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Aviation History
1962
1962 - 1302.PDF
144 FLIGHT International, 26 July 1%2 Omt-*NTEMU M«GNETB«*nt« SENSOR HADIOMFTH HEfEftEKCE H08.HS «*DI0*ttTE« TEMfCTSUMiE CONTSOt SHIttO soul) n»sm* DETECTOR «m! CONTMM. tOUVERS MRTICLE RBS DETECTOR stUUNB ANTENNA HI6H 6*IN ANTENNA I6N CfMMSEf! SEGQNfiASY COSMIC D»ST DETECTOR WHMMfr tt> IESKHS 10N6 RfWOS BOTH SENSOR Sca/e mode/ showing location of main Mariner components. Developed for NASA by the Jet Propulsion Laboratory, Mariner I is 16ft 6in in span in the "cruise" configuration here illustrated Missiles and Spaceflight The high-gain antenna is hinged and equipped with a drive mechanism allowing it to be pointed at the Earth on command. An Earth sensor is mounted on the antenna yoke near the rim of the high-gain dish-shaped antenna to search for and keep the an tenna pointed at the Earth. Stabilization of the spacecraft for yaw, pitch and roll is provided by ten cold gas jets, mounted in pairs and threes at four locations, and fed by two titanium bottles containing 4.31b of nitrogen gas pressurized to 3,5001b/sq in. The jets are linked by logic circuitry to three gyros in the attitude-control subsystem, to the Earth sensor on the parabolic antenna and to six Sun sensors. The four primary Sun sensors are mounted on four of the six lees of the hexagon, and the two secondary sensors on the backs of the solar panels. These are light-sensitive diodes which inform the attitude control system—gas jets and gyros—when they see the Sun. The attitude control system responds to these signals by turning the spacecraft and pointing the longitudinal or roll axis towards the Sun. Torquing of the spacecraft for these manoeu vres is provided by the cold gas jets fed by the nitrogen gas regulated to 151b/sq in pressure. Sufficient nitrogen is carried to maintain attitude control for an estimated niinimum of 200 days. Computation for the subsystems and the issuance of commands is a function of the digital central computer and sequencer (CC&S). All mission events are controlled in three CC&S sequences. The launch sequence controls events from launch up to the cruise mode. The midcourse propulsion sequence controls the midcourse trajec tory correction manoeuvre. The encounter sequence provides the required commands for data collection in the vicinity of Venus. The CC&S provides the basic timing for the spacecraft subsystems. This time-base will be supplied by a crystal-control oscillator operating at 307.2kc/s. This is divided to 38.4kc/s for timing in the power subsystem, and again to 2,400 and 400c/s for use by various other subsystems. The subsystems clustered around the base of the spacecraft are insulated from the Sun's heat by a shield covered with layers of aluminium-coated plastic film. At the bottom of the spacecraft, just below the subsystem modules, is a second temperature control shield. Temperature control of the attitude control subsystem is provided by louvres actuated by coiled bi-metallic strips. The strips act as coil springs which expand and contract as they are heated and cooled. Temperature control of this subsystem is important, since some of the equipment may not function properly above 130'I Paint patterns, aluminium sheet, thin gold plate and polishe/l aluminium surfaces are used on the Mariner for passive control of internal temperatures. These surfaces control both the amount c f internal heat dissipated into space and the amount of solar heat reflected away. Communication with the spacecraft will be in digital form. The command subsystem aboard the Mariner will decode mcoming digital commands and send them to the designated subsystem;. Data from engineering and scientific sources will be encoded to digital form for transmission to earth. Synchronizing pulses will be spaced at regular intervals between the data signals from Mariner. Ground-based receiving equipmen: will generate identical pulses and match them with the pulses from the spacecraft. This will provide a reference to determine the location of the data signals. Seven scientific experiments will be carried aboard the Mariner. Five of these are designed to collect information in space and in the vicinity of Venus. The other two will provide information solely on Venus and operate only as Mariner passes the planet. Mariner Scientific Experiments Purpose Sponsors Determine temperature distribution MIT, JPL, of Venus surface and details of AOMC, HCO atmosphere Determine details of atmosphere JPL, UN, including structure of cloud cover UCB Magnetometer Measure strength and direction of NASA, Caltech, the interplanetary and planetary JPL magnetic fields Measure distribution and intensity JPL. Caltech, of charged particles SL'I Experiment 1 Microwave radiometer 2 Infra-red radiometer Ionization chamber and particle-flux detector Solar plasma spectrometer Cosmic dust detector Measure intensity of low-energy JPL protons from the Sun Measure density and distribution GSFC of micrometeorites MIT, Massachusetts Institute of Technology; JPL, Jet Propulsion Laboratory; AOMC, Army Ordnance Missile Command; HCO, Harvard College Observatory; UN, University of Nevada; UCB, University of California at Berkely; NASA, National Aeronautics and Space Admin istration; Caltech, California Institute of Technology; SUI, State University of Iowa; GSFC, Goddard Space Flight Center. Mariner I and JPL technicians at Pasadena. The large dish aerial in the foreground is the high-gain antenna
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