Instrument Host Overview
  ========================
    The Apollo 17 Lunar Module (LM) 'Challenger' was the sixth and last
    crewed vehicle to land on the Moon as part of NASA's Apollo program.
    It carried two astronauts, Commander Eugene A. Cernan and LM pilot
    Harrison H. Schmitt, the eleventh and twelfth men to walk on the Moon.
    The LM also carried a Lunar Roving Vehicle (LRV), an Apollo Lunar
    Surface Experiments Package (ALSEP) that contained scientific
    experiments to be deployed and left on the lunar surface, and other
    scientific and sample collection apparatuses. The experiments performed
    on the Moon, in addition to the ALSEP suite, were geologic sample
    collection, surface photography, gravitation acceleration measurements
    at the lunar surface, and soil mechanics.
 
    The LM separated from the Command and Service Module (CSM) at 17:20:56
    UT on 11 December 1972 and landed on the Moon at 19:54:57 UT on 11
    December 1972, on the southeastern rim of Mare Serenitatis in a valley
    at Taurus-Littrow (20.19 North longitude, 30.77 East latitude
    [DAVIES&COLVIN2000]).
 
    Cernan and Schmitt made three moonwalk extra-vehicular activities
    (EVAs) totaling 22 hours, 4 minutes.  During this time they covered 30
    km using the Lunar Roving Vehicle, collected 110.52 kg of lunar
    samples, took photographs, and set up the ALSEP and performed other
    scientific experiments.  Evans performed experiments from orbit in the
    CSM during this time.
 
    The Lunar Roving Vehicle (LRV) was used during EVAs to extend the range
    of manned lunar exploration.  The first EVA was from 23:54:49 UT on 11
    December to 07:06:42 UT on 12 December, during which the LRV was
    deployed and driven and the ALSEP was set up.  During the second EVA,
    which began at 23:28:06 UT on 12 December and ended at 07:05:02 UT on
    13 December, the astronauts deployed explosive packages for the active
    seismic experiment and Schmitt discovered a patch of orange soil.  The
    third EVA involved more traverses and sample collection and lasted from
    22:25:48 UT on 13 December to 05:40:56 UT on 14 December.
 
    The LM lifted off from the Moon at 22:54:37 UT on 14 December 1972
    after 75 hours on the lunar surface.  After the LM docked with the CSM
    at 01:10:15 UT on 15 December 1972 the lunar samples and other
    equipment were transferred from the LM and the LM was jettisoned at
    04:51:31 UT.  The LM impacted the Moon at 06:50:20.8 UT on 15 December
    1972 at 19.96 North longitude, 30.50 East longitude, approximately 15
    km from the Apollo 17 landing site, with an estimated impact velocity
    of 1.67 km/s at an angle ~4.9 degrees from horizontal.
 
    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 16,448 kg
      was the mass of the LM including astronauts, expendables, and
      approximately 12,000 kg of propellants.  The fully fueled mass of the
      ascent stage was about 4985 kg and the descent stage 11,463 kg.  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 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 transceivers 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 near
      the Apollo 17 Lunar Module:
 
      - The Lunar Traverse Gravimeter Experiment carried on board the LRV
        was designed to make a high-accuracy survey of the gravitational
        field in the Apollo 17 landing area;
 
      - The Soil Mechanics Experiment studied the physical properties of
        the lunar regolith using observations recorded by video and audio;
 
      - The Surface Electrical Properties Experiment obtained data about
        the electromagnetic energy transmission, absorption, and reflection
        characteristics of the lunar surface and subsurface.
 
      - The Lunar Surface Cosmic Ray Experiment was a set of detectors hung
        from the LM, designed to measure solar wind particles, low energy
        cosmic rays, and radon;
 
      - The Neutron Probe was designed to measure the rates of low-energy
        neutron capture as a function of depth in the lunar regolith.
 
      - Apollo Lunar Surface Experiments Package of experiments.
 
    For more information about the LM, the LRV, and the associated
    experiments, see the Apollo 17 Preliminary Science Report
    [APOLLO17A1973].
 
  This instrument host description was provided by the NASA National Space
  Science Data Center.