The Arecibo observatory shuts down its science.

This looks like the last step in its long decline caused by gradually reducing funding over time: the huge legendary radio telescope cannot be properly maintained, it collapses, there is no money to repair it, and it now, finally, reached its end (there are still other, yet smaller telescopes remaining.). There was a time when there was money to build the telescope. Why did this change so much?

The legitimate explanation would be that this radiotelescope was no longer scientifically interesting, or at least less than when it was built. Or was it a defense project that lost its military significance? Or just palace intrigues over funding? Or something else?


5 Answers 5


When Arecibo was built it was the largest radio telescope. There is now the larger filled aperture system in China and several very large array telescopes.

As such rebuilding Arecibo as it was would be a lot of money to be 'somewhere in the top 10', which is a hard sell politically.

It is possibly also relevant that radio telescopes built into terrain can only point at a very small volume of space because they are rather immobile, this means that Arecibo has scanned all the sky it can see from that location to the precision the system allowed, and the China 500 meter array has similar sky coverage (18 vs 25 degrees north) and is generally more capable. The loss of Arecibo does impact high power active radio astronomy, but most of the bodies of interest now have orbiting radar equipped space probes.

If building a similar capability doing so in the southern hemisphere would probably offer the highest science per $ return as the skies would 'new' for this type of study, rather than trying to fit a larger/more capable system into the Arecibo geography.

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    In recent years, the technical advantage of Arecibo was its radar transmitter, not its size. As far as I know, no radar is planned for FAST. Aug 20 at 15:53

A bit of a contrarian answer: Arecibo's funding lasted much longer than normal. Arecibo is older than Voyager, Green Bank, Hubble, Keck, Mauna Kea ...

Lovell and Haystack are the only major facilities I can think of that are older than Arecibo.

Arecibo lost funding because it reached the end of an exceptional streak of funding successes.

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    McMath-Pierce had a slightly shorter life than Arecibo, being built shortly before and also decommissioned slightly earlier. Aug 20 at 17:42

Arecibo was funded by DoD, NSF, and NASA.

DoD lost interest in 1969.

From 1998 to 2020, NASA's budget increased from $25.48 billion to $25.51 billion in 2022 dollars. The cost of the Webb telescope increased from $1.83 billion to $9.66 billion in 2022 dollars.

LIGO cost over a billion dollars. Over the lifetime of LIGO, NSF's inflation-adjusted budget decreased by over a billion dollars per year. Astronomy gets a small slice of NSF's budget, which is smaller than NASA's budget.

A lot of stuff got cancelled.


it collapses, no money to repair

The simple answer is that the 2020 collapse was irreparable. Much of the telescope was destroyed and would have had to be completely rebuilt. Spending so much to rebuild a 60 year old telescope does not represent a good value proposition. It is true that an updated, modern telescope at the same site has since been proposed, and rebuilding at the same site would offer cost savings and cultural benefits. However, this proposal's price tag still comes to a $400 M, so the odds of funding seem remote.

The more interesting question is perhaps: why wasn't avoiding this collapse more of a priority? The NSF drastically cut funding to Arecibo in 2007 and was already planning a "controlled demolition" rather than a costly repair in 2020, when the telescope was in danger but hadn't yet collapsed.

To me, the official explanation is plausible. Astronomy budgets in the US are always tight. Arecibo was built in 1963, and while it remained relevant 45 years later (in 2007), it also remained costly. And by 2020, the value proposition was even worse: if NSF had only tepid interest in funding the observatory when it was fully functional, it's unsurprising that they would not be interested in funding costly repairs fifteen years later.

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    "The entire telescope was destroyed" is false. In the November 7 2020 incident, one tower collapsed and part of the dish was damaged. Wikipedia's picture dated December 2021 shows large parts of the telescope still present, but perhaps unsafe to work on. Aug 20 at 15:59
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    A main asset of Arecibo is the sinkhole. It would be very expensive to recreate in another location. The sinkhole is still available for use in a telescope. Aug 20 at 16:00
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    @AnonymousPhysicist Parts don't have to be physically destroyed to be effectively destroyed (i.e. damaged beyond repair). The earthquake prior the collapse already caused severe structural damage to the site, to the extent that scientific work had to be suspended. The collapse was the icing on the cake - not only did it destroy part of the dish and the whole (costly!) detector unit, but it surely caused further structural damage to the remaining towers and parts of the dish. I'd bet that at this point rebuilding from scratch would be more cost-effective than fixing the structure.
    – Neinstein
    Aug 21 at 0:27
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    @Neinstein Yes, and the answer's been fixed now. Aug 21 at 10:28

Because the whole one mega project solution mindset is pretty outdated? Today you take software, several small distributed radio telescopes with excellent time measurements and combine them into one huge virtual telescope the size of the planet.


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