On August 10, as later forensic analysis would later discover, an auxiliary cable supporting a metal platform above the 1,000-foot-wide main reflector slipped out of its socket and cut a 100-foot-long gash through the dish. That dish is crucial to the observatory’s operations, as the radio telescope relies on it to collect atmospheric data and to scan the sky and conduct radio telemetry as well as track astronomical bodies.
Repairs to the main dish were well underway when the second cable fell last Friday evening, November 6. According to the University of Central Florida, which manages the observatory (owned by the National Science Foundation, or NSF), a detailed structural model of the dish was completed in October and cable sag estimates had been run to make sure the remaining cables above could support the additional load. The faulty cable socket had been shipped to a NASA facility in Florida for examination, and a temporary repair plan had been put in place.
However, while waiting for the emergency repair team to arrive, an auxiliary cable attached to the same tower as the cable that slipped in August seems to have snapped, potentially due to the extra load it was carrying. While neither the University nor NSF provided estimates of the damage, the cable reportedly tore through the main dish in much the same way as the first.
A safety zone has now been established around the central dish and only authorized personnel working on the repair plan are allowed inside (important to note as Arecibo is also a tourist draw in non-COVID times).
“This is certainly not what we wanted to see, but the important thing is that no one got hurt,” Francisco Cordova, the observatory’s director, said in a press release. “We have been thoughtful in our evaluation and prioritized safety in planning for repairs that were supposed to begin Tuesday. Now this. There is much uncertainty until we can stabilize the structure. It has our full attention. We are evaluating the situation with our experts and hope to have more to share soon.”
However, as Science pointed out, if repairs aren’t undertaken quickly, the latest failures could prompt a devastating cascade effect. The 3.5-inch cable that snapped was a main support cable (of four) anchoring one of the three towers stabilizing a 900-ton antenna platform; the auxiliary cable that fell in August was attached to the same tower. Now down two cables, the affected tower will need immediate shoring up to prevent any further breakages.