page_title: Solo operations of Apollo 15
section_title: Day 1
hierarchical_section_title: Solo operations of Apollo 15 / Day 1
context_page_description: During the 1971 Apollo 15 mission to the Moon, and its three days of exploration on the lunar surface by David Scott and James Irwin, Command Module Pilot Al Worden had a busy schedule of observations. Apollo 15 was the first mission to carry the Scientific Instrument Module bay, which contained a panoramic camera, gamma ray spectrometer, mapping camera, laser altimeter and mass spectrometer. Worden had to operate the shutter and lenses on the cameras and turn on and off the various instruments. During the coast back to Earth, he would perform an EVA to retrieve film cassettes from the cameras.
context_section_description: Many of his observations were of far side features that had not been seen in great detail. The panoramic camera was a modified version of the U.S. Air Force's KA-80A camera for its spy satellites, using a 610 mm f/3.5 lens. This particular camera was similar to those used by the Lockheed U-2, A-12 Oxcart and SR-71 Blackbird. It could see features as small as 3 ft (1 m) across on the lunar surface. It would take long strips, 205 by 13 mi (330 by 21 km) of the surface, on 3.8 foot by 4.5 inch (114.8 by 11.4 cm) strips of film. Over the course of the mission it would take 1,529 usable images, exposing 2 km of film. The film cassette weighed 55 lb (25 kg).
  The other camera in the SIM bay was the Mapping Camera. This consisted of two cameras, the Metric Camera and the Stellar Camera. The Metric Camera took square frames of film, covering about 27,000 km² of the lunar surface, with a resolution of about 20 m. Using the stellar camera, Réseau plates (which added the familiar crosses to Apollo photographs), and other data provided by the laser altimeter, it was possible to identify the exact position on the lunar surface of the photograph taken. A total of 2,240 usable photographs were produced.
  The Laser Altimeter could measure the height of the CSM above the lunar surface to within one meter. It used a pulsed ruby laser operating at 694.3 nanometers and 200 millijoule pulses of 10 nanoseconds duration. The Stellar Camera was used during the runs of the Laser Altimeter on the night side of the Moon. It would show the exact position of the laser beam, for calibration of the altimeter's results.
  During his first pass over the landing site, after landing, Worden attempted to see Falcon using the 28 times magnification sextant. He was successful, refining the position of the site. This was of great help to mission planners as it would help them further refine the planning of the traverses by Scott and Irwin, and also help with photographic interpretation from the surface.
  Another experiment performed on Apollo 15 involved using the radio signal of Endeavour and was termed the Downlink bistatic radar Experiment to find the dielectric constant of the surface material. During the 17th near side pass, while Worden was eating his dinner, the spacecraft was oriented so that its radio signal would reflect off the Moon and be received by the Earth. The strength of this signal varies with the angle of incidence. The Brewster's angle is when the signal is the weakest and is a function of the dielectric constant.
  Before going to sleep, Worden orientated the spacecraft best for the various experiments of the SIM bay, specifically the spectrometers.
  The Gamma-ray Spectrometer detected radiation with energies of 1 MeV to 10 MeV. As the gamma ray passed through a cylinder of doped sodium iodide, it would emit light that would be detected by a photomultiplier tube. Another photomultiplier tube detected charged particles that passed through a plastic shield around the cylinder. All of this was on the end of a 25 ft (7.6 m) boom that would be deployed and retracted periodically during the mission. It sat at the end of the boom so that it would not be contaminated by the spacecraft.
  The Alpha Particle Spectrometer measured the alpha particles emitted by the surface, specifically by the gaseous radon-222 and radon-220. It was optimized to detect particles of energies of 4.7 to 9.1 MeV. It was built into the same casing as the X-ray Spectrometer.
  The X-ray Spectrometer was used to investigate the properties of the upper layers of the lunar surface. As solar X-rays strike the surface, they cause the elements to fluoresce X-rays with well defined energies. The spectrometer could measure these and determine the composition of the lunar surface.
caption: A section of a panoromic camera photograph showing a high resolution view of the landing site. Boulders are easily seen in the rille and the ground disturbed by the lunar module engine shows as a white patch at lower left. South is up.
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