Mars probe program

From Academic Kids

The Mars program was a series of Mars unmanned landers and orbiters launched by the Soviet Union in the early 1970s.

Mars 1 was launched in 1962 but failed en route to Mars. Two other Soviet launches at around the same time, Mars 1962A and Mars 1962B, were likely similar or identical spacecraft but both of these failed during launch and did not leave Earth orbit.

The Mars 2 through Mars 7 spacecraft were of a new, heavy design, weighing approximately 5 metric tons and requiring the Proton booster for launch. They were designed to deliver an orbiter and a lander to Mars. The orbiter design was similar to the later heavy Venera probes to Venus (Veneras 9 through the Vega probes to Venus and Halley's comet in 1985). The orbiter bus design was likely somewhat rushed into service and immature, considering that it performed very reliably in the Venera variant after 1975. This reliability problem was common to much Soviet space hardware from the late 1960s and early 1970s and was largely corrected with a deliberate policy of consolidating (or "debugging") existing designs rather than introducing new ones which was implemented in the mid-1970s.


Mars 2 and 3

  • Launch Date/Time:
    • Mars 2: May 19 1971 at 16:22:44 UTC
      Missing image
      Mars 3 orbiter with lander attached

    • Mars 3: May 28 1971 at 15:26:30 UTC
  • Launch mass (including fuel):
    • Combined: 4650 kg
    • Orbiter: 3440 kg
    • Lander: 1210 kg
  • On-orbit dry mass: 2265 kg
  • Dimensions: 4.1 meters tall, 2 meters across (5.9 meters across with solar panels deployed)

The Mars 2 and Mars 3 missions consisted of identical spacecraft, each with an orbiter and an attached lander; they were the first human artifacts to touch down on Mars. The orbiters' primary scientific objectives were to image the Martian surface and clouds, determine the temperature on Mars, study the topography, composition and physical properties of the surface, measure properties of the atmosphere, monitor the solar wind and the interplanetary and Martian magnetic fields, and act as communications relays to send signals from the landers to Earth. Mars 2 and 3 were launched by Tyazheliy Sputniks.

Mars 2 released the descent module 4.5 hours before reaching Mars on November 27 1971.
Missing image
Mars 3 lander

The descent module entered the Martian atmosphere at roughly 6.0 km/s at a steeper angle than planned. The descent system malfunctioned and the lander crashed at 45 S, 302 W, delivering the Soviet Union coat of arms to the surface. Meanwhile, the orbiter engine performed a burn to put the spacecraft into a 1380 x 24,940 km, 18 hour orbit about Mars with an inclination of 48.9 degrees. Scientific instruments were generally turned on for about 30 minutes near periapsis.

Mars 3's descent module was released at 09:14 UT on December 2 1971, 4 hours 35 minutes before reaching Mars. The descent module entered the Martian atmosphere at roughly 5.7 km/s. Through aerodynamic braking, parachutes, and retro-rockets, the lander achieved a soft landing at 45 S, 158 W and began operations. However, after 20 seconds the instruments stopped working for unknown reasons, perhaps as a result of the massive surface dust storms raging at the time of landing. Meanwhile, the orbiter had suffered from a partial loss of fuel and did not have enough to put itself into a planned 25 hour orbit. The engine instead performed a truncated burn to put the spacecraft into a long 12 day, 19 hour period orbit about Mars with an inclination thought to be similar to that of Mars 2 (48.9 degrees).

Missing image
Highly speculative processing of the only partial photo to come from Mars 3, colorized and enhanced by Ted Stryk

The Mars 2 and 3 orbiters sent back a large volume of data covering the period from December 1971 to March 1972, although transmissions continued through August. It was announced that Mars 2 and 3 had completed their missions by 22 August 1972, after 362 orbits completed by Mars 2 and 20 orbits by Mars 3. The probes sent back a total of 60 pictures. The images and data enabled creation of surface relief maps, and gave information on the Martian gravity and magnetic fields.

