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FOR IMMEDIATE RELEASE                                                September 15, 1990

       The Magellan spacecraft began radar mapping the surface of Venus Saturday morning, signaling recovery from a series of problems aboard the spacecraft during the past month.

       Flight controllers at NASA's Jet Propulsion Laboratory said the spacecraft's imaging radar was turned on Friday and mapping began Saturday over Venus' north pole.

       "We've kicked off radar mapping," said Project Manager Anthony Spear. "We're acquiring data and everything looks good."

       Magellan Project engineers, however, were still working to find the cause of the spacecraft's two earlier losses of signal.

       Magellan lost radio contact with Earth during the second orbit of a radar mapping test Aug. 16. The signal was reacquired the next day, but was lost again for several hours Aug. 21

       Saturday, the radar mapping operations were performed under the control of a stored onboard computer sequence. The spacecraft turned its high-gain antenna away from Earth at 9:29 a.m. PDT in preparation for the start of mapping. The radar began to illuminate the surface of the planet at 9:35 a.m. as it passed over the north pole and the first mapping orbit data collection was completed at 10:13 a.m.

       The high-gain antenna was then turned back to Earth and the signal was acquired at the Goldstone Deep Space Network station in California using two 34-meter antennas connected in an array.

       Magellan played back one of its two tape recorders, and turned away from Earth to perform a star scan to correct its attitude. The tar scan was successful, with an attitude update of 0.017 degrees. Playback of the second tape recorder was completed shortly after noon.

       That sequence of activities will be repeated continuously for the duration of the 243-day mapping mission, with the exception of a four-orbit break for radar accuracy and performance assessment on Sept. 25-26.

       On Saturday, about two and one-half mapping orbits were acquired at the Goldstone station and then the spacecraft signal was handed over to the Canberra DSN station in Australia, and subsequently to the Madrid station in Spain.

       Data from the initial Goldstone orbits was to be processed during the weekend.

       Before the start of radar operations, the project completed playback of all the radar data and engineering telemetry stored on the spacecraft tape recorders before the loss of signal experienced Aug. 16. That data was being analyzed for evidence of the source of the problems.

       The spacecraft was 156-million miles from Earth Saturday. Radio signals took 13 minutes and 53 seconds to travel each way between Venus and Earth.

       A Magellan news conference is scheduled for Sept. 25. The location is to be announced.


9/15/90 JJD