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Let's go to Mars

The Soviet Union loses both Phobos probes

Phobos 1 died in September 1988 to a flawed command sequence. Phobos 2 reached Mars orbit and failed in March 1989, weeks before dropping its landers.

A detailed museum model of a Soviet interplanetary probe: an instrument-covered body ringed with sensors, a dish antenna on top, flat panels spread to each side, standing on a cluster of white spherical propellant tanks.
A model of the Phobos spacecraft in the Memorial Museum of Cosmonautics in Moscow. Each of the two craft launched at 6,220 kilograms, the missions drew contributions from fourteen countries besides the Soviet Union, and Phobos 2 carried two landers — a mobile hopper and a stationary platform — that it never got to release. · Image: Музей Космонавтики (Museum of Cosmonautics, Moscow)

Phobos 1 left Baikonur on 7 July 1988, Phobos 2 five days later: six-tonne spacecraft carrying instruments from fourteen countries, built to orbit the planet, creep up on its inner moon and set landers on it — a long-lived station harpooned to the surface, and, on Phobos 2, a hopper, PROP-F, that would travel by jumping.

A command sequence killed Phobos 1. On 29–30 August instructions were uplinked without the usual ground verification, the checking software being unavailable, and a single wrong character switched off the attitude-control system. The spacecraft drifted, its solar panels slid off the Sun, the batteries ran flat, and the scheduled contact on 2 September never came.

Phobos 2 was the most productive Soviet Mars mission since 1974. It entered orbit on 29 January 1989, moved inward to match Phobos's 9,400-kilometre orbit, and returned 37 images of the moon at a best resolution of about 40 metres, with infrared spectra of its surface. Its ASPERA instrument measured ions streaming off the top of the Martian atmosphere, early direct evidence of the solar wind stripping the planet's air away. The same team flew ASPERA-3 on Mars Express fifteen years later; no firm number was put on the loss rate until MAVEN.

On 27 March 1989 the on-board computer failed, shortly before the spacecraft was to close to within 50 metres of Phobos's surface and release the landers. Controllers got one weak, garbled transmission from a tumbling spacecraft, then nothing.

The Soviet Union dissolved in 1991 without launching anything else toward Mars. Russia's Mars 96 came back down on 17 November 1996, its upper stage having misfired in Earth parking orbit, scattering debris across the Pacific and the Andes with two surface stations and two penetrators aboard. Viking 1's lander had gone quiet in November 1982, and nothing worked on the surface of Mars again until July 1997; in that fifteen-year gap the only spacecraft to return anything from Martian orbit was Phobos 2, for two months.