![]() ![]() The scientific payload had a total mass of approximately 91 kg.įollowing launch and a 304 day cruise to Mars, the orbiter began returning global images of Mars about 5 days before orbit insertion. A pressure sensor was attached under the lander body. The X-ray flourescence spectrometer was also mounted within the structure. An interior environmentally controlled compartment held the biology experiment and the gas chromatograph mass spectrometer. A seismometer, magnet and camera test targets, and magnifying mirror are mounted opposite the cameras, near the high-gain antenna. ![]() A meteorology boom, holding temperature, wind direction, and wind velocity sensors extended out and up from the top of one of the lander legs. From the center of this side extended the sampler arm, with a collector head, temperature sensor, and magnet on the end. Two 360-degree cylindrical scan cameras were mounted near one long side of the base. The lander carried instruments to achieve the primary scientific objectives of the lander mission: to study the biology, chemical composition (organic and inorganic), meteorology, seismology, magnetic properties, appearance, and physical properties of the martian surface and atmosphere. Data storage was on a 40 Mbit tape recorder, and the lander computer had a 6000 word memory for command instructions. A UHF (381 MHz) antenna provided a one-way relay to the orbiter using a 30 W relay radio. Both these antennae allowed for communication directly with the Earth. An omnidirectional low-gain S-band antenna also extends from the base. A 2-axis steerable high-gain parabolic antenna was mounted on a boom near one edge of the lander base. Control was achieved through the use of an inertial reference unit, four gyros, an aerodecelerator, a radar altimeter, a terminal descent and landing radar, and the control thrusters.Ĭommunications were accomplished through a 20 W S-band transmitter and two 20 W TWTA's. The lander carried 85 kg of propellant at launch, contained in two spherical titanium tanks mounted on opposite sides of the lander beneath the RTG windscreens, giving a total launch mass of 657 kg. The hydrazine was purified to prevent contamination of the martian surface. The engines had 18 nozzles to disperse the exhaust and minimize effects on the ground and were throttleable from 276 N to 2667 N. ![]() Terminal descent and landing was achieved by three (one affixed on each long side of the base, separated by 120 degress) monopropellant hydrazine engines. These nozzles also acted as the control thrusters for translation and rotation of the lander. Propulsion was provided for deorbit by a monopropellant hydrazine (N2H4) rocket with 12 nozzles arranged in four clusters of three that provided 32 N thrust, giving a delta-V of 180 m/s. Four wet-cell sealed nickel-cadmium 8 amp-hour, 28 volt rechargeable batteries were also onboard to handle peak power loads. Each generator was 28 cm tall, 58 cm in diameter, had a mass of 13.6 kg and provided 30 W continuous power at 4.4 volts. Power was provided by two radioisotope thermal generator (RTG) units containing plutonium 238 affixed to opposite sides of the lander base and covered by wind screens. Instrumentation was attached to the top of the base, elevated above the surface by the extended legs. The leg footpads formed the vertices of an equilateral triangle with 2.21 m sides when viewed from above, with the long sides of the base forming a straight line with the two adjoining footpads. 56 m long sides, supported on three extended legs attached to the shorter sides. The lander consisted of a six-sided aluminum base with alternate 1.09 m and. The lander was encased in a bioshield at launch to prevent contamination by terrestrial organisms. ![]() After separation and landing, the lander had a mass of about 600 kg and the orbiter 900 kg. The fully fueled orbiter-lander pair had a mass of 3530 kg. The orbiters continued imaging and other scientific operations from orbit while the landers deployed instruments on the surface. 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. Each spacecraft consisted of an orbiter and a lander. The Viking project consisted of launches of two separate spacecraft to Mars, Viking 1, launched on 20 August 1975, and Viking 2, launched on 9 September 1975. ![]()
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