L.; Fredrick, L. W.; van Altena, Wm. F.

    1994-12-01

    Astrometric (``unseen'') companions provide a plausible interpretation of periodic, low--amplitude variations (perturbations) in the proper motions of some nearby M--dwarfs (Lippincott 1978, Space Sci. Rev. 22, 153--189). Using the Fine Guidance Sensors (FGS) in the Transfer Function Scan mode, we have searched for five of these astrometric companions. We report the confirmed detection, at visible wavelengths, of a faint orbiting companion to each of the following M--dwarfs: BD+67.552 = GL310, AC+48.1595-89 = GL623, W1062 = GL748, and W922 = GL831. This work is supported by NASA under grant NAG5--1603 to UTexas.

  10. Analysis of the photometric and astrometric fidelity of high-resistivity, p- channel CCDs

    NASA Astrophysics Data System (ADS)

    Abunaemeh, Malek Amir Mahmoud

    Photometry and astrometry performed with charge coupled devices (CCDs) at the focal planes of large telescopes are indispensable tools of modern observational cosmology, astrophysics and astronomy. In the modern era of precision cosmology, variations in the sub-pixel sensitivity and spectral response of CCDs can affect the science yield of observations and must be characterized. Unfortunately, there have been very few studies to measure the sub-pixel response variations of CCDs, particularly in the context of observational cosmology. It is the aim of this thesis to perform the first measurement of the photometric and astrometric fidelity of high-resistivity, p- channel CCDs. These devices have been selected for major upcoming observational cosmology missions such as the space-based Supernova Acceleration Probe satellite (SNAP) and the ground-based Dark Energy Survey. An experimental study has been performed to make detailed measurements of the intrapixel response variations of these devices at a precision exceeding 2%, which is the level of precision required for the missions mentioned above. A 300 mm thick, 10.5 mm pixel pitch, 1.4k×1.4k format, high-resistivity, p-channel CCD operated fully depleted was illuminated by a 1.3 mm pinhole projector. The illuminated spot was moved in sub-pixel steps through various patterns to measure several properties of the device including the lateral charge diffusion, the intrapixel sensitivity variations, the effective diffusion near the edge of the device active region where electric field lines in the device may diverge, to test the photometric performance of a new technique for acquiring dithered astronomical observations coined "CCD Phase Dithering." It was determined that the intrapixel sensitivity variations were less than ˜ 0.5% in most cases. The lateral diffusion in the device was measured to be 7.41 mm in the device center, consistent with theoretical predictions. Charge spreading near the device edge resulted in an

  11. Astrometric sky survey of the zone +2° – +5.5° with the telescope MAC

    NASA Astrophysics Data System (ADS)

    Lazorenko, P.; Karbovsky, V.; Svachiy, L.; Buromsky, M.; Kasyan, S.

    2016-06-01

    We describe the results of the astrometric sky survey with the telescope MAC which was performed in 2010–2014 by the Main Astronomical observatory of NAS of Ukraine and Astronomical observatory of Taras Shevchenko Kiev national University. We obtained about 6 million of images of the sky objects to 17m in equatorial zone δ = +2°÷+5.5°. All images were obtained during 188 night observational series with use of V-band filter. Now we obtained the preliminary version of KMAC2.0 catalogue. We estimate that precision of positions for bright V<14m stars is 50–90 milliarcsecond and for fainter 14m

  12. 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

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  17. 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

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

    NASA Technical Reports Server (NTRS)

    Pravdo, Steven H.

    1991-01-01

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

  19. CCD Astrometric Measurements of WDS 08167+4053 Using the iTelescope Network

    NASA Astrophysics Data System (ADS)

    Riley, Bill; Li, Dewei; Li, Junyao; Dennis, Aren; Boyce, Grady; Boyce, Pat

    2016-10-01

    Separations and position angle astrometric measurements were made of the multiple star system WDS 08167+4053 AB, AC, and BC components. Our measurements compared favorably with historical measurements from the United States Naval Observatory Washington Double Star Catalog, confirming the trend.

  20. 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…

  1. 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…

  2. 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.

  3. 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.

  4. Multiple-planet Orbit-fitting with Joint Radial Velocity and Astrometric Data

    NASA Astrophysics Data System (ADS)

    Catanzarite, Joseph

    2009-05-01

    Astrometry alone does not constrain the direction of circulation of the star in its reflex motion orbit. Practically, this means that astrometry cannot distinguish between the ascending and descending nodes in the reflex motion orbit. Consequently, Omega (the longitude of ascending node) and omega (the longitude of periastron, which is measured with respect to Omega in the direction of the orbit) can only be determined modulo 180 degrees. Radial velocity data can provide the information needed to break this degeneracy. When combining RV and astrometric data to fit an orbit, one must check that the fitted orbit is physically consistent with both data sets. The astrometric orbit problem can be partially linearized via transformation to four Thiele-Innes parameters plus three nonlinear parameters: eccentricity, period and periastron time. On the other hand, the RV orbit problem can be partially linearized via transformation to two additional Thiele-Innes parameters plus the same three nonlinear parameters. Unfortunately, the two RV Thiele-Innes parameters are not linearly related to the four astrometric ones. Because of this difficulty, currently available algorithms for jointly fitting RV and astrometric data to multiple-planet systems employ five nonlinear parameters per planet. We have developed an algorithm that satisfies the RV-astrometry consistency requirement, while using only three nonlinear parameters per planet. We have successfully tested this algorithm in the context of a recent double-blind planet detection simulation study. We expect the reduction in nonlinearity to give the algorithm a significant advantage in computation speed over existing algorithms, making it ideally suited to carry out further simulation studies of joint astrometric and RV orbit-fitting for multiple-planet systems via application of computation-intensive Bayesian methods based on Markov Chain Monte Carlo. This work was carried out at the Jet Propulsion Laboratory, California

  5. 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.

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

    NASA Technical Reports Server (NTRS)

    Sovers, O. J.

    1994-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  8. 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.

  9. Influence of variable milk quality premiums on observed milk quality.

    PubMed

    Nightingale, C; Dhuyvetter, K; Mitchell, R; Schukken, Y

    2008-03-01

    The objective of this study was to evaluate a premium program for very high quality milk in a US cooperative. Data were available on a monthly basis from a large US milk cooperative from April 1998 through December 2005. The data set consisted of 36,930 observations representing producer-months. The actual amount of the low bulk tank somatic cell count (BTSCC) premium varied from $0.15 per hundred pounds (cwt.) of milk to $1.00/cwt. with steps in between of $0.50 and $0.60 per cwt. of milk during the data collection period. Data analysis was done to evaluate the impact of the premium program on average BTSCC and on the probability of a producer to ship milk with <100,000 cells/mL in a given month. The results showed a strong effect of the premium program on both the average BTSCC and the probability of producing milk with very low BTSCC. On average, the BTSCC of all the milk in the cooperative was reduced by 22,000 cells during the high premium period. The probability of producing milk with BTSCC <100,000 doubled during some months of the high premium period from 4 to 8%, and an associated 10% increase in probability to produce milk below 200,000 cells/mL was observed. The data clearly indicate that premium offerings for very high quality milk affect the overall milk quality in the population affected by the premium. Producers responded to the high premiums and the overall impact on milk quality was substantial. We argue that the combination of a penalty program for high BTSCC milk with a premium program for very high quality milk (low BTSCC) provides a strong incentive for improvement of milk quality.

  10. Elucidation of the tidal influence on bacterial populations in a monsoon influenced estuary through simultaneous observations.

    PubMed

    Khandeparker, Lidita; Eswaran, Ranjith; Gardade, Laxman; Kuchi, Nishanth; Mapari, Kaushal; Naik, Sneha D; Anil, Arga Chandrashekar

    2017-01-01

    The influence of tides on bacterial populations in a monsoon influenced tropical estuary was assessed through fine resolution sampling (1 to 3 h) during spring and neap tides from mouth to the freshwater end at four stations during pre-monsoon, monsoon and post-monsoon seasons. Higher abundance of total bacterial count (TBC) in surface water near the river mouth, compared to the upstream, during pre-monsoon was followed by an opposite scenario during the monsoon When seasonally compared, it was during the post-monsoon season when TBC in surface water was highest, with simultaneous decrease in their count in the river sediment. The total viable bacterial count (TVC) was influenced by the depth-wise stratification of salinity, which varied with tidal fluctuation, usually high and low during the neap and spring tides respectively. The abundance of both the autochthonous Vibrio spp. and allochthonous coliform bacteria was influenced by the concentrations of dissolved nutrients and suspended particulate matter (SPM). It is concluded that depending on the interplay of riverine discharge and tidal amplitude, sediment re-suspension mediated increase in SPM significantly regulates bacteria populations in the estuarine water, urging the need of systematic regular monitoring for better prediction of related hazards, including those associated with the rise in pathogenic Vibrio spp. in the changing climatic scenarios.

  11. Io's volcanic influence on the Jovian magnetosphere: Observational evidence from the HISAKI observation

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Long term and continuous observation of Io plasma torus and Jovian UV aurora brightness from an earth orbiting EUV spectroscope HISAKI have revealed responses of the plasma torus and Jovian magnetosphere to volcanic activity change at the satellite Io. The HISAKI observation shows that brightness of singly ionized sulfur and oxygen and atomic oxygen due to electron impact excitation increased from DOY 20 to 40 in 2015. Doubly ionized sulfur began to increase several days after the singly ionized ion and reached a maximum around DOY 60. The intensities of these ions and atom kept intense until DOY 70. Subsequently, the atomic oxygen and singly charged sulfur showed two-step decreased on DOY 70 and 90. The singly ionized oxygen and doubly ionized sulfur begins to decrease on DOY 90. The ion intensities returned to the usual level until DOY 120. These behaviors are consistent with response of the plasma torus to the dramatic change in neutral source from Io. To evaluate mass supply rate from inner to middle magnetospheres qualitatively, radial gradient of emission intensity which was proportional to radial gradient of ion flux tube content was derived from spatially resolved HISAKI data set. The radial gradient at 8.5 Jovian radii from Jupiter suggested that the mass loading could keep higher rate from DOY 40 to 80. During this period unusually strong transient enhancements of Jovian aurora were observed by HISAKI. Time interval of each enhancement was a few days, which is consistent with quasi-periodic substom-like event identified by the Galileo spacecraft. Several hours after the aurora enhancement, short-live brightening was also identified in the Io plasma torus. Possible interpretation is injection of hot electron population into the inner magnetosphere with density depleted interchange flux tube as enhanced mass loading of iogenic plasma could drive enhancement of returning flux tube. After DOY 90 when the radial gradient almost returned to the value before the

  12. Astrometric Studies of Aldebaran, Arcturus, Vega, the Hyades, and Other Regions

    NASA Astrophysics Data System (ADS)

    Gatewood, George

    2008-07-01

    The results of astrometric studies in the regions of Groombridge 34A, the Hyades, Aldebaran, Ross 47, BD+5° 1668, 81 Cancri, BD+15° 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.

  13. 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.

  14. Using the microcomputer system for the 1.56 M astrometric telescope

    NASA Astrophysics Data System (ADS)

    Wan, Y.; Dai, C.

    This paper deals with the method of using a microcomputer system to steer the 1.56 m astrometric telescope at Shanghai Observatory. The main computer of this system is used for the general control of the telescope system, and single board computers are used for carrying out its operation instructions and orders. Its software and hardware design is also described in this paper. It is economical and practicable to apply this microcomputer system to the equipment with many auxiliary instruments.

  15. Gravity wave amplitudes changes observed in different airglow emissions: influence of wave breaking and observational selection

    NASA Astrophysics Data System (ADS)

    Schmidt, Carsten; Wüst, Sabine; Hannawald, Patrick; Bittner, Michael

    2016-04-01

    The upper mesosphere lower thermosphere region is well known for enhanced gravity wave breaking. Airglow emissions originating in this height region provide a good possibility for detailed studies of gravity wave behavior in this altitude. Therefore, rotational temperatures and intensities of the OH(3-1), OH(4-2), OH(6-2) and O2b(0-1)-transitions recorded at the NDMC (Network for the Detection of Mesospheric Change) site Oberpfaffenhofen (48.1°N, 10.3°E), Germany are examined. First results indicate, that both significant amplitude growth from the lower (~87km) OH airglow emissions to the higher (~95km) O2 airglow emissions of more than 100% as well as strong damping can be observed. On several occasions OH- and O2-emissions show completely independent behavior - probably related to the complete breakup of a gravity wave. These amplitude changes are set into relation to emission layer height, vertical wavelength, absolute temperature and potential seasonal dependence. Observations from further NDMC sites in France, Germany and Austria are used to discuss the evolution of these waves on horizontal scales from 100km to 1000km.

