Losing Arecibo’s giant dish leaves humans more vulnerable to space rocks, scientists say

Ignorance may feel like bliss, but preparedness offers better odds of surviving what is to come. And when it comes to planetary defense, ignorance just became a bit more inevitable.

Planetary defense is the art of identifying and mitigating threats to Earth from asteroid impacts. And among its tools is planetary radar, an unusual capability that can give scientists a much better look at a nearby object. Arecibo Observatory in Puerto Rico was one of only a couple such systems on the planet, and that instrument’s long tenure is over now after two failed cables made the telescope so unstable that there was no way to even evaluate its status without risking workers’ lives, according to the U.S. National Science Foundation (NSF), which owns the site. Instead, it will be decommissioned.

And when it comes to planetary defense, there’s nothing like it.

“There’s been statements in the media that, ‘Oh we have other systems that can kind of replace what Arecibo is doing,’ and I don’t think that’s true,” Anne Virkki, who leads the planetary radar team at Arecibo Observatory, told Space.com. “It’s not obsolete and it’s not easily replaceable by other existing facilities and instruments.”

Related: Losing Arecibo Observatory would create a hole that can’t be filled, scientists say

Planetary defense begins with spotting as many near-Earth asteroids as possible — nearly 25,000 to date, according to NASA — and estimating their sizes and their orbits around the sun. Arecibo never played a role in discovering asteroids; that task is much more easily completed by a host of telescopes that see large swaths of the sky in visible and infrared light and are able to catch the sudden appearance of a bright, fast-moving dot between the stars, telescopes like the PanSTARRS observatory in Hawaii. With those first observations, the smallest asteroids and those that stay far from Earth can be safely labeled and more or less forgotten.

But larger asteroids with orbits that might bring them too close for comfort get additional study, and often, that work has been Arecibo Observatory’s. The facility sported a powerful radar transmitter that could bounce a beam of light off an object in Earth’s neighborhood. Then, the observatory’s massive radio dish could catch the echo of that signal, letting scientists decipher precise details about an asteroid’s location, size, shape and surface.

The same telescopes that identify asteroids in the first place can also give scientists the data they need to track a space rock’s orbit, but when planetary radar can spot the object, it completes the same work more quickly.

Sometimes that speed will matter, said Bruce Betts, chief scientist at the Planetary Society, a nonprofit space-exploration advocacy group that includes planetary defense among its key issues. “You want to define an orbit as quickly as you can to figure out whether the asteroid is going to hit Earth,” Betts told Space.com.

That’s because with enough warning, humans could theoretically do something to prevent the collision — likely by nudging

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Scientists Reflect on Arecibo’s Doomed Big Dish

Aerial view of the big dish and platform, showing the Arecibo Observatory prior to the recent damage.

Aerial view of the big dish and platform, showing the Arecibo Observatory prior to the recent damage.
Image: NIAC

The big dish at the Arecibo Observatory in Puerto Rico is on the verge of collapse, leaving officials with no choice but to retire the famous radio telescope. Astronomers around the world are now having to face a grim reality: that this dutiful dish—in service for the past 57 years—is no more.

I have to admit, the thought that the 1,000-foot (305-meter) dish at Arecibo would have to be torn down never occurred to me when I first started to cover this story during the summer. The first disturbing development came on August 10, when an auxiliary cable slipped out from its socket, crashing through the dish below. The falling cable created an unsightly 100-foot scar, but at the time, the incident seemed more of a nuisance than a catastrophic problem. And indeed, officials with the observatory soon made arrangements to repair the damage and replace the missing cable.

Things took a dramatic turn for the worse on November 6, when a main cable snapped and also fell onto the structure. This was the moment when I really started to worry. A missing auxiliary cable is one thing, but a missing auxiliary cable and a main cable? Not good. In my mind’s eye, I imagined the 900-ton platform, which is suspended 450 feet (137 meters) above the dish, being held together by string. A new image of a badly frayed cable didn’t ease my anxiety.

The platform above the dish.

The platform above the dish.
Image: NIAC

I reached out to the Arecibo Observatory, the National Science Foundation, and the University of Central Florida, which manages the facility on behalf of the NSF. On the morning of Thursday November 19, I woke up to an NSF email alerting me to a press conference that was to be held later the same morning. Finally, I thought, I would be able to report on pending repairs and a strategy for bringing the beleaguered facility back online. After registering for the press conference, however, the NSF sent me further details: The iconic dish was slated for demolition.

It felt like a punch to the stomach.

Engineering teams brought in to evaluate the situation said the platform could undergo a catastrophic collapse at any time, making it unsafe for workers. The dish, in operation since 1963, would have to undergo controlled disassembly in such a way to preserve other assets at Arecibo, including a LIDAR facility and visitor’s center.

Illustration for article titled A Magically Surreal Symbol of Human Ingenuity: Scientists Reflect on Arecibo’s Doomed Big Dish

While scientific work at the Arecibo Observatory will continue, the radio dish is done. And that’s a huge shame. In addition to its cultural importance, the dish fostered some excellent science, including the first detection of a binary pulsar (which earned the team a Nobel Prize in Physics), the first radar maps of Venus, the detection of potentially hazardous asteroids, the first exoplanets ever discovered, and insights into gravitational waves. The facility

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