| Mars 4 | |||||||
| Mission Type: | Mars orbiter[1] | ||||||
| Operator: | Soviet space program | ||||||
| Cospar Id: | 1973-047A | ||||||
| Satcat: | 6742 | ||||||
| Spacecraft: | 3MS No.52S | ||||||
| Manufacturer: | NPO Lavochkin | ||||||
| Launch Mass: | [2] | ||||||
| Launch Date: | UTC[3] | ||||||
| Launch Site: | Baikonur 81/23 | ||||||
| Last Contact: | 10 February 1974, 15:38 UTC | ||||||
| Launch Contractor: | Khrunichev | ||||||
| Orbit Reference: | Heliocentric[4] | ||||||
| Orbit Periapsis: | 1.02 AU | ||||||
| Orbit Apoapsis: | 1.63 AU | ||||||
| Orbit Inclination: | 2.2° | ||||||
| Orbit Period: | 556 days | ||||||
| Apsis: | helion | ||||||
| Interplanetary: |
| ||||||
| Programme: | Mars program | ||||||
| Previous Mission: | Mars 3 | ||||||
| Next Mission: | Mars 5 | ||||||
Mars 4, also known as 3MS No.52S was a 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 orbital insertion from occurring.[5]
The Mars 4 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 analyzer, a gamma-ray spectrometer, and a radio probe.[6]
Built by Lavochkin, Mars 4 was the first of two 3MS spacecraft launched to Mars in 1973, being followed by Mars 5. 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.
Mars 4 was launched by a Proton-K carrier rocket, a Blok D upper stage, flying from Baikonur Cosmodrome Site 81/23.[3] The launch occurred at 19:30:59 UTC on 21 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 4 into heliocentric orbit bound for Mars.
Shortly after performing a course correction on 30 July 1973, two onboard computers failed, leaving Mars 4 unable to perform maneuvers. As a result of this, it was unable to enter orbit around Mars. Twelve photographs were taken on 10 February 1974 from 15:32 UTC to 15:38 UTC as the probe flew past Mars with a closest approach of at 15:34 UTC.[7]
Mars 4 orbiter carried 15 scientific instruments on board to study Mars from orbital trajectory