  16. Observable Priors: Limiting Biases in Estimated Parameters for Incomplete Orbits

    NASA Astrophysics Data System (ADS)

    Kosmo, Kelly; Martinez, Gregory; Hees, Aurelien; Witzel, Gunther; Ghez, Andrea M.; Do, Tuan; Sitarski, Breann; Chu, Devin; Dehghanfar, Arezu

    2017-01-01

    Over twenty years of monitoring stellar orbits at the Galactic center has provided an unprecedented opportunity to study the physics and astrophysics of the supermassive black hole (SMBH) at the center of the Milky Way Galaxy. In order to constrain the mass of and distance to the black hole, and to evaluate its gravitational influence on orbiting bodies, we use Bayesian statistics to infer black hole and stellar orbital parameters from astrometric and radial velocity measurements of stars orbiting the central SMBH. Unfortunately, most of the short period stars in the Galactic center have periods much longer than our twenty year time baseline of observations, resulting in incomplete orbital phase coverage--potentially biasing fitted parameters. Using the Bayesian statistical framework, we evaluate biases in the black hole and orbital parameters of stars with varying phase coverage, using various prior models to fit the data. We present evidence that incomplete phase coverage of an orbit causes prior assumptions to bias statistical quantities, and propose a solution to reduce these biases for orbits with low phase coverage. The explored solution assumes uniformity in the observables rather than in the inferred model parameters, as is the current standard method of orbit fitting. Of the cases tested, priors that assume uniform astrometric and radial velocity observables reduce the biases in the estimated parameters. The proposed method will not only improve orbital estimates of stars orbiting the central SMBH, but can also be extended to other orbiting bodies with low phase coverage such as visual binaries and exoplanets.

  17. 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

  18. Astrometric Measurements of WDS 15482+0134 EIS 1AB

    NASA Astrophysics Data System (ADS)

    Kraver, Cassandra; Van Steenwyk, Charles; Ryan, Charles; Forrest, Nancy; Irving, Jenae; Krueger, Aaron; Genet, Russell; Johnson, Jo; Clifford, Matthew

    2017-04-01

    Ten separations and position angles were obtained of WDS 15482+0134 AB with the CDK-700 telescope in the iTelescope array. The mean values of these measurements were compared to historical observations. Although there was a discrepancy between our separations and the historical data, the position angle matched quite well.

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

    NASA Astrophysics Data System (ADS)

    Piattoni, Jacopo; Ceruti, Alessandro; Piergentili, Fabrizio

    2014-10-01

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

  20. Astrometric Observations of Phobos and Deimos During the 1971 Opposition of Mars

    DTIC Science & Technology

    2014-10-06

    green circles Phobos, and blue triangles Deimos. is not as systematic as we could find from USNO Jupiter ob- servations (Robert et al. 2011) or USNO...important for the large-scale system of Jupiter and Saturn (Robert 2011). In the present work, we found an overall rms (O-C) of about 50 mas, that is to

  1. 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.

  2. 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.

  3. Gaia, an all sky astrometric and photometric survey

    NASA Astrophysics Data System (ADS)

    Carrasco, J. M.

    2017-04-01

    Gaia space mission includes a low resolution spectroscopic instrument to classify and parametrize the observed sources. Gaia is a full-sky unbiased survey down to about 20th magnitude. The scanning law yields a rather uniform coverage of the sky over the full mission. The data reduction is a global one over the full mission. Both sky coverage and data reduction strategy ensure an unprecedented all-sky homogeneous spectrophotometric survey. Certainly, that survey is of interest for future on-ground and space projects (LSST, PLATO, EUCLID, ...). This work addresses the exploitation of the Gaia spectrophotometry as standard photometry reference through the discussion of the sky coverage, the spectrophotometric precision and the expected uncertainties of the synthetic photometry derived from the low resolution Gaia spectra and photometry.

  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.; 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.

  5. 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.

  6. 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.

  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. Astrometric Analysis of the Homunculus of eta Carinae With the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Currie, Douglas G.; Dowling, Daniel M.; Shaya, Edward J.; Hester, Jeff; Scowen, Paul; Groth, Edward J.; Lynds, Roger; O'neil, Earl J., Jr.; Wide Field/Planetary Camera Instrument Definition Team

    1996-09-01

    Images of η Carinae, obtained with the HST Wide Field/Planetary Camera in 1990 October (WFl), 1991 April (PC 1), and 1992 December (WF2) have been used to perform a detailed study of the proper motion of the homunculus of η Carinae. This analysis yields the plane-of-the-sky astrometric velocities which range from tens of kilometers per second to over 1000 kin/sec with estimated uncertainties on the order of 40 km/sec. Our primary conclusion from these astrometric measurements is that the motion of the homunculus of η Carinae is largely radial, increasing linearly with distance from the central star. We measure an average radial expansion rate of 0.66% per year. The deviations from a pure linear expansion are 12 mas and 17 mas for the PC 1 :WF2 and WFl :WF2 measurements, respectively. These deviations are the computed standard deviation from linear expansion. The deviation between the two comparisons is 12 mas. Thus we believe the deviations seen in the comparison pairs to be somewhat correlated, implying that some of the non-linearities in the expansion are real. Our direct measurements imply a single eruptive event centered in 1841.2±0.8 years (standard deviation of mean) or ±4 years when one includes some corrections in the error estimate for the correlated motions and relative plate scale errors. This agrees well with the historical "Great Eruption" which peaked in 1843. The motion of the individual fragments indicates "times of ejection" for the fragments occurred over an interval of less than 20 years. We include astrometric measurement of the North "Jet" containing the NN and NS knots and find the knots generally follow the linear radial expansion rate of the homunculus. The NN and NS knots are "bullets" emitted at the time of the eruption (or up to 10 years later), rather than a part of a continuing jet. Finally, we demonstrate that astrometric measurements of extended objects with the Hubble Space Telescope (pre- and post-repair) are feasible at the 5

  9. Iterative methods used in overlap astrometric reduction techniques do not always converge

    NASA Astrophysics Data System (ADS)

    Rapaport, M.; Ducourant, C.; Colin, J.; Le Campion, J. F.

    1993-04-01

    In this paper we prove that the classical Gauss-Seidel type iterative methods used for the solution of the reduced normal equations occurring in overlapping reduction methods of astrometry do not always converge. We exhibit examples of divergence. We then analyze an alternative algorithm proposed by Wang (1985). We prove the consistency of this algorithm and verify that it can be convergent while the Gauss-Seidel method is divergent. We conjecture the convergence of Wang method for the solution of astrometric problems using overlap techniques.

  10. Gaia's Cepheids and RR Lyrae stars and luminosity calibrations based on Tycho-Gaia Astrometric Solution

    NASA Astrophysics Data System (ADS)

    Clementini, Gisella; Eyer, Laurent; Muraveva, Tatiana; Garofalo, Alessia; Ripepi, Vincenzo; Marconi, Marcella; Sarro, Luis; Palmer, Max; Luri, Xavier; Molinaro, Roberto; Rimoldini, Lorenzo; Szabados, Laszlo; Anderson, Richard I.; Musella, Ilaria

    2017-09-01

    Gaia Data Release 1 contains parallaxes for more than 700 Galactic Cepheids and RR Lyrae stars, computed as part of the Tycho-Gaia Astrometric Solution (TGAS). We have used TGAS parallaxes, along with literature (V, I, J, Ks, W1) photometry and spectroscopy, to calibrate the zero point of the period-luminosity and period-Wesenheit relations of classical and type II Cepheids, and the near-infrared period-luminosity, period-luminosity-metallicity and optical luminosity-metallicity relations of RR Lyrae stars. In this contribution we briefly summarise results obtained by fitting these basic relations adopting different techniques that operate either in parallax or distance (absolute magnitude) space.

  11. Study of the true performance limits of the Astrometric Multiplexing Area Scanner (AMAS)

    NASA Technical Reports Server (NTRS)

    Frederick, L. W.; Mcalister, H. A.

    1975-01-01

    The Astrometric Multiplexing Area Scanner (AMAS) is an instrument designed to perform photoelectric long focus astrometry of small fields. Modulation of a telescope focal plane with a rotating Ronchi ruling produces a frequency modulated signal from which relative positions and magnitudes can be extracted. Evaluation instrumental precision, accuracy and resolution characteristics with respect to a variety of instrumental and cosmical parameters indicates 1.5 micron precision and accuracy for single stars under specific conditions. This value decreases for increased number of field stars, particularly for fainter stars.

  12. Modulation of brain activity during action observation: influence of perspective, transitivity and meaningfulness.

    PubMed

    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.

  13. 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,…

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

    ERIC Educational Resources Information Center

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

    2007-01-01

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

  15. 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,…

  16. The Influence of Publication Delays on the Observed Aging Distribution of Scientific Literature.

    ERIC Educational Resources Information Center

    Egghe, Leo; Rousseau, Ronald

    2000-01-01

    Discusses the influence of publication delays on the aging of scientific literature and explains how the undisturbed aging function and the publication delay combine to give the observed aging function through a mathematical operation called convolution. Shows the convolution of various distributions and considers a paradox between theory and real…

  17. The Astrometric Calibration of Hubble Space Telescope Fine Guidance Sensor 1r - Fringe Tracking

    NASA Astrophysics Data System (ADS)

    Benedict, G. F.; McArthur, B. E.; Nelan, E. P.; Jefferys, W. H.

    2001-05-01

    We report on our progress towards an astrometric calibration of Fine Guidance Sensor 1r, installed during an HST refurbishment mission a few years ago. The calibration of this space-based interferometer will complete the commissioning of FGS1r as a sub-milliarcsecond astrometric science instrument for Cycle 10 and all future HST cycles, and permit the final reduction and analysis of ~100 orbits of FGS1r data acquired by a variety of GO programs during HST Cycles 8 and 9. These calibration data were secured in December 2000. We map the optical field angle distortions of FGS1r to facilitate the goal of millisecond of arc precision astrometry for FGS1r's fringe tracking (Position) mode. Our results will populate the FGS1r calibration database and will be available to all FGS GOs through the use of STScI's calibration pipeline. A second result will be an improved M35 calibration field, one that takes into account proper motions in the catalog. This will allow for more accurate monitoring of the FGS1r plate scale and distortions during future HST cycles.

  18. 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.

  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. 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.

  1. 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

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

    PubMed

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

    1999-08-20

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

  4. Lysimeter vs. superconducting gravimeter: Measuring the influence of local water storage changes on temporal gravity observations.

    NASA Astrophysics Data System (ADS)

    Creutzfeldt, Benjamin; Güntner, Andreas; Wziontek, Hartmut

    2010-05-01

    Temporal gravimeter observations, which are used in geodesy and geophysics to study changes in the Earth's gravity field like tidal or mass transfer effects, are influenced by local water storage change (WSC). This study presents the first comparison of lysimeter measurements with temporal gravimeter observations made by a superconducting gravimeter (SG). Lysimeter measurements in combination with complementary hydrological observations and a rigid hydrological 1D model give the unique opportunity to estimate WSC from the snow down to the groundwater at the field scale. At the Geodetic Observatory Wettzell (Germany), water storage changes in the snow pack, top soil, unsaturated saprolite and fractured aquifer are all important terms for the local water budget. The hydrological influence on SG measurements is estimated by calculating the gravity response of local WSC. We find a high correlation of local WSC and SG residuals on the event and seasonal scale. Lysimeter measurements significantly improve the estimation of WSC on the field scale and consequently provide a better reduction of local hydrological influence on temporal gravimeter measurements. Hence, at temporal gravity observation sites a lysimeter installation is recommended in case that the gravity signal should be reduced from local WSC.

  5. Incoherent pion photoproduction on the deuteron with polarization observables. II. Influence of final state rescattering

    NASA Astrophysics Data System (ADS)

    Fix, A.; Arenhövel, H.

    2005-12-01

    Incoherent pion photoproduction on the deuteron is studied for photon energies from threshold up to 1 GeV, with special emphasis on polarization observables. The elementary γN→πN amplitude is taken from the MAID model. We investigate the influence of final state interactions on total and semi-exclusive cross sections d→(γ→,π)NN by including complete rescattering in the final NN and πN subsystems. For charged-pion production the influence of NN rescattering is moderate whereas πN rescattering is almost negligible. Much stronger influences of NN rescattering are seen in neutral-pion production, which are due to the elimination of a significant spurious coherent contribution in the impulse approximation. Sizable effects are also found in some of the beam, target, and beam-target asymmetries of the differential cross section.

  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. 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

  8. Influences on the use of observational methods by practitioners when identifying risk factors in physical work.

    PubMed

    Diego-Mas, Jose-Antonio; Poveda-Bautista, Rocio; Garzon-Leal, Diana-Carolina

    2015-01-01

    Most observational methods for musculoskeletal disorder risk assessment have been developed by researchers to be applied in specific situations, and practitioners could find difficulties in their use in real-work conditions. The main objective of this study was to identify the factors which have an influence on how useful the observational techniques are perceived to be by practitioners and to what extent these factors influence their perception. A survey was conducted on practitioners regarding the problems normally encountered when implementing these methods, as well as the perceived overall utility of these techniques. The results show that practitioners place particular importance on the support the methods provide in making decisions regarding changes in work systems and how applicable they are to different types of jobs. The results of this study can serve as guide to researchers for the development of new assessment techniques that are more useful and applicable in real-work situations.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  10. 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.

  11. Brassboard Astrometric Beam Combiner (ABC) development for the Space Interferometry Mission (SIM)

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  13. 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.

  14. 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.

  15. Multi-dimensional Quasar Selection from Optical, Near-IR, and Astrometric Data

    NASA Astrophysics Data System (ADS)

    Richards, Gordon T.; Mehta, S. S.; Peters, C. M.; Myers, A. D.; Ross, N. P.

    2012-01-01

    In the future, quasar selection will be much more multi-dimensional than it is today. Algorithms will go far beyond simple optical color or variability selection. Instead quasar selection will rely on simultaneous usage of multi-wavelength photometry, variability, and even astrometry. The SDSS Southern Equatorial Stripe (aka Stripe 82) is an ideal proving ground for such future algorithms. Herein we take the first steps in true multi-dimensional analysis by describing an algorithm that uses multi-epoch optical data from the SDSS, near-IR data from UKIDSS, and astrometric information to select quasars (and determine photometric redshifts). We present the resulting catalog and compare our results to existing spectroscopic surveys.

