Catalogue reduction techniques

1978 ◽  
Vol 48 ◽  
pp. 389-390 ◽  
Author(s):  
Chr. de Vegt
Keyword(s):  
Adjustment Process ◽  
Proper Motions ◽  
Measuring Process ◽  
Aerial Photogrammetry ◽  
Reduction Techniques ◽  
Observational Technique ◽  
The Common ◽  
Astrometric Data

AbstractReduction techniques as applied to astrometric data material tend to split up traditionally into at least two different classes according to the observational technique used, namely transit circle observations and photographic observations. Although it is not realized fully in practice at present, the application of a blockadjustment technique for all kind of catalogue reductions is suggested. The term blockadjustment shall denote in this context the common adjustment of the principal unknowns which are the positions, proper motions and certain reduction parameters modelling the systematic properties of the observational process. Especially for old epoch catalogue data we frequently meet the situation that no independent detailed information on the telescope properties and other instrumental parameters, describing for example the measuring process, is available from special calibration observations or measurements; therefore the adjustment process should be highly self-calibrating, that means: all necessary information has to be extracted from the catalogue data themselves. Successful applications of this concept have been made already in the field of aerial photogrammetry.

scholarly journals Corrected μβ for stars of Hipparcos catalogue from independent latitude observations over many decades

2011 ◽  
pp. 35-41 ◽  
Author(s):  
G. Damljanovic ◽  
I.S. Milic
Keyword(s):  
International Organizations ◽  
Sufficient Accuracy ◽  
Proper Motions ◽  
Earth Orientation Parameters ◽  
Method Of Calculation ◽  
The Earth ◽  
Hipparcos Catalogue ◽  
International Polar ◽  
The Common ◽  
Orientation Parameters

During the last century, there were many so-called independent latitude (IL) stations with the observations which were included into data of a few international organizations (like Bureau International de l'Heure - BIH, International Polar Motion Service - IPMS) and the Earth rotation programmes for determining the Earth Orientation Parameters - EOP. Because of this, nowadays, there are numerous astrometric ground-based observations (made over many decades) of some stars included in the Hipparcos Catalogue (ESA 1997). We used these latitude data for the inverse investigations - to improve the proper motions in declination ?? of the mentioned Hipparcos stars. We determined the corrections ??? and investigated agreement of our ?? and those from the catalogues Hipparcos and new Hipparcos (van Leeuwen 2007). To do this we used the latitude variations of 7 stations (Belgrade, Blagoveschtschensk, Irkutsk, Poltava, Pulkovo, Warsaw and Mizusawa), covering different intervals in the period 1904.7 - 1992.0, obtained with 6 visual and 1 floating zenith telescopes (Mizusawa). On the other hand, with regard that about two decades have elapsed since the Hipparcos ESA mission observations (the epoch of Hipparcos catalogue is 1991.25), the error of apparent places of Hipparcos stars has increased by nearly 20 mas because of proper motion errors. Also, the mission lasted less than four years which was not enough for a sufficient accuracy of proper motions of some stars (such as double or multiple ones). Our method of calculation, and the calculated ?? for the common IL/Hipparcos stars are presented here. We constructed an IL catalogue of 1200 stars: there are 707 stars in the first part (with at least 20 years of IL observations) and 493 stars in the second one (less than 20 years). In the case of ?? of IL stars observed at some stations (Blagoveschtschensk, Irkutsk, Mizusawa, Poltava and Pulkovo) we find the formal errors less than the corresponding Hipparcos ones and for some of them (stations Blagoveschtschensk and Irkutsk) even less than the new Hipparcos ones.

scholarly journals A Comprehensive Astrometric Data Base: An Instrument for Combining Earth-Bound Observations With Hipparcos Data

1990 ◽  
Vol 141 ◽  
pp. 483-488
Author(s):  
Roland Wielen
Keyword(s):  
Data Base ◽  
Proper Motion ◽  
Data Bank ◽  
Space Missions ◽  
Proper Motions ◽  
Astrometric Data

The astrometric data bank ARIGFH will contain all relevant astrometric data on stellar positions and proper motions of stars from ground-based observations and space missions. For each star in the ARIGFH, the best available position and proper motion shall be derived. We rediscuss the accuracy of proper motions and positions of fundamental stars, resulting from a combination of data in the FK5 with the expected results from a revised HIPPARCOS mission. The FK5 data could be significantly improved even by rather degraded positions from a revised HIPPARCOS mission.

scholarly journals The Gaia mission: science, organization and present status

2007 ◽  
Vol 3 (S248) ◽  
pp. 217-223 ◽  
Author(s):  
L. Lindegren ◽  
C. Babusiaux ◽  
C. Bailer-Jones ◽  
U. Bastian ◽  
A. G. A. Brown ◽  
...  
Keyword(s):  
Proper Motions ◽  
Velocity Measurements ◽  
Expected Performance ◽  
Wide Range ◽  
Operational Lifetime ◽  
Optical Reference ◽  
Spectrophotometric Data ◽  
Space Astrometry ◽  
Technical Features ◽  
Astrometric Data

AbstractThe ESA space astrometry mission Gaia will measure the positions, parallaxes and proper motions of the 1 billion brightest stars on the sky. Expected accuracies are in the 7–25 μas range down to 15 mag and sub-mas accuracies at the faint limit (20 mag). The astrometric data are complemented by low-resolution spectrophotometric data in the 330–1000 nm wavelength range and, for the brighter stars, radial velocity measurements. The scientific case covers an extremely wide range of topics in galactic and stellar astrophysics, solar system and exoplanet science, as well as the establishment of a very accurate, dense and faint optical reference frame. With a planned launch around 2012 and an (extended) operational lifetime of 6 years, final results are expected around 2021. We give a brief overview of the science goals of Gaia, the overall project organisation, expected performance, and some key technical features and challenges.

scholarly journals Around Gaia Alerts in 20 questions

2011 ◽  
Vol 7 (S285) ◽  
pp. 425-428 ◽  
Author(s):  
Łukasz Wyrzykowski ◽  
Simon Hodgkin
Keyword(s):  
Data Stream ◽  
European Space Agency ◽  
Space Mission ◽  
Proper Motions ◽  
Space Agency ◽  
Large Numbers ◽  
Formation History ◽  
The Galaxy ◽  
Optical Wavelengths ◽  
Astrometric Data

AbstractGaia is a European Space Agency (ESA) astrometry space mission, and a successor to the ESA Hipparcos mission. Gaia's main goal is to collect high-precision astrometric data (positions, parallaxes, and proper motions) for the 1 billion brightest objects in the sky. Those data, complemented with multi-band, multi-epoch photometric and spectroscopic data observed from the same observing platform, will allow astronomers to reconstruct the formation history, structure, and evolution of the Galaxy.Gaia will observe the whole sky for 5 years, providing a unique opportunity for the discovery of large numbers of transient and anomalous events such as supernovæ, novæ and microlensing events, GRB afterglows, fallback supernovæ, and other theoretical or unexpected phenomena. The Photometric Science Alerts team has been tasked with the early detection, classification and prompt release of anomalous sources in the Gaia data stream. In this paper we discuss the challenges we face in preparing to use Gaia to search for transient pheonomena at optical wavelengths.

scholarly journals New accuracy levels for solar system ephemerides

1996 ◽  
Vol 172 ◽  
pp. 29-36 ◽  
Author(s):  
E. M. Standish ◽  
X X Newhall
Keyword(s):  
Solar System ◽  
Reference Frame ◽  
Data Reduction ◽  
Equations Of Motion ◽  
Adjustment Process ◽  
Dynamical Modeling ◽  
Reduction Techniques ◽  
Condensed Representation ◽  
Lunar Ephemeris ◽  
Hipparcos Catalogue

DE403/LE403 is the latest JPL Planetary and Lunar Ephemeris. It represents a number of changes and improvements to previous JPL ephemerides: the reference frame is now that of the IERS, newer and more accurate observations are used in the adjustment process, some of the data reduction techniques have been refined, and improved dynamical modeling has been incorporated into the equations of motion. As a result, the internal accuracy of the inner four planets has been improved. Further, various measurements accurately tie Jupiter onto the IERS Reference Frame. In the future, use of CCD measurements and the Hipparcos Catalogue should improve the ephemerides of the outermost four planets.DE403/LE403 has been integrated over 6000 years, from 3000 BC to 3000 AD. A more condensed representation has been made from this, named DE404/LE404. It replaces DE102 as the new JPL “Long Ephemeris”.

scholarly journals Hipparcos: An Example Of Astrophysical Uses Of Astrometric Data

1988 ◽  
Vol 133 ◽  
pp. 259-264
Author(s):  
A.E. Gómez ◽  
F. Crifo
Keyword(s):  
Spectral Type ◽  
Open Cluster ◽  
Proper Motions ◽  
Distribution Versus ◽  
Mean Error ◽  
Double Stars ◽  
Rr Lyrae ◽  
Scale Calibration ◽  
Stellar Masses ◽  
Astrometric Data

Hipparcos will measure positions, proper motions and parallaxes for about 110 000 stars brighter than B = 13, with an expected mean error of 2.10−3 arcsec in positions and parallaxes and 2.10−3 arcsec/year in proper motions. The contents of the first provisional catalogue with respect to astrophysical problems is described, and the star distribution versus spectral type, magnitude and distance is given. All types of stars are well represented (spectral types, various evolutionary stages, giants, white dwarfs, …). Precise parallaxes for 29 000 stars closer than 100 pc will provide a new base for luminosity calibration, and will allow accurate stellar masses to be determined from double stars with known orbits. Precise proper motions, in conjunction with the improved distances, will substantially improve our knowledge of galactic structure. All types of stars used for the cosmic distance scale calibration are well represented: Cepheids, RR Lyrae, supergiants, open cluster stars.

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