Apollo Lunar Surface Experiments Package

The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the astronauts at the landing site of each of the five Apollo missions to land on the Moon following Apollo 11 (Apollos 12, 14, 15, 16, and 17). Apollo 11 left a smaller package called the Early Apollo Scientific Experiments Package, or EASEP.

The instrumentation and experiments that would comprise ALSEP were decided in February 1966. Specifically, the experiments, institutions responsible, and principal investigators and coinvestigators were:

The ALSEP was built and tested by Bendix Aerospace in Ann Arbor, Michigan. The instruments were designed to run autonomously after the astronauts left and to make long term studies of the lunar environment. They were arrayed around a Central Station which supplied power generated by a radioisotope thermoelectric generator (RTG) to run the instruments and communications so data collected by the experiments could be relayed to Earth. Thermal control was achieved by passive elements (insulation, reflectors, thermal coatings) as well as power dissipation resistors and heaters. Data collected from the instruments were converted into a telemetry format and transmitted to Earth.

The ALSEP was stored in the LM's Scientific Equipment (SEQ) Bay in two separate subpackages. The base of the first subpackage formed the Central Station while the base of the second subpackage was part of the RTG. A subpallet was also attached to the second subpackage which usually carried one or two of the experiments and the antenna gimbal assembly. On Apollo 12, 13, and 14, the second subpackage also stored the Lunar Hand Tool Carrier (HTC). The exact deployment of experiments differed by mission. The following pictures show a typical procedure from Apollo 12.

Each ALSEP station had some common elements.

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