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7982Re: History...

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  • Don R Surles
    Dec 1, 2008
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      The following story describes the first soft landing on Mars which occurred tomorrow,  Dec 2, 1971.   I deleted one very significant fact on purpose.  After reading the story does anyone have a clue about the missing "Fact"?

      Don...
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      The Mars program was a series of Mars unmanned Landers and Orbiters in the early 1970s.

      The Mars 2 and Mars 3 missions consisted of identical spacecraft, each with an Orbiter and an attached Lander; they were the first human artifacts to touch down on Mars. Launch Date/Time:

      Mars 3: May 28, 1971 at 15:26:30 UTC

      Launch mass (including fuel):

      Combined: 4650 kg

      Orbiter: 3440 kg

      Lander: 1210 kg

      On-orbit dry mass: 2265 kg

      Dimensions: 4.1 meters tall, 2 meters across (5.9 meters across with solar panels deployed)

      Orbiter

      The orbiter suffered from a partial loss of fuel and did not have enough to put itself into a planned 25 hour orbit. The engine instead performed a truncated burn to put the spacecraft into a long 12 day, 19 hour period orbit about Mars.

      The orbiter primary scientific objectives were to image the Martian surface and clouds, determine the temperature on Mars, study the topography, composition and physical properties of the surface, measure properties of the atmosphere, monitor the solar wind and the interplanetary and Martian magnetic fields, and act as communications relays to send signals from the landers to Earth.

      The Mars 3 orbiter sent back a large volume of data covering the period from December 1971 to March 1972, although transmissions continued through August. It was announced that Mars 3 had completed their mission by 22 August 1972, after 20 orbits. The probe, combined with Mars 2, sent back a total of 60 pictures. The images and data revealed mountains as high as 22 km, atomic hydrogen and oxygen in the upper atmosphere, surface temperatures ranging from -110 C to +13 C, surface pressures of 5.5 to 6 mb, water vapor concentrations 5000 times less than in Earth's atmosphere, the base of the ionosphere starting at 80 to 110 km altitude, and grains from dust storms as high as 7 km in the atmosphere. The images and data enabled creation of surface relief maps, and gave information on the Martian gravity and magnetic fields.

      Lander

      The Mars 3 descent module was mounted on the bus/orbiter opposite the propulsion system. It consisted of a spherical 1.2 m diameter landing capsule, a 2.9 m diameter conical aerodynamic braking shield, a parachute system and retro-rockets.

      The entire descent module had a fueled mass of 1210 kg, the spherical landing capsule accounted for 358 kg of this. An automatic control system consisting of gas micro-engines and pressurized nitrogen containers provided attitude control. Four "gunpowder" engines were mounted to the outer edge of the cone to control pitch and yaw.

      The main and auxiliary parachutes, the engine to initiate the landing, and the radar altimeter were mounted on the top section of the Lander. Foam was used to absorb shock within the descent module. The landing capsule had four triangular petals which would open after landing, righting the spacecraft and exposing the instrumentation.

      The Lander was equipped with two television cameras with a 360 degree view of the surface as well as a mass spectrometer to study atmospheric composition; temperature, pressure, and wind sensors; and devices to measure mechanical and chemical properties of the surface, including a mechanical scoop to search for organic materials and signs of life. It also contained a pennant with the Soviet coat of arms.

      Four aerials protruded from the top of the sphere to provide communications with the orbiter via an onboard radio system. The equipment was powered by batteries which were charged by the orbiter prior to separation. Temperature control was maintained through thermal insulation and a system of radiators. The landing capsule was sterilized before launch to prevent contamination of the Martian environment.

      Mars 3's descent module was released at 09:14 UT on December 2, 1971, 4 hours 35 minutes before reaching Mars. The descent module entered the Martian atmosphere at roughly 5.7 km/s.

      Through aerodynamic braking, parachutes, and retrorockets, the lander achieved a soft landing at 45° S, 158° W and began operations.

      After 14.5 seconds, at 13:52:25, transmission on both data channels stopped for unknown reasons and no further signals were received at Earth from the Martian surface. It is not known whether the fault originated with the Lander or the communications relay on the orbiter. A partial panoramic image returned showed no detail and a very low illumination of 50 lux. The cause of the failure may have been related to the extremely powerful Martian dust storm taking place at the time which may have induced a coronal discharge, damaging the communications system. The dust storm would also explain the poor image lighting.

      Prop-M Rover

      Mars 3 Lander had a small 4.5 kg Mars 'rover' on board, which would move across the surface on skis while connected to the Lander with a 15-meter umbilical. Two small metal rods were used for autonomous obstacle avoidance, as radio signals from Earth would take too long to drive the rovers using remote control. The Rover carried a dynamic penetrometer and a radiation densitometer.

      The main PROP-M frame was a squat box with a small protrusion at the center. The frame was supported on two wide flat skis, one extending down from each side elevating the frame slightly above the surface. At the front of the box were obstacle detection bars.

      The rover was planned to be placed on the surface after landing by a manipulator arm and to move in the field of view of the television cameras and stop to make measurements every 1.5 meters. The traces of movement in the Martian soil would also be recorded to determine material properties.

      Because of the demise of the Lander, the Rover never saw action

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