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.
The Viking 2 lander operated on the surface for 1316 days, or 1281
sols, and was turned off on April 11, 1980 when its batteries failed.
The orbiter worked until July 25, 1978, returning almost 16,000 images in 706 orbits around Mars.
Mission profile
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 1500 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 1499 km and an inclination of 55.2 degrees on 9 August. Imaging of
candidate sites was begun and the landing site was selected based on
these pictures and the images returned by the Viking 1 Orbiter.
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 30 September
1976.
Orbiter
The
orbiter primary mission ended at the beginning of solar conjunction on
October 5, 1976. The extended mission commenced on 14 December 1976
after solar conjunction. On 20 December 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 23 October 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 25 July
1978 after returning almost 16,000 images in about 700–706 orbits
around Mars.
Lander
The lander and its aeroshell
separated from the orbiter on 3 September 19:39:59 UT. At the time of
separation, the lander was orbiting at about 4 km/s. After separation,
rockets fired to begin lander deorbit. After a few hours, at about 300 km attitude, the lander was reoriented for entry. The aeroshell with its ablative heat shield slowed the craft as it plunged through the atmosphere.
The Viking 2 Lander touched down about 200 km west of the crater Mie in Utopia Planitia.
Approximately 22 kg (49 lb) of propellants were left at landing. Due
to radar misidentification of a rock or highly reflective surface, the
thrusters fired an extra time 0.4 second before landing, cracking the
surface and raising dust. The lander settled down with one leg on a
rock, tilted at 8.2 degrees. The cameras began taking images immediately
after landing.
The Viking 2 lander was powered by radioisotope generators and
operated on the surface until April 11, 1980, when its batteries failed.
First color image (Viking Lander 2 Camera 2 sol 2, September 5, 1976) 14:36
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