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This week, a snapped cable tore a 30-meter gash in Arecibo’s iconic 307-meter dish.

Arecibo Observatory

Arecibo radio telescope goes dark after snapped cable shreds dish

The iconic Arecibo radio telescope in Puerto Rico was damaged early on 10 August when a snapped steel cable smashed into one of its antennas and tore a 30-meter gash in its 307-meter-wide dish. Observations have been halted for at least 2 weeks while investigations are carried out, say Ramon Lugo, director of the Florida Space Institute at the University of Central Florida (UCF), which manages the observatory for the National Science Foundation (NSF). “My primary focus right now is the safety of people and the facility,” he says. The accident happened at 2:45 a.m., he says, but if it had been during the day when more staff were on site, there could have been injuries.

For nearly 60 years Arecibo has been a mainstay of radio astronomy, atmospheric research, and planetary science. For decades, it was the main telescope used in the search for extraterrestrial intelligence. Its dramatic appearance has won it supporting roles in several films. Its fixed dish, built into a natural depression in the surrounding hills, was the largest single dish in the world until 2016, when it was overtaken by China’s Five-hundred-meter Aperture Spherical radio Telescope (FAST). Arecibo can only look straight up, but some steering is possible by moving the receivers, or antennas, around a platform suspended by cables high above the dish.

The cable that broke this week was not one of the main support cables but one of several auxiliary ones added in the 1990s to stabilize the platform when a large new antenna, known as the Gregorian dome, was added. The cable failed where it was attached to the platform. Because it contained a lot of stored energy from tension, it flailed around wildly, damaging the Gregorian dome and the main reflector of the dish, Lugo says. The platform itself appears to be twisted, he adds. 

Typically, such cables don’t fail in that way, which is “concerning,” he says. “We don’t know why it happened. … It’s conceivable that recent weather and seismic events could have contributed.” The telescope did sustain some damage from Hurricane Maria in 2017 but Lugo says right now it does not look like the two events are connected. If it turns out to be a manufacturing defect, they will need to examine the other auxiliary cables. Until investigations are complete, Lugo couldn’t say how much the repairs would cost or how long they would take. It could be anywhere from days to months, he says.

Arecibo’s status has been precarious in recent years. Its scientific importance has diminished as newer facilities have come online, and NSF has sought to divert its funding to new projects. In 2018, UCF took over management of the facility in a deal that allowed NSF to reduce its investment. Nevertheless, this new blow, on top of Hurricane Maria, will likely reopen the debate over Arecibo’s future. “There are some segments of the population who will start that conversation,” Lugo says. “We have to stay focused on the end goal of returning to full capability.”