A golf cart-sized spacecraft will intentionally smash into a small asteroid at about 14,000 miles per hour on September 26. It is humanity’s first test of our ability to deflect dangerous incoming space rocks.
NASA currently knows the location and orbit of approximately 28,000 nearby asteroids. To be clear, scientists have not found any asteroid that poses an immediate threat to human civilization. But experts say it’s a matter of when — not if — Earth is about to be hit by one.
NASA’s Double Asteroid Redirection Test (DART) mission launched atop a SpaceX Falcon 9 in November 2021, aiming to nudge a space rock into a slightly tighter orbit around its companion asteroid. It’s a test of whether such a push could one day deflect a rogue space rock headed for Earth. The $308 million spacecraft traveled 6.8 million miles from Earth to Dimorphos, a small asteroid orbiting the asteroid Didymos.
“I’m very confident that we’re going to hit on Monday and that it’s going to be a complete success,” Lindley Johnson, NASA’s first planetary defense officer, told reporters at a news conference Thursday.
On Monday 26 September, four hours before impact, DART will switch to autonomous mode, steering itself towards the target. If all goes according to plan, the 1,376-pound spacecraft will collide with Dimorphos, slightly altering its orbit around Didymos. Scientists expect the collision to change the speed of Dimorphos by a fraction of 1%.
(The asteroid’s name, Dimorphos, is Greek for “having two shapes” and was chosen because the asteroid will have one shape before DART crashes into it, and another shape after.)
Dimorphos is about 525 feet in diameter, and it orbits another, larger asteroid — the 2,650-foot-wide Didymos.
According to Elena Adams, a DART mission systems engineer, the team will know that DART is successful in smashing Dimorphos when they lose the spacecraft’s signal. “We’re all going to celebrate,” Adams told reporters Thursday.
The asteroid system poses no threat to Earth, according to NASA, making it the perfect target to test our ability to slam into asteroids, to alter their orbits and move them out of Earth’s path.
Although the spacecraft will not survive the encounter, its only science instrument – the Didymos Reconnaissance and Asteroid Camera for Optical Navigation (DRACO) – will be turned on for the death dive, taking one image per second to document the impact and aftermath.
“We are excited about what DRACO will reveal about Didymos and Dimorphos in the hours and minutes leading up to impact,” Carolyn Ernst, DRACO instrument scientist at APL, said in a press release.
About three minutes after the collision, a shoebox-sized CubeSat developed by the Italian space agency, LICIAcube, will take high-resolution images of the event. On September 11, the CubeSat left the spacecraft and is now at a safe distance of about 34 miles from the surface of Dimorphos.
A live stream of images taken by the spacecraft will be available on NASA’s website beginning at 5:30 PM ET on Monday, September 26. Impact is expected to occur around 7:14 PM ET.
“Even after DART is gone, images traveling through space will continue to come back for about eight seconds,” Ed Reynolds, DART’s project manager, told reporters Thursday.
Once DART has been destroyed in the collision, follow-up observations with ground- and space-based telescopes will evaluate the asteroid system to see how much its orbit changed.
The mission’s data will provide astronomers with important information about how well the spacecraft can protect Earth from an incoming asteroid, and inform any adjustments that need to be made to the probe.
Two years after DART’s collision with Dimorphos, the European Space Agency will launch a mission called Hera to study Didymos and Dimorphos in depth. By observing the deformations caused by the impact, the spacecraft aims to gain a better understanding of Dimorphos’ composition and formation.
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