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       A new radio-astronomy technique using an orbiting satellite to study celestial objects has been successfully tested by an international team of scientists led by researchers from JPL.

       Conducting experiments in July and August 1986, the scientists were able to obtain resolutions of three quasars better than that possible in any ground-based radio studies at the same wavelength. Quasars, or quasi-stellar objects, are among the most distant objects known.

       Experimenters used the technique of very long baseline interferometry (VLBI) to combine data from radio telescopes on the ground with data from an antenna on Tracking and Data Relay Satellite System (TDRSS) spacecraft, managed by NASA's Goddard Space Flight Center.

       The experiments success, researchers said, demonstrates the feasibility of proposed orbiting VLBI mission, QUASAT, under study by NASA and the European Space Agency. That mission would use satellite dedicated to radio- astronomy observations, and would yield new data on many celestial phenomena, such as the nature of galactic nuclei, the overall distance scale of the universe and the formation of new stars.

       This is the first time VLBI experiment has used an orbiting satellite as one of its radio telescopes. In the past scientists have linked widely separated antennas on the ground with VLBI techniques to produce high-resolution radio astronomy studies of celestial objects.

       The resolution obtained from the orbiting VLBI experiment, however, was equivalent to that of radio telescope with size of 1.4 Earth diameters. The quasars studied are designated 1730-130, 1741-038 and 1510-089.

       Results of the experiment will appear in the Oct. 10 issue of Science.

       Chief ground observatories in the experiment were NASA's Deep Space Network 64-meter (210-foot) antenna in Australia and the Institute of Space and Astronautical Sciences' 64-meter antenna at Usuda, Japan. 25-meter (80- foot) antenna at the Radio Research Laboratory in Kashima, Japan, was also used to check performance of the larger ground antennas.

       The experiment team, led by Gerald S. Levy of JPL, included scientists from JPL; the Massachusetts Institute of Technology, Cambridge, Massachusetts; the Haystack Observatory, Westford, Massachusetts; NASA's Goddard Space Flight Center, Greenbelt, Maryland; Bendix Field Engineering Corp., Columbia, Maryland; and the SpaceCom/TRW/Bendix team, White Sands, New Mexico. Participants in Australia represented the Commonwealth Scientific and Industrial Research Organization and Australian National University's Mount Stromlo Observatory. Japanese experimenters represented that country's Institute of Space and Astronautical Science, the Nobeyama Radio Observatory and the Radio Research Laboratory.

       JPL portions of the experiment were sponsored by NASA's Office of Space Tracking and Data Systems and Office of Space Science and Applications.

10/2/86 FOD