Lunar Surface Experiments[1]



Central Station


The heart of the experiment package, provided the radio frequency link to Earth for telemetering data, command/control, and power distribution to the experiments.



Early Apollo Scientific Experiment Package (EASEP)


Flown on Apollo 11 only, this experiment package was powered by solar energy and contained an abbreviated set of experiments. It continued to return data for 71 days.



Active Seismic


Used an astronaut-activated thumper device and mortar firing explosive charges to generate seismic signals. This experiment used geophone seismic listening devices to determine lunar structure to depths of about 1,000 feet.



Heat Flow


Probes containing temperature sensors were implanted in holes to depths of 8 feet to measure the near-surface temperature gradient and thermal conductivity from which heat flow from the lunar interior could be determined.



Lunar Mass Spectrometer


Used a magnetic deflection mass spectrometer to identify lunar atmospheric components and their relative abundance.



Lunar Seismic Profiling


Flown on Apollo 17 only, this experiment was an advanced version of the Active Seismic Experiment. It used four geophones to detect seismic signals generated by eight explosive charges weighing from about 1/10 to 6.5 pounds. The charges were deployed at distances up to 2 nautical miles from the Lunar Module and were detonated by timers after the Lunar Module departed. Lunar structure to depths of 1.5 nautical miles was measured. Used in a listening mode, the experiment continued to provide data on Moon/thermal quakes and meteoroid impacts beyond its planned lifetime



Solar Wind Spectrometer


Measured interaction between the Moon and the solar wind by sensing flow-direction and energies of both electrons and positive ions. Results showed that solar wind plasma measurements on the lunar surface are indistinguishable from simultaneous plasma measurements made by nearby satellites



Suprathermal Ion Detector


Provided information on the energy and mass spectra of positive ions near the lunar surface. Evidence of prompt ionization and acceleration of gases generated on the Moon was found in the return data.



Charged Particle Lunar Environment


Measured the fluxes of charged particles, both electrons and ions, having energies from 50 to 50,000 electron volts. The instrument measured plasma particles originating in the Sun and low-energy particle flux in the magnetic tail of the Earth.



Laser Ranging Retroreflector


The retroreflector bounced laser pulses back to Earth ground stations to provide data for precise measurements of the Earth-Moon distance to determine Earth wobble about its axis, continental drift, lunar librations, etc. Arrays of 100 retroreflecting corners were flown on Apollos 11 and 14, and an array of 300 corners was flown on Apollo 15.



Lunar Surface Magnetometer


Measured the intrinsic remnant lunar magnetic field and the magnetic response of the Moon to large-scale solar and terrestrial magnetic fields. The electrical conductivity of the lunar interior was also determined from measurements of the Moon’s response to magnetic field step-transients. Three boom-mounted sensors measured mutually-orthogonal components of the field



Lunar Ejecta and Meteorites


Three separate detectors which measured energy, speed, and direction of dust particles. Oriented east, west, and up. The dust particles measured were meteorites, secondary ejecta from meteorites, and, possibly, lunar surface particles levitated and accelerated by lunar surface phenomena.



Cold Cathode Ion Gauge


A separate experiment combined in an integrated package with the Suprathermal Ion Detector. It determined the density of neutral gas particles in the lunar atmosphere.



Passive Seismic


Detected Moon-quakes and meteoroid impacts to enable scientists to determine the Moon’s internal composition.



Radioisotope Thermoelectric Generator


Supplied about 70 watts of electrical power for continuous day-night operation.



Lunar Surface Gravimeter


Measured and sensed changes in the vertical component of lunar gravity, using a spring mass suspension. It also provided data on the lunar tides.

[1]Apollo Lunar Surface Experiments Package (ALSEP): Five Years of Lunar Science and Still Going Strong, Bendix Aerospace.