Editing Viking program (section)

===Propulsion===

Propulsion for deorbit was provided by the [[monopropellant]] [[hydrazine]] (N<sub>2</sub>H<sub>4</sub>), through a rocket with 12 [[Rocket engine nozzles|nozzle]]s arranged in four clusters of three that provided {{convert|32|N|lk=in|sp=us}} thrust, translating to a [[delta-V|change in velocity]] of {{convert|180|m/s|abbr=on}}. These nozzles also acted as the control [[Spacecraft propulsion|thrusters]] for [[translation (geometry)|translation]] and [[rotation]] of the lander.

Terminal [[descent (aircraft)|descent]] (after use of a [[parachute]]) and [[landing]] used three (one affixed on each long side of the base, separated by 120&nbsp;degrees) monopropellant hydrazine engines. The engines had 18 [https://artsandculture.google.com/asset/_/fgFN2s2GG-OfQA nozzles] to disperse the exhaust and minimize effects on the ground, and were [[throttle]]able from {{convert|276|to|2667|N|lk=in|sp=us}}. The hydrazine was purified in order to prevent contamination of the Martian surface with Earth [[microbes]]. The lander carried {{convert|85|kg|abbr=on}} of propellant at launch, contained in two spherical [[titanium]] tanks mounted on opposite sides of the lander beneath the RTG windscreens, giving a total launch mass of {{convert|657|kg|abbr=on}}. Control was achieved through the use of an [[inertial reference unit]], four [[gyroscope|gyros]], a [[radar altimeter]], a terminal descent and landing [[radar]], and the control thrusters.