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I first tried to include this in the question Why were the “perfectly functioning” seismometers placed by Apollo 12, 14, 15 and 16 astronauts all shut off in 1977? but after three comments from three different users stressed some aspect of it being "common sense" to shut it down since NASA would no longer be listening or talking to them, I decided that it would be more prudent to ask this separately rather than to swim upstream against the tide.

Question: Was there any particular rule, directive, policy, SOP, or special or technical consideration behind the deliberate powering-off of all of the Apollo ALSEP systems on the moon in September of 1977, beyond "it's just good practice to shut things off when you are no longer using them"?

The answer there explains that for budgetary reasons things like control of the system and collection of data from it from Earth were shut down in late 1977. This question addresses only the command sent from Earth for them to be actively powered down. As pointed out in the answer, their lifetime was finite anyway due to the half-life of the isotope in their RTG power sources, so they would have powered down anyway.

I'm of course not suggesting it's not common sense, I'm just curious if there were any particular rules, directives, SOP,s or special or technical considerations behind it as well.

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    $\begingroup$ I don’t know enough specifically to make this an answer, but back then the FCC (and perhaps ITU, but that might have been later) insisted on a plan for “ensured termination of (space) transmitter operation”. You could no longer just let them run down, in case they started bleating all over their frequency band. There were also license renewal reviews associated with that. So they might have felt unable to just leave them running. I worked a LEO project in 1975-79 that had issues with this, but I don’t know anything specific about the Apollo transmitters. $\endgroup$ Apr 8, 2018 at 3:46
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    $\begingroup$ @BobJacobsen this sounds exactly like the kind of answer I was hoping for. Thanks for the information! $\endgroup$
    – uhoh
    Apr 8, 2018 at 3:51
  • $\begingroup$ @BobJacobsen I wonder if that can be an answer here? $\endgroup$
    – uhoh
    Aug 18, 2021 at 1:12
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    $\begingroup$ Interesting factoid about ALSEP RTGs, "SNAP-27 RTGs were not shipped as complete units. The Pu-238 fuel rod was carried in a special transport case located on the outside of the descent stage of the lunar module. This location was inaccessible during flight operations; there was no way to assemble the power supply in an emergency", such as the Apollo 13 situation. $\endgroup$
    – Fred
    Oct 30, 2021 at 6:10
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    $\begingroup$ For 30 September 1977, this page states, "Because of US budget cuts and dwindling power reserves, the Apollo program’s ALSEP experiment packages left on the Moon are shut down." $\endgroup$
    – Fred
    Oct 30, 2021 at 6:30

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A number of online resources (NASA & https://astronomy.com/news/2019/06/what-did-the-apollo-astronauts-leave-behind) state the reason for decommissioning the Apollo ALSEPs on September 30, 1977 was due to lack of funding resulting from budget cuts.

Apparently the ALSEPS received 153,000 commands while operational.

Although the experiments were turned off, the transmitters continued to send carrier signals which were used by various institutions, including the Jet Propulsion Laboratory, for geodetic and astrometric studies, and spacecraft navigation.

After four years of sending a steady flow of data, the Apollo 14 ALSEP developed an intermittent fault. It began an intermittent ‘on’ and ‘off’ cycle for its last two years, due to a short circuit in one of the power conditioning units. It seemed related to the temperature of the unit, reacting to the position of the Sun over the site.

The ALSEP program cost NASA an estimated \$US200 million, including the design and development of the stations and experiments, support engineering work in Houston, and the analysis of the data by dozens of University laboratories around the world. It cost NASA \$US2 million a year to operate.

Due to other budgetary issues some of the data from the ALSEPs was lost when the recording tapes were wiped, so they could be used for other projects.

“Before (March 1976) NASA wanted us to read the data, extract what we want and send it back to NASA for archiving,” said Nakamura. “Then somebody in a committee said there’s no use keeping those.”

Magnetic tape reels were expensive and bulky. Under pressure to supply other projects and control cost, NASA, like many others at the time, wiped and reused tapes. The unfortunate reality is that data recorded during the first five years of the Apollo program, before NASA began keeping ARCSAV tapes, is likely lost forever.


Not from the most authoritative source, some facts about Moon quakes.

There are four separate kinds of moonquakes, registering as shadowy echoes on the Apollo mission seismometers.

The first type is deep, occurring about 700 km below the surface, and believed to be caused by tides and linked to its orbit around the earth.

A second type, the result of a meteorite crashing into the surface, takes the form of vibrations.

The third type is thermal in nature; after two weeks of lunar night (and deep-freeze temperatures), the morning sun causes an expansion, and ultimately cracking, of the moon's frigid crust.

Finally, the fourth type is a shallow quake occurring 20 or 30 kilometers (about 12 to 19 miles) below the surface.

While deep moonquakes are generally only magnitude 2 or smaller, they occur on a monthly basis, whereas quakes occurring along the same fault line on Earth may be decades or centuries apart.

Moonquakes also last longer than earthquakes, which typically cease within a few minutes.

Since the moon is much drier and cooler than Earth, the vibrations carry for longer, whereas Earth’s more compressible structure acts like a sponge to absorb vibrations.

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