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Hipparcos catalogue orientation as obtained from observations of minor planets
Yu.V. Batrakov 1,
Yu.A. Chernetenko 1,
G.K. Gorel 2 and
L.A. Gudkova 2
Received 27 October 1998 / Accepted 15 April 1999
Ground-based photographic observations of 12 minor planets obtained at Nikolaev observatory (Ukraine) between 1961-1995 were reduced to the Hipparcos catalogue system and processed by the least squares method (LSM) separately and in combination with the Hipparcos NDAC (the Northern Data Analysis Consortium) and FAST (the Fundamental Astronomy by Space Techniques) observations of 48 minor planets. The aim was to estimate the accuracy of the Nikolaev observations and to determine the orientation of the International Celestial Reference System (ICRS) with respect to the DE200/LE200 dynamic frame of reference. The Nikolaev observations proved to be sufficiently accurate, the unit weight error being of order of . The results of separate processing of Nikolaev and Hipparcos observations were not satisfactory for two reasons. First, the Nikolaev observations only measured accurately the changes of orientation parameters, and second, the Hipparcos observations only accurately measured the values of the orientation parameters themselves. However by combining the observations, the accuracy was greatly enhanced. The weight of the Hipparcos observations was taken to be unity and that one of the Nikolaev observations was chosen as 0.01, in accordance with the corresponding unit weight errors. The photocentre offsets were taken into account and three models of these offsets were considered. In the final processing the offset model based on the Lommel-Seeliger law of light scattering at the asteroid surface was used.
The values of the orientation parameters of the ICRS and their time changes were obtained for epoch JD 2448439.5 (in mas for and mas/year for ). The combined solution based on NDAC and Nikolaev observations is . The combined solution based on FAST and Nikolaev observations is . The values obtained for are of the same order as their errors. The obtained estimates and those of Folkner et al. (1994) range in accordance with 3-tolerances.
Key words: astrometry reference systems minor planets, asteroids
Send offprint requests to: Yu.A. Chernetenko
Online publication: December 2, 1999