[ad_1]
Ignorance may seem like bliss, but preparation offers a better chance of surviving what is to come. And when it comes to planetary defense, ignorance has become a little 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 ability that can give scientists a much better look at a nearby object. Arecibo Observatory in Puerto Rico was one of the only such systems on the planet, and the long tenure of this instrument is now over after two faulty cables made the telescope so unstable that there was no way to assess its status without risking the lives of workers, according to the United States’ National Science Foundation (NSF), which owns the site. Instead, it will be put out of service.
And when it comes to planetary defense, there is no such thing.
“There have 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,” said Anne Virkki, who leads the planetary radar team at the Arecibo Observatory. Space.com. “It is not obsolete and it is not easily replaced by other existing installations and instruments.”
Related: Loss of Arecibo observatory would create hole that cannot be filled, scientists say
Planetary defense begins by spotting as many asteroids close to Earth as possible – nearly 25,000 to date, according to NASA – and estimate their sizes and orbits around the sun. Arecibo never played a role in the discovery of asteroids; this task is much more easily accomplished by a multitude of telescopes which see large parts of the sky in visible and infrared light and are able to catch the sudden appearance of a bright and rapid point between the stars, telescopes like the PanSTARRS Observatory in Hawaii. With these early observations, the smallest asteroids and those that stay away from Earth can be safely tagged and more or less forgotten.
But larger asteroids with orbits that could bring them too close together for comfort are the subject of further study, and often that work has been that of the Arecibo Observatory. The facility sported a powerful radar transmitter that could bounce a beam of light off an object in the vicinity of Earth. Then the observatory’s massive radio dish could pick up the echo of that signal, allowing scientists to decipher precise details about the location, size, shape and surface of an asteroid.
The same telescopes that identify asteroids in the first place, can also give scientists the data they need to track a rock’s orbit in space, but when planetary radar can spot the object, it does the same job faster.
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 set up an orbit as quickly as possible to determine if the asteroid is going to hit Earth,” Betts told Space.com.
This is because with enough warning, humans could do something in theory to avoid the collision – likely by pushing the asteroid out of its path or smashing it into small pieces that wouldn’t wreak as much havoc on the Earth’s surface as a single larger object.
“This is actually a preventable natural disaster if we work hard enough,” Betts said. “Although it’s rare, it’s something that we can actually do something about, unlike hurricanes or earthquakes in terms of prevention.”
And radar can more quickly offer other details about a space rock that can inform planetary defense, including vital information as if an asteroid is actually an asteroid. single object or a pair objects in disguise, like 15% of near-Earth asteroids turn out to be, Betts said. “If you needed to deflect it, obviously it’s crucial to know if there are one or two objects.”
Ditto with the composition of space rock. “Some are solid metal, some are fluff balls or piles of rubble, so their density varies widely,” Betts said. “If you have to really deflect an asteroid, if it is actually aimed at Earth, the techniques can react differently depending on whether you are dealing with a very dense asteroid or a very fluffy asteroid.”
Radar is therefore a valuable skill for a planet.
Arecibo was not the only radar installation, but it is a rare capability given the cost of the technology involved. With its disappearance, the only remaining radar transmitter is at Goldstone Deep Space Communications Center in California, operated by NASA’s Jet Propulsion Laboratory. But this facility has a host of additional responsibilities – it is part of the Deep Space Network which handles communication with spacecraft throughout the solar system, and it also has military responsibilities.
“They won’t be as flexible with planning these sightings of newly discovered targets as Arecibo is,” Virkki said. “If you can’t see these targets when they’re in the window, then you might lose the opportunity very quickly, and then you have these asteroids that have higher uncertainties in their orbits.” And that uncertainty could be the difference between worrying about a Space Rock is going to hit Earth and be sure it won’t.
Goldstone’s radar system is also about 20 times less sensitive than Arecibo’s, and the two systems could see different subsets of space, she said. “So it’s not exactly going to replace Arecibo.”
Virkki said there were plans underway to add radar capability to the Green Bank Observatory in West Virginia, but then again, he won’t be able to take over Arecibo’s work. Green Bank will use a slightly different flavor of radar than Arecibo and will be more vulnerable to weather conditions, she said.
And it will have a narrow beam, which will make it a bit more insightful in tracking down asteroids. “If you have a very narrow beam, you have to have a really good idea of where you are pointing your radar,” Virkki said. “You can’t go, like, look around with that narrow beam.” Arecibo was more forgiving when the asteroid orbits weren’t so certain.
These factors combine to make the loss of Arecibo a big blow to planetary defense capability, according to Ed Lu, former NASA astronaut and executive director of the B612 Asteroid Institute, a nonprofit focused on human science. asteroids and deviation studies. “It’s a big loss for the community,” he said. “It’s not like we don’t have that ability, but it’s definitely going to be reduced.”
And then, of course, there is the risk that something will go wrong. “Radars are, of course, complicated and things get broken,” Betts said. “You don’t have any redundancy in your system anymore, it’s a one-time failure with the Goldstone radar. So if it breaks at the wrong time, you don’t get what you need.”
The weakness comes at a delicate time for planetary defense experts, Lu said. New asteroids are being identified more and more quickly – a few thousand a year, these days – and that trend will only accelerate when the Vera Rubin observatory will start to operate next year, he said.
“It will discover almost a factor of 10 more asteroids than all other telescopes combined,” Lu said of the Rubin Observatory. “What we’re going to have is quite a number of new asteroid sightings, and in this dataset there will be asteroids that are known to come very close to Earth, and that we won’t be. not initially able to rule out either hitting or not hitting. “
The risk of impact is of course always the same, but increasing our research capacity while losing the capacity for characterization is a recipe for greater uncertainty.
There is no easy way to replace the radar capability that is lost with Arecibo, the three experts said.
“Obviously we would be in favor of finding a way to either fix it or rebuild it no matter what, update it,” Lu said. “It’s all about the money. “
“But sometimes, sometimes, if you don’t make the investment, you’re sorry later.”
Email Meghan Bartels at [email protected] or follow her on Twitter @meghanbartels. follow us on Twitter @Spacedotcom and on Facebook.
[ad_2]
Source link