Editing Apollo 12 (section)

=== ALSEP ===
{{Main|Apollo Lunar Surface Experiments Package}}
[[File:ALSEP AS12-47-6917.jpg|thumb|left|Apollo 12's Passive Seismic Experiment]]

The [[Apollo Lunar Surface Experiments Package]] (ALSEP) was a suite of scientific instruments designed to be emplaced on the lunar surface by the Apollo astronauts, and thereafter operate autonomously, sending data to Earth.<ref name = "astro" /> Development of the ALSEP was part of NASA's response to some scientists who opposed the crewed lunar landing program (they felt that robotic craft could explore the Moon more cheaply) by demonstrating that some tasks, such as deployment of the ALSEP, required humans.{{sfn|Harland 2011|pp=265–266}} In 1966, a contract to design and build the ALSEPs was awarded to the [[Bendix Corporation]].<ref>{{cite news|title=NASA giving Bendix $17 million lunar pact|url=https://aadl.org/aa_news_19660317_p29-nasa_giving_bendix_17_million_lunar_pact|newspaper=[[Ann Arbor News]]|date=March 17, 1966}}</ref> Due to the limited time the Apollo 11 crew would have on the lunar surface, a smaller suite of experiments was flown, known as the Early Apollo Surface Experiment Package (EASEP). Apollo 12 was the first mission to carry an ALSEP; one would be flown on each of the subsequent lunar landing missions, though the components that were included would vary.<ref name = "astro" /> Apollo 12's ALSEP was to be deployed at least {{convert|300|ft}} away from the LM to protect the instruments from the debris that would be generated when the ascent stage of the LM took off to return the astronauts to lunar orbit.{{sfn|Harland 2011|p=279}}

[[File:Putting the Plutonium 238 fuel into the SNAP 27.jpg|thumb|left|Bean places the fuel element into the SNAP-27 RTG.]]

Apollo 12's ALSEP included a [[Lunar Surface Magnetometer]] (LSM), to measure the magnetic field at the Moon's surface, a Lunar Atmosphere Detector (LAD, also known as the [[Cold Cathode Gauge Experiment]]), intended to measure the density and temperature of the thin lunar atmosphere and how it varies, a Lunar Ionosphere Detector (LID, also known as the [[Suprathermal Ion Detector Experiment]], or SIDE), intended to study the charged particles in the lunar atmosphere, and the [[Solar Wind Spectrometer]], to measure the strength and direction of the [[solar wind]] at the Moon's surface—the free-standing Solar Wind Composition Experiment, to measure what makes up the solar wind, would be deployed and then brought back to Earth by the astronauts.{{sfn|Press Kit|pp=30–36}} A Dust Detector was used to measure the accumulation of [[lunar dust]] on the equipment.{{sfn|Press Kit|p=42}} [[Apollo 12 Passive Seismic Experiment|Apollo 12's Passive Seismic Experiment]] (PSE), a seismometer, would measure moonquakes and other movements in the Moon's crust, and would be calibrated by the nearby planned impact of the ascent stage of Apollo 12's LM, an object of known mass and velocity hitting the Moon at a known location, and projected to be equivalent to the explosive force of one ton of TNT.{{sfn|Press Kit|p=40}}

The ALSEP experiments left on the Moon by Apollo 12 were connected to a Central Station, which contained a transmitter, receiver, timer, data processor, and equipment for power distribution and control of the experiments.{{sfn|Mission Report|p=A-5}} The equipment was powered by [[SNAP-27]], a [[radioisotope thermoelectric generator]] (RTG) developed by the [[United States Atomic Energy Commission|Atomic Energy Commission]]. Containing [[plutonium]], the RTG flown on Apollo 12 was the first use of atomic energy on a crewed NASA spacecraft—some NASA and military satellites had previously used similar systems. The plutonium core was brought from Earth in a cask attached to an LM landing leg, a container designed to survive re-entry in the event of an aborted mission, something NASA considered unlikely.{{sfn|Press Kit|pp=33–34}} The cask would survive re-entry on [[Apollo 13]], sinking in the [[Tonga Trench]] of the Pacific Ocean, apparently without radioactive leakage.<ref name = "Cass 3">{{cite web|last=Cass|first=Stephen|title=Houston, we have a solution, part 3|url=https://spectrum.ieee.org/apollo-13-we-have-a-solution-part-3|date=April 1, 2005|website=IEEE|access-date=September 8, 2019}}</ref>

The Apollo 12 ALSEP experiments were activated from Earth on November 19, 1969.{{sfn|Orloff & Harland 2006|pp=601–602}} The LAD returned only a small amount of useful data due to the failure of its power supply soon after activation.{{sfn|Harland 2011|p=325}} The LSM was deactivated on June 14, 1974, as was the other LSM deployed on the Moon, from Apollo 15. All powered ALSEP experiments that remained active were deactivated on September 30, 1977,{{sfn|Orloff & Harland 2006|pp=601–602}} principally because of budgetary constraints.<ref name = "astro">{{cite news|newspaper=[[Astronomy (magazine)|Astronomy]]|access-date=February 1, 2021|title=What did the Apollo astronauts leave behind?|date=June 21, 2019|last=Talcott|first=Richard|url=https://astronomy.com/news/2019/06/what-did-the-apollo-astronauts-leave-behind}}</ref>