  16. Accurate Mass Determination of the Ancient White Dwarf ER 8 Through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2005-07-01

    We propose to determine the mass of the very cool white dwarf ER 8 through astrometric microlensing. We have predicted that ER 8 will pass very close to a 15th-mag background star in January 2006, with an impact parameter of less than 0.05 arcsec. As it passes in front, it will cause a deflection of the background star's image by >8 milliarcsec, an amount easily detectable with HST/FGS. The gravitational deflection angle depends only on the distances and relative positions of the stars, and on the mass of the white dwarf. Since the distances and positions can be determined precisely before the event, the astrometric measurement offers a unique and direct method to measure the mass of the white dwarf to high accuracy {<5%}. Unlike all other stellar mass determinations, this technique works for single stars {but only if they are nearby and of sufficient mass}. The mass of ER 8 is of special interest because it is a member of the Galactic halo, and appears to be the oldest known field white dwarf. This object can thus set a lower limit on the age of the Galactic halo, but since white-dwarf cooling rates depend on their masses, the mass is a necessary ingredient in the age determination. As a byproduct, we will obtain an accurate parallax for ER 8, and thus its luminosity and {from its effective temperature} its radius. Such quantities are at present rather poorly known for the coolest white dwarfs, and will provide strong constraints on white-dwarf physics.

  17. Accurate Mass Determination of the Ancient White Dwarf ER 8 Through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2004-07-01

    We propose to determine the mass of the very cool white dwarf ER 8 through astrometric microlensing. We have predicted that ER 8 will pass very close to a 15th-mag background star in January 2006, with an impact parameter of less than 0.05 arcsec. As it passes in front, it will cause a deflection of the background star's image by >8 milliarcsec, an amount easily detectable with HST/FGS. The gravitational deflection angle depends only on the distances and relative positions of the stars, and on the mass of the white dwarf. Since the distances and positions can be determined precisely before the event, the astrometric measurement offers a unique and direct method to measure the mass of the white dwarf to high accuracy {<5%}. Unlike all other stellar mass determinations, this technique works for single stars {but only if they are nearby and of sufficient mass}. The mass of ER 8 is of special interest because it is a member of the Galactic halo, and appears to be the oldest known field white dwarf. This object can thus set a lower limit on the age of the Galactic halo, but since white-dwarf cooling rates depend on their masses, the mass is a necessary ingredient in the age determination. As a byproduct, we will obtain an accurate parallax for ER 8, and thus its luminosity and {from its effective temperature} its radius. Such quantities are at present rather poorly known for the coolest white dwarfs, and will provide strong constraints on white-dwarf physics.

  18. Seeing or doing? Influence of visual and motor familiarity in action observation.

    PubMed

    Calvo-Merino, Beatriz; Grèzes, Julie; Glaser, Daniel E; Passingham, Richard E; Haggard, Patrick

    2006-10-10

    The human brain contains specialized circuits for observing and understanding actions. Previous studies have not distinguished whether this "mirror system" uses specialized motor representations or general processes of visual inference and knowledge to understand observed actions. We report the first neuroimaging study to distinguish between these alternatives. Purely motoric influences on perception have been shown behaviorally, but their neural bases are unknown. We used fMRI to reveal the neural bases of motor influences on action observation. We controlled for visual and knowledge effects by studying expert dancers. Some ballet moves are performed by only one gender. However, male and female dancers train together and have equal visual familiarity with all moves. Male and female dancers viewed videos of gender-specific male and female ballet moves. We found greater premotor, parietal, and cerebellar activity when dancers viewed moves from their own motor repertoire, compared to opposite-gender moves that they frequently saw but did not perform. Our results show that mirror circuits have a purely motor response over and above visual representations of action. We understand actions not only by visual recognition, but also motorically. In addition, we confirm that the cerebellum is part of the action observation network.

  19. How the choice of the observable may influence the analysis of nonlinear dynamical systems

    NASA Astrophysics Data System (ADS)

    Letellier, Christophe; Aguirre, Luis; Maquet, Jean

    2006-08-01

    A great number of techniques developed for studying nonlinear dynamical systems start with the embedding, in a d-dimensional space, of a scalar time series, lying on an m-dimensional object, d > m. In general, the main results reached at are valid regardless of the observable chosen. In a number of practical situations, however, the choice of the observable does influence our ability to extract dynamical information from the embedded attractor. This may arise in standard problems in nonlinear dynamics such as model building, control theory and synchronization. To some degree, ease of success will thus depend on the choice of observable simply because it is related to the observability of the dynamics. Investigating the Rössler system, we show that the observability matrix is related to the map between the original phase space and the differential embedding induced by the observable. This paper investigates a form for the observability matrix for nonlinear system which is more general than the previous one used. The problem of controllability is also mentioned.

  20. [Observations upon some factors which influence the laboratory maintenance of Schistosoma mansoni (author's transl)].

    PubMed

    De Souza, C P; Dias, E P; De Azevedo, M D; Paulini, E

    1979-12-01

    Schistosoma mansoni has been maintained in the laboratory using a laboratory strain of B. glabrata, white mice (Mus musculus) and golden hamster (Cricetus auratus). Observations were collected during five consecutive years and the results were analysed for factors which might have influenced them. The analysis has shown that--(1) snail mortalities were independent of the relatively small variation in temperature and of the mean number of miracidia used for infection; (2) rate of infection of snails increased slowly with the increase of the mean number of miracidia; (3) the temperature was in reciprocal proportion with the logarithm of the cercarial development period; (4) the yield of viable eggs has increased steadily in white mice during the observation period; (5) significant increase of egg production was observed in golden hamsters when subcutaneous route of inoculation was used instead of inoculation through the alimentary pouch.

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

    PubMed

    Mancuso, Salvatore; Giordano, Silvio

    2013-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

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

  3. Influences of sea ice on the Eastern Bering Sea: NCAR CESM simulations and comparison with observations

    NASA Astrophysics Data System (ADS)

    Cheng, Wei; Curchitser, Enrique; Ladd, Carol; Stabeno, Phyllis; Wang, Muyin

    2014-11-01

    We examine the influences of sea ice on the Eastern Bering Sea (EBS) regional oceanography on seasonal and inter-annual time scales using the National Center for Atmospheric Research-Community Earth System Model (NCAR CESM) simulations, comparing the modeling results with satellite and in situ observations when possible. While the modeled mean seasonal cycle of ice cover in the EBS middle shelf is generally within the uncertainty range of satellite observations, in the northern domain (north of 59°N), the simulation reaches its annual maximum in April instead of in March, as observed by satellite remote sensing; modeled ice reduction in late spring in the region is also slower than observations. Despite this bias, the simulation captures the observed seasonal transit of freshwater from the north to the south via ice advection; en route, the sea ice melts, cooling and freshening the local water column. On inter-annual time scales, modeling results suggest that extensive ice cover persisting into spring in the central EBS leads to cold anomalies in the bottom water, especially on the middle and inner shelves of the southern domain. The corresponding salinity anomalies are positive in the northern coastal domain, and weak but negative in the southern middle shelf. The associated 10-m ocean current anomalies are southward on the shelf and directed offshore in the slope region. Comparing years 1961-2005 versus years 2005-2050, the Probability Distribution Function of ice cover on the EBS middle shelf shifts northward by ~2° latitude.

  4. Observing and engaging in purposeful actions with objects influences estimates of their size.

    PubMed

    Wesp, Richard; Cichello, Paula; Gracia, Erica B; Davis, Kathryn

    2004-11-01

    A ladle was recalled as being taller by participants who observed tedious removal of sand from it with a small teaspoon than by those who observed removal with a larger spoon. A second experiment showed that the number of darts thrown in order to hit a target correlated negatively with memory estimates of the size of the target, a finding replicated in a third experiment with size estimates made while the target was visible. The first two experiments suggest that the way an object is used can influence memory of its size. The third experiment supports the hypothesis that in vivo size estimation of familiar objects may employ a mechanism that derives size from memory and that size memory can be distorted by the way an object was used.

  5. 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. © 2015 The British Psychological Society.

  6. 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.

  7. 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.

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

    PubMed

    Verrel, Julius; Lisofsky, Nina; Kühn, Simone

    2014-07-01

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

  9. Factors influencing the length of hospitalisation in intensive care units: a prospective observational study.

    PubMed

    Vacca, Franca; Vaiani, Monica; Messori, Andrea; Trippoli, Sabrina; Maltoni, Susanna; Pelaotti, Filippo; Santarlasci, Benedetta; Bardelli, Filippo

    2004-10-01

    The length of stay (LOS) in patients admitted to intensive care units (ICUs) is influenced by the clinical history of the patient, so the main factors affecting clinical outcome are logical candidates to be predictors of LOS. Since there is still limited information about which factors can influence LOS in these patients, we undertook this observational study in Italian hospitals. From 1 August to 31 October 2001 we enrolled a maximum of 10 consecutive patients admitted to ICUs in 16 Italian hospitals. The following information was recorded from each patient: date of admission; APACHE II score on admission; active sepsis and/or septic shock on admission; sepsis and/or septic shock developed during the stay in ICU; Glasgow coma scale on the third day; date and clinical outcome upon discharge from the hospital (alive or dead). In the study 131 patients were enrolled; 31 (23.7%) had active sepsis upon admission to ICU and 10 (7.6%) had septic shock; 12 (9.2%) developed sepsis during hospitalization and 12 (9.2%) developed septic shock. At the end of the study, 101 patients were alive and 30 had died. The overall mean LOS was 12 days. The mean LOS was 18.3 days for the subgroup with sepsis and 8.3 days in the subgroup without sepsis. Sepsis was the only factor that significantly influenced the LOS (P = 0.016). Our study was aimed to analyse the factors that influence the LOS in ICU patients and found that among the variables that affected LOS, sepsis had the greatest impact. Other studies had evaluated the impact of some variables on LOS and identified sepsis and infection as a determinant prolonging LOS.

  10. Angle of Observation Influence on Emission Signal from Spatially Confined Laser-Induced Plasmas.

    PubMed

    Weiss, Jiri; Cabalín, Luisa Maria; Laserna, J Javier

    2017-01-01

    The present work focuses on the influence of the angle of observation on the emission signal from copper plasmas. Plasma plumes have been generated inside a home-made chamber consisting of two parallel glass windows spaced by 2.5 mm. This chamber allows observing plasma plumes from different collection angles throughout their perimeter, spanning from 20° to 80° with respect to the surface of the Cu target. In order to minimize the observed volume of the plasma, measurements were made from the closest distance possible through a metallic hollow tube. Single-pulse and collinear double-pulse excitation schemes with a Nd:YAG laser (1064 nm, 5 ns) have been investigated. The results have shown that the selection of the best angle to collect light from the plasma is related to the excitation mode. On the other hand, the shot-to-shot signal variability has been found to depend on the shape of plasma plumes. In single-pulse excitation, a good correlation between the observed laser-induced breakdown spectroscopy (LIBS) emission (from spatially confined plumes) and their integrated signal of plasma image has been ascertained. However, this fact was less evident in double-pulse LIBS, which could be due to a different mechanism involved in the ablation process.

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

    PubMed Central

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

    2016-01-01

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

  12. Investigating nonlinear dynamics from time series: The influence of symmetries and the choice of observables

    NASA Astrophysics Data System (ADS)

    Letellier, Christophe; Aguirre, Luis A.

    2002-09-01

    When a dynamical system is investigated from a time series, one of the most challenging problems is to obtain a model that reproduces the underlying dynamics. Many papers have been devoted to this problem but very few have considered the influence of symmetries in the original system and the choice of the observable. Indeed, it is well known that there are usually some variables that provide a better representation of the underlying dynamics and, consequently, a global model can be obtained with less difficulties starting from such variables. This is connected to the problem of observing the dynamical system from a single time series. The roots of the nonequivalence between the dynamical variables will be investigated in a more systematic way using previously defined observability indices. It turns out that there are two important ingredients which are the complexity of the coupling between the dynamical variables and the symmetry properties of the original system. As will be mentioned, symmetries and the choice of observables also has important consequences in other problems such as synchronization of nonlinear oscillators.

  13. Observation

    ERIC Educational Resources Information Center

    Helfrich, Shannon

    2016-01-01

    Helfrich addresses two perspectives from which to think about observation in the classroom: that of the teacher observing her classroom, her group, and its needs, and that of the outside observer coming into the classroom. Offering advice from her own experience, she encourages and defends both. Do not be afraid of the disruption of outside…

  14. Observations

    ERIC Educational Resources Information Center

    Joosten, Albert Max

    2016-01-01

    Joosten begins his article by telling us that love and knowledge together are the foundation for our work with children. This combination is at the heart of our observation. With this as the foundation, he goes on to offer practical advice to aid our practice of observation. He offers a "List of Objects of Observation" to help guide our…

  15. 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

  16. Canopy structural complexity influences forest canopy reflectance: linking terrestrial lidar with Landsat observations

    NASA Astrophysics Data System (ADS)

    Hardiman, B. S.; Atkins, J.; Dahlin, K.; Fahey, R. T.; Gough, C. M.

