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Update: Sadly, parts of the dish have collapsed, several cables have snapped, and the Arecibo radio telescope is now decommissioned and demolition has been recommended because it is now too unsafe to do anything else.

Perhaps an answer now can pay tribute to Arecibo's monumental half-century contribution to science!


Although it is technically a radio telescope for astronomy and radar ranging, the Arecibo Observatory has been used for Messaging for Extra-Terrestrial Intelligence (). For how many total hours had Arecibo been used to transmit a signal?

If your reference source distinguishes between METI, radar, and/or other types of transmissions, please include this information in your answer.

Related: Does man send any signal to attract aliens?

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The telescope had a very powerful (1 MW at 12.6 cm wavelength) radar that has been used to investigate surroundings. Radar images of asteroids and planets like Venus, Mars, Lunar poles have been obtained. The total time of transmission is not obvious but assuming multiple projects, it was definitely much more than just Arecibo message that was transmitted only at 450 kW with the older system before upgrade. Other sources also mention 5 MW transmissions.

The alien mind may or may not figure out that they origin of these pulses is not natural.

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  • $\begingroup$ That is a good point. My answer was clearly and specifically about only the total hours of official METI broadcasts. $\endgroup$ Dec 23, 2022 at 15:00
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I believe the only official METI messages broadcast by Arecibo were the original 3 minute 1974 message, and a WOW! Reply in 2012 that took not more than 8 hours.

The Wow! Reply broadcast was booked in the Arecibo telescope schedule from 9 am to 5 pm AST on 15 August 2012. About 20000 tweets were broadcast at about 1 Tweet per second, plus some invited 72-second videos. This is consistent with the 8-hour broadcast window.

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