The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the

astronaut An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally r ...

s at the landing site of each of the five Apollo missions to land on the Moon following

Apollo 11 Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon. Commander Neil Armstrong and lunar module pilot Buzz Aldrin landed the Apollo Lunar Module ''Eagle'' on July 20, 1969, at 20:17 UTC, ...

(Apollos 12, 14, 15, 16, and 17). 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 The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of th ...

Frank Press Frank Press (December 4, 1924 – January 29, 2020) was an American geophysicist. He was an advisor to four U.S. presidents, and later served two consecutive terms as president of the U.S. National Academy of Sciences (1981–1993). He was the au ...

;

Columbia University Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manhatt ...

, George Sutton; Georgia Tech, Robert Hostetler * Lunar Tri-axis

Magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...

: Ames Research Center, C. P. Sonett;

Marshall Space Flight Center The George C. Marshall Space Flight Center (MSFC), located in Redstone Arsenal, Alabama (Huntsville postal address), is the U.S. government's civilian rocketry and spacecraft propulsion research center. As the largest NASA center, MSFC's firs ...

, Jerry Modisette. * Medium-Energy Solar Wind:

Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a Federally funded research and development centers, federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, La Cañada Flintridge, California ...

, C. W. Snyder and M. M. Neugebauer. * Suprathermal Ion Detection:

Rice University William Marsh Rice University (Rice University) is a Private university, private research university in Houston, Houston, Texas. It is on a 300-acre campus near the Houston Museum District and adjacent to the Texas Medical Center. Rice is ranke ...

, J. W. Freeman, Jr.; Marshall Space Flight Center, Curt Michel. * Lunar Heat Flow Management: Columbia University, M. Langseth;

Yale University Yale University is a private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and among the most prestigious in the w ...

, S. Clark. * Low-Energy Solar Wind: Rice University, B. J. O'Brien. * Active Lunar Seismic Experiment:Apollo 16 Missio
Science Experiments - Active Seismic
Lunar and Planetary Institute (accessed 11 Dec 2015)
(accessed 11 Dec 2015)

Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is conside ...

, R. L. Kovach;

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

, 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 Ann Arbor is a city in the U.S. state of Michigan and the county seat of Washtenaw County. The 2020 census recorded its population to be 123,851. It is the principal city of the Ann Arbor Metropolitan Statistical Area, which encompasses all ...

. 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 A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioa ...

(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.

Deployment

The ALSEP was stored in the

Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed ...

'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.

Common elements

Each ALSEP station had some common elements.

List of experiments

List of missions

Each mission had a different array of experiments.

Apollo 11 Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon. Commander Neil Armstrong and lunar module pilot Buzz Aldrin landed the Apollo Lunar Module ''Eagle'' on July 20, 1969, at 20:17 UTC, ...
(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.Don L. Lind oral history transcript
NASA Johnson Space Center Oral History Project, 27 May 2005. As a result, Apollo 11 did not leave a full ALSEP package, but left a simpler version called the Early Apollo Surface Experiments Package (EASEP). 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 Retro Reflector (LRRR) also deployed within ten minutes. Despite the simpler design, the seismometer was sensitive enough to detect

Neil Armstrong Neil Alden Armstrong (August 5, 1930 – August 25, 2012) was an American astronaut and aeronautical engineer who became the first person to walk on the Moon in 1969. He was also a naval aviator, test pilot, and university professor. ...

's movements during sleep.

Apollo 12 Apollo 12 (November 14–24, 1969) was the sixth crewed flight in the United States Apollo program and the second to land on the Moon. It was launched on November 14, 1969, by NASA from the Kennedy Space Center, Florida. Commander Charles ...

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 Apollo 13 (April 1117, 1970) was the seventh crewed mission in the Apollo space program and the third meant to land on the Moon. The craft was launched from Kennedy Space Center on April 11, 1970, but the lunar landing was aborted aft ...

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. 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 Apollo 14 (January 31, 1971February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to land on the Moon, and the first to land in the lunar highlands. It was the last of the " H missions", landings at ...

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 15 Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the United States' Apollo program and the fourth to land on the Moon. It was the first J mission, with a longer stay on the Moon and a greater focus on science than ear ...

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

Apollo 16 Apollo 16 (April 1627, 1972) was the tenth human spaceflight, crewed mission in the United States Apollo program, Apollo space program, administered by NASA, and the fifth and penultimate to Moon landing, land on the Moon. It was the second o ...

Apollo 17 Apollo 17 (December 7–19, 1972) was the final mission of NASA's Apollo program, the most recent time humans have set foot on the Moon or traveled beyond low Earth orbit. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walke ...

After Apollo

The ALSEP system and instruments were controlled by commands from Earth. The stations ran from deployment until the support operations were terminated on 30 September 1977 due primarily to budgetary considerations. Additionally, by 1977 the power packs could not run both the transmitter and any other instrument. However, the transmitters were not switched off,Charles Redmond
National Aeronautics and Space Administration lyndon B. JohMon Spece Cent. Houston, Texas 77058 AC713 483-5111 Charles Redmond RELEASE NO: 77-47. September 12, 1977. "...Even though the experiments will be terminated, the transmitters will continue to serve Earth as a reference point in astronomy. The Jet Propulsion Laboratory will continue to use the signals from the ALSEP transmitters to assist in the Lab's deep space work including geodetic and astrometric studies and spacecraft navigation. Also, the motion of the lunar orbit will be accurately monitored against a background of extra-galactic stars to test gravitational theories". and all 5 ALSEPs were observed by the Soviet radio telescope RATAN-600 between 18 October and 28 November 1977, after the official termination of their mission.Naugolnaia, M. N.; Spangenberg, E. E.; Soboleva, N. S.; Fomin, V. A
Determination of selenographic coordinates of objects by RATAN-600.
Pisma v Astronomicheskii Zhurnal, vol. 4, Dec. 1978, p. 562-565. (Soviet Astronomy Letters, vol. 4, Nov.-Dec. 1978, p. 302-303). ALSEP systems are visible in several images taken by the

Lunar Reconnaissance Orbiter The Lunar Reconnaissance Orbiter (LRO) is a NASA robotic spacecraft currently orbiting the Moon in an eccentric polar mapping orbit. Data collected by LRO have been described as essential for planning NASA's future human and robotic missions t ...

during its orbits over Apollo landing sites. File:Apollo 17 landing site, labeled.jpg, LRO photo showing the Apollo 17 ALSEP (science package) File:Apollo 12 LRO.jpg, LRO photo showing the Apollo 12 ALSEP

Notes

Encyclopedia Astronautica website, 14 February 1966 entry.

References

Bibliography

* Brzostowski, M.A., and Brzostowski, A.C., ''Archiving the Apollo active seismic data'', The Leading Edge, Society of Exploration Geophysicists, April, 2009.

External links

Astronautix Site

Apollo Scientific Experiments Data Handbook

ALSEP Termination Report

Catalog of Apollo Experiment Operations

Apollo Lunar Surface Experiments Package, Design Certification Review (1971)

Archive of ALSEP documents
from the Lunar and Planetary Institute {{Use American English, date=January 2014 Apollo program hardware Lunar science Bendix Corporation