Feb 3 1982
From The Space Library
On the basis of data acquired in support of its mission objectives, NASA declared successful the Viking extended mission conducted from the end of its primary mission in 1976 until August 1980. Viking's mission was to explore the planet Mars using two instrumented orbiters operating in con-junction with two instrumented landers on the surface. Identical spacecraft launched in 1975, each consisting of an orbiter and a lander, began operating at Mars in 1976. The design life of the spacecraft was 90 days following orbit insertion or landing on the Martian surface; however, the Viking flight team found "ingenious ways" to extend the operating lifespans and obtain the maximum possible science data.
When the extended mission began November 15, 1976, Orbiter 2 operated until July 24, 1978 (another 20 months), when a small leak in its attitude-control system depleted its gas supply. Lander 2 operated on the planet's surface for 41 months, until April 12, 1980; its transmitter was turned off when its batteries could no longer hold a charge. Orbiter 1 lasted even longer, a total of 45 months after orbital insertion, and completed is operations August 7, 1980, when its control gas was also exhausted. The end of Orbiter 1 operation was to be the official end of the Viking extended mission; however, Lander 1-designated the Mutch Memorial Station January 7, 1981-was still operating in a continuation automatic-mission mode and providing important science data.
Extended-mission 'objectives were "to obtain seasonal variations, long-duration sampling for statistically important experiments, and to obtain data not possible during the primary mission due to time constraints or observational limitations" Mission results were "far in excess of those expected." The program now consisted of Lander 1's acquiring and storing imaging, meteorology, and engineering data in a seven-plus day cycle and transmitting to Earth on command. Data should continue until the end of 1994, when the radioisotope thermoelectric generator (RTG) could no longer power the transmitters. (NASA MOR S-815-75-01/02 [postlaunch] Feb 3/82; NASA Release 82-36)
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