Ed Rivera-Valentin grew up in Arecibo, Puerto Rico, less than 15 minutes away from the jungle home of a 1,000-foot-wide radio telescope. When he was four or five, his parents brought him to the observatory for the first time. He saw the telescope’s mesh dish, resting inside a huge sinkhole in the soft rock formations that shape the region. If he had walked around the Arecibo radio telescope’s dish, he would have clocked more than half a mile.
The young Rivera-Valentin was awed. “I worked the rest of the time to make sure I would be able to do astronomy,” he says. He came to the mainland for school and a postdoc but returned for his first permanent job, at the observatory, in 2014.
But just a few years after Rivera-Valentin’s homecoming, the telescope is in jeopardy. The National Science Foundation wants to cut back its Arecibo expenditures, from around $8 million to $2 million a year.
That’s not just a problem for astronomers like Rivera-Valentin. It is a problem for civilization. Because with the telescope that has shaped his life, Rivera-Valentin is trying to save yours. Together with a cadre of other planetary scientists, he sends radio waves flying from Puerto Rico toward asteroids that venture near Earth. Sometimes too near. Sometimes so near they kill the dinosaurs. “It’s not that different from having a super high-powered version of the radar gun that police have,” says Patrick Taylor, Arecibo’s lead radar scientist. But instead of aiming that gun at your Kia, they aim it at a ragged rock in space.
Just this year, over the course of four weeks, three asteroids buzzed between Earth and the moon---and no one knew they existed until they were almost here. Every year, a few dozen asteroids between 20 and 40 feet across do the same. Astronomers are working to find more of these smaller-sized asteroids before they come so close. Then radar systems like Arecibo jump in to size up the asteroid, help map its path, and project that path into the future.
Now, Arecibo faces endangerment and, perhaps, extinction---just like humans could if we don’t know what’s about to hit us.
Only two facilities in the world do serious planetary radar work. Arecibo, obviously. And the Goldstone Deep Space Communications Complex in the Mojave desert. But Goldstone’s priority is communicating with spacecraft, and its many nearby military installations mean operators have to ask permission before turning on their transmitter. Arecibo is also much bigger: It’s 20 times more sensitive, and its transmitters pound out twice as many kilowatts of radio waves. Losing its capabilities would have a huge impact, pun intended, on scientists’ ability to predict and avoid asteroidal threats.
Here’s why you should care: the dinosaurs. They died (except the flying ones), after an approximately six-mile-wide asteroid smashed into Central America around 65 million years ago.
You don’t have to worry about a full-on global catastrophe quite yet. Scientists have discovered almost all the extinction-sized near-Earth asteroids, and none of them have Earth’s number. Astronomers haven’t been able to rule out one big rock---named 1950DA---that could smash here in 2880. But without planetary radar, your great32 grandchildren wouldn’t even know they should be worried.
Species don’t have to go extinct for an asteroid crash to be meaningful, either. Rocks around 100 meters hit here every few thousand years. “These objects cannot cause global destruction,” says astronomer Michael Busch of the SETI Institute, “but they can cause damage on the scale of small country or a big US state.”
With radar observations, scientists like Busch can nail down orbits and accurately fast-forward them hundreds of years, giving civilization advance notice---so we end up more Armageddon than Deep Impact. NASA is already practicing the skills that will be necessary to hustle asteroids to more benign orbits with a mission called DART. They’ll send a spacecraft to the double-asteroid system Didymos, which will “intercept” (read: crash into) the smaller of the two asteroids, changing the rock’s course.
If and when rocket scientists deflect an asteroid, radar astronomers will grade their work, pinging the newly-nudged asteroids and projecting their new, hopefully benign orbits.
“You can’t undo a hurricane; you can’t undo a tornado,” says Rivera-Valentin. “You can undo an asteroid impact.” But only if you know it’s coming.
Right now, the National Science Foundation funds about two-thirds of Arecibo’s operations, backing its radio astronomy and atmospheric work. The remaining third comes from NASA, which funds all the radar research. The NSF wants to cut its Arecibo contribution back over five years, starting in 2018. And in January, it solicited proposals for outside organizations to pick up the fiscal slack.
At the end of that solicitation, new partners could come on board and Arecibo operations could stay the same. If not, Arecibo could become a kind of educational museum, or the foundation could “mothball” the site. They could also blow it to smithereens. (Do note that “explosives, if used, would be limited to low-force charges designed to transfer the explosive force only to the structure designated for removal.”)
NASA, for its part, wants to continue funding Arecibo’s radar operations. But their one-third contribution wouldn’t run the telescope one-third of the time and let it sleep for the remainder. That’s not how telescopes work: You have to keep their electronics cool. You have to continually paint their metal so it doesn’t rust. You have to pay the people who do day-to-day work.
Even with the hours the radar team currently gets on the telescope and Goldstone, they can't keep up. With more sensitive instruments and dedicated rock-spotting programs, astronomers are discovering asteroids faster and faster, a pattern that will likely continue for a while. And if it does, and the observing hours stay static? “We just won’t be able to observe 75 or 80 percent of the objects we could detect,” Busch says.
And that means they won’t have a precise idea of where 75 or 80 percent of those objects---from the car-sized ones to the state-crushers---are going, now or in 2417. Now imagine the discovery rate goes up, but Arecibo’s radar facility sits idle. Only Goldstone remains.
Consider this: That’s only one more radar system than the dinosaurs had.
