Viking 2 Lander
By Marty McDowell/NASA
The Viking project consisted of launches of two separate spacecraft to
Mars, Viking 1, launched on 20 August 1975, and
Viking 2, launched on September 9, 1975.
Each spacecraft consisted of an orbiter and a lander. After orbiting
Mars and returning images used for landing site selection, the orbiter and
lander detached and the lander entered the martian atmosphere and
soft-landed at the selected site. The orbiters continued imaging and other
scientific operations from orbit while the landers deployed instruments on
the surface. The fully fueled orbiter-lander pair had a mass of 3530 kg.
After separation and landing, the lander had a mass of about 600 kg and
the orbiter 900 kg. The lander was encased in a bioshield at launch to
prevent contamination by terrestrial organisms.
This color image shows a
thin layer of water ice frost on the martian
surface at Utopia Planitia. It was taken by Viking
2 Lander camera 2 on 18 May 1979, almost exactly
one martian year (687 days) after frost first
appeared at this spot and was imaged by Viking 2.
The layer is thought to be only a couple
thousandths of a centimeter thick. It is
speculated that dust particles in the atmosphere
pick up tiny bits of water. When it gets cold
enough for carbon dioxide to solidify, some of it
attaches to the dust and ice and it falls to the
Image courtesy of NASA.
Following launch 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 hr Mars orbit on 7
August 1976 and trimmed to a 27.3 hr 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 and its aeroshell separated from the orbiter on September 3,
1976. 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 altitude, the lander was reoriented for entry. The
aeroshell with its ablatable heat shield slowed the craft as it plunged
through the atmosphere. During this time, entry science experiments were
performed. At 6 km altitude at about 250 m/s the 16 m diameter lander
parachutes were deployed. Seven seconds later the aeroshell was
jettisoned, and 8 seconds after that the three lander legs were extended.
In 45 seconds the parachute had slowed the lander to 60 m/s. At 1.5 km
altitude, retro-rockets were ignited and fired until landing 40 seconds
later at about 2.4 m/s. The landing rockets used an 18 nozzle design to
spread the hydrogen and nitrogen exhaust over a wide area. It was
determined that this would limit surface heating to no more than 1 degree
C and that no more than 1 mm of the surface material would be stripped
The Viking 2 Lander touched down about 200 km west of the crater Mie in
Utopia Planitia at 48.269 deg N latitude and 225.990 deg W longitude at
22:58:20 UT (9:49:05 a.m. local Mars time). Due to radar misidentification
of a rock or highly reflective surface, the thrusters fired an extra time
0.4 seconds 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 operated on the surface for 1281 Mars days and was
turned off on April 11, 1980 when its batteries failed.
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Courtesy of NASA
Launched: September 9, 1975
Arrival: August 7, 1976
Mission: Mars landing and photography.