Smithsonian Air and Space Museum

Apollo 15

Lunar Geology Investigation

The Hadley/Apennine site was selected for multiple objectives:

  1. The Apennine Mountain front
  2. The sinuous Hadley Rille
  3. The dark mare material of Palus Putredinis
  4. The complex of domical hills in the mare

The Apennine Mountain front forms the arcuate southeastern rim of Mare Imbrium. It borders Palus Putredinis and, in the area of the site, it rises 12,000 feet (3658 m) above the surrounding mare. The Apennine Mountain front was believed to have been exposed at the time of the excavation of the giant Imbrium basin. The cratering event must have, therefore, exposed materials which are pre-Imbrian in age. Examination and collection of this ancient material as well as deep-seated Imbrium ejecta were the prime objectives of the mission. This was accomplished during the first and second EVAs when Scott and Irwin selected samples from the foot of the mountain scarp and from the ejecta blankets of craters which excavate mountain materials.

The second important objective of the mission was to study and sample the Hadley Rille, which runs parallel to the Apennine Mountain front and incises the Palus Putredinis mare material. The rille is a sinuous or meandering channel, much like a river gorge on Earth. It displays a V-shaped cross section, with an average slope of about 25 degrees. In the vicinity of the landing site, the rille is about one mile (1.6 km) wide and 1,300 feet (396 meters) deep.

The third objective of the mission was to study and sample the reasonably flat mare material of Palus Putredinis on which the LM landed. Analysis of the samples showed that this mare surface was younger than that visited on Apollo 11, and was closer to the age of the Apollo 12 mare site.

A complex of domical structures about 5 km north of the landing site constituted another objective of the mission. The hills may be made of volcanic domes superposed on the surrounding mare or buried domical structures thinly covered by the mare-like material.

Lunar Orbital Science

The Scientific Instrument Module (SIM) bay of the Apollo J missions was located in Sector 1 of the Service Module. The SIM shared this space with a third cyrogenic oxygen tank that was added after the Apollo 13 incident.

Eight experiments were carried in the SIM bay:

  1. X-ray fluorescence detector
  2. gamma ray spectrometer
  3. alpha-particle spectrometer
  4. panoramic camera
  5. 3-inch mapping camera
  6. laser altimeter
  7. dual-beam mass specrometer
  8. a subsatellite

X-Ray Fluorescence Spectrometer: Second of the geochemical experiment trio for measuring the composition of the lunar surface from orbit. Detects X-ray fluorescence caused by solar X-ray interaction with the Moon. Analyzes the sunlit portion of the Moon under the spacecraft groundtrack.

Gamma-Ray Spectrometer: On a 25-foot (7.6 m) extendable boom. Measures chemical composition of lunar surface in conjuction with X-ray and alpha-particle experiments to gain a compositional "map" of the lunar surface ground track. The device could measure energy ranges between 0.1 to 10 million electron volts.

Alpha-Particle Spectrometer: Measures mono-energetic alpha-particles emitted from the lunar crust and fissures as products of radon gas isotopes in the energy range of 4.7 to 9.3 million electron volts. The sensor was made up of an array of 10 silicon surface barrier detectors.

24-inch Panoramic Camera (SM orbital photo task): Gathered stereo and high-resolution (1 meter) photographs of the lunar surface from orbit. The camera produced an image size of 11.4 cm x 114.8 cm with a field of view 11 degrees downtrack and 108 degrees cross track. The rotating lens system could be stowed face-inward to avoid contamination during effluent dumps and thruster firings. The 72-pound film cassette of 1,650 frames was retrieved by the command module pilot during a transearth coast EVA. This camera worked in conjunction with the 3-inch mapping camera and the laser altimeter to gain data for construction of a comprehensive map of the lunar surface. About 8 percent of the lunar surface was covered by this mission.

3-inch Mapping Camera: Provided 20-meter resolution terrain mapping photography on five-inch film with 3-inch focal length lens. Also included stellar camera shooting the star field on 35mm film simultaneously at 96° from the surface camera optical axis. The stellar photos allowed accurate correlation of mapping photography by comparing simultaneous star field photos with lunar surface photos of the nadir (straight down). The stellar camera film was retrieved during the same EVA as the panoramic camera.

Laser Altimeter: Measures spacecraft altitude above the lunar surface to within one meter. The instrument was boresighted with the 3-inch mapping camera to provide altitude correlation data. The laser altimeter light source was a ruby laser operating at 6,943 angstroms, and 200-millijoule pulses of 10 nanoseconds duration. The laser had a repetition rate up to 3.75 pulses per minute.

Mass Spectrometer: Attempts to measure composition and distribution of the ambient lunar atmosphere. The mass spectrometer was on a 24-foot (7.3 m) extendable boom.

Subsatellite: Ejected into lunar orbit from the SIM bay and carried three experiments : S-Band Transponder, Particle Shadows/Boundary Layer Experiment, and Subsatellite Magnetometer Experiment. The subsatellite was 31 inches long, (78.7 cm) had a 14-inch (35.6 cm) hexagonal diameter and weighed 78.5 pounds (35.6 kg).

From Apollo 15 Press Kit.