Arecibo : the end of a giant

Arecibo : the end of a giant

An iconic radio telescope with its imposing 305 m fixed antenna, used for scientific advances and even a movie star, the observatory, located on the island of Puerto Rico, collapsed in the morning of 1 December 2020.

A giant of radio astronomy has probably suffered a fatal injury. This radio telescope managed by the National Science Foundation, an American governmental agency, was built in Arecibo on the north coast of the island of Puerto Rico in the Antilles. Officially known as the National Astronomy and Ionosphere Center (NAIC), it is better known as the Arecibo radio telescope or even just Arecibo.

On 1 December 2020, its reception platform collapsed onto its main antenna after cables broke. A few days after the disaster the National Science Foundation (NSF) published this video showing the event from two different angles, one of which was filmed by a drone.


When it came into operation in 1963, it became the world’s biggest radio telescope with its impressive 305 m diameter antenna installed in a natural bowl. Its receiver was perched 150 m above, held by cables anchored through three concrete pylons. In 1973, the 305 m antenna, which in fact consists of a mesh of cables, was covered by 38,778 aluminium panels of 1×2 m, which greatly improved its performance. As it was fixed, it could not be directly oriented towards a sector of the sky to observe, but, to make up for that, its suspended receiver could be oriented. Designed to study the ionosphere, it also turned out to be an excellent astronomical instrument. For example, in 1964, it enabled us to determine Mercury’s rotation period (59 days) and to produce the first radar image of an asteroid (Casteria) in 1989. This technology was subsequently refined and gave spectacular results.

Imagerie radar de l’astéroïde 2014 HQ124 de 370 m de large alors qu’il passait à 1,3 million de kilomètres de la Terre le 8 juin 2014. L’objet fut observé conjointement par Arecibo et le radiotélescope de Goldstone (Californie). Crédit : NASA/USRA

Radar imaging of the 370 m wide asteroid 2014 HQ124 passing 1.3 million kilometres from Earth on 8 June 2014. The object was observed jointly by Arecibo and the Goldstone radio telescope (California).

In 1974 the radio telescope transmitted the famous Arecibo message. A 1679 bit graphic representation of the observatory and a human figure with scientific data. It was sent to the Messier 13 globular cluster 25,000 light years away.

Représentation graphique (couleurs ajoutées, elles n’étaient pas dans le signal d’origine) du message d’Arecibo envoyé vers l’amas globulaire Messier 13. Crédit : CC-BY-SA 3.0

Graphic representation (the added colours were not part of the original signal) of the Arecibo message sent to the Messier 13 globular cluster.
Credit : CC-BY-SA 3.0

In 2008, Arecibo succeeded in detecting pre-biotic molecules (methaminine and hydrogen cyanide) in a distant galaxy.

The radio telescope was also used for the SETI programme to try to seek out radio signals transmitted by possible extra-terrestrial civilisations, without success. This use of the observatory was popularised by the film Contact in 1997, directed by Robert Zemeckis with Jodie Foster, based on the book of the same name by American astronomer, Carl Sagan (1934-1996). It features in this scene in particular.

Previously, Arecibo had been used as a secret base in the James Bond film GoldenEye in 1995. It features in the background in other productions.


Arecibo had lost the title of the world’s largest radio telescope after the 500 m Chinese FAST came into operation in 2016, which also used the principle of a wide fixed antenna installed in a natural bowl.

More seriously, the Puerto Rico observatory suffered the ravages of time. In 2017, Hurricane Maria caused an instrument located on the suspended structure to fall onto the antenna. In August 2020, one of the cables holding this platform gave way and destroyed an area of around 30 metres on the main antenna below. In November, further similar damage occurred.

Le radiotélescope d’Arecibo photographié le 7 novembre 2020. On remarque l’entaille dans son antenne de 305 m. Crédit : NSF

The Arecibo radio telescope photographed on 7 November 2020. The gash in its 305 m antenna can be seen.
Credit: NSF

The National Science Foundation (NSF) ended up announcing what many feared: the radio telescope was considered so dangerous that its repair was no longer possible. A press release on 19 November 2020 stated that the installation would therefore be dismantled. Five days later, an examination of the cables made engineers fear its collapse. On 1 December at 7.55 a.m., local time, that diagnosis became reality since the 900-tonne suspended instrumental platform fell onto the 305 m antenna. The NSF reported that no-one had been injured. Because of the danger, a safety area had in fact been declared and access to the site was strictly limited.

The news which had been circulating on social networks on the very day of the collapse was confirmed by the NSF’s tweet below.

The following tweet shows some of the first images of the disaster with views from the air taken by Dennis Vazquez.

The photos from NotiCel media (photographer Juan R. Costa) confirm the magnitude of the damage and the end of a giant.




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