    2016-12-01

    Canopy physical structure - leaf quantity and arrangement - strongly affects light interception and distribution. As such, canopy physical structure is a key driver of forest carbon (C) dynamics. Terrestrial lidar systems (TLS) provide spatially explicit, quantitative characterizations of canopy physical structure at scales commensurate with plot-scale C cycling processes. As an example, previous TLS-based studies established that light use efficiency is positively correlated with canopy physical structure, influencing the trajectory of net primary production throughout forest development. Linking TLS measurements of canopy structure to multispectral satellite observations of forest canopies may enable scaling of ecosystem C cycling processes from leaves to continents. We will report on our study relating a suite of canopy structural metrics to well-established remotely sensed measurements (NDVI, EVI, albedo, tasseled cap indices, etc.) which are indicative of important forest characteristics (leaf area, canopy nitrogen, light interception, etc.). We used Landsat data, which provides observations at 30m resolution, a scale comparable to that of TLS. TLS data were acquired during 2009-2016 from forest sites throughout Eastern North America, comprised primarily of NEON and Ameriflux sites. Canopy physical structure data were compared with contemporaneous growing-season Landsat data. Metrics of canopy physical structure are expected to covary with forest composition and dominant PFT, likely influencing interaction strength between TLS and Landsat canopy metrics. More structurally complex canopies (those with more heterogeneous distributions of leaf area) are expected to have lower albedo, suggesting greater canopy light absorption (higher fAPAR) than simpler canopies. We expect that vegetation indices (NDVI, EVI) will increase with TLS metrics of spatial heterogeneity, and not simply quantity, of leaves, supporting our hypothesis that canopy light absorption is

  17. Current problems of dynamics of moons of planets and binary asteroids based on observations

    NASA Astrophysics Data System (ADS)

    Emel'yanov, N. V.

    2017-01-01

    The general approach to studying the dynamics of moons of planets and asteroids consists in developing more and more accurate models of motion based on observational data. Not only the necessary ephemerides, but also some physical parameters of planets and moons are obtained this way. It is demonstrated in the present study that progress in this field is driven not only by the increase in accuracy of observations. The accuracy of ephemerides may be increased by expanding the observation time interval. Several problems arise on the way toward this goal. Some of them become apparent only when the procedure of observational data processing and use is examined in detail. The method used to derive astrometric data by processing the results of photometric observations of mutual occultations and eclipses of planetary moons is explained below. The primary contribution to the error of astrometric results is produced by the unaccounted noise level in photometric readings and the inaccuracy of received values of the albedo of moons. It is demonstrated that the current methods do not allow one to eliminate the noise completely. Extensive additional photometric measurements should be performed at different angles of rotation of moons and in different spectral bands of the visible wavelength range in order to obtain correct values of the albedo of moons. Many new distant moons of the major planets have been discovered in the early 21st century. However, the observations of these moons are scarce and were performed over short time intervals; as a result, some of the moons were lost. The necessity of further observations of these Solar System bodies is pointed out in the present study. Insufficient knowledge of asteroid masses is an obstacle to improving the accuracy of the ephemerides of Mars. The basic method for determining the masses of large asteroids consists in analyzing their influence on the motion of Mars, the Earth, and spacecraft. The masses of more than 100 large

  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 the hadronic phase on observables in ultrarelativistic heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Steinheimer, J.; Aichelin, J.; Bleicher, M.; Stöcker, H.

    2017-06-01

    The hadronic phase in ultrarelativistic nuclear collisions has a large influence on final state observables like multiplicity, flow, and pt spectra, as studied in the UrQMD approach. In this model one assumes that a nonequilibrium decoupling phase follows a fluid dynamical description of the high density phase. Hadrons are produced assuming local thermal equilibrium and dynamically decouple during the hadronic rescattering until the particles are registered in the detectors. This rescattering of hadrons modifies every hadronic bulk observable. The apparent multiplicity of resonances is suppressed as compared to a chemical equilibrium freeze-out model, because the decay products rescatter. Therefore the resonances, which decay in the early hadronic phase, cannot be identified anymore by the invariant mass method. Stable and unstable particles change their momentum distribution by more than 30 % through rescattering and their multiplicity is modified by resonance production and annihilation on a similar magnitude. These findings show that it is all but trivial to conclude from the final state observables on the properties of the system at an earlier time where it may have been in local equilibrium.

  1. 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.

  2. First experimental results of very high accuracy centroiding measurements for the neat astrometric mission

    NASA Astrophysics Data System (ADS)

    Crouzier, A.; Malbet, F.; Preis, O.; Henault, F.; Kern, P.; Martin, G.; Feautrier, P.; Stadler, E.; Lafrasse, S.; Delboulbé, A.; Behar, E.; Saint-Pe, M.; Dupont, J.; Potin, S.; Cara, C.; Donati, M.; Doumayrou, E.; Lagage, P. O.; Léger, A.; LeDuigou, J. M.; Shao, M.; Goullioud, R.

    2013-09-01

    NEAT is an astrometric mission proposed to ESA with the objectives of detecting Earth-like exoplanets in the habitable zone of nearby solar-type stars. NEAT requires the capability to measure stellar centroids at the precision of 5e-6 pixel. Current state-of-the-art methods for centroid estimation have reached a precision of about 2e-5 pixel at two times Nyquist sampling, this was shown at the JPL by the VESTA experiment. A metrology system was used to calibrate intra and inter pixel quantum efficiency variations in order to correct pixelation errors. The European part of the NEAT consortium is building a testbed in vacuum in order to achieve 5e-6 pixel precision for the centroid estimation. The goal is to provide a proof of concept for the precision requirement of the NEAT spacecraft. In this paper we present the metrology and the pseudo stellar sources sub-systems, we present a performance model and an error budget of the experiment and we report the present status of the demonstration. Finally we also present our first results: the experiment had its first light in July 2013 and a first set of data was taken in air. The analysis of this first set of data showed that we can already measure the pixel positions with an accuracy of about 1e-4 pixel.

  3. Tycho-Gaia Astrometric Solution parallaxes and proper motions for 5 Galactic globular clusters

    NASA Astrophysics Data System (ADS)

    Watkins, Laura L.; Van Der Marel, Roeland P.

    2017-06-01

    The Tycho-Gaia Astrometric Solution (TGAS) catalogue from Gaia Data Release 1 provided proper motions (PMs) and parallax estimates for over 2 million stars in the Tycho2 catalogue. Although this catalogue provides PMs for only a very small fraction of stars, compared with the expected catalogues from later data releases, already TGAS has been used to study parallaxes and PMs for a variety of objects in the Local Group. I will present results from our recent pilot in which we searched the TGAS catalogue for stars in Galactic globular clusters (GCs). We identified a total of 20 member stars across 5 GCs -- NGC 104 (47 Tucanae), NGC 5272 (M3), NGC 6121 (M4), NGC 6397, and NGC 6656 (M22) -- and used them to estimate parallaxes (and hence distances) to the clusters, along with their global proper motions. Combined with literature line-of-sight velocities, we also calculated full space motions for the clusters. I will outline the membership selection process and discuss the subsequent space-motion analysis. I will also compare our PM results to both previous Hubble Space Telescope and ground-based estimates. Our Gaia results compare very well, and highlight the amazing potential of future Gaia data releases.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  8. The influence of the Great East Japan earthquake on microscopic polyangiitis: A retrospective observational study.

    PubMed

    Takeuchi, Yoichi; Saito, Ayako; Ojima, Yoshie; Kagaya, Saeko; Fukami, Hirotaka; Sato, Hiroyuki; Matsuda, Ken; Nagasawa, Tasuku

    2017-01-01

    Antineutrophil cytoplasmic antibody-associated vasculitis is triggered by environmental factors, including silica dust exposure. Repeated tsunami waves brought a large volume of silica-containing sludge inland after the Great East Japan earthquake in 2011. We aimed to determine if the serious disaster influenced the clinical features of the microscopic polyangiitis. This is an observational retrospective study conducted in a single institute. A total of 43 patients were included based on the CHCC2012 criteria for microscopic polyangiitis from 2007 to 2015. We used the Poisson regression model to determine the incidence of microscopic polyangiitis within the annual population of the medical district. The participants were selected during a 3-year period from before (N = 13) to after the disaster (N = 20). The differences of parameters and the overall survival between the groups were analyzed. The incidence of microscopic polyangiitis increased after the disaster (λ = 17.4/million/year [95%CI: 7.66-39.6] before the disaster and λ = 33.1/million/year [17.7-61.7] after the disaster, P = 0.044). A high Birmingham Activity Score was associated with a high incidence of microscopic polyangiitis after the disaster. The overall survival of the patients with microscopic polyangiitis declined significantly after the disaster. The Great East Japan earthquake influenced the development of the microscopic polyangiitis in our restricted area. The patients who developed after the disaster had severe symptoms and a high mortality rate.

  9. 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.

  10. 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

  11. An Illustration of the Influence of John Schaake on Modern Hydroclimatological Observation Networks

    NASA Astrophysics Data System (ADS)

    Burges, S. J.; Sieck, L. C.; Steiner, M.

    2001-12-01

    John Schaake made seminal contributions to many aspects of hydrologic science individually and through his leadership role at the National Weather Service Office of Hydrology. His work extends from detailed measurement of rainfall and the resulting flow from parking areas, to disaggregation of rainfall, to continental-scale hydroclimatology, particularly in the context of GEWEX-GCIP. He has been a strong supporter of the development of the hydrologic modeling and measurement systems that can make maximum use of remotely sensed information from space based platforms and NEXRAD radar. He has been a career-long supporter of younger colleagues and his enthusiasm has inspired many to make advances to the field that might not have otherwise been made. We illustrate some of the breadth of his influence on today's hydroclimatological observing systems and research using features of a major storm system that stretched from the US-Mexico border to the US-Canada border in late April 2001.

  12. Observation

    ERIC Educational Resources Information Center

    Patell, Hilla

    2016-01-01

    In order to achieve the goal of observation, preparation of the adult, the observer, is necessary. This preparation, says Hilla Patell, requires us to "have an appreciation of the significance of the child's spontaneous activities and a more thorough understanding of the child's needs." She discusses the growth of both the desire to…

  13. Observation

    ERIC Educational Resources Information Center

    Kripalani, Lakshmi A.

    2016-01-01

    The adult who is inexperienced in the art of observation may, even with the best intentions, react to a child's behavior in a way that hinders instead of helping the child's development. Kripalani outlines the need for training and practice in observation in order to "understand the needs of the children and...to understand how to remove…

  14. The influence of comorbidities on mortality in sarcoidosis: a observational prospective cohort study.

    PubMed

    Nowiński, Adam; Puścińska, Elzbieta; Goljan, Anna; Peradzynska, Joanna; Bednarek, Michal; Korzybski, Damian; Kamiński, Dariusz; Stokłosa, Anna; Czystowska, Monika; Śliwiński, Pawel; Górecka, Dorota

    2017-09-01

    The aim of this study was to identify the frequency and prevalence of comorbidities in sarcoid patients and to assess their influence on overall mortality in the cohort of patients with sarcoidosis. A cohort of 557 patients with histologically confirmed sarcoidosis diagnosed between 2007 and 2011 and a group of non-sarcoid controls were observed. All patients were carefully observed for comorbidities and mortality. 291 males (52.2%) and 266 females (47.8%) with mean age 48.4 ± 12.0 years in sarcoidosis group and a group of 100 controls with mean age (49.25 ± 10.3) were observed. The mean number of comorbidities in both groups was similar (0.9 ± 0.99 vs 0.81 ± 0.84 NS). The frequency of thyroid disease was significantly higher in sarcoidosis group comparing to controls at the time of diagnosis (OR = 3.62 P = 0.0144). During the observation period (median 58.0 months), 16 patients died (2.9%). The mean number of comorbidities was significantly higher in the groups of non-survivors as compared to survivors (2.8 ± 1.0, vs 0.8 ± 0.9), P < 0.0001. The comorbidity burden has strong impact on mortality in sarcoidosis. Thyroid diseases are more frequent in sarcoidosis than in non-sarcoid controls. © 2015 John Wiley & Sons Ltd.

  15. Noise peaks influence communication in the operating room. An observational study.

    PubMed

    Keller, Sandra; Tschan, Franziska; Beldi, Guido; Kurmann, Anita; Candinas, Daniel; Semmer, Norbert K

    2016-12-01

    Noise peaks are powerful distractors. This study focuses on the impact of noise peaks on surgical teams' communication during 109 long abdominal surgeries. We related measured noise peaks during 5-min intervals to the amount of observed communication during the same interval. Results show that noise peaks are associated with less case-relevant communication; this effect is moderated by the level of surgical experience; case-relevant communications decrease under high noise peak conditions among junior, but not among senior surgeons. However, case-irrelevant communication did not decrease under high noise level conditions, rather there was a trend to more case-irrelevant communication under high noise peaks. The results support the hypothesis that noise peaks impair communication because they draw on attentional resources rather than impairing understanding of communication. As case-relevant communication is important for surgical performance, exposure to high noise peaks in the OR should be minimised especially for less experienced surgeons. Practitioner Summary: This study investigated whether noise during surgeries influenced the communication within surgical teams. During abdominal surgeries, noise levels were measured and communication was observed. Results showed that high noise peaks reduced the frequency of patient-related communication, but did not reduce patient-irrelevant communication. Noise may negatively affect team coordination in surgeries.

