Learn about the Viking 1 and Spacecraft

The lander for Viking 1 and Viking 2 were identical. Yet, their mission was different. The lander consisted of a 6-sided aluminum base with alternate 1.09m and .56m long sides supported on three extended legs attach to the shorter sides. The leg footpads formed the vertices of a triangle with 2.21m sides when viewed from above. Instrumentation was attached to the top of the base, elevated above the surface by the extended legs. Two-radioisotope thermal generator unit containing plutonium provided power. Each generator was 28cm tall, 58cm in diameter, had a mass of 13.6 kg and provided 30W continuos power at 4.4 volts.

Propulsion was provided for deorbit by a monopropellant hydrazine rocket with 12 nozzles arranged in four clusters of three that provided 32 Newtons of power. These sets of nozzles also acted as the control thruster for translation and rotation of the lander. Three monopropellant hydrazine engines achieved terminal descent and landing. The engines had 18 nozzles to disperse the exhaust and minimize effects on the ground and were throttleable from 276 N to 2667 N. The hydrazine was purified to prevent contamination of the Martian surface. In order to maintain the Martian surface for examination environment, this type of landing technique was necessary.

Communication was established through a 20W S-band transmitter and two 20W TWTA. A 2-axis steerable high-gain parabolic antenna was mounted on a boom near one edge of the lander base. An omnidirectional low-gain S-band antenna also extends from the base. Both these antennas allowed for communication directly with Earth. A UHF antenna provided a one-way relay to the orbiter using a 30 W relay radio. Data storage was on a 40Mbit tape recorder, and the lander computer had a 6000 word memory for command instructions.

The lander carried instruments to achieve the primary scientific objectives of the lander mission. It was to study the biology, chemical composition, meteorology, seismology, magnetic properties, appearance and physical properties of the Martian surface and atmosphere. Two 360-degree cylindrical scan cameras were mounted near one long side of the base. From the center of this side extended the sampler arm, with a collector hear, temperature sensor, and magnet on the end. A meteorology boom, holding temperature, wind direction, and wind velocity sensors extended out and up from the top of on of the landers legs. A seismometer, magnet and camera test targets, and magnifying mirror are mounted opposite the cameras, near the high-gain antenna. An interior environmentally controlled compartment held the biology experiments. The X-ray fluorescence spectrometer was also mounted within the structure. A pressure sensor was attached under the lander body. The scientific payload had a total mass of approximately 91 kg.