The Viking mission to Mars sent to identical crafts to The Red Planet. Each of the crafts were made of two parts: a “lander” and an “orbiter”. The orbiters initial function was to survey the planet for a suitable landing site. Later, the orbiter’s instruments studied the planet and its atmosphere, while the orbiter acted as a radio relay station for transmitting lander data. Once on the surface of Mars, the lander surveyed soil, wind, and of course atmosphere. It conducted numerous experiments to determine if life existed on Mars either now or in the past.
Once the Viking orbiters were attached to their lander pods, they were positioned inside the nose cones of the Titan Centaur launch vehicles. The landers were folded inside their pods. These pods were designed to keep any biological contamination from getting inside while on earth.
When the craft’s parachute was deployed, the pod was at 6km. (4mi.) and traveling at a speed of 900kph (600mph.). Soon after the lower part of the heat shield fell off and the lander’s legs unfolded. At an altitude of about 1.5km (5000ft.) the lander pod broke away from the parachute and started using retro boosters to control its descent. It landed on Mars safely.
At this stage of the landing, the landers terminal descent system (three retro boosters) had slowed the craft down where the speed at landing was about 10.5kph. (7mph). Seconds after this historical event, the lander began transmitting images to the orbiter and back to earth.
On The Surface of Mars
The first of the two landers landed on Mars on July 20, 1976.The second on September 3, 1976. Each lander housed instruments that examined the physical and magnetic properties of the soil. They also analyzed atmosphere and weather on Mars.