Maigurova N. Refinement of Linkage between the Radio and Optical Coordinate Systems by using CCD Observations of Selected Extragalactic Radio Sources in Optical Band

The dissertation is devoted to the problem of linkage between the HIPPARCOS Celestial Reference Frame (HCRF) and ICRF. Positions of extragalactic radio sources (ERS) in ICRF were determined with VLBI methods. CCD observations of optical counterparts of the ERS were used. The optical positions of 213 selected ERS in declination zone from -30° to + 80° were obtained with accuracy at the level of 40 mas. The astrometric reductions were mainly made by using reference stars from the UCAC2 and the USNO B1.0 catalogues. The obtained catalogue is the basement to refine mutual orientation angles between the optical and radio systems as well it may be used to increase the accuracy of the optical coordinates of the radio sources which have been used to determine ICRF. Comparison between mean optical and radio positions of the ERS were made. This comparison allowed us to obtain orientation angles between radio and optical coordinate systems at accuracy level of 6 mas. In order to spread the HIPPARCOS catalogueover more faint stars the catalogue of positions more than 10000 stars of 10-21 magnitude around the ERS was obtained. Positional accuracy of stars in the catalogue is between 25 and 60 mas for 14-20 stellar magnitude.