Apollo Lunar Surface Experiments Package

The Apollo Lunar Surface Experiments Package 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. Apollo 11 left a smaller package called the Early Apollo Scientific Experiments Package, or EASEP.

Background

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

Passive Lunar Seismic Experiment: Massachusetts Institute of Technology, Frank Press; Columbia University, George Sutton; Georgia Tech, Robert Hostetler
Lunar Surface Magnetometer: Ames Research Center, C. P. Sonett; Marshall Space Flight Center, Jerry Modisette.
Medium-Energy Solar Wind: Jet Propulsion Laboratory, C. W. Snyder and M. M. Neugebauer.
Suprathermal Ion Detection: Rice University, J. W. Freeman, Jr.; Marshall Space Flight Center, Curt Michel.
Heat Flow Experiment: Columbia University, M. Langseth; Yale University, S. Clark.
Low-Energy Solar Wind Charged Particle Lunar Environment Experiment: Rice University, B. J. O'Brien.
Active Seismic Experiment: Stanford University, R. L. Kovach; United States Geological Survey, J. S. Watkins.
SNAP-27 isotopic power system: Sandia National Laboratories, Jim Leonard

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 to run the instruments and communications so data collected by the experiments could be relayed to Earth. Thermal control was achieved by passive elements as well as power dissipation resistors and heaters. Data collected from the instruments were converted into a telemetry format and transmitted to Earth.

Deployment

The ALSEP was stored in the Lunar Module's Scientific Equipment 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. The exact deployment of experiments differed by mission. The following pictures show a typical procedure from Apollo 12.

Picture	Description
150px	Pete Conrad opens the SEQ bay doors through a system of lanyards and pulleys.
150px	Alan Bean removes the second subpackage from the SEQ bay. This was accomplished by using the boom which can be seen extended and a pulley system to set it on the ground. By Apollo 17, astronauts felt that the use of the boom and pulley system complicated the operation. And as such, the entire system was removed for Apollo 17. On Apollo 11, Buzz Aldrin chose not to use the system because of a lack of time.
150px	The first subpackage, which Conrad had removed from the SEQ bay earlier.
150px	Bean lowers the RTG cask into a position where he can access it.
150px	Bean is beginning to remove the dome from the RTG cask. He is using a specialized tool called the Dome Removal Tool. Note how he has already prepared the RTG for fueling and has already deployed the HTC. Conrad has already removed the subpallet from the RTG subpackage.
150px	Bean discards the dome with the DRT still attached. Neither had a use afterward.
150px	Bean is attempting to remove the fuel element from the cask using the Fuel Transfer Tool. Note one of the Universal Hand Tools attached to the RTG subpackage. On Apollo 12, the fuel element stuck in the cask because of thermal expansion. Conrad pounded the side of the cask with a hammer while Bean successfully worked it loose. He then inserted it into the RTG and discarded the FTT.
150px	Bean attaches the RTG subpackage to the carrybar in preparation for the traverse to the ALSEP deployment site. The carrybar would later be used as the mast for the antenna on the Central Station.
150px	During the traverse to the ALSEP deployment site, Conrad took this picture. His shadow indicates that he is carrying the subpallet with one of the two UHTs.
150px	Bean carries the ALSEP out to the deployment site.
150px	Conrad holds the carrybar in his left hand while he releases the antenna gimbal assembly with a UHT.
150px	This photo shows Jim Lovell training for Apollo 13. He is currently deploying a mock-up of the Central Station. The Station was spring-loaded. After releasing Boyd bolts, the top of the Station would spring up, deploying it. Note the various locations on top of it which held some of the experiments before deployment. They were also held down with Boyd bolts that were released with a UHT.

Common elements

Each ALSEP station had some common elements.

