Mars 7 (), also known as 3MP No.51P was a

Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

spacecraft launched in 1973 to explore

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...

. A 3MP bus spacecraft which comprised the final mission of the

Mars program The Mars program was a series of uncrewed spacecraft launched by the Soviet Union between 1960 and 1973. The spacecraft were intended to explore Mars, and included flyby probes, landers and orbiters. Early Mars spacecraft were small, and launche ...

me, 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 The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and no ...

, missing the planet and remaining in

heliocentric orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun i ...

along with the coast stage.

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 Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used ...

. The coast stage, or bus, carried a

magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, o ...

, plasma traps, cosmic ray and micrometeoroid detectors, stereo antennae, and an instrument to study

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

and

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...

es from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. Built by Lavochkin, Mars 7 was the second of two 3MP spacecraft launched to Mars in 1973, having been preceded by

Mars 6 Mars 6 (), also known as 3MP No.50P was a Soviet spacecraft launched to explore Mars. A 3MP bus spacecraft launched as part of the Mars program, it consisted of a lander, and a coast stage with instruments to study Mars as it flew past. Spacecr ...

. Two orbiters,

Mars 4 Mars 4 (), also known as 3MS No.52S was a Soviet Union, Soviet spacecraft intended to explore Mars. A 3MS spacecraft launched as part of the Mars programme, it was intended to enter orbit around Mars in 1974. However, computer problems prevented ...

and

Mars 5 Mars 5 (), also known as 3MS No.53S was a Soviet spacecraft launched to explore Mars. A 3MS spacecraft launched as part of the Mars programme, it successfully entered orbit around Mars in 1974. However, it failed a few weeks later. Spacecraft T ...

, 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. 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 A parking orbit is a temporary orbit used during the launch of a spacecraft. A launch vehicle boosts into the parking orbit, then coasts for a while, then fires again to enter the final desired trajectory. The alternative to a parking orbit is ''di ...

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, 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 . Known faults with the spacecraft's

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...

s were blamed for the failure, along with that of Mars 4.

References

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Spacecraft

Launch

See also

References