  16. Observations of the Influence of Protons on Argon Z-pinches

    NASA Astrophysics Data System (ADS)

    Coleman, Philip; Bixler, Alex; Knight, Jason; Krishnan, Mahadevan; Lee, Susan; Parks, Donald; Thompson, John; Wilson, Kristi

    2004-11-01

    Recent observations [Ref.1] showed that a low level of a H2S tracer could dramatically reduce the K-shell x-ray output of a double ``shell'' argon z-pinch. When the 5% (by partial pressure) H2S tracer was used in the outer gas plenum, the K-shell yield was reduced by about 30%. When the tracer was used in the inner gas plenum, the K-yield reduction was over 350%. Comparable tracers containing chlorine but not hydrogen have not had such an effect. Thus the data suggest that it is the presence of about 1 proton per 20 argon atoms, if concentrated near the pinch axis, that can strongly influence the pinch behavior. An understanding of the mechanism for this may enhance overall understanding of z-pinch dynamics. The data also suggest that extraneous sources of protons must be controlled to prevent inadvertent degradation in the z-pinch's implosion. We report here additional observations and analysis of this effect. The tests, conducted on the Double-EAGLE simulator at ˜3.5 MA peak current, utilized a large 12 cm diameter double-shell nozzle that was designed for use with the 300 ns rise-time pulse of the DECADE QUAD (DQ) pulsed power machine. * Work supported by the U. S. Defense Threat Reduction Agency. 1. P.L.Coleman, et.al., BEAMS 2004 Conference Proceedings, July 2004.

  17. 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

  18. Influence of the display monitor on observer performance in detection of dental caries.

    PubMed

    Esmaeili, Farzad; Balaei, Esrafil; Pouralibaba, Firoz; Kaviani, Farzaneh; Kashefimehr, Atabak

    2007-01-01

    Digital imaging continues to gain acceptance in dentistry and video display used for this becomes important. The aim of this study was to assess the influence of the display monitor on observer performance on caries detection. Artificial enamel lesions were created in 40 extracted teeth at random using 1/4 and 1/2 round burs. Teeth were mounted in dental stone blocks to simulate a hemi-dentition. Approximate exposures were recorded at 70 kVp using a Planmeca (Planmeca Co, Helsinki, Finland) digital imaging system. Three oral and maxillofacial radiologists rated each image on a five-point scale for the presence or absence of lesion. Radiographic images were viewed on the following monitors: (1) LG Flatron 700p (LG Electronics Co., South Korea); (2) Samsung Magicgreen (Samsung Electronics Corp., South Korea); (3) Hansol 710p (Hansol Electronics Corp., South Korea) and (4) Toshiba satellite laptop (Toshiba Computer Corp., Philippines). Examiners were allowed to magnify and adjust density and contrast of each image at will. Receiver Operating Characteristic (ROC) analysis was performed. Data was subjected to repeated measures analysis of variance and ordinal logistic regression to test for significance between variables and to determine odds ratios. Mean ROC curve areas ranged from 0.8728 for the LG monitor to 0.8395 for the Samsung. Repeated measures analysis of variance showed significant differences between observers (P<0.0001), lesion size (P<0.0001), examiner/monitor interaction (P<0.033) and examiner/block interaction (P<0.013). However, no significant difference was found between monitors. This study suggests that observer performance is independent of the visual characteristics of the display monitor.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  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. Satellite observations of fog over Indo-Gangetic Plains and its influence on solar irradiance

    NASA Astrophysics Data System (ADS)

    Kharol, Shailesh Kumar; Rani Sharma, Anu; Kvs, Badarinath; Roy, P. S.

    Every year, the Northern region of India, especially the Indo-Gangetic Plains (IGPs) region ex-perience severe fog conditions during winter season due to typical meteorological, environmental and prevailing terrain conditions. The IGP region is highly influenced by western disturbances during winter season, which provide ideal conditions for accumulation of pollutants within the boundary layer and often results in fog formation. The formation of fog over IGPs is believed to create numerous health hazards, economic loss and cross-country transportation of aerosols. The fog is also expected to have impact on agriculture, general economy, global and regional climate. It has attracted the global scientific community attention to address the uncertainties pertaining to its formation and physico-chemical properties. The increase in aerosol concen-tration in the lower atmosphere due to biomass-burning events and anthropogenic activities provides more fog formation with water vapor present in atmosphere over IGP region. In the present study, we made an attempt to study the fog conditions that occurred over North In-dian region and long range transport of aerosols from fog region towards southern region during November, 2008 using multi-satellite data sets and ground based observations on aerosol prop-erties and solar irradiance at urban region of Hyderabad, India. False Color Composites (FCC) of IRS-P6 AWiFS, IRS-P4 OCM and Terra/Aqua MODIS images showed an intense fog/aerosol layer over IGP region on 07th -09th November, 2008. The Terra/Aqua MODIS AOD500 and OMI-AI observations showed high values over IGP region due to fog layer and long range trans-port of aerosols from IGP to Southern Indian region. CALIPSO LIDAR observation showed thick layer of fog/aerosols up to above northern/central Indian region with thickness ranging from 1.5 to 3 Kms. NCEP temperature anomaly variation at 700 hPa showed higher values over IGP region attributed upper atmospheric heating due to

  3. 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.

  4. Quantitative assessments of mantle flow models against seismic observations: Influence of uncertainties in mineralogical parameters

    NASA Astrophysics Data System (ADS)

    Schuberth, Bernhard S. A.

    2017-04-01

    synthetic traveltime data can then be compared - on statistical grounds - to the traveltime variations observed on Earth. Here, we now investigate the influence of uncertainties in the various input parameters that enter our modelling. This is especially important for the material properties at high pressure and high temperature entering the mineralogical models. In particular, this concerns uncertainties that arise from relating measurements in the laboratory to Earth properties on a global scale. As one example, we will address the question on the influence of anelasticity on the variance of global synthetic traveltime residuals. Owing to the differences in seismic frequency content between laboratory measurements (MHz to GHz) and the Earth (mHz to Hz), the seismic velocities given in the mineralogical models need to be adjusted; that is, corrected for dispersion due to anelastic effects. This correction will increase the sensitivity of the seismic velocities to temperature variations. The magnitude of this increase depends on absolute temperature, frequency, the frequency dependence of attenuation and the activation enthalpy of the dissipative process. Especially the latter two are poorly known for mantle minerals and our results indicate that variations in activation enthalpy potentially produce the largest differences in temperature sensitivity with respect to the purely elastic case. We will present new wave propagation simulations and corresponding statistical analyses of traveltime measurements for different synthetic seismic models spanning the possible range of anelastic velocity conversions (while being based on the same mantle circulation model).

  5. 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

  6. 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

  7. Longitudinal observation of influence of "taspo" on smoking behavior among high school students.

    PubMed

    Miyajima, Sayo; Fukuda, Yoshiharu; Yoshimi, Itsuro; Hayashi, Kenji

    2010-08-01

    A system with an adult discrimination IC card "taspo" was introduced in 2008 to prevent minors from purchasing cigarettes in Japan. This study aimed to elucidate the short-term change in smoking behavior among a cohort of high school students through the introduction of the taspo system. We conducted a questionnaire survey in students at one high school in the metropolitan area of Japan in 2008. In this area, the taspo system was introduced on July 1, and the survey was conducted before and after its introduction (June and September). Change in smoking behavior was examined by linking the two questionnaires using a unique identification number for each participant. The questionnaire included basic characteristics, smoking-related behavior, and means of obtaining tobacco. Of 133 students, 123 (response rate 84.7%) completed the before and after questionnaire forms and could be linked. The smoking rate was 22.8% in June and 25.2% in September, with no statistically significant change. Vending machines were the major means of obtaining tobacco in June, while the use of cigarette shops and supermarkets increased after the introduction of taspo. The introduction of taspo hardly influenced underage smoking behavior during the observation period in our study subjects. The only significant change was in the means of obtaining tobacco. To prevent underage smoking, the importance of comprehensive restriction of the procurement route was suggested.

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

    PubMed

    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.

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

    PubMed

    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.

  10. Atmospheric influence on a laser beam observed on the OICETS - ARTEMIS communication demonstration link

    NASA Astrophysics Data System (ADS)

    Löscher, A.

    2010-05-01

    In 2006 bi-directional optical inter-satellite communication experiments have been conducted between the Japan Aerospace Exploration Agency (JAXA) Optical Inter-orbit Communications Engineering Test Satellite (OICETS) and the European Space Agency (ESA) multi purpose telecommunications and technology demonstration satellite (Advanced Relay and Technology MISsion) ARTEMIS. On 5 April 2006 an experiment was successfully carried out maintaining the inter-satellite link during OICETS's setting behind the Earth limb until the signal was lost. This setup resembles an occultation observation where the influence of Earth's atmosphere is evident in the power fluctuations recorded at ARTEMIS's (and OICETS's) receiver. These fluctuations are not existing or at a low level at a link path above the atmosphere and steadily increase as OICETS sets behind the horizon until the tracking of the signal is lost. This specific experiment was performed only once since atmospheric science was not the goal of this demonstration. Nevertheless this kind of data, if available more frequently in future, can help to study atmospheric turbulence and validate respective models. The data presented here had been recorded at ARTEMIS.

  11. Atmospheric influence on a laser beam observed on the OICETS - ARTEMIS communication demonstration link

    NASA Astrophysics Data System (ADS)

    Löscher, A.

    2010-09-01

    In 2006 bi-directional optical inter-satellite communication experiments were conducted between the Japan Aerospace Exploration Agency (JAXA) Optical Inter-orbit Communications Engineering Test Satellite (OICETS) and the European Space Agency (ESA) multi-purpose telecommunications and technology demonstration satellite (Advanced Relay and Technology MISsion) ARTEMIS. On 5 April 2006, an experiment was successfully carried out by maintaining the inter-satellite link during OICETS's setting behind the Earth limb until the signal was lost. This setup resembles an occultation observation where the influence of Earth's atmosphere is evident in the power fluctuations recorded at ARTEMIS's (and OICETS's) receiver. These fluctuations do not exist or are at a low level at a link path above the atmosphere and steadily increase as OICETS sets behind the horizon until the tracking of the signal is lost. This specific experiment was performed only once since atmospheric science was not the goal of this demonstration. Nevertheless, this kind of data, if available more frequently in future, can help to study atmospheric turbulence and validate models. The data present here were recorded at ARTEMIS.

  12. The influence of program acceptability on the effectiveness of public health policy: a study of directly observed therapy for tuberculosis.

    PubMed Central

    Heymann, S J; Sell, R; Brewer, T F

    1998-01-01

    OBJECTIVES: This study examined how patient acceptability influences the effectiveness of directly observed therapy for tuberculosis. METHODS: Decision and sensitivity analyses were used in assessing influences. RESULTS: If mandatory directly observed therapy discourages 6% of initial tuberculosis patients (range: 4% to 10%) from seeking care, then such therapy will be less effective than self-administered therapy. Directly observed therapy is more effective than repeated self-administered therapy for patients failing to complete initial treatment unless 32% (range: 27% to 38%) of patients avoid seeking care. CONCLUSIONS: Patient acceptability must be taken into consideration before selecting public health strategies. PMID:9518978

  13. Spacecraft observations of NEOs: a Mars Express demonstration

    NASA Astrophysics Data System (ADS)

    Duxbury, Thomas; Roatsch, Thomas; Jaumann, Ralf; Hoffmann, Harald; Giorgini, J. D.

    To demonstrate the astrometric capability of the Mars Express Super Resolution Channel for observing Near Earth Asteroids, asteroid 4 Vesta was imaged against a star field in two five-picture sequences. While at a solar phase angle of 40.5 degrees and visual magnitude of 7.2, Vesta was imaged along with a 7.4 and 8.2 visual magnitude reference star in all ten pictures. Mars Express centered astrometric observations of Vesta were then produced using flight camera geometric calibrations, optical photogrammetric techniques, and the Tycho 2 star catalog. The astrometric measurements, validated to an accuracy of 0.4 arc-sec, were delivered to the IAU's Minor Planet Center. Such observations provide geometrically powerful samples of the target body's state vector when combined with Earth-based astrometric observations, substantially improving orbit reconstruction and prediction compared to data obtained while viewing from the Earth direction only. Based on this success, Mars Express will routinely image Near Earth Objects, asteroids and comets passing within 20,000,000 km of Mars that are brighter than 9th magnitude to support the Near Earth Object Observation program

  14. 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.

  15. Aircraft Observations of Soil Hydrological Influence on the Atmosphere in Northern India

    NASA Astrophysics Data System (ADS)

    Taylor, Christopher M.; Barton, Emma J.; Belusic, Danijel; Böing, Steven J.; Hunt, Kieran M. R.; Mitra, Ashis K.; Parker, Douglas J.; Turner, Andrew G.

