Instrument Host Overview
  ========================
    The Apollo 12 Command and Service Module (CSM) spacecraft orbited the
    Moon during the Apollo 12  mission.  It was piloted by Richard F.
    Gordon.
 
 
    Spacecraft and Subsystems
    -------------------------
      As the name implies, the Command and Service Module (CSM) for the
      Apollo 12 mission was comprised of two distinct units:  the Command
      Module (CM), which housed the crew, spacecraft operations systems,
      and re-entry equipment, and the Service Module (SM) which carried
      most of the consumables (oxygen, water, helium, fuel cells, and fuel)
      and the main propulsion system. The total length of the two modules
      attached was 11.0 meters with a maximum diameter of 3.9 meters.
      Block II CSM's were used for all the crewed Apollo missions.  The
      launch mass, including propellants and expendables, of the Apollo 12
      CSM was 28,790 kg of which the Command Module (CM-108) had a mass of
      5609 kg and the Service Module (SM-108) 23,181 kg.  The Apollo 12 CM
      was named ''Yankee Clipper''.
 
      Telecommunications included voice, television, data, and tracking and
      ranging subsystems for communications between astronauts, CM, LM, and
      Earth.  Voice contact was provided by an S-band uplink and downlink
      system.  Tracking was done through a unified S-band transponder.  A
      high gain steerable S-band antenna consisting of four 79-cm diameter
      parabolic dishes was mounted on a folding boom at the aft end of the
      SM.  Two VHF scimitar antennas were also mounted on the SM.  There
      was also a VHF recovery beacon mounted in the CM.  The CSM
      environmental control system regulated cabin atmosphere, pressure,
      temperature, carbon dioxide, odors, particles, and ventilation and
      controlled the temperature range of the electronic equipment.
 
 
    Command Module
    --------------
      The CM was a conical pressure vessel with a maximum diameter of 3.9 m
      at its base and a height of 3.65 m.  It was made of an aluminum
      honeycomb sandwich bonded between sheet aluminum alloy.  The base of
      the CM consisted of a heat shield made of brazed stainless steel
      honeycomb filled with a phenolic epoxy resin as an ablative material
      and varied in thickness from 1.8 to 6.9 cm.  At the tip of the cone
      was a hatch and docking assembly designed to mate with the lunar
      module.  The CM was divided into three compartments.  The forward
      compartment in the nose of the cone held the three 25.4 m diameter
      main parachutes, two 5 m drogue parachutes, and pilot mortar chutes
      for Earth landing.  The aft compartment was situated around the base
      of the CM and contained propellant tanks, reaction control engines,
      wiring, and plumbing.  The crew compartment comprised most of the
      volume of the CM, approximately 6.17 cubic meters of space.  Three
      astronaut couches were lined up facing forward in the center of the
      compartment.  A large access hatch was situated above the center
      couch.  A short access tunnel led to the docking hatch in the CM
      nose. The crew compartment held the controls, displays, navigation
      equipment and other systems used by the astronauts.  The CM had five
      windows: one in the access hatch, one next to each astronaut in the
      two outer seats, and two forward-facing rendezvous windows.  Five
      silver/zinc-oxide batteries provided power after the CM and SM
      detached, three for re-entry and after landing and two for vehicle
      separation and parachute deployment.  The CM had twelve 420 N
      nitrogen tetroxide/hydrazine reaction control thrusters.  The CM
      provided the re-entry capability at the end of the mission after
      separation from the Service Module.
 
 
    Service Module
    --------------
      The SM was a cylinder 3.9 meters in diameter and 7.6 m long which was
      attached to the back of the CM. The outer skin of the SM was formed
      of 2.5 cm thick aluminum honeycomb panels.  The interior was divided
      by milled aluminum radial beams into six sections around a central
      cylinder.  At the back of the SM mounted in the central cylinder was
      a gimbal mounted restartable hypergolic liquid propellant 91,000 N
      engine and cone shaped engine nozzle.  Attitude control was provided
      by four identical banks of four 450 N reaction control thrusters each
      spaced 90 degrees apart around the forward part of the SM.  The six
      sections of the SM held three 31-cell hydrogen oxygen fuel cells
      which provided 28 volts, two cryogenic oxygen and two cryogenic
      hydrogen tanks, four tanks for the main propulsion engine, two for
      fuel and two for oxidizer, and the subsystems the main propulsion
      unit.  Two helium tanks were mounted in the central cylinder.
      Electrical power system radiators were at the top of the cylinder and
      environmental control radiator panels spaced around the bottom.
 
 
    Scientific Experiments
    ----------------------
      The following scientific experiments were performed on board the
      Apollo 12 Command and Service Module:
 
      - The Photography Experiment (1) obtained photographs of the
        transposition, docking, lunar module ejection maneuver, and the LM
        rendezvous sequence from both the command and lunar modules, (2)
        obtained photos of the lunar ground track and of the landing site
        from the low point of the LM's flight path, (3) recorded the
        operational activities of the crew, (4) obtained long-distance
        earth and lunar terrain photographs with 70-mm still cameras, and
        (5) obtained photos of lunar surface features and of the activities
        of the astronauts who landed on the Moon.
 
      - The Multispectral Photography Experiment obtained photographs
        showing lunar surface color variations for use in geologic mapping
        and correlation with surface samples from spectral reflectance.
 
      - The Window Meteoroid Detector Experiment used the CM heat shield
        window surfaces (fused silica) to obtain information about the flux
        of meteoroids with masses of 1 nanogram or less.  About 0.4 square
        meters of the window surfaces were used as meteoroid impact
        detectors.
 
      - The S-Band Transponder Experiment measured the lunar gravitational
        field by observing the dynamical motion of the spacecraft in free
        fall orbits to provide information about the distribution of lunar
        mass.
 
    For more information about the CSM and its experiments, see the Apollo
    12 preliminary science report (1970) [APOLLO12A1970] and the report
    ''Apollo 12, A New Vista for Lunar Science'' (1970) [APOLLO12B1970].
 
 
  This instrument host description was provided by the NASA National Space
  Science Data Center (NSSDC).