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A dramatic video released Thursday shows the catastrophic failure of a support cable and the subsequent 450-foot dive of a 900-ton truss-shaped instrument platform onto the massive satellite dish of the iconic Arecibo radio telescope.
Already planned for demolition following two previous cable failures, the sudden collapse on December 1 marked the end of the road for an observatory that was once the largest such facility in the world.
“I want to express how deeply saddened we are here,” said Ralph Gaume, director of astronomy at the National Science Foundation. “And the NSF is very grateful that no one was injured. As you know, safety has always been and continues to be our top priority.”
The National Science Foundation, which operates the Arecibo Observatory through the University of Central Florida, released video of the collapse Thursday in a Zoom update with reporters.
One view, from a camera on the roof of the observatory’s control center, showed the instrument platform crashing into Earth, along with the top 60 feet of two concrete cable support towers armed which were ripped off. Another view came from a drone parked just above Support Tower 4 where two cables failed on August 10 and November 6.
As the drone’s camera watched, another support cable unwound and suddenly snapped. A moment later, the support platform began to fall towards the 45 story flat below. The drone operator managed to rotate the camera in time to capture the moment of impact and the failures of the other two support towers.
“You can see the platform suspended in the center of the screen, you see in the distance just to the left of the center, tower 4,” said John Abruzzo, director of Thornton Tomasetti, an engineering company called s collapse to assess the structure.
“You can see, I hope, the cables going from the top of Tower 4 to the platform. … and so it’s these cables that break down near the top of the tower first. And once they fail, the platform loses its stability and starts going down. “
The Arecibo Observatory consisted of a 1,000-foot fixed satellite dish built in a natural depression that reflected radio waves or radar beams to the array of receivers suspended 450 feet above by cables extending of three support towers.
While the antenna itself only moved with the Earth’s rotation, the instrument platform featured a steerable receiver paddle that allowed astronomers to observe targets up to 40 degrees away from the Earth. vertical axis of the telescope.
In operation for over half a century, the the observatory played an important role observe deep space targets, bodies in the solar system and, in an adjacent facility using powerful lasers, the composition and behavior of Earth’s upper atmosphere.
National Science Foundation / University of Central Florida
But on August 10, an auxiliary cable disengaged from its socket on Support Tower 4 and crashed into the dish below, tearing a gash 100 feet long. Engineers were making repair plans when one of the main 3-inch-wide support cables attached to the same tower unexpectedly broke on November 6.
Due to the strain on the remaining cables, engineers concluded that the system could not be safely repaired and NSF announced on November 19 that the observatory would be taken out of service.
“We knew it was only a matter of time,” Abruzzo said. “And it was a very dangerous and precarious situation, because (the remaining cables) could have really gone at any time.”
Engineers were evaluating how to perform a controlled demolition when the third cable broke, knocking down the instrument platform.
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