Name	Diagram	Picture	Description
Central Station	150px	150px	The picture shows the Central Station from Apollo 16's ALSEP. The Central Station was essentially the command center for the entire ALSEP station. It received commands from Earth, transmitted data, and distributed power to each experiment. Communications with Earth were achieved through a 58 cm long, 3.8 cm diameter modified axial-helical antenna mounted on top of the Central Station and pointed towards Earth by the astronauts. Transmitters, receivers, data processors and multiplexers were housed within the Central Station. The Central Station was a 25 kg box with a stowed volume of 34,800 cubic cm. In addition, on Apollos 12 to 15, a Dust Detector was mounted on the Central Station which measured the accumulation of Lunar dust.
Radioisotope Thermoelectric Generator		150px	The picture shows the RTG from Apollo 14 with the Central Station in the background. The RTG was the power source for the ALSEP. It utilized the heat from the radioactive decay of plutonium-238 and thermocouples to generate approximately 70 watts of power. The base of the RTG was the base of the second ALSEP subpackage.
RTG Cask		150px	The RTG cask stored the plutonium-238 fuel element. It was located to left of the SEQ bay. The cask was designed to withstand a launch vehicle explosion in the event of an abort or a re-entry into Earth's atmosphere. The picture shows Edgar Mitchell practicing the removal of the fuel element.

List of experiments

List of missions

Each mission had a different array of experiments.

Apollo 11 (EASEP)

Because of the risk of an early abort on the Moon, geologists persuaded NASA to permit only experiments that could be set up or completed in 10 minutes. As a result, Apollo 11 did not leave a full ALSEP package, but left a simpler version called the Early Apollo Surface Experiments Package. Since there was only one 2 hour 40 minute EVA planned, the crew would not have enough time to deploy a full ALSEP, which usually took one to two hours to deploy. Both packages were stored in the LM's SEQ bay.
Engineers designed the EASEP to deploy with one squeeze handle, and the Laser Ranging Retroreflector also deployed within ten minutes. Despite the simpler design, the seismometer was sensitive enough to detect Neil Armstrong's movements during sleep.

Name	Picture	Notes
LRRR	150px	The transparent dust cover has already been removed and is 3–4m further to the right. The metal reflector mirrors the black sky.
PSEP	150px	Failed after 21 days

Apollo 12

Name	Picture	Notes
LSM	150px	Stored on the first subpackage
PSE	150px	Stored on the first subpackage
SWS	150px	Stored on the first subpackage
SIDE/CCGE	150px	Stored on the second subpackage as part of the subpallet. The CCIG can be seen to the left of the SIDE. The CCIG failed after only 14 hours.

The antenna gimbal assembly was stored on the subpallet. The stool for the PSE, the ALSEP tools, carrybar, and HTC was stored on the second subpackage.

Apollo 13

Because of the aborted landing, none of the experiments were deployed. However, the Apollo 13 S-IVB stage was deliberately crashed on the Moon to provide a signal for the Apollo 12 PSE.

Name	Notes
CPLEE	Stored on the first subpackage
CCGE	Stored on the first subpackage
HFE	Stored on the first subpackage
PSE	Stored on the first subpackage

The antenna gimbal assembly was stored on the first subpackage. The stool for the PSE, the ALSEP tools, carrybar, and the Lunar drill was stored on the subpallet. The HTC was stored on the second subpackage.

Apollo 14

Name	Picture	Notes
ASE	150px 150px	The above image shows the mortar device. The lower one shows Lunar Module Pilot Edgar Mitchell operating the Thumper. The mortar, geophones, and Thumper was stored on the first subpackage. Thirteen of the twenty-two Thumper charges were fired successfully. Because of concerns about the deployment of the mortar, none of the four explosives were fired. There was an attempt to fire them at the end of the ALSEP's operational lifetime, but the charges failed to work after being dormant for so long.
CPLEE	150px	Stored on the first subpackage
LRRR	150px	Stored in Quad I of the LM and brought to the ALSEP site separately
PSE	150px	Stored on the first subpackage
SIDE/CCGE	150px	Stored on the subpallet. The SIDE is in the upper-left corner while the CCIG is in the center of the picture.

The antenna gimbal assembly was stored on the subpallet. The stool for the PSE, the ALSEP tools, carrybar, and HTC was stored on the second subpackage.