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Aviation History
1972
1972 - 0055.PDF
FLIGHT International, 6 January 1972 The photograph of the back of Mars 3, right, gives a clear view of the heat shield and of the enshrouded main instrument compartment from under which protrudes the rim of the engine nozzle. The solar panels are folded for launch. The landing capsule is shown above without its heat shield, which is probably supported in the large arms protruding from the base and the small braces fitted on top of the parachute compartment. The engine nozzle can be seen below the assembly therefore, the parachute was designed to withstand deploy ment at higher speeds. The parachute was in fact explosively deployed—a drogue chute first and the main canopy following in two stages—while the spacecraft was still travelling at supersonic speeds, but it would have been subjected to relatively moderate strain in the tenuous Martian atmosphere. The heat shield was discarded shortly before the parachute was released and the parachute and its container were in turn jettisoned at about 100ft altitude, so that the final landing weight was reduced to a minimum just before, according to Soviet reports, a solid-fuel braking engine was fired automatically by a radar altimeter. Assuming this to be the case, the lander, appearing to have no legs, presumably collapsed the engine nozzle and rested on the flat base of the lower cylinder. Soviet statements asserted that a large number of new systems and components were used in the two Mars probes. The Mars 3 landing capsule carried mass spectrometers for chemical analysis of the atmosphere and equipment to analyse the chemical content of the surface soil as well as to determine its physical and mechanical properties, and was probably similar to such equipment carried on Lunokhod. It also carried a wind anemometer, thermometer and pressure gauge as well as one or more television cameras. Data from the landing capsule was to have been relayed by the Mars 3 orbiter, and possibly Mars 2 as well, but signals from the capsule ceased after only 20sec of transmission. Both orbiters are equipped for ultra-violet, infra-red and optical examination of Mars and its atmosphere, the sensors and cameras being mainly fitted around and within the circular instrument compartments. From u-v measure ments already taken the Russians have detected the presence of hydrogen and oxygen, and water itself, in the atmosphere. Each spacecraft also carries a unit of three infra-red sensors. One measures wavelengths of 8/;-40/i to build up a thermal map of Mars for comparison with surface photography. The second measures the thickness of the carbon-dioxide atmosphere to detect variation in surface height in order to build up a relief map. The third operates within the visible-light bandwidth to measure the dust concentration at different altitudes, to study twilight atmospheric phenomena and to define the surface colouring. All three operate autonomously but share a number of basic systems to save power consumption and weight. The photographs taken by the orbiters are automatically developed and the image transmitted directly to Earth, unlike the American method whereby Mariner breaks down the picture into coded dots which are then recon structed on Earth by computer. This probably accounts for the size of the parabolic S-band aerial, which appears to be about 80in, 200cm in diameter, twice the size of that on Mariner. Each orbiter carries two cameras, one a telescopic 4° narrow-angle lens for detailed work, and the other wide- angled. All cameras are equipped with a selection of colour filters. Izvestia reported, however, that the Soviet photo graphic programme has, too, been suffering because of the dust storm which covered most of the planet. Mars 3 also carries a French experiment, Stereo 1, which has been operating throughout the flight to collect data on solar emissions for correlation with data obtained by a similar instrument on Earth. A more advanced version, Stereo V, is now under preparation, along with two other experiments, by CNES, France's national space agency. CNES reports that it expects that these will be included in a Soviet Mars probe to be launched in July 1973. Nasa's Jet Propulsion Laboratory was last week planning joint US-Soviet experiments for study of Mars using the spacecraft of both countries now in orbit around the planet. In order to prepare such proposals, JPL requested more detailed description of the instruments and capa bilities of the Mars 2 and 3 spacecraft. The interchange of information is reported to have been, so far, somewhat one-sided, with Russian material apparently duplicating what is published in official state ments. The Russians have insisted, as an essential part of the agreement, however, that none of the information given to JPL should be made public, nor should Soviet replies to US questions nor even the Soviet questions themselves be disclosed by the Americans.
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