On 1 December 2020, the 900-ton instrument platform of the Arecibo Observatory crashed into its dish, which is cradled in a natural sinkhole.

In the early morning of 10 August 2020, Sravani Vaddi, a postdoc astronomer at the Arecibo Observatory in Puerto Rico, was working from home, but her thoughts were at Arecibo’s giant radio telescope.

A second support cable snapped 3 months later, on 6 November, and the National Science Foundation (NSF), which owns the observatory, said attempting repairs was too dangerous: Arecibo would be dismantled.

And it was a bitter blow to the people of Puerto Rico, who embraced hosting the technological marvel.

Every schoolchild on the island goes on a field trip to see the telescope, and those experiences often lead to science careers, says astrobiologist Abel Méndez of the University of Puerto Rico, Arecibo.

“Somehow, we lost a $300 million instrument, a magnificent, really expensive instrument, for a few million dollars,” says Richard Behnke, an Arecibo staffer from 1970 to 1982 who went on to head the geospace science division at NSF.

“First we mourned, then we had a wake, then we got down to work,” says Joanna Rankin, an astronomer at the University of Vermont.

Together with Arecibo staff, researchers last month delivered a white paper to NSF describing plans for a new $400 million telescope on the same site.

“It became a completely different telescope and enabled it to stay on the cutting edge,” says Robert Kerr, who was observatory director for two spells in the past 15 years.

That surprises Robert Lark, a civil engineer at Cardiff University, who says that bridge cables typically have safety factors of six or more.

Although six auxiliary cables were added to bring the safety factor back to two, Kerr says it never quite got there.

It was one of these auxiliary cables that failed in August.

“One of the difficulties of adding or replacing cables is the accurate distribution of load,” Lark says.

The end of the cable pulled free from its socket at the top of one of the platform’s three support towers, says engineer Ramón Lugo, principal investigator for Arecibo at the University of Central Florida (UCF), which leads the consortium that now manages the observatory for NSF.

Engineers from Cornell University, which managed Arecibo from its construction until 2011, got an unexpected glimpse into one of Arecibo’s sockets in the early 1980s, after an old cable was replaced and shipped to Cornell for inspection.

Engineer Leigh Phoenix, who was on the team that carried out the postmortem, says the socket appeared to be faulty.

“It provided an avenue for water to get in,” Phoenix says.

Their suspicion was that similar manufacturing faults in this cable’s socket were to blame, Lugo says.

Lugo says Arecibo staff wrote up a 500-page proposal for the repairs in 2 weeks.

For most of its 57 years, the 305-meter-wide dish of the Arecibo Observatory was the largest in the world.

One firm—Wiss, Janney, Elstner Associates—favored stabilizing the telescope by relaxing the backstays that stretch from the towers to the ground, installing extra support cables, and removing mass from the platform before starting restoration work.

On 1 December, less than 2 weeks later, Lugo, who had temporarily relocated to Puerto Rico, stopped to buy breakfast before driving up to the observatory.

Phoenix says that reduced the rate of wire breaks, but it’s unclear how long those practices were maintained.

Kerr says the fans weren’t in use when he took over in 2007, nor was he aware of when the cables were last painted.

“The Puerto Rico staff are incredible: They did every possible thing.”.

Hurricane Maria battered Puerto Rico in 2017.

Phoenix says it was “an opportunity for trouble,” because the storm’s winds could have picked up seawater, whose salt makes it especially corrosive, and dumped some on the telescope.

In 2018, UCF stepped up to take over management, with support from Puerto Rico’s Metropolitan University and the company Yang Enterprises, on the understanding that the astronomy division would gradually reduce its contribution to $2 million annually.

The best people would go elsewhere,” says planetary scientist Michael Nolan of the University of Arizona, who was Arecibo director from 2008 to 2011.

And when old hands move on, something goes with them, Phoenix says.

After the shock of last month’s collapse wore off, observatory managers gave a group of staff and outside researchers 3 weeks to come up with a plan to replace the telescope.

Steering “will be a great mechanical challenge,” says Anish Roshi, head of astrophysics at the observatory.

In theory, Congress could choose to set aside extra funds for a pet project, as happened after the 90-meter telescope at Green Bank Observatory collapsed in 1988.

But Puerto Rico, with only a nonvoting representative in Congress, has little clout, even though it could use a leg up after being battered by earthquakes and hurricanes.

“In terms of economy, [Puerto Rico] needs it,” Méndez says.

Lugo says advocates for a new telescope are talking to private foundations.

And late last month Puerto Rico Governor Wanda Vázquez Garced allocated $8 million to clean up the site and design a replacement