Science.gov

Sample records for astrometric observations influence

  1. CCD astrometric observations of Amalthea and Thebe

    NASA Astrophysics Data System (ADS)

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

    2005-07-01

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

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

    NASA Technical Reports Server (NTRS)

    Marsden, B. G.

    1991-01-01

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

  3. New astrometric observations of Triton in 2007-2009

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    SciTech Connect

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

    2011-05-15

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

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

    NASA Technical Reports Server (NTRS)

    Marsden, Brian G.; McCrosky, Richard E.

    1997-01-01

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

  6. An improved astrometric calibration technique for space debris observation

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    NASA Technical Reports Server (NTRS)

    Mccrosky, Richard E.; Marsden, Brian G.

    1987-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Klemola, A. R.

    1981-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

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

    SciTech Connect

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

    2011-02-15

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

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Dement'eva, A. A.

    2015-09-01

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

  8. Astrometric education in China†

    NASA Astrophysics Data System (ADS)

    Jin, W. J.; Zhu, Z.

    2008-07-01

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

  9. The Astrometric Telescope Facility

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2002-02-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Wünsch, J.

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

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

    SciTech Connect

    Pavlov, N.V.

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Dorland, Bryan N.

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

  3. The PRIMA Astrometric Planet Search project

    NASA Astrophysics Data System (ADS)

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

    2004-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  5. UCAC3: ASTROMETRIC REDUCTIONS

    SciTech Connect

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

    2010-06-15

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

  6. ASTROMETRIC REVERBERATION MAPPING

    SciTech Connect

    Shen Yue

    2012-10-01

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

  7. Astrometric and Photometric Variability in Quasars

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  8. Astrometric and photometric variability in quasars

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

  9. NEAT: A Microarcsec Astrometric Telescope

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  10. NEAT: A Microarcsec Astrometric Telescope

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Asada, Hideki

    2006-11-01

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

  12. Astrometric positions of minor planets in 1978

    NASA Astrophysics Data System (ADS)

    Debehogne, H.; Houziaux, L.

    1980-04-01

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

  13. Aiming Schedule For Orbiting Astrometric Telescope

    NASA Technical Reports Server (NTRS)

    Mascy, Alfred C.; Sobeck, Charlie

    1991-01-01

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

  14. Astrometric solar system anomalies

    SciTech Connect

    Nieto, Michael Martin; Anderson, John D

    2009-01-01

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

  15. COMPANIONS TO NEARBY STARS WITH ASTROMETRIC ACCELERATION. II

    SciTech Connect

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

    2013-07-01

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

  16. Gaia astrometric data reduction one year into science operations

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  17. Astrometric exoplanet detection with Gaia

    SciTech Connect

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

    2014-12-10

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

  18. PACMAN: PRIMA astrometric instrument software

    NASA Astrophysics Data System (ADS)

    Abuter, Roberto; Sahlmann, Johannes; Pozna, Eszter

    2010-07-01

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

  19. Gravitation Astrometric Measurement Experiment (GAME)

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

  20. 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.

  1. The ESPRI project: astrometric exoplanet search with PRIMA

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

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

  2. Forthcoming Occultations of Astrometric Radio Sources by Planets

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  3. On the sources of astrometric anomalous refraction

    NASA Astrophysics Data System (ADS)

    Taylor, M. Suzanne

    2009-06-01

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

  4. 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.

  5. Astrometric microlensing with the GAIA satellite

    NASA Astrophysics Data System (ADS)

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

    2002-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  7. Gamma Astrometric Measurement Experiment

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  9. Astrometric Study of Lo 1339

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  10. Astrometric Discovery of GJ 164B

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  11. Newcomb Astrometric Satellite: Preliminary Design

    NASA Astrophysics Data System (ADS)

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

    1993-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Biretta, John; Lockwood, Sean; Debes, John

    2015-09-01

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

  14. Reduction of the Gaia astrometric data

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  15. Metrology for AGP - Astrometric Gravitation Probe

    NASA Astrophysics Data System (ADS)

    Gai, Mario; et al.

    2015-08-01

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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-05-01

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

  19. The Full-sky Astrometric Mapping Explorer Concept Study

    NASA Astrophysics Data System (ADS)

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

    1999-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1999-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  3. An Optical/Infrared Astrometric Satellite Project LIGHT

    NASA Astrophysics Data System (ADS)

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

    1997-08-01

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

  4. FAME- Full-sky Astrometric Mapping Explorer

    NASA Astrophysics Data System (ADS)

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

    1999-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

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

    SciTech Connect

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

    2012-07-15

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

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

    NASA Astrophysics Data System (ADS)

    Crosta, M.; Vecchiato, A.

