On the Feasibility of a Star Coordinate Determination in the Radio Astrometry Reference System

Extract

At present it is evident that the stability of a celestial coordinates system with an accuracy of at least per century, with respect to an internal frame can be derived only from VLBI observations of compact extragalactic radio sources. At the same time it is expected that the need for improved stars' coordinates will be strongly felt at least up to the end of this century, because stars are important and more convenient observational objects then very weak extragalactic sources or artificial Earth satellites (AES). One therefore wonders if one can use the high precision and stability of the radio astrometric reference frame to stabilize and improve the reference frame given by star catalogues. The problem of the relationship between these systems has so far been investigated in the form of determining the parameters of their mutual orientation, and/or studying systematic errors of star catalogues (Gubanov, 1978; Gubanov and Kumkova, 1978, 1981). This problem has been attacked by direct photography of several optically identified radio sources or VLBI observations of few radio stars. The present paper shows the feasibility of determining the place of any star of sufficient magnitude with reference to the radio astrometric frame, as given by extragalactic source positions (Gubanov, 1983). This is done by introducing an AES, equipped with radio signal for VLBI observations and a corner reflector for laser ranging, which can be observed by radio methods as well as optically (Gubanov, 1976). This satellite should also be bright enough in the reflected sun's light to be observed in the star field with a precision photoelectric satellite camera.