Abstract:
Current release of the Gaia mission provides representation of a new reference frame on an unprecedent level of accuracy. This astrometric catalogue is practically free of systematic errors with respect to astrometric ground-based observations. First applications Gaia DR1 and Gaia DR2 as a reference in an analysis of CCD-observations of asteroids and planetary satellites demonstrated small decrease of formal positional errors. The basic reasons are unaccounted systematic effects of telescope projection and offsets caused by atmospheric dispersion. As a result, positional error of the Solar system bodies` observations performed with the "Saturn" 1-m telescope at Pulkovo Observatory (F/D = 4) is in the range of 20 — 80 mas. A frame-to-frame astrometric transformation gives the error level less than 5 — 30 mas. One of possible ways to transfer subpixel accuracy to the final positions of the Solar system bodies are observations of close approaches of satellites or asteroids to the Gaia stars. The main idea is that systematic displacements caused by atmospheric effects and telescope optics that occur in close approaches (<10 arcsec) are the same for asteroids and the Gaia stars. This makes it possible to significantly improve the quality of ground-based astrometry of the Solar system bodies, taking into account the fairly dense distribution of Gaia stars across the celestial sphere.
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