Viking 2

The Viking 2 mission was part of the American Viking program to Mars, and consisted of an orbiter and a lander essentially identical to that of the Viking 1 mission. Viking 2 was operational on Mars for sols ( days; ). The Viking 2 lander operated on the surface for days, or sols, and was turned off on April 12, 1980, when its batteries failed. The orbiter worked until July 25, 1978, returning almost 16,000 images in 706 orbits around Mars. The craft was launched on September 9, 1975. Following launch using a Titan/Centaur launch vehicle and a 333-day cruise to Mars, the Viking 2 Orbiter began returning global images of Mars prior to orbit insertion. The orbiter was inserted into a 1,500 x 33,000 km, 24.6 h Mars orbit on August 7, 1976, and trimmed to a 27.3 h site certification orbit with a periapsis of 1,499 km and an inclination of 55.2 degrees on August 9. The orbiter then began taking photographs of candidate landing sites, which were used to select the final landing site. The lander separated from the orbiter on September 3, 1976, at 22:37:50 UT and landed at Utopia Planitia. Normal operations called for the structure connecting the orbiter and lander (the bioshield) to be ejected after separation, but because of problems with the separation the bioshield was left attached to the orbiter. The orbit inclination was raised to 75 degrees on September 30, 1976. The orbiter primary mission ended at the beginning of solar conjunction on October 5, 1976. The extended mission commenced on December 14, 1976, after solar conjunction. On December 20, 1976, the periapsis was lowered to 778 km and the inclination raised to 80 degrees. Operations included close approaches to Deimos in October 1977 and the periapsis was lowered to 300 km and the period changed to 24 hours on October 23, 1977. The orbiter developed a leak in its propulsion system that vented its attitude control gas. It was placed in a 302 × 33,176 km orbit and turned off on July 25, 1978, after returning almost 16,000 images in about 700–706 orbits around Mars.