|Mission type||Mars flyby
|Launch date||9 August 1973, 17:00:17UTC|
|Launch site||Baikonur 81/24|
|COSPAR ID||Bus: 1973-053A
Mars 7 (Russian: Марс-7), also known as 3MP No.51P was a Soviet spacecraft launched to explore Mars. A 3MP spacecraft which comprised the final mission of the Mars programme, it consisted of a lander and a coast stage with instruments to study Mars as it flew past. Due to a malfunction, the lander failed to perform a manoeuvre necessary to enter the Martian atmosphere, missing the planet and remaining in heliocentric orbit along with the coast stage.
Mars 7 spacecraft carried an array of instruments to study Mars. The lander was equipped with a thermometer and barometer to determine the surface conditions, an accelerometer and radio altimeter for descent, and instruments to analyse the surface material including a mass spectrometer. The coast stage, or bus, carried a magnetometer, plasma traps, cosmic ray and micrometeoroid detectors, stereo antennae, and an instrument to study proton and electron fluxes from the Sun.
Built by Lavochkin, Mars 7 was the second of two 3MP spacecraft launched to Mars in 1973; having been preceded by Mars 6. Two orbiters, Mars 4 and Mars 5 were launched earlier in the 1973 Mars launch window, and were expected to relay data for the two landers, however Mars 4 failed to enter orbit, and Mars 5 failed after a few days in orbit.
Mars 7 was launched by a Proton-K carrier rocket with a Blok D upper stage, flying from Site 81/24 at the Baikonur Cosmodrome. The launch occurred at 17:00:17 UTC on 9 August 1973, with the first three stages placing the spacecraft and upper stage into a low Earth parking orbit before the Blok D fired to propel Mars 7 into heliocentric orbit bound for Mars. The spacecraft performed a course correction on 16 August 1973.
Mars 7's lander separated from the flyby bus on 9 March 1974. Initially if failed to separate, however it was eventually released to begin its descent. Due to a retrorocket failure, the probe missed the atmosphere of Mars, and instead of landing flew past along with the coast stage, with a closest approach of 1,300 kilometres (810 mi). Known faults with the spacecraft's transistors were blamed for the failure, along with that of Mars 4.
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- Siddiqi, Asif A. (2002). "1973". Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000. Monographs in Aerospace History, No. 24. NASA History Office. pp. 101–106.