Mars 4, 5, 6 and 7

Missing image
Mars 4
Missing image
Mars 6

Mars 4 and 5:

  • Launch Date/Time:
  • On-orbit mass:
    • Dry: 2270 kg
    • Fully-fuelled: 3440 kg

The 1973 Mars launch window was inefficient and thus the Proton rocket could not deliver the mass to Mars that year that had been possible in 1971. Thus, the mission was split somewhat extravagantly into four separate, but lighter vehicles: two relay orbiters without landers and two orbiter type buses with landers but without fuel to enter orbit. The political purpose of these missions was to beat the American Viking probes (scheduled for 1975 launches) to be the first spacecraft to soft land on Mars, at which they unfortunately did not succeed.

Mars 4, 5, 6, and 7 comprised an associated group of Soviet spacecraft launched towards Mars in July and August of 1973. The Mars 4 and 5 automatic stations were designed to orbit Mars and return information on the composition, structure, and properties of the Martian atmosphere and surface. The spacecraft were also designed to act as communications links to the Mars 6 and 7 landers. They were launched from Earth by Proton SL-12/D-1-e boosters.

The Mars 4 orbiter reached Mars on 10 February 1974. Due to a flaw in the computer chip which resulted in degradation of the chip during the voyage to Mars, the retro-rockets never fired to slow the craft into Mars orbit, and Mars 4 flew by the planet at a range of 2200 km. It returned one swath of pictures and some radio occultation data which constituted the first detection of the nightside ionosphere on Mars. It continued to return interplanetary data from solar orbit after the flyby.

Mars 5 reached Mars on February 12 1974 at 15:45 UT and was inserted into an elliptical 1755 by 32,555 km, 24 h 53 min orbit with an inclination of 35.3 degrees. Mars 5 collected data for 22 orbits until a loss of pressurization in the transmitter housing ended the mission. About 60 images were returned over a nine day period showing swaths of the area south of Valles Marineris, from 5 N, 330 W to 20 S, 130 W.

Mars 6 successfully lifted off into an intermediate Earth orbit on a Proton SL-12/D-1-e booster and then launched into a Mars transfer trajectory. Total fueled launch mass of the lander and bus was 3260 kg. It reached Mars on March 12 1974. The descent module separated from the bus at a distance of 48,000 km from Mars. The bus continued on into a heliocentric orbit after passing within 1600 km of Mars. The descent module entered the atmosphere at 09:05:53 UT at a speed of 5.6 km/s. The parachute opened at 09:08:32 UT after the module had slowed its speed to 600 m/s by aerobraking. During this time the craft was collecting data and transmitting it directly to the bus for immediate relay to Earth. Contact with the descent module was lost at 09:11:05 UT in "direct proximity to the surface", probably either when the retrorockets fired or when it hit the surface at an estimated 61 m/s. Mars 6 landed at 23.90 S, 19.42 W in the Margaritifer Sinus region of Mars. The landed mass was 635 kg. The descent module transmitted 224 seconds of data before transmissions ceased, the first data returned from the atmosphere of Mars. Unfortunately, much of the data were unreadable due to a flaw in a computer chip which led to degradation of the system during its journey to Mars.

Mars 7 successfully lifted off into an intermediate Earth orbit on a Proton SL-12/D-1-e booster and then launched into a Mars transfer trajectory. Total fueled launch mass of the lander and bus was 3260 kg. It reached Mars on March 9 1974. Due to a problem in the operation of one of the onboard systems (attitude control or retro-rockets) the landing probe separated prematurely (4 hours before encounter) and missed the planet by 1300 km. The early separation was probably due to a computer chip error which resulted in degradation of the systems during the trip to Mars. The intended landing site was 50 S, 28 W. The lander and bus continued on into heliocentric orbits.

Later missions


Two Phobos spacecrafts were launched 1988 to study Mars and his moon Phobos, but neigther of them was successfull in its mission.

Mars 96

Mars 96 was an orbiter launched in 1996 by Russia and not directly related to the Soviet series of probes.

Related articles

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