Instrument Host Overview
  ========================
    The Apollo 12 Lunar Module (LM) ''Intrepid'' was the second crewed
    vehicle to land on the Moon.  It carried two astronauts, Commander
    Charles P. ''Pete'' Conrad and LM pilot Alan L. Bean, the third and
    fourth men to walk on the Moon.  Also included on the LM was the Apollo
    Lunar Surface Experiments Package (ALSEP) containing scientific
    experiments to be deployed and left on the lunar surface and other
    scientific and sample collection apparatus.  The experiments performed
    on the Moon, in addition to the ALSEP suite, were geologic sample
    collection, surface photography, soil mechanics investigations to study
    the physical properties of the lunar regolith, the solar wind
    composition experiment which collected samples of solar wind for return
    to Earth, and collection of parts of the Surveyor 3 spacecraft.
 
    The LM separated from the Command and Service Module (CSM) at 04:16:03
    UT and landed at 06:54:35 UT (1:54:35 a.m. EST) on 19 November 1969 in
    the Oceanus Procellarum area at 3.0124 S latitude, 23.4216 W longitude
    (IAU Mean Earth Polar Axis coordinate system [DAVIES&COLVIN2000])
    within about 180 meters of the Surveyor 3 spacecraft, which had landed
    on April 20, 1967.  Conrad and Bean took two moonwalks of a total
    duration of 7 hours 45 minutes covering a total traverse distance of
    1.35 km.  The first was from 11:32:35 to 15:28:38 UT (6:32 a.m. to
    10:28 a.m. EST) and involved sample collections in the vicinity of the
    LM and deployment of the ALSEP and solar wind composition foil
    collector.  The TV camera was inadvertantly pointed towards the Sun
    when it was being set up and the vidicon tube was damaged rendering the
    camera inoperable.  On the second of these walks, on November 20 from
    03:54:45 to 07:44:00 UT (10:54 p.m. Nov. 19 to 2:44 a.m. Nov. 20 EST)
    they completed a 1.3 km geology traverse, collecting samples and taking
    photographs, and visited the Surveyor 3 spacecraft, bringing back about
    10 kg of parts for later examination on Earth.  They collected a total
    of 34.35 kg of rock and soil samples and also collected the soalr wind
    foil.
 
    The LM lifted off on 20 November at 14:25:47 UT (9:25 a.m. EST) after
    spending 31 hours 31 minutes on the Moon.  After docking with the CSM
    (piloted by Richard F. Gordon Jr.) at 17:58:22 UT, the LM was
    jettisoned at 20:21:30 and intentionally crashed into the Moon,
    striking at 3.94 S, 338.80 E, about 60 km from the seismic station at
    the Apollo 12 landing site, creating the first recorded artificial
    moonquake.
 
 
    Lunar Module Spacecraft and Subsystems
    --------------------------------------
      The lunar module was a two-stage vehicle designed for space
      operations near and on the Moon.  The spacecraft mass of 15,116 kg
      was the mass of the LM including astronauts, propellants and
      expendables.  The dry mass of the ascent stage was 2159 kg and it
      held 2615 kg of propellant.  The descent stage dry mass was 2211 kg
      and 8131 kg of propellant were onboard initially.  The ascent and
      descent stages of the LM operated as a unit until staging, when the
      ascent stage functioned as a single spacecraft for rendezvous and
      docking with the command and service module (CSM).  The descent stage
      comprised the lower part of the spacecraft and was an octagonal prism
      4.2 meters across and 1.7 m thick.  Four landing legs with round
      footpads were mounted on the sides of the descent stage and held the
      bottom of the stage 1.5 m above the surface.  The distance between
      the ends of the footpads on opposite landing legs was 9.4 m.  One of
      the legs had a small astronaut egress platform and ladder.  A one
      meter long conical descent engine skirt protruded from the bottom of
      the stage.  The descent stage contained the landing rocket, two tanks
      of aerozine 50 fuel, two tanks of nitrogen tetroxide oxidizer, water,
      oxygen and helium tanks and storage space for the lunar equipment and
      experiments, and in the case of Apollo 15, 16, and 17, the lunar
      rover.  The descent stage served as a platform for launching the
      ascent stage and was left behind on the Moon.
 
      The ascent stage was an irregularly shaped unit approximately 2.8 m
      high and 4.0 by 4.3 meters in width mounted on top of the descent
      stage.  The ascent stage housed the astronauts in a pressurized crew
      compartment with a volume of 6.65 cubic meters.  There was an
      ingress-egress hatch in one side and a docking hatch for connecting
      to the CSM on top.  Also mounted along the top were a parabolic
      rendezvous radar antenna, a steerable parabolic S-band antenna, and 2
      in-flight VHF antennas.  Two triangular windows were above and to
      either side of the egress hatch and four thrust chamber assemblies
      were mounted around the sides.  At the base of the assembly was the
      ascent engine.  The stage also contained an aerozine 50 fuel and an
      oxidizer tank, and helium, liquid oxygen, gaseous oxygen, and
      reaction control fuel tanks.  There were no seats in the LM.  A
      control console was mounted in the front of the crew compartment
      above the ingress-egress hatch and between the windows and two more
      control panels mounted on the side walls.  The ascent stage was
      launched from the Moon at the end of lunar surface operations and
      returned the astronauts to the CSM.
 
      The descent engine was a deep-throttling ablative rocket with a
      maximum thrust of about 45,000 N mounted on a gimbal ring in the
      center of the descent stage.  The ascent engine was a fixed,
      constant-thrust rocket with a thrust of about 15,000 N. Maneuvering
      was achieved via the reaction control system, which consisted of the
      four thrust modules, each one composed of four 450 N thrust chambers
      and nozzles pointing in different directions.  Telemetry, TV, voice,
      and range communications with Earth were all via the S-band antenna.
      VHF was used for communications between the astronauts and the LM,
      and the LM and orbiting CSM.  There were redundant tranceivers and
      equipment for both S-band and VHF.  An environmental control system
      recycled oxygen and maintained temperature in the electronics and
      cabin. Power was provided by 6 silver-zinc batteries.  Guidance and
      navigation control were provided by a radar ranging system, an
      inertial measurement unit consisting of gyroscopes and
      accelerometers, and the Apollo guidance computer.
 
 
    Scientific Experiments
    ----------------------
      The following scientific experiments were performed on board or at
      the Apollo 12 Lunar Module:
 
      - The Photography Experiment documented the deployment of
        experiments, augmented crew observations and descriptions of the
        lunar traverses, and recorded the effects of the interaction
        between Apollo equipment and the lunar surface.
 
      - The Lunar Field Geology Experiment entailed the collection and
        documentation fo geologic rock samples.
 
      - The Soil Mechanics Experiment studied the properties of the lunar
        soil.
 
      - The Solar Wind Composition Experiment collected samples of the
        solar wind for analysis on Earth.
 
      - 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 lunar module 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).