Results and communications considerations of the very long baseline interferometry demonstration using the tracking and data relay satellite system

Abstract

A desire for increased angular resolution at microwave frequencies has led to the development of radio telescopes with very large effective apertures. Very long baseline interferometry (VLBI) has made it possible to synthesize telescopes with effective dimensions of a large fraction of an Earth diameter. By using a satellite-borne radio telescope as part of a VLBI array, the dimensions of the Earth cease to be a limitation. The use of a satellite VLBI telescope puts stringent requirements on the communication links between the spacecraft and the ground. A demonstration was performed to show that the orbiting VLBI (OVLBI) concept is feasible. The Tracking and Data Relay Satellite System (TDRSS) was used as the orbiting element of the VLBI demonstration. Stability tests were made before the observations to determine the suitability of the TDRSS for OVLBI use. The first successful OVLBI observations were performed using the 64-m antenna observatories of NASA's Deep Space Network in Tidbinbilla, Australia, and of the Institute for Space and Astronautical Science in Usuda, Japan in conjunction with the TDRSS. Data from three quasars were successfully correlated at the Haystack Observatory in Westford, Mass.; the results were used to deduce the system performance.