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

  9. Analysis of an astrometric Fizeau interferometer for GAIA

    NASA Technical Reports Server (NTRS)

    Loiseau, Sacha; Shaklan, Stuart

    1995-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-08-01

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

  13. SIM Lite Astrometric Observatory Progress Report

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  16. Star Confusion Effect on SIM PlanetQuest Astrometric Performance

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Astrometric properties of the Tautenburg Plate Scanner

    NASA Astrophysics Data System (ADS)

    Brunzendorf, Jens; Meusinger, Helmut

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

  2. Optical design of an astrometric space telescope

    NASA Astrophysics Data System (ADS)

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

    1986-01-01

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

  3. Measurement of CFHT Images II. Astrometric Reduction

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  5. Full-sky Astrometric Mapping Explorer (FAME)

    NASA Astrophysics Data System (ADS)

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

    2000-12-01

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

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

    SciTech Connect

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

    2014-11-01

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

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

    NASA Technical Reports Server (NTRS)

    Meurers, J.

    1971-01-01

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

  8. Astrometric positioning and orbit determination of geostationary satellites

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Baturin, A. P.

    2015-12-01

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

  12. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  15. Astrometric Telescope Facility isolation and pointing study

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

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

    SciTech Connect

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

    2012-07-01

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

  17. Astrometric detection of gravitational effects of quantum vacuum

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Gai, Mario; Hajdukovic, Dragan

    2015-08-01

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

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

    NASA Technical Reports Server (NTRS)

    Pravdo, Steven H.; Shaklan, Stuart B.

    1996-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Sahlmann, Johannes

    2015-08-01

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

  1. 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.

  2. The Astrometric Calibration of the Gemini Planet Imager

    NASA Astrophysics Data System (ADS)

    Tran, Debby; Konopacky, Quinn; GPIES Collaboration

    2016-06-01

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

  3. Astrometric Support for the Lunar-based Ultraviolet Telescope

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  7. Revisiting TW Hydrae in light of new astrometric data

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  9. Astrometric Models of the Phobos Orbiter TV Cameras

    NASA Technical Reports Server (NTRS)

    Duxbury, T. C.

    1993-01-01

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

  10. Optical design for the Laser Astrometric Test of Relativity

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Technical Reports Server (NTRS)

    Spahr, Timothy

    2004-01-01

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

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

    SciTech Connect

    Perlmutter, S.

    1986-11-25

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

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

    SciTech Connect

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

    2011-10-20

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

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

    DOE PAGESBeta

    Beamer, Benjamin; Nomerotski, Andrei; Tsybychev, Dmitri

    2015-05-22

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

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

    SciTech Connect

    Beamer, Benjamin; Nomerotski, Andrei; Tsybychev, Dmitri

    2015-05-22

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

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

    ERIC Educational Resources Information Center

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

    2007-01-01

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

  5. Global Sphere Reconstruction in the Astrometric Verification Unit

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  7. The parallax and astrometric orbit of Mu Cassiopeiae

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  8. FAME - The Full-sky Astrometric Mapping Explorer

    NASA Astrophysics Data System (ADS)

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

    1998-12-01

    The Full-sky Astrometric Mapping Explorer (FAME) is a small satellite designed to perform an all-sky, astrometric survey with unprecedented accuracy. FAME will create an accurate astrometric catalog of 40,000,000 stars with visual band magnitudes 5 < V < 15. For bright stars, 5 < V < 9, FAME will determine positions and parallaxes accurate to < 50 microarcseconds, with proper motion errors < 50 microarcseconds/year. For fainter stars, 9 < V < 15, FAME will determine positions and parallaxes accurate to < 300 microarcseconds, with proper motion errors < 300 microarcseconds/year. FAME will also collect photometric data on these 40,000,000 stars in four Sloan DSS colors. FAME will map our quadrant of the galaxy out to 2 kpc from the Sun providing the information needed to calibrate the standard candles that define the extragalactic distance scale, calibrate the absolute luminosities of stars of all spectral types for studies of stellar structure and evolution, and detect orbital motions caused by brown dwarfs and giant planets. FAME will not only improve on the accuracies of star positions determined by Hipparcos but also expand the volume of space for which accurate positions are known by a factor of 8,000. FAME is a joint development effort of the US Naval Observatory, the Smithsonian Astrophysical Observatory, the Infrared Processing and Analysis Center, Lockheed Martin Missiles and Space, the Naval Research Laboratory, and Omitron Incorporated.

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

    NASA Astrophysics Data System (ADS)

    Schulze-Hartung, Tim

    2012-08-01

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

  10. 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.

  11. 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.

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

    SciTech Connect

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

    2012-12-20

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

  13. Evaluating Observation Influence on Regional Water Budgets in Reanalyses

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  15. Orbit of an Astrometric Binary System

    NASA Astrophysics Data System (ADS)

    Descamps, Pascal

    2005-08-01

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

  16. Performance analysis of the multichannel astrometric photometer

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2005-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

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

    NASA Technical Reports Server (NTRS)

    Robertson, D. S.

