Mars 7

Mars 7 (Russian: Марс-7), also known as 3MP No.51P was a Soviet spacecraft launched in 1973 to explore Mars. A 3MP bus 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 maneuver necessary to enter the Martian atmosphere, missing the planet and remaining in heliocentric orbit along with the coast stage.

Mars 7

Mission type	Mars flyby/lander[1]
Operator	Soviet space program
COSPAR ID	1973-053A 1973-053E
SATCAT no.	6776[2] 7224
Mission duration	7 months, 16 days
Spacecraft properties
Spacecraft	3MP No.51P
Manufacturer	NPO Lavochkin
Launch mass	3,260 kg (7,190 lb)[2]
Landing mass	635 kg (1,400 lb)
Start of mission
Launch date	9 August 1973, 17:00:17 (1973-08-09UTC17:00:17Z) UTC[3]
Rocket	Proton-K/D
Launch site	Baikonur 81/24
Contractor	Khrunichev
End of mission
Last contact	25 March 1974[4]
Orbital parameters
Reference system	Heliocentric
Flyby of Mars
Spacecraft component	Bus
Closest approach	9 March 1974
Mars flyby (failed landing)
Spacecraft component	Lander
Closest approach	9 March 1974
Distance	1,300 km (810 mi)
Mars program ← Mars 6

Spacecraft

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.^[5] 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.^[5]

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.

Launch

Mars 7 was launched by a Proton-K carrier rocket with a Blok D upper stage, flying from Baikonur Cosmodrome Site 81/24.^[3] 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.^[5]

Mars 7's lander separated from the flyby bus on 9 March 1974. Initially, it 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 km (810 mi).^[5] Known faults with the spacecraft's transistors were blamed for the failure, along with that of Mars 4.^[5]

See also

• List of missions to Mars
• Timeline of artificial satellites and space probes