Mars program

Starting with two failures in 1969, the heavier Proton-K rocket was used to launch larger 5 tonne spacecraft, consisting of an orbiter and a lander to Mars.

The orbiter bus design was likely somewhat rushed into service and immature,[citation needed] considering that it performed very unreliably 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, implemented in the mid-1970s, of consolidating (or "debugging") existing designs rather than introducing new ones.

In 1996, Russia launched Mars 96, its first interplanetary mission since the dissolution of the Soviet Union, however it failed to depart Earth orbit.

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.

Two small metal rods were used for autonomous obstacle avoidance, as radio signals from Earth would take too long to drive the rovers using remote control.

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.

The images and data enabled creation of surface relief maps, and gave information on the Martian gravity and magnetic fields.