Mars 4

Mars 4 (Марс-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.

Spacecraft
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.

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.

Launch
Mars 4 was launched by a Proton-K carrier rocket, a Blok D upper stage, flying from Baikonur Cosmodrome Site 81/23. 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 1844 km at 15:34 UTC.

Scientific Instruments
Mars 4 orbiter carried 15 scientific instruments on board to study Mars from orbital trajectory


 * Atmospheric Radio-probing Instrument
 * Radio Telescope
 * Infrared Radiometer
 * Spectrophotometer
 * Narrow-band Photometer
 * Narrow-band Interference-Polarization Photometer
 * Imaging System
 * Photometers
 * Two Polarimeters
 * Ultraviolet Photometer
 * Scattered Solar Radiation Photometer
 * Gamma Spectrometer
 * Magnetometer
 * Plasma Traps
 * Multichannel Electrostatic Analyzer