Online Reference: http://www-pdsimage.wr.usgs.gov/PDS/public/mapmaker/mapmkr.htm

 
 
 
    Instrument Host Overview
    ========================
      The Viking spacecraft consisted of two orbiters, each with a
      heat-sterilized lander within a capsule.  Together with fuel
      they each weighed 3530 kg just after launch.  After landing,
      their masses were about 900 kg for the orbiters and 600 kg for
      each lander.
 
      The orbiters, derived from earlier Mariner designs, were
      powered by solar panels and were stabilized in three axes by
      use of solar and star sensors in conjunction with attitude
      control jets.  Three remote sensing science investigations
      resided on the two-axis scan platform: a pair of high
      resolution slow scan televison framing cameras (the Visual
      Imaging Subsystem, or VIS); a near-infrared spectrometer for
      atmospheric water detection (the Mars Atmosphere Water
      Detector, MAWD); and a visual and thermal infrared radiometer
      system (Infrared Thermal Mapper, IRTM).
 
      The landers each carried two facsimile cameras providing stereo
      views of the surface; a boom-mounted set of meteorology
      instruments; an X-ray fluorescence experiment for inorganic
      chemical analysis of soil; a gas chromatograph mass
      spectrometer to measure the soil and atmosphere; three biology
      experiments: the pyrolytic release, labeled release, and gas
      exchange systems; a seismometer; a magnetic properties
      experiment.  Soil physical properties experiments were carried
      out using several of the abovementioned systems.  Upper
      atmosphere measurements were performed using detectors on the
      landers during entry through the atmosphere.  Finally, radio
      science was done using transmitters and receivers on both the
      orbiters and landers.  An extensible arm and scoop system on
      each lander was programmable to acquire samples of soil and
      rock for analysis on board the landers and to affect the local
      environment for visual inspection.
 
    Platform Descriptions
    =====================
 
      SCAN PLATFORM
      -------------
        The three Viking orbiter science instruments are mounted on a
        scan platform that provides temperature control for them and
        pointing in two axes: cone and clock.  The platform can be
        rotated in cone and/or clock at rates of 0.25 or 1.0
        degree/sec.  Subroutines stored in the memory of the on-board
        computer can be called upon to move the platform in specified
        patterns.  The nominal range of motion possible for the scan
        platform is from 45 to 175 degrees cone and 80 to 310 clock;
        however, there are mechanical constraints that reduce this
        range.  See reference.