    1975-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  1. Detecting human influence in observed changes in precipitation

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    SciTech Connect

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

    2010-05-15

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

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Markos, A.

    1984-01-01

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

  6. Observations of swell influence on ocean surface roughness

    NASA Astrophysics Data System (ADS)

    Hwang, Paul A.

    2008-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2000-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1987-03-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  11. Analysis of astrometric catalogues with vector spherical harmonics

    NASA Astrophysics Data System (ADS)

    Mignard, F.; Klioner, S.

    2012-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Michalik, Daniel; Lindegren, Lennart

    2016-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2000-12-01

    The FAME project began Phase B development in September 2000. FAME is a MIDEX class NASA Explorer mission that will perform an all-sky, astrometric survey with unprecedented accuracy. FAME will produce an astrometric catalog of 40 million stars between 5th and 15th magnitude. For the bright stars (5th to 9th magnitude) FAME will determine positions and parallaxes accurate to better than 50 microarcseconds, with proper motion errors less than 50 microarcseconds per year. For the fainter stars (between 9th and 15th magnitude) FAME will determine positions and parallaxes accurate to better than 500 microarcseconds, with proper motion errors less than 500 microarcseconds per year. FAME will also collect photometric data on these 40 million stars in four Sloan DSS colors. The FAME instrument design, integration, and testing is the responsibility of the Lockheed Martin Advanced Technology Center in Palo Alto. Here we present the updated instrument design and discuss some of the trade studies that have been completed or are in progress. CCD tests are being made to investigate (1) the use of start-stop technique for bright stars with the time delay integration (TDI), (2) techniques for fitting point spread functions under conditons of noise and smearing, (3) the use of charge injection preceding stars to mitigate the effects of traps, and (4) the effects of radiation over the lifetime of the mission. The FAME project is funded by the NASA Explorer program administered by Goddard Space Flight Center for the Office of Space Science under contract number S-13610-Y.

  14. Automated Astrometric and Photometric TASS Data Reduction Techniques

    NASA Astrophysics Data System (ADS)

    Gombert, G.

    1997-05-01

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

  15. Determining the Mass of Proxima Centauri through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2012-10-01

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

  16. Determining the Mass of Proxima Centauri through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2013-10-01

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

  17. Determining the Mass of Proxima Centauri through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2014-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  20. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Sigismondi, Costantino

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

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

    ERIC Educational Resources Information Center

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

    2012-01-01

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

  6. 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

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

    SciTech Connect

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

    2012-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  9. 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

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

    NASA Astrophysics Data System (ADS)

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

    1999-12-01

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

  11. Astrometric Calibration of Digitized Wide-Field Photographic Plates

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    PubMed Central

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

    2014-01-01

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

  14. Hand Dominance Influences the Processing of Observed Bodies

    ERIC Educational Resources Information Center

    Gardner, Mark R.; Potts, Rosalind

    2010-01-01

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

  15. External Influences on Modeled and Observed Cloud Trends

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

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

    SciTech Connect

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

    2013-06-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  18. Global Lidar Observations of Aerosol Distribution and Radiative Influence

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Graham, W. D.

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

    Anglada-Escudé, G.; Torra, J.

    2006-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Frink, Sabine

    2003-10-01

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

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Torres, Guillermo

    2006-02-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Yatskiv, Ya. S.

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

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

    PubMed Central

    Avarguès-Weber, Aurore; Chittka, Lars

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

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

    SciTech Connect

    Gatewood, George

    2008-07-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  19. Astrometric Follow-Up of Faint Near Earth Objects

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    PubMed Central

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

    2011-01-01

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

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

    ERIC Educational Resources Information Center

    Napoles, Jessica; MacLeod, Rebecca B.

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Kohlhauf, Lucia; Rutke, Ulrike; Neuhaus, Birgit

    2011-10-01

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

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

    NASA Technical Reports Server (NTRS)

    Marston, Anthony P.

    1995-01-01

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

  4. JASMINE-astrometric map of the galactic bulge .

    NASA Astrophysics Data System (ADS)

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

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

  5. JASMINE-Astrometric Map of the Galactic Bulge-

    NASA Astrophysics Data System (ADS)

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

    2006-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  9. Optical system for an astrometric survey from space

    NASA Astrophysics Data System (ADS)

    Phillips, James D.; Reasenberg, Robert D.

    1998-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-10-01

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

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

    NASA Astrophysics Data System (ADS)

    White, J.

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

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Gaudi, B. Scott; Bloom, Joshua S.

    2005-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    PubMed

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

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

    PubMed

    Vogel, H G; Hilgner, W

    1979-03-31

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-08-01

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

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

    PubMed

    Hermens, Frouke; Walker, Robin

    2016-08-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

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

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

    PubMed

    Lansu, Tessa A M; Cillessen, Antonius H N

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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