    2017-04-01

    India is considered to be a region of the world where the influence of land surface fluxes of sensible and latent heat play an important role in regional weather and climate. Indian rainfall simulations in GCMs are known to be particularly sensitive to soil moisture. However, in a monsoon region where seasonal convective rainfall dominates, it is a big challenge for GCMs to capture, on the one hand, a realistic depiction of surface fluxes during wetting up and drying down at seasonal and sub-seasonal scales, and on the other, the sensitivity of convective rainfall and regional circulations to space-time fluctuations in land surface fluxes. On top of this, most GCMs and operational atmospheric forecast models don't explicitly consider irrigation. In the Indo-Gangetic plains of the Indian sub-continent, irrigated agriculture has become the dominant land use. Irrigation suppresses temporal flux variability for much of the year, and at the same time enhances spatial heterogeneity. One of the key objectives of the Anglo-Indian Interaction of Convective Organization and Monsoon Precipitation, Atmosphere, Surface and Sea (INCOMPASS) collaborative project is to better understand the coupling between the land surface and the Indian summer monsoon, and build this understanding into improved prediction of rainfall on multiple time and space scales. During June and July 2016, a series of research flights was performed across the sub-continent using the NERC/Met Office BAe146 aircraft. Here we will present results for a case study from a flight on 30th June which sampled the Planetary Boundary Layer (PBL) on a 700 km low level transect, from the semi-arid region of Rajasthan eastwards into the extensively irrigated state of Uttar Pradesh. As well as crossing different land uses, the flight also sampled mesoscale regions with contrasting recent rainfall conditions. Here we will show how variations in surface hydrology, driven by both irrigation and rainfall, influence the

  16. The Exoplanet Simple Orbit Fitting Toolbox (ExoSOFT): An Open-source Tool for Efficient Fitting of Astrometric and Radial Velocity Data

    NASA Astrophysics Data System (ADS)

    Mede, Kyle; Brandt, Timothy D.

    2017-03-01

    We present the Exoplanet Simple Orbit Fitting Toolbox (ExoSOFT), a new, open-source suite to fit the orbital elements of planetary or stellar-mass companions to any combination of radial velocity and astrometric data. To explore the parameter space of Keplerian models, ExoSOFT may be operated with its own multistage sampling approach or interfaced with third-party tools such as emcee. In addition, ExoSOFT is packaged with a collection of post-processing tools to analyze and summarize the results. Although only a few systems have been observed with both radial velocity and direct imaging techniques, this number will increase, thanks to upcoming spacecraft and ground-based surveys. Providing both forms of data enables simultaneous fitting that can help break degeneracies in the orbital elements that arise when only one data type is available. The dynamical mass estimates this approach can produce are important when investigating the formation mechanisms and subsequent evolution of substellar companions. ExoSOFT was verified through fitting to artificial data and was implemented using the Python and Cython programming languages; it is available for public download at https://github.com/kylemede/ExoSOFT under GNU General Public License v3.

  17. Astrometric Detection of Terrestrial Planets in the Habitable Zones of Nearby Stars with SIM PlanetQuest

    NASA Astrophysics Data System (ADS)

    Catanzarite, Joseph; Shao, M.; Tanner, A.; Unwin, S.; Yu, J.

    2006-12-01

    SIM PlanetQuest is a space-borne Michelson interferometer with a 9 m baseline, currently slated for launch in 2016. One of the principal science goals of the mission is the astrometric detection and orbital characterization of terrestrial planets in the habitable zones of nearby stars. Differential astrometry of the target star against a set of reference stars lying within a degree will allow measurement of the target star’s reflex motion with astrometric accuracy of one micro-arcsecond in a single measurement. In this study, we define survey strategies and planet-search target lists adapted to different occurrence frequencies of terrestrial planets in the habitable zone. We introduce the joint periodogram as a tool for astrometric planet detection, and assess SIM’s sensitivity for detection of terrestrial planets in the habitable zone using realistic target star lists and testbed-validated assumptions about instrument performance. We find that for the best 120 planet-search targets, SIM PlanetQuest will be able to detect Earth-size planets (or smaller) around 6 stars, planets of 2 Earth masses (or smaller) around 30 stars, and planets of triple Earth’s mass (or smaller) around all 120 stars. For details of this study, see Catanzarite, et al. 2006 PASP 118:1322-1342. We conclude that SIM PlanetQuest will be capable of probing populations of terrestrial and ice giant planets residing in the habitable zones of a large sample of stars within 30 pc. SIM PlanetQuest’s scientific discoveries will potentially unveil the erstwhile hidden regime of rocky planets, allowing the first thorough checks of predictions of theories of planet formation. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.

  18. 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.

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

    PubMed

    Al-Yousefi, Nada A

    2012-06-01

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

  20. Baseline pressure errors (BPEs) extensively influence intracranial pressure scores: results of a prospective observational study

    PubMed Central

    2014-01-01

    Background Monitoring of intracranial pressure (ICP) is a cornerstone in the surveillance of neurosurgical patients. The ICP is measured against a baseline pressure (i.e. zero - or reference pressure). We have previously reported that baseline pressure errors (BPEs), manifested as spontaneous shift or drifts in baseline pressure, cause erroneous readings of mean ICP in individual patients. The objective of this study was to monitor the frequency and severity of BPEs. To this end, we performed a prospective, observational study monitoring the ICP from two separate ICP sensors (Sensors 1 and 2) placed in close proximity in the brain. We characterized BPEs as differences in mean ICP despite near to identical ICP waveform in Sensors 1 and 2. Methods The study enrolled patients with aneurysmal subarachnoid hemorrhage in need of continuous ICP monitoring as part of their intensive care management. The two sensors were placed close to each other in the brain parenchyma via the same burr hole. The monitoring was performed as long as needed from a clinical perspective and the ICP recordings were stored digitally for analysis. For every patient the mean ICP as well as the various ICP wave parameters of the two sensors were compared. Results Sixteen patients were monitored median 164 hours (ranges 70 – 364 hours). Major BPEs, as defined by marked differences in mean ICP despite similar ICP waveform, were seen in 9 of them (56%). The BPEs were of magnitudes that had the potential to alter patient management. Conclusions Baseline Pressure Errors (BPEs) occur in a significant number of patients undergoing continuous ICP monitoring and they may alter patient management. The current practice of measuring ICP against a baseline pressure does not comply with the concept of State of the Art. Monitoring of the ICP waves ought to become the new State of the Art as they are not influenced by BPEs. PMID:24472296

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

    PubMed Central

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

    2016-01-01

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

  2. Observed and simulated influence of rainy-region SST on the tropical upper tropospheric humidity (UTH)

    NASA Astrophysics Data System (ADS)

    Chuang, H.; Huang, X.

    2008-12-01

    Tropical deep convections play a key role in vertically transporting moisture from the boundary layer to the upper troposphere. In this study we investigate how the variations of surface temperature over the tropical deep convective regions (hereafter, rainy-region SST) affect the interannual variations of tropical UTH profiles. Interannual anomalies of UTH profiles from the 20th-century run of four IPCC-AR4 GCMs (GFDL- CM2.1, ECHAM5, MRI-CGCM2.3.2, and NCAR-CCSM3) are analyzed. For comparison, rainy-region SST is derived from the observed SST and GPCP pentad-resolution dataset and UTHs from ECMWF and AIRS are used. The four models have consistently high correlation (>0.9) between interannual anomalies of humidity and tropical-mean surface temperature, but it is not the case of the ECMWF and AIRS data. When the inner tropical (15S-15N) rainy-region surface temperature is used instead of the mean surface temperature, the correlations between UTH (250-450mb) anomalies and surface temperature anomalies are improved by 14.6% for ECMWF and by 24.6% for AIRS, but only slightly improved for four GCMs (between 0.6-4.9%). These results indicate that the GCMs, though consistent with each other, have difficulties in capturing observed influence of rainy-region SST on the UTH anomalies. We then examine the fractional change of specific humidity with respect to the inner tropical rainy-region SST as well as the cloud radiative forcing and the cloud fraction to investigate the connection between the maximum outflow level of deep convection and UTH variability. Though the fractional changes of specific humidity with rainy-region SST tend to have a maximum around 200mb for all GCMs, the analysis of cloud properties suggests that, in all GCMs, the variation of maximum outflow level should not dictate the UTH variability. Given that the air parcel more closely follows the isentropic surfaces rather than the isobaric surfaces, we further examine the UTH variability over the constant

  3. Modeling and Observational Study of the Stratospheric Ozone Influences on the Tropospheric Circulation Patterns

    NASA Astrophysics Data System (ADS)

    Barodka, S.; Krasouski, A.; Shalamyansky, A.

    2013-12-01

    It seems to be universally recognized that stratospheric ozone distribution and tropospheric dynamical formations are interconnected and both affect each other in manifold processes of stratosphere-troposphere interactions. In particular, numerous observational studies suggest a clear relation between the total ozone column (TOC) field and the distribution of air-masses in both the stratosphere and the troposphere. The tropopause height being a result of two rival categories of processes (the tropospheric vertical convection and the radiative heating of the stratosphere resulting from the ozone cycle), it is natural that tropospheric and stratospheric phenomena can have an effect on each other. Indeed, it has been shown that virtually all local ozone anomalies (synoptic-scale deviations in the TOC field) correspond to local uplifts of the tropopause level, and a significant amount of research was dedicated to identification of local patterns in the stratospheric ozone distribution as the outcome of tropospheric synoptic formations and weather systems. However, in the present study we focus our attention to the opposite side of the interaction: the impact of stratospheric ozone distribution on the features of tropospheric circulation and the associated weather and regional climate conditions. For that purpose, we proceed from analyzes of the observational data performed at the A.I. Voeikov Main Geophysical Observatory, which suggest a distinct correlation between stratospheric ozone distribution, synoptic formations and air-masses boundaries in the upper troposphere and the temperature field of the lower stratosphere. Furthermore, we perform a series of numerical simulations of formation, evolution and decay of ozone anomalies of different spatial and temporal scales, introducing disturbances to the stratospheric ozone and temperature variable fields and tracing the propagation of this perturbation to tropospheric model levels. Aiming to simulate dynamical processes

  4. 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…

  5. 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

  6. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  8. 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.

  9. 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…

  10. 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…

  11. Astrometric observations of the satellites of the outer planets. V - The oppositions of 1978-1979, 1980, and 1981

    NASA Technical Reports Server (NTRS)

    Rohde, J. R.; Ianna, P. A.; Stayton, L. C.; Levinson, F. H.

    1982-01-01

    Accurate photographic positions obtained during the 1978-1979, 1980 and 1981 oppositions are presented for the positions of the Galilean and the Saturn satellites. Spherical-equatorial coordinates are presented for a total of 1032 pairs, for the equator and equinox of 1950.0 and 1316 intersatellite positions. The data were obtained by the Leander McCormick Observatory's 67-cm refractor telescope, and answers the need for more refined orbital element data on these satellites required by the Galileo Jupiter orbiter vehicle.

  12. 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.

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

    PubMed

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

    2009-05-04

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

  14. 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…

  15. 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…

  16. 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…

  17. Calibration of Hipparcos Long Period Variable Start Fields Using Multi-Color CCD Observations

    NASA Astrophysics Data System (ADS)

    Howell, Steve B.; Mattei, Janet; Benson, Priscilla J.; Reyes, Adriana

    The first set of 4-color AAVSO CCD finder charts has been prepared using the 0.9-m telescope at Kitt peak national Observatory in Arizona. The stars selected were northern long period variable stars observed with the Hipparcos astrometric satellite, since multicolor photometry was needed on these stars to calibrate and reduce the photometric and astrometric data obtained by the satellite. We describe the criteria in choosing the stars for which to prepare CCD finder charts, the observation process, and the reduction of the CCD to obtain 4-color CCD magnitude sequences to use in the creation of AAVSO finder charts.

  18. Observations on the Influence of Tool-Sheet Contact Conditions on an Incremental Forming Process

    NASA Astrophysics Data System (ADS)

    Durante, M.; Formisano, A.; Langella, A.

    2011-08-01

    The influence of tool-sheet contact conditions on features such as surface roughness, forming force, and formability was evaluated for components produced by incremental forming, a highly flexible innovative sheet metal-forming process. Experimental tests were carried out on sheets of AA7075T0 to create two types of component: pyramid frusta (for the evaluation of roughness and force) and cone frusta (for the evaluation of formability). Four different types of tool-sheet contact were analyzed, using two types of tool. From the experimental tests, the influence on the surface finishing and on the trend of the forming forces depending on contact type was revealed. Contact types do not, however, influence sheet formability.

  19. Influence of finger and mouth action observation on random number generation: an instance of embodied cognition for abstract concepts.

    PubMed

    Grade, Stéphane; Badets, Arnaud; Pesenti, Mauro

    2017-05-01

    Numerical magnitude and specific grasping action processing have been shown to interfere with each other because some aspects of numerical meaning may be grounded in sensorimotor transformation mechanisms linked to finger grip control. However, how specific these interactions are to grasping actions is still unknown. The present study tested the specificity of the number-grip relationship by investigating how the observation of different closing-opening stimuli that might or not refer to prehension-releasing actions was able to influence a random number generation task. Participants had to randomly produce numbers after they observed action stimuli representing either closure or aperture of the fingers, the hand or the mouth, or a colour change used as a control condition. Random number generation was influenced by the prior presentation of finger grip actions, whereby observing a closing finger grip led participants to produce small rather than large numbers, whereas observing an opening finger grip led them to produce large rather than small numbers. Hand actions had reduced or no influence on number production; mouth action influence was restricted to opening, with an overproduction of large numbers. Finally, colour changes did not influence number generation. These results show that some characteristics of observed finger, hand and mouth grip actions automatically prime number magnitude, with the strongest effect for finger grasping. The findings are discussed in terms of the functional and neural mechanisms shared between hand actions and number processing, but also between hand and mouth actions. The present study provides converging evidence that part of number semantics is grounded in sensory-motor mechanisms.

  20. Children's Attributions for Their Own Versus Others' Behavior: Influence of Actor Versus Observer Differences

    ERIC Educational Resources Information Center

    Johnston, C.; Lee, C.M.

    2005-01-01

    In attempts to make assessments less threatening, children are sometimes asked to respond to questions about another child rather than about themselves. Little is known about how this manipulation of response format (self versus other) might influence children's responses. This study compared responses of 58 younger (5-7 years) and 68 older (8-11…

  1. 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.

