A golf-sized spacecraft will smash into a tiny asteroid deliberately at about 14,000 miles per hour on September 26. This 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 finds itself on track to be hit by a human.
NASA’s Double Asteroid Test (DART) mission launched atop the SpaceX Falcon 9 in November 2021, aiming to push a space rock into a slightly tighter orbit around its companion asteroid. It’s a test of whether such a nudge could one day redirect a rogue space rock toward 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 Monday and be completely successful,” Lindley Johnson, NASA’s first planetary protection officer, told reporters at a press conference Thursday.
On Monday, September 26, four hours before impact, DART will switch into autonomous mode, steering towards its target. If all goes as planned, the 1,376-pound spacecraft will collide with Dimorphos, changing its orbit around Didymos a bit more. 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 forms” and was chosen because the asteroid will have one form before DART crashes into it, and another after.)
Dimorphos is about 525 feet in diameter, and orbits another larger asteroid – the 2,650-foot-wide Didymos.
According to Elena Adams, DART’s mission systems engineer, the crew will know that DART has successfully entered Dimorphos when they lose the spacecraft’s signal. “We will all 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 asteroids, alter their orbits, and move them out of Earth’s path. .
Although the spacecraft will not survive the encounter, its single science instrument – the Didymos Exploration and Asteroid Camera for Optical Navigation (DRACO) – will be launched for the death dive, taking one image per second to document the impact and the outcome.
“We are excited about what DRACO will reveal about Didymos and Dimorphos in the hours and minutes before impact,” said Carