Instrument Host Overview
  ========================
    The Apollo 15 Command and Service Module (CSM) spacecraft orbited the
    Moon during the Apollo 15  mission.  It was piloted by Alfred M.
    Worden.
 
 
    Spacecraft and Subsystems
    -------------------------
      As the name implies, the Command and Service Module (CSM) 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.  Apollo 15 was
      the first of the Apollo J-series spacecraft.  The launch mass,
      including propellants and expendables, of the Apollo 15 CSM was
      30,371 kg of which the Command Module (CM-112) had a mass of 5875 kg
      and the Service Module (SM-112) 24,496 kg.  The Apollo 15 CM was
      named ''Endeavour''.
 
      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, an auxiliary battery, three cryogenic oxygen
      tanks (the battery and an extra oxygen tank were added after the
      Apollo 13 mishap as backups), 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 15 Command and Service Module:
 
      - The Handheld Photography Experiment included Hasselblad and Maurer
        cameras that were used (1) to obtain photographs of the
        transposition, docking, lunar module ejection maneuver, and LM
        rendezvous sequence from both the command and lunar modules, (2) to
        obtain photographs of the lunar ground track and of future landing
        sites, (3) to record the operational activities of the crew, (4) to
        obtain long-distance earth and lunar photographs for areas of
        scientific interest, and (5) to obtain photos of lunar surface
        features and of the activities of the astronauts after their
        landing on the Moon.
 
      - The Panoramic Photography Experiment obtained high-resolution
        panoramic photographs with stereoscopic and monoscopic coverage of
        the lunar surface using a panaromic camera.
 
      - The Metric Photography Experiment obtained high-quality metric
        photographs of the lunar surface and stellar photographs exposed
        simultaneously with the metric photographs.
 
      - The Mapping Camera Aspect Stellar Photography was part of the
        mapping camera subsystem which provided cartographic pointing
        references for the metric camera through the use of the star field
        photographed.
 
      - The Laser Altimeter Experiment obtained data on the altitude of the
        CSM above the lunar surface to support mapping and panoramic camera
        photography, to provide altitude data for other orbital
        experiments, and to relate lunar topographical features for a
        better definition of lunar shape.
 
      - The UV Photography Experiment obtained ultraviolet photographs of
        the Earth and Moon for comparison with similar photographs of Mars
        and Venus for atmospheric and surface studies.
 
      - The Gegenschein Experiment photographed the reflection from dust
        particles at the Moulton point to determine the contribution of
        such reflections to the gegenschein.  This experiment did not yield
        any data because of pointing errors.
 
      - The Gamma-Ray Spectrometer Experiment conducted a geochemical
        mapping of the lunar surface by observing emitted gamma radiation.
 
      - The X-Ray Fluorescence Spectrometer Experiment was used for orbital
        mapping of the lunar surface composition and X-ray galactic
        observations during the transearth coast.
 
      - The Alpha Particle Spectrometer Experiment determined the lunar
        surface radon evolution and indentified localized sources of
        enhanced radon emission that may correspond to regions of enhanced
        lunar outgassing.
 
      - 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.
 
      - 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 Mass Spectrometer Experiment measured the composition of the
        ambient lunar atmosphere for studying source, sink, and transport
        mechanisms.
 
      - The Down-Link Bistatic Radar Experiment utilized the S-band (13-cm)
        and very high frequency (VHF, 116-cm) transmitters on the CSM.
        Radio signals reflected from the lunar surface were received at the
        earth to derive quantitative inferences about the Moon.
 
    For more information about the CSM and its experiments, see the Apollo
    15 preliminary science report (1972) [APOLLO15A1972].
 
 
  This instrument host description was provided by the NASA National Space
  Science Data Center (NSSDC).