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Fobos 2
Fobos 2 (click to enlarge)

Fobos 2
Date: 12 Jul 1988

Fobos 2 had the same mission as its twin Fobos 1 but had an additional payload on board, a 110-kilogram hopper designed to make up to ten 20-meter jumps across the Phobos surface to gather surface data on the tiny Martian moon. The orbiter also had a slightly different instrument complement.

Fobos 2 carried out two en route course corrections on 21 July 1988 and 23 January 1989, despite some major problems. One of the two radio transmitters failed when there were spuriously generated commands in one channel of its computer.

At 12:55 UT on 29 January 1989, the spacecraft fired its engine to enter orbit around Mars. Initial orbital parameters were 819 x 81,214 kilometers at 1.5° inclination. After four further orbital corrections, its trajectory was put on an encounter course with Phobos.

Fobos 2 took high-resolution photos of the moon on 23 February (at a range of 860 kilometers), 28 February (320 kilometers), and 25 March 1989 (191 kilometers).

Release of its lander was scheduled for 45 April 1989, but on 27 March, during a regularly planned communications session at 15:58 UT, there was no word from the spacecraft. A weak signal was received between 17:51 and 18:03 UT, but there was no telemetry information. The nature of the signal indicated that the spacecraft had lost all orientation. Future attempts to regain communication were unsuccessful, and the mission was declared lost on 15 April 1989. The most probable cause of failure was simultaneous malfunctions in both channels of the onboard computer (due to insufficiently robust software) that put the spacecraft into an improper tumble.

Credit: NSSDC Photo Gallery

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