PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
FOR IMMEDIATE RELEASE                                                May 11, 1991

       Ten and one-half orbits of Venus mapping were lost over one and a half days by the Magellan spacecraft when the high-gain antenna pointed away from Earth early Friday following a routine star calibration.

       Pointing was recovered by another star calibration Saturday morning at 9:55 a.m. PDT.

       The interruption began at 1:22 a.m. PDT Friday. Although the Deep Space Network station in Madrid, Spain, reacquired the radio signal from Magellan about six hours later which was adequate for engineering data, the radar mapping data was not received.

       It was the third interruption in the signal since Magellan began mapping Venus last Sept. 15. Previous incidents were in mid-November 1990 when the mapping data was lost for 9 hours and in early March this year when the data was lost for 10 hours. Analysis then indicated the interruption may have been caused by noise on the spacecraft circuits. Engineers are analyzing the current data to determine if this also caused the most recent problem.

       Only 0.3 percent of the surface map was lost. Magellan will have mapped 83 percent of the planet by May 15, the end of its primary mapping cycle, and the lost data will be acquired in the next cycle.


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5/11/91 JJD
#1375