Mars 5 (Russian: Марс-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.[4]
Spacecraft
The Mars 5 spacecraft carried an array of instruments to study Mars. In addition to cameras, it was equipped with a radio telescope, an IR radiometer, multiple photometers, polarimeters, a magnetometer, plasma traps, an electrostatic analyser, a gamma-ray spectrometer, and a radio probe.[5] The Three cameras were a 52mm Vega, a 350mm Zulfar and a panoramic camera.[6]
Built by Lavochkin, Mars 5 was the second of two 3MS spacecraft launched to Mars in 1973, following Mars 4. A 3MS was also launched during the 1971 launch window as Kosmos 419. However, due to a launch failure, it failed to depart Earth orbit.
In addition to the orbiters, two 3MP lander missions, Mars 6 and Mars 7, were launched during the 1973 window.
Launch
Mars 5 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 18:55:48 UTC on 25 July 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 5 into heliocentric orbit bound for Mars.
The spacecraft performed course correction manoeuvres on 3 August 1973 and 2 February 1974.[5]
Mars orbit
The probe reached Mars on 12 February 1974. At 14:44:25 the spacecraft's engines ignited to begin its orbit insertion burn, which successfully placed it into an Areocentric orbit with a periapsis of 1,760 kilometres (1,090 mi), an apoapsis of 32,586 kilometres (20,248 mi), and 35.3 degrees inclination.[4][5]
The spacecraft's pressurised instrument compartment began to leak as soon as the spacecraft entered orbit around Mars, which controllers believed to be the result of a micrometeoroid impact during orbital insertion. It ceased operations on 28 February, having returned 180 photographic frames, 43 of which were of usable quality.[5] The probe's original planned lifetime in Mars orbit had been three months.[7] The probe's gamma ray spectrometer measured the uranium, thorium and potassium content of the surface the probe passed over and found they were similar to igneous rocks on Earth.[7] The exact ratios of the elements varied with the age of the surface.[7] Mars 5's Infrared radiometer reported a daytime surface temperature of between −44 and −2 °C (−47 and 28 °F).[6][7] Night time temperatures were measured at −73 °C (−99 °F).[7]
The probe also made a number of observations of Mars's atmosphere.[7] It found an ozone layer at an altitude of 30 kilometres (19 mi) and observed clouds.[7]
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