There will be no more radio light for the legendary Arecibo telescope

Arecibo telescope

Image credit: Evilkalla at English Wikipedia, CC BY-SA 3.0licenses/by-sa/3.0, via Wikimedia Commons


Things were looking grim for the 305 meter Arecibo radio telescope these past few months. Following two recent cable failures in August and November, the giant telescope was on the verge of collapse. Today the US National Science Foundation made the decision to decommission the legendary observatory. 


A is for Aliens. And Arecibo.

When you say ALIENS, we think ARECIBO. After all, it was the Arecibo Radio Telescope that beamed the powerful Arecibo Message into space in an attempt to reach intelligent aliens back in 1974. 

It was Arecibo that was featured in the sci-fi classic 1997 movie Contact, the film that reportedly inspired so many young women (including some of the WonderDome Portable Planetarium staff) to choose a career in Astronomy.

And it is Arecibo that we consider the birthplace of SETI research.

But the Arecibo observatory is more than just a cultural landmark. It is, first of all, a World leading research facility where some of the most significant discoveries were made, from the first ever exoplanet and millisecond pulsar to the Nobel Prize-winning study of the double pulsar behavior.

Then, there is planetary defense. Out of all the end-of-the-world scenarios, asteroid impact seems most likely to wipe humanity off the face of the Earth. Luckily, we have a giant radio telescope to keep an eye on those potentially dangerous space rocks. Well…used to have. 


The observatory

Arecibo observatory is located south of the city of Arecibo, in Puerto Rico’s North-West. It became operational in 1963 and until 2016 the observatory held the title of the biggest single aperture radio telescope in the World. 

Arecibo is a colossal structure:  the 305 meter dish is built into a karst sinkhole; 500 feet above the dish, the giant 900-ton platform is suspended in the air on 18 steel cables supported by 3 concrete towers. There is no other such telescope anywhere in the World!.



The observatory didn’t always have it easy. In nearly 6 decades of continuous work, it’s been through earthquakes, hurricanes, tropical storms and what not.

Most recently, in September 2017, it was hit by hurricane Maria. The deadly category 5 hurricane destroyed the small 12 meter dish and damaged some of the instruments. 

The observatory resumed observations a week after the hurricane struck the island, although, initially, at a reduced capacity. Truth to be told, Arecibo is still recovering from that disaster as engineers continue to work to restore the telescope’s former sensitivity.

But the worst disaster for the observatory of this magnitude is, of course, finances.

Long before hurricane Maria hit Puerto Rico, the US National Science Foundation, who owned the telescope, began to look into the possibility of getting rid of some of their older telescopes, 10 of them in total (including Green Bank Observatory, VLBA array and Arecibo), to free the money for the new projects. For the telescopes in question that meant two possible futures: being shut down or going under the new management.

Arecibo got lucky. The management and operations of the observatory was handed over to the consortium led by the University of Central Florida. Radio astronomers breathed a sigh of relief.

Then came 2020.


Cables failure and the future of the observatory

On August 10th a cable supporting a platform above the dish “slipped from its socket” and crashed into the dish, smashing some of the instruments and damaging the telescope. 

Before engineers even had a chance to repair the damage, another cable, this time one of the main cables, gave in on November 6th.

The 900-ton platform is ‘hanging in there’, but not for long. After careful evaluation the engineers decided that repairs are not possible. Any attempt at stabilizing the structure would put lives at risk. The uncontrolled collapse, on the other hand, might damage or even destroy the surrounding visitor’s centre and other buildings that the observatory very much hopes to save. Therefore it was decided the Arecibo telescope would have to be dismantled. The how and whens will be decided on in the next few weeks. 

So long, Arecibo telescope. You were one of a kind.


Further reading

Still curious? Learn about the The World’s biggest radio telescopes and join WonderDome on a Tour of the 100m Effelsberg radio telescope in Germany.