  2. 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

  3. On measuring bird habitat: influence of observer variability and sample size

    Treesearch

    William M. Block; Kimberly A. With; Michael L. Morrison

    1987-01-01

    We studied the effects of observer variability when estimating vegetation characteristics at 75 0.04-ha bird plots. Observer estimates were significantly different for 31 of 49 variables. Multivariate analyses showed significant interobserver differences for five of the seven classes of variables studied. Variable classes included the height, number, and diameter of...

  4. 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.…

  5. 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…

  6. Observation of atmospheric influence on OICETS inter-orbit laser communication demonstrations

    NASA Astrophysics Data System (ADS)

    Takayama, Y.; Jono, T.; Koyama, Y.; Kura, N.; Shiratama, K.; Demelenne, B.; Sodnik, Z.; Bird, A.; Arai, K.

    2007-09-01

    The experimental results of an inter-orbit laser communication performed under an atmospheric influence is presented. The demonstration was planned so that the optical link was supposed to graze the earth's rim because of the satellite revolution around the earth. The trial was successfully carried out on 5th April, 2006. The measured experimental data are introduced to show the temporal behavior of the OICETS's optical terminal. The atmospheric influence on the optical link is calculated with a theoretical model to obtain a probability density of normalized intensity as a predictive value. The probability density is also estimated from the experimentally measured data. The comparison shows that the theoretical prediction well describes the experimental results.

  7. What influences the transfer of research into health policy and practice? Observations from England and Australia.

    PubMed

    Nutbeam, D; Boxall, A-M

    2008-08-01

    To explore the role of evidence in the public health policy-making process, and show how the way in which public health problems are defined and measured influences policy outcomes. The policy responses of the Blair Labour Government in the UK and the Howard Coalition Government in Australia to persistent health inequalities over the last decade are examined as a case study. Soon after being elected, the Blair Government commissioned an independent inquiry into health inequalities, signalling the priority it gave to addressing this longstanding challenge. It chose to take a 'whole-of-government' approach, combining actions that addressed both personal risk factors and the social determinants of health. This approach reflects the long-established tradition in England of routinely measuring disparities in health outcomes and correlating them with socio-economic status and underlying social determinants of health. Over the same period, the Howard Government also outlined its 'whole-of-government' approach to addressing the most extreme and persistent health inequalities between indigenous and non-indigenous Australians. In contrast, its approach focused primarily on modifying risk factors and improving service provision. This approach reflects the different historical circumstances in Australia and a different tradition in the collection of health data, focused more on health service access and personal risk factors. This case study offers some insight into the ways in which the production and presentation of evidence can influence and shape governmental responses to public health problems. The usefulness of available evidence is dependent upon the type of data that is produced routinely by government, as well as more deliberate decisions concerning public health research funding. Researchers can maximize the influence of research evidence on the policy process by engaging in the policy-making process, presenting research in ways that fit with the political context of

  8. 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.

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

    PubMed

    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.

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

    PubMed Central

    Scocchia, Lisa; Valsecchi, Matteo; Triesch, Jochen

    2014-01-01

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

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

    PubMed

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

    2015-07-01

    Fundamental to performing actions is the acquisition of motor behaviours. We examined if motor learning, through observational practice, occurs by viewing an agent displaying naturalistic or constant velocity, and whether motion trajectory, as opposed to end-state, information is required. We also investigated if observational practice is sensitive to belief regarding the origin of an agent. Participants had to learn a novel movement sequence timing task, which required upper-limb movements to a series of targets within a pre-specified absolute and relative time goal. Experiment 1 showed learning after viewing naturalistic and constant velocity, but not end-state information. For Experiment 2, in addition to learning the movement sequence, participants observed a series of movement stimuli that were either the trained or new sequences and asked to rate their confidence on whether the observed sequence was the same or different to observational practice. The results indicated that agency belief modulates how naturalistic and constant velocity is coded. This indicated that the processes associated with belief are part of an interpretative predictive coding system where the association between belief and observed motion is determined. When motion is constant velocity, or believed to be computer-generated, coding occurs through top-down processes. When motion is naturalistic velocity, and believed to be human-generated, it is most likely coded by gaining access to bottom-up sensorimotor processes in the action-observation network. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

  12. 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.

  13. Photographic observations of major planets and their moons in MAO NAS of Ukraine during 1961-1990

    NASA Astrophysics Data System (ADS)

    Yizhakevych, O.; Andruk, V.; Pakuliak, L.; Lukianchuk, V.

    2017-06-01

    We present the results of digitizing and processing of archival observations to obtain the astrometric positions and stellar magnitudes of major planets and their satellites. The work has been done within the framework of the national project "Ukrainian Virtual Observatory" on the basis of photographic observations carried out in MAO NASU. The processing of digital images and the astrometric reduction of data was made in the software package created and developed in MAO for the reduction astrometric negatives. The catalogue includes data of Saturn's moons (S2-S9), obtained using 4 telescopes in 1961-1990. The stellar catalogue TYCHO2 was used as the reference. The internal positional accuracy is ˜ 0.09 - ˜ 0.25 arcsec.The same procedure is now applying for the processing of photographic observations of Neptune, Uranus, and their moons, obtained in MAO during the same period.

  14. 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).

  15. Nurses' understanding influences comprehension of patients admitted in the observation unit.

    PubMed

    Desme, Aline; Mendes, Nathalie; Perruche, Franck; Veillard, Elsa; Elie, Caroline; Moulinet, Françoise; Sanson, Fabienne; Georget, Jean-Michel; Tissier, Anne; Pourriat, Jean-Louis; Claessens, Yann-Erick

    2013-01-01

    Comprehension is poor in patients admitted in the emergency observation unit. Teamwork communication gaps could contribute to patients' misunderstanding of their health condition. To determine in patients admitted in the emergency observation unit whether comprehension of diagnosis, prognosis, and management depended on nurses' comprehension, the authors conducted a prospective observational study in a busy adult emergency department of a tertiary teaching hospital in Paris over 2 months. Consecutive patients admitted in the emergency observation unit were included. Patients' and nurses' comprehension of diagnosis, prognosis, and management was compared with the statements of the emergency department attending physicians for these items. The authors observed whether patients' misunderstanding was associated with nurses' misunderstanding. A total of 544 patients were evaluated. For each patient, nurses' and patients' comprehension was available. Patients understood severity in 40%, organ involved in 69%, medical wording in 57%, reason for admission in 48%, and discharge instruction in 67%. In comparison with patients, nurses better understood each item except for discharge instruction. The authors observed that patients' comprehension was better when nurses understood diagnosis (p <.0001), reasons for admission (p =.032) and discharge instructions (p =.002). Nurses' understanding of severity did not modify patients' comprehension. These results support the conclusions that communication gaps in teamwork alter patients' comprehension and that nurses' and patients' misunderstandings are associated. Therefore, improving communication by nurses and physicians to patients may improve patients' understanding.

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

    NASA Astrophysics Data System (ADS)

    Fu, R.; Wang, H.

    2007-05-01

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

  17. M-estimation with probabilistic models of geodetic observations

    NASA Astrophysics Data System (ADS)

    Wiśniewski, Z.

    2014-10-01

    The paper concerns -estimation with probabilistic models of geodetic observations that is called estimation. The special attention is paid to estimation that includes the asymmetry and the excess kurtosis, which are basic anomalies of empiric distributions of errors of geodetic or astrometric observations (in comparison to the Gaussian errors). It is assumed that the influence function of estimation is equal to the differential equation that defines the system of the Pearson distributions. The central moments , are the parameters of that system and thus, they are also the parameters of the chosen influence function. The estimation that includes the Pearson type IV and VII distributions ( method) is analyzed in great detail from a theoretical point of view as well as by applying numerical tests. The chosen distributions are leptokurtic with asymmetry which refers to the general characteristic of empirical distributions. Considering -estimation with probabilistic models, the Gram-Charlier series are also applied to approximate the models in question ( method). The paper shows that estimation with the application of probabilistic models belongs to the class of robust estimations; method is especially effective in that case. It is suggested that even in the absence of significant anomalies the method in question should be regarded as robust against gross errors while its robustness is controlled by the pseudo-kurtosis.

  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. Absolute Nuv magnitudes of Gaia DR1 astrometric stars and a search for hot companions in nearby systems

    NASA Astrophysics Data System (ADS)

    Makarov, V. V.

    2017-10-01

    Accurate parallaxes from Gaia DR1 (TGAS) are combined with GALEX visual Nuv magnitudes to produce absolute Mnuv magnitudes and an ultraviolet HR diagram for a large sample of astrometric stars. A functional fit is derived of the lower envelope main sequence of the nearest 1403 stars (distance <40 pc), which should be reddening-free. Using this empirical fit, 50 nearby stars are selected with significant Nuv excess. These are predominantly late K and early M dwarfs, often associated with X-ray sources, and showing other manifestations of magnetic activity. The sample may include systems with hidden white dwarfs, stars younger than the Pleiades, or, most likely, tight interacting binaries of the BY Dra-type. A separate collection of 40 stars with precise trigonometric parallaxes and Nuv-G colors bluer than 2 mag is presented. It includes several known novae, white dwarfs, and binaries with hot subdwarf (sdOB) components, but most remain unexplored.

  20. 'Sometimes the work just needs to be done': socio-cultural influences on direct observation in medical training.

    PubMed

    Watling, Christopher; LaDonna, Kori A; Lingard, Lorelei; Voyer, Stephane; Hatala, Rose

    2016-10-01

    Direct observation promises to strengthen both coaching and assessment, and calls for its increased use in medical training abound. Despite its apparent potential, the uptake of direct observation in medical training remains surprisingly limited outside the formal assessment setting. The limited uptake of observation raises questions about cultural barriers to its use. In this study, we explore the influence of professional culture on the use of direct observation within medical training. Using a constructivist grounded theory approach, we interviewed 22 residents or fellows (10 male, 12 female) about their experiences of being observed during training. Participants represented a range of specialties and training levels. Data collection and analysis were conducted iteratively. Themes were identified using constant comparative analysis. Observation was used selectively; specialties tended to observe the clinical acts that they valued most. Despite these differences, we found two cultural values that consistently challenged the ready implementation of direct observation across specialties: (i) autonomy in learning and (ii) efficiency in health care provision. Furthermore, we found that direct observation was a primarily learner-driven activity, which left learners caught in the middle, wanting observation but also wanting to appear independent and efficient. The cultural values of autonomy in learning and practice and efficiency in health care provision challenge the integration of direct observation into clinical training. Medical learners are often expected to ask for observation, but such requests are socially and culturally fraught, and likely to constrain the wider uptake of direct observation. © 2016 John Wiley & Sons Ltd and The Association for the Study of Medical Education.

  1. Contextual influences on concordance between maternal report and laboratory observation of toddler fear.

    PubMed

    Kiel, Elizabeth J; Hummel, Alexandra C

    2017-03-01

    Emotion and temperament researchers have faced an enduring issue of how to best measure children's tendencies to express specific emotions. Inconsistencies between laboratory observation and parental report have made it challenging for researchers to determine the utility of these different forms of measurement. The current study examined the effect of laboratory episode characteristics (i.e., threat level of the episode, maternal involvement) on concordance between maternal report and laboratory observation of toddler fear. The sample included 111 mother-toddler dyads who participated in a laboratory assessment when toddlers were approximately 24 months old. Toddler fear was assessed both via maternal report and observation from a number of laboratory episodes that varied in their level of threat and whether mothers were free or constrained in their involvement in the task. Results indicated that maternal report related to the observed fear composites for low threat, but not high threat episodes. On the contrary, maternal involvement in the laboratory episodes did not moderate the relation between maternal report and laboratory observation of fear. These results suggest that the threat level of laboratory episodes designed to elicit fear, but not maternal involvement in these episodes, may be important to take into consideration when assessing their relation to maternal report of fear and fearful temperament. (PsycINFO Database Record

  2. Observations of and Influences on Low-Latitude Vertical Plasma Drifts

    NASA Astrophysics Data System (ADS)

    Miller, E. S.; Chartier, A.; Paxton, L. J.

    2016-12-01

    Many workers have suggested that the morphology (position and relative intensities) of the crests of the equatorial ionization anomaliesis related to the time history of the equatorial vertical drift. In this work, we compare observations of the vertical drift using an HF radiosignals of opportunity in the Central Pacific with UV 135.6-nm observations of the equatorial anomalies from the DMSP/SSUSI andTIMED/GUVI instruments. Furthermore, we explore the role of E region density in modulating the vertical plasma drift using a passive HFsounding experiment in the Caribbean. Coupling between nighttime medium-scale traveling ionospheric disturbances (MSTIDs) and sporadic-Elayers has been suggested as a growth-rate-increasing process. While we observe sporadic-E in the local hemisphere coincident to increases in thealtitude of the F-region altitude, we also observe uplifts without sporadic-E in the local hemisphere. Apart from the trivial explanation that sporadic-E is occurring in the conjugate hemisphere, another possible explanation is that the E region may enhance the vertical drift, but is not required to produce enhanced vertical drifts. These studies represent fruitful areas of future intersection between ground-based observations and ICON and GOLD science.

  3. Early menopause does not influence left ventricular diastolic dysfunction: A clinical observational study in healthy subjects.

    PubMed

    Hirokawa, Megumi; Daimon, Masao; Lee, Seitetsu L; Nakao, Tomoko; Kawata, Takayuki; Kimura, Koichi; Kato, Tomoko S; Mizuno, Yoshiko; Watanabe, Masafumi; Yatomi, Yutaka; Yamazaki, Tsutomu; Komuro, Issei

    2016-12-01

    The prevalence of left ventricular diastolic dysfunction (LVDD) sharply increases in women after their 50s and may contribute to the high prevalence of diastolic heart failure in elderly women. A decrease in estrogen levels after menopause is postulated to be one of the mechanisms responsible for this phenomenon. However, there is a paucity of data on the relationship between the timing of menopause and the progression of LVDD in the clinical setting; thus, we investigated this relationship in healthy postmenopausal women. We enrolled 115 women and divided them into two groups according to median menopause age: 61 who experienced menopause at ≤50 years (early menopause group), and 54 who experienced menopause at >50 years (late menopause group). We compared the echocardiographic and clinical characteristics between the two groups. There were no significant differences in LV diastolic parameters (mitral E/A, p=0.561; e', p=0.052; E/e', p=0.081; DCT, p=0.082; prevalence of LVDD class, p=0.801), as well as other echocardiographic parameters and clinical characteristics between the two groups. Multivariate linear regression analysis showed that the independent determinants of LVDD were age and body mass index, but not the timing of menopause. Early menopause did not influence the progression of LVDD in postmenopausal women. The sharp progression of LVDD in elderly women is complex and probably influenced by multiple factors. Copyright © 2015 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

  4. VizieR Online Data Catalog: USNO Saturnian observations 1974-1998 (Robert+, 2016)

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    Astrometric and measured data of Saturn, Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion and Iapetus, taken with the U.S. Naval Observatory 26-inch refractor from 1974 to 1998. 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. Raw data with (x,y) positions of the stars and satellites are available on demand (Vincent Robert, vincent.robert(at)obspm.fr). (9 data files).

  5. Does resolution of flow field observation influence apparent habitat use and energy expenditure in juvenile coho salmon?

    USGS Publications Warehouse

    Tullos, Desiree D.; Walter, Cara; Dunham, Jason

    2016-01-01

    This study investigated how the resolution of observation influences interpretation of how fish, juvenile Coho Salmon (Oncorhynchus kisutch), exploit the hydraulic environment in streams. Our objectives were to evaluate how spatial resolution of the flow field observation influenced: (1) the velocities considered to be representative of habitat units; (2) patterns of use of the hydraulic environment by fish; and (3) estimates of energy expenditure. We addressed these objectives using observations within a 1:1 scale physical model of a full-channel log jam in an outdoor experimental stream. Velocities were measured with Acoustic Doppler Velocimetry at a 10 cm grid spacing, whereas fish locations and tailbeat frequencies were documented over time using underwater videogrammetry. Results highlighted that resolution of observation did impact perceived habitat use and energy expenditure, as did the location of measurement within habitat units and the use of averaging to summarize velocities within a habitat unit. In this experiment, the range of velocities and energy expenditure estimates increased with coarsening resolution (grid spacing from 10 to 100 cm), reducing the likelihood of measuring the velocities locally experienced by fish. In addition, the coarser resolutions contributed to fish appearing to select velocities that were higher than what was measured at finer resolutions. These findings indicate the need for careful attention to and communication of resolution of observation in investigating the hydraulic environment and in determining the habitat needs and bioenergetics of aquatic biota.

  6. Does resolution of flow field observation influence apparent habitat use and energy expenditure in juvenile coho salmon?

    NASA Astrophysics Data System (ADS)

    Tullos, Desirée.; Walter, Cara; Dunham, Jason

    2016-08-01

    This study investigated how the resolution of observation influences interpretation of how fish, juvenile Coho Salmon (Oncorhynchus kisutch), exploit the hydraulic environment in streams. Our objectives were to evaluate how spatial resolution of the flow field observation influenced: (1) the velocities considered to be representative of habitat units; (2) patterns of use of the hydraulic environment by fish; and (3) estimates of energy expenditure. We addressed these objectives using observations within a 1:1 scale physical model of a full-channel log jam in an outdoor experimental stream. Velocities were measured with Acoustic Doppler Velocimetry at a 10 cm grid spacing, whereas fish locations and tailbeat frequencies were documented over time using underwater videogrammetry. Results highlighted that resolution of observation did impact perceived habitat use and energy expenditure, as did the location of measurement within habitat units and the use of averaging to summarize velocities within a habitat unit. In this experiment, the range of velocities and energy expenditure estimates increased with coarsening resolution (grid spacing from 10 to 100 cm), reducing the likelihood of measuring the velocities locally experienced by fish. In addition, the coarser resolutions contributed to fish appearing to select velocities that were higher than what was measured at finer resolutions. These findings indicate the need for careful attention to and communication of resolution of observation in investigating the hydraulic environment and in determining the habitat needs and bioenergetics of aquatic biota.

  7. Does resolution of flow field observation influence apparent habitat use and energy expenditure in juvenile coho salmon?

    NASA Astrophysics Data System (ADS)

    Tullos, D. D.; Walter, C.; Dunham, J.

    2016-12-01

    This study investigated how the resolution of observation influences interpretation of how fish, juvenile Coho Salmon (Oncorhynchus kisutch), exploit the hydraulic environment in streams. Our objectives were to evaluate how spatial resolution of the flow field observation influenced: 1) the velocities considered to be representative of habitat units; 2) patterns of use of the hydraulic environment by fish; and 3) estimates of energy expenditure. We addressed these objectives using observations within a 1:1 scale physical model of a full-channel log jam in an outdoor experimental stream. Velocities were measured with Acoustic Doppler Velocimetry at a 10 cm grid spacing, whereas fish locations and tailbeat frequencies were documented over time using underwater videogrammetry. Results highlighted that resolution of observation did impact perceived habitat use and energy expenditure, as did the location of measurement within habitat units and the use of averaging to summarize velocities within a habitat unit. In this experiment, the range of velocities and energy expenditure estimates increased with coarsening resolution, reducing the likelihood of measuring the velocities locally experienced by fish. In addition, the coarser resolutions contributed to fish appearing to select velocities that were higher than what was measured at finer resolutions. These findings indicate the need for careful attention to and communication of resolution of observation in investigating the hydraulic environment and in determining the habitat needs and bioenergetics of aquatic biota.

  8. 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.

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

    NASA Technical Reports Server (NTRS)

    Harrison, J. C.

    1978-01-01

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

  10. 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.

  11. Spontaneous movement tempo can be influenced by combining action observation and somatosensory stimulation

    PubMed Central

    Bisio, Ambra; Avanzino, Laura; Lagravinese, Giovanna; Biggio, Monica; Ruggeri, Piero; Bove, Marco

    2015-01-01

    Spontaneous movement tempo (SMT) was a popular field of study of the Gestalt psychologists It can be determined from subjects freely tapping out a rhythm with their finger, and it has been found to average about 2 Hz. A previous study showed that SMT changed after the observation of rhythmical movements performed at frequency different from the SMT. This effect was long-lasting only when movement execution immediately followed action observation (AO). We recently demonstrated that only when AO was combined with peripheral nerve stimulation (AO-PNS) was it possible to induce plastic changes in the excitability of the motor cortex, whereas AO and PNS alone did not evoke any changes. Here we investigated whether the observation of rhythmical actions at a frequency higher than the SMT combined with PNS induced lasting changes in SMT even in absence of immediate movement execution. Forty-eight participants were assigned to four groups. In AO-PNS group they observed a video showing a right hand performing a finger opposition movement sequence at 3 Hz and contemporarily received an electrical stimulation at the median nerve; in AO group and PNS group participants either observed the same video or received the same electrical stimulation of the AO-PNS group, respectively; in LANDSCAPE group subjects observed a neutral video. Participants performed a finger opposition movement sequence at spontaneous movement rate before and 30 min after the conditioning protocols. Results showed that SMT significantly changed only after AO-PNS. This result suggested that the AO-PNS protocol was able to induce lasting changes in SMT due to neuroplasticity mechanisms, indicating possible application of AO-PNS in rehabilitative treatments. PMID:26441565

  12. Motor facilitation during action observation: topographic mapping of the target muscle and influence of the onlooker's posture.

    PubMed

    Urgesi, Cosimo; Candidi, Matteo; Fabbro, Franco; Romani, Michela; Aglioti, Salvatore M

    2006-05-01

    Transcranial magnetic stimulation (TMS) studies report that viewing a given action performed by a model activates the neural representation of the onlooker's muscles that are activated during the actual execution of the observed action. Here we sought to determine whether this mirror observation-execution facilitation reflects only muscular specificity or whether it is also influenced by postural congruency between onlooker/model body parts. We recorded motor potentials evoked by single-pulse TMS from the first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles during observation of the right index and little finger abduction/adduction movements of models who kept their hands in a palm-down or palm-up position. Moreover, in different experiments observers kept their right hand palm down or palm up. Selective motor facilitation was observed during observation of movements that map the motor function of the targeted muscles, regardless of the posture of the observed hand. Modulation of FDI, however, was obtained only when participants kept their hand palm down; by contrast, modulation of ADM was obtained only when participants kept their hand palm up. Interestingly, electromyographic recordings showed that FDI is mostly active when index abduction/adduction movements are performed in the palm-down position, whereas ADM is mostly active when little finger abduction/adduction movements are performed in the palm-up position. Results show that the influence of the onlooker's hand posture is comparable in action execution and observation, thus indicating a fine-grain functional correspondence between these two processes.

  13. CCD observations of Phoebe, 9th satellite of Saturn

    NASA Astrophysics Data System (ADS)

    Fienga, A.; Arlot, J.-E.; Baron, N.; Bec-Borsenberger, A.; Crochot, A.; Emelyanov, N.; Thuillot, W.

    2002-08-01

    In 1998 and 1999, we started observations of the 9th satellite of Saturn. We made 163 observations using the 120 cm-telescope of Observatoire de Haute-Provence, France. We used the USNO A2 catalogue of stars for the astrometric reduction. With the help of observations of optical counterparts of ICRF sources, a zonal correction to the USNO A2.0 catalogue was computed and applied to the Phoebe positions. A comparison with the most recent theories was made.

  14. Does an Observer's Content Knowledge Influence the Feedback Offered about Mathematics Lessons?

    ERIC Educational Resources Information Center

    Peck, Duane C.

    2016-01-01

    The purpose of this study was two-fold. First, feedback from 3 different groups of observers: math content specialists, content specialists in areas other than mathematics, and building principals, was analyzed using an inductive approach to identify themes within the feedback. Second, differences in the feedback offered by participants of the 3…

  15. Influence of perspective on the neural correlates of motor resonance during natural action observation.

    PubMed

    Vingerhoets, Guy; Stevens, Lenny; Meesdom, Morgan; Honoré, Pieterjan; Vandemaele, Pieter; Achten, Eric

    2012-01-01

    We investigated the neural correlates of motor resonance during the observation of natural transitive actions and determined how the observer's perspective modulates the neural activation. Seventeen right-handed participants observed right and left hand tool grasping actions from a first-person or third-person perspective while undergoing fMRI. A two-factorial analysis of variance over the parietal region revealed no main effects of hand identity or perspective, but unveiled a hand by perspective interaction effect. The first-person perspective elicited parietal activation in the hemisphere contralateral to the performing hand as if the modelled action was mimicked with the same anatomical hand. In the third-person perspective, parietal activation ipsilateral to the modelled hand was found, indicating a specular strategy, rather than an anatomical imitation. Motor resonance was maximal in three foci in the superior parietal lobule and intraparietal sulcus that have been associated with prehensile actions. Our results suggest that therapeutic strategies aimed to elicit motor resonance, such as motor imagery and observational modelling, can adjust their spatial frame of reference according to the hemisphere they intend to stimulate.

  16. 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.

  17. 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.

  18. 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

  19. Influence of weight loss on pain, perceived disability and observed functional limitations in obese women.

    PubMed

    Larsson, U Evers

    2004-02-01

    To evaluate the effects of weight reduction by dieting on musculoskeletal pain, perceived disability and observed functional limitations in everyday life. : Female outpatients in weight-loss programmes at the Karolinska Hospital, who met the criteria for participating in this study: age 20-65 y and body mass index (BMI) > or =30 kg/m(2). In all, 57 entered the programme studied and 43 completed it. Diet programmes for 8-12 weeks and thereafter 6688 kJ/day for >52 weeks. Questionnaires on musculoskeletal symptoms and obesity-specific questions on basic activities of daily living (ADL), mobility, housework, occupational disability and activities outside home. Test protocol developed for observation of functional limitations in obese women. Assessments at baseline, after 12 and after 64 weeks of dieting. In all, 75% completed the study. Weight loss was 14% (14.7+/-6.1 kg) at 12 weeks and, due to a weight relapse, 10% (10.1+/-8.1 kg) at 64 weeks. At the end of the study period, the proportion of current pain from lower backs and feet had normalised. Important perceived improvements were ability to rise from having fallen over, to walk up stairs and to lift heavy things. Most functional limitations improved, such as climbing onto high stools, walking up stairs with grocery bags, doing pedicure, rising from floor or low furniture. The questionnaire results partly followed the weight development, but the observed improvements were long-lasting. Weight reduction had positive short-term effects on musculoskeletal pain, perceived disability and observed functional limitations. A partial weight relapse had some impact on perceived pain and disability, but not on observed limitations. The maintained improvements may be due to weight loss, but also less pain and increased physical activity.

  20. 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