An illustration of the DART spacecraft approaching two asteroids, one of which will crash into the smaller one to try to change how it is seen by its larger companion.
Steve Gribben is a NASA/JohnsHopkins APL.
NASA is going to launch a mission to knock an asteroid off-course.
The first real-world test of a technique that could someday be used to protect Earth from a threatening space rock is scheduled to take place on Tuesday, November 23.
The golf-cart-sized craft will ram into the asteroid and it will not pose a threat to Earth. Scientists will watch to see how the asteroid's trajectory changes.
NASA has tracked almost all of the nearby asteroids that are larger than the size of a grain of rice. None of those that big are going to be here in the foreseeable future. There are a lot of smaller asteroids that are still not found and tracked.
The DART mission will be taking a space rock of that size.
Nancy Chabot, a planetary scientist at the University Applied Physics Laboratory, says that sometimes people don't believe her when she tells them that NASA is doing a mission.
Saving humanity usually requires blowing up an asteroid with a nuclear bomb in movies like Armageddon.
Nuclear weapons are not the preferred choice of planetary defense experts, who prefer to identify dangerous space rocks in advance of any possible collision and use more controlled methods to alter its path.
Lindley Johnson, NASA's planetary defense officer, says that the right time is far away from the Earth. The strategy is to find these objects before they are a threat to the Earth.
NASA's DART spacecraft is moved into a specialized shipping container at the APL and will be flown to California.
NASA/JohnsHopkins APL.
NASA could send out a spaceship that would push an asteroid to the side so that it wouldn't pose a problem. NASA is testing out a new approach with DART.
DART is showing how an asteroid can be hit. "It is not asteroid disruption, which is how it goes a lot of times in the movies," says Chabot, who serves as DART's coordination lead.
The DART mission is not likely to make it one because the asteroid is not a danger to the planet now. She says that the DART test is not a threat to the Earth.
After the launch of DART, it will take about ten months for it to reach an asteroid called Didymos, which is 2,500 feet across. The asteroid is about 525 feet across and is being circled by a smaller asteroid called Dimorphos.
The small asteroid, Dimorphos, will be hit by the spaceship. "So it's like a small golf cart running into a Great Pyramid, and only this golf cart will be going 15,000 miles per hour," says Chabot.
Managers back on Earth will only be able to watch as the mission ends, as the spaceship flies itself and homes in on its target.
Elena Adams, the mission systems engineer at the Applied Physics Laboratory, says that it is four hours of watching paint dry, but terrifying at the same time.
Adams says that the spaceship will aim for the larger asteroid. In the last hour or so, it will detect the smaller one and switch to that target.
Scientists will be able to see Dimorphos for the first time after images from the doomed craft are sent back. No one knows what shape the asteroid is in or whether it is smooth or rugged. telescopes see the asteroids as little more than a point of light, because they are so small.
When the Dimorphos passes in front of its companion, changes in brightness tell scientists. Dimorphos goes around every 11 hours and 55 minutes. Scientists don't know how long the impact will shorten.
telescopes will be watching closely in the weeks and months after the impact to see how it reacts to being pushed.
The debris from the collision should be sent back to Earth by a tiny satellite that was thrown from the craft 10 days before the crash.
The European Space Agency is expected to launch a mission in 2024 that will travel to these two asteroids and be able to observe the crater on Dimorphos and determine the mass of this asteroid.
If an asteroid is headed towards Earth, the results of these tests should help NASA and other space agencies understand what could be done with this kind of impact.
"If we don't have any major surprises, we think that this technique would be available, which would be a part of the toolbox that we are starting to build of capabilities to defend against asteroids," says Johnson.
He says NASA will want to try out other asteroid deflection techniques, like the so called "gravity tractor" approach, which involves stationing a spaceship near an asteroid to apply a small tug of gravity.
The impact on the moonlet of Didymos is shown in the schematic.
The Applied Physics Lab is at NASA.
Once NASA knows they exist, asteroids can be diverted. Astronomers believe that they have located and tracked at least 90 percent of the largest nearby asteroids, which are more than 3,280 feet across.
"None of them are a threat for the foreseeable future," says Chabot. That's the good news.
A hit from a smaller asteroid, about 450 feet in diameter, could take out a city. Only about 40 percent of the objects are believed to be out there.
NASA's planetary defense office is supporting the development of a new space telescope to find more in that size range.
There is a large population of near-Earth asteroids out there, although there isn't a currently known asteroid that is on an impact course with the Earth.
