HomeScienceOuter SpaceNASA tests planetary defenses by crashing spacecraft into an asteroid

NASA tests planetary defenses by crashing spacecraft into an asteroid

Heart rates skyrocket in suburban Washington, where scientists and engineers hope to witness an automaton-sized spacecraft located 11 million miles from Earth Monday night. crash into an asteroid.

If everything goes as planned, and the laws of gravity and motion don’t change at the last minute, it will happen at 7:14 p.m. Eastern Time — or, to be more precise: 7:14:23.

Nothing major is at stake here except demonstrating a technology that could one day save civilization.

It is important to note that the targeted asteroid poses no threat to Earth and has done nothing wrong to deserve this attention. But the space collision is a critical moment for the Double Asteroid Redirection Test (DART), NASA’s first test of “planetary defense.”

This mission is designed to show how a “kinetic impactor” can deflect a dangerous asteroid that could hit Earth. There are lots of space rocks beyond that could interrupt our typically peaceful journey around the sun. The general strategy in planetary defense is to alter the orbits of asteroids so that even if they get close to Earth, they will pass harmlessly.

The DART team members are confident they will succeed, but they admit this is no slam dunk. The spacecraft could miss. There will be no consolation for the scientists and engineers if they almost hit the target. These aren’t horseshoes or hand grenades: Close doesn’t count when trying to change an asteroid’s course.

“The success of the mission is pretty clear: You have to hit that asteroid,” said Elena Adams, an engineer at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, who is conducting the mission under contract with NASA.

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The asteroid is called Dimorphos. It is about 500 feet in diameter. Nobody knows exactly what it looks like. It’s just a blurry blob in telescopes. The first time Earthlings get a good look is less than an hour before the impact.

Dimorphos orbits another, larger asteroid, called Didymos (Greek for “twin”), as both races around the sun. Such “binary” asteroids are common.

The spacecraft was launched from California last November. The larger asteroid essentially serves as the mission’s guide star. But only the smaller asteroid is under attack. When the spacecraft gets close to the large Didymos, it should see the small Dimorphos swinging around from behind its companion. It’s going to be a head-on collision.

It will certainly be tense in the Mission Operations room in Laurel. The Laboratory of Applied Physics handles a lot of classified government research, but sometimes also useful space missions. Seven years ago it successfully flew NASA’s New Horizons spacecraft by Pluto and got the first close-up images of the dwarf planet.

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This mission is similar in that it is fraught with difficulties and uncertainties. The spacecraft must autonomously make crucial last-minute navigation decisions. Flying a spacecraft at high speed — about 14,000 miles per hour — into a relatively small asteroid is something no one has ever done before.

If the DART spacecraft misses the mark, it theoretically has a second chance for a smashup encounter with Dimorphos in another two years — but the engineers aren’t even thinking about taking a mulligan.

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Previous NASA and Japanese space science missions sampled asteroids, but those were carefully choreographed rendezvous with gradual approaches. DART anticipates a high-speed crash. The scientists and engineers behind the mission say they won’t know if they’ll hit the asteroid until about 20 seconds before the impact.

“The asteroids are extremely dark,” Adams said. “We have to hit something the size of two stadiums. You don’t see them until an hour before you hit them… Even then it’s just a pixel in our camera.”

Mission engineers are making their final adjustments to the spacecraft’s trajectory, but the final approach, in the hours before the expected collision, will be automated. A camera onboard the spacecraft will capture images of the smaller asteroid while also helping the vehicle aim at the target.

The last Pictures emitted by the spacecraft’s camera will show a small white dot growing into something brighter, bigger and more asteroid. Then, if all goes as hoped, Dimorphos will loom large enough to fill the field of view.

And that will be the last thing anyone will see when the spacecraft makes the ultimate sacrifice.

Telescopes on Earth and the Webb and Hubble in space will also observe the consequences.

The most worrisome asteroids with potential global climate impacts are those over 1 kilometer in diameter. They are the easiest to spot. More than 95 percent of the estimated population of such killer rocks has been identified, said planetary scientist Nancy Chabot, DART’s coordination leader.

Less than half of the asteroids between 140 meters and 1 kilometer have been identified. That is an ongoing effort. Rocks of that size – and Dimorphos is one of them – could destroy a large city with a direct hit. Chabot said early detection is key to planetary defense.

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“This is something you don’t do at the last minute. This is something you do years in advance,” she says.

NASA and its partners currently have a catalog of 30,000 objects, said the agency’s planetary defense officer, Lindley Johnson. Scientists can calculate their jobs for several decades into the future, but as the timeline gets longer, job uncertainties increase.

Not a dangerous asteroid seems on track to hit Earth right now, as far as these things can be calculated, Johnson said. But he will keep a close eye on Monday night’s asteroid bypass test.

“We need to have such technology,” he said. “It would be wise to test all that beforehand, so we’re not trying to do it for the first time when we really need it to work.”



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