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Calculation of the new series of the Earth orientation parameters in the HIPPARCOS reference frame.

Vondrak, J.

The succesful lauchch of the HIPPARCOS astrometric satellite by the ESA in August 1989 enables the past observations, obtained by optical astrometry all over the world since the beginning of the century, to be re-reduced in order to get the Earth orientation parameters in a homogeneous and unique celestial reference frame. Completely new algorithm…

Quasr link conditions for Hipparcos.

Ducourant, C.; Brosche, P.; Geffert, M. +2 more

Fictitious proper motions of quasars and of their surrounding stars have been determined based on plates with epoch differences of up to 90 yrs. From the fact that the true proper motions of the quasar are vanishingly small, we obtain conditions for the extragalactic calibration of the preliminary Hipparcos system. We present results for the field…

Modern Photographic Catalogue Work - Aspects of Observing Techniques and Reduction Methods

de Vegt, Chr.

The consequent application of present optical technology for the construction of substantially improved instrumentation in photographic astrometry and the application of rigorous reduction techniques provide all means for the construction of new, global position catalogs with a precision of a few 0.01 arcsec. At the same time the limiting magnitud…

Objectives of ground-based astrometry after HIPPARCOS

Kovalevsky, J.

After a short summary of the results expected from the HIPPARCOS mission, the author gives several examples illustrating the needs that will arise afterwards in order to maintain the level of precision achieved and to extend it to many more objects. Three domains are particularly dealt with in this paper:The maintenance of the HIPPARCOS reference …

Tautenburg proper motion fields

Scholz, R. -D.; Hirte, S.

The possible use of Tautenburg Schmidt plates to determine proper motions was analyzed using the new data base of the Tautenburg plate archive. All fields with at least four first epoch plates were included along with the 10 Hipparcos-Tautenburg link fields and the 17 fields in the program of the main meridional section of the Galaxy. The distribu…

Speckle interferometry of HIPPARCOS link stars - III.

White, G. L.; Argue, A. N.; Reynolds, J. E. +5 more

A third list of stars is presented which have been tested by speckle interferometry for use in the Hubble Space Telescope link between the Hipparcos astrometric reference frame and the extragalactic VLBI reference frame. Structural information on angular scales of 0.15-1.2 arcsec for 34 Southern Hemisphere stars is reported from observations made …

Scientific requirements for very accurate astrometry

Turon, C.; Kovalevsky, J.

Two types of accurate astrometric data are considered:

1) Survey astrometry providing absolute parallaxes and annual proper motions with an accuracy of 2 milli-arcsec, to a few tenth of a milli-arcsec. Parallax determinations will advance our basic knowledge of the Universe by giving the necessary strong foundations for the first steps of the…

UBVRI photometry of G, K, M HIPPARCOS stars. II.

Jordi, C.; Figueras, F.; Torra, J. +2 more

As indicated by Grenon (1989), the data of the present series of reports on the UBVRI photometry of late-type stars in the Hipparcos Input Catalog are to be employed in computations of Hipparcos observing time, as well as in evaluating the observability of faint stars by the satellite. Attention is here given to late type stars in the V = 8-12 ran…

Hipparcos calibration

Schrijver, Hans

The methods and results of various Hipparcos in-flight calibrations are described. The geometrical calibrations allow the determination of the instrument distortions in the main field of view to better than a milli-arcsecond. A systematic decrease of the basic angle at a rate of two milli-arcseconds per month has been measured during the first 7 m…

A comparison between two strategies of data reduction for the Hipparcos project

Lattanzi, M. G.; Bucciarelli, B.; Sarasso, M. +2 more

Two different strategies for reducing HIPPARCOS data are directly compared and their respective impact on the final precision of the HIPPARCOS Catalog is evaluated. These strategies are the FAST (Fundamental Astronomy by Space Techniques) Consortium's Baseline and GLOBUS procedures. The Baseline is already operating on satellite data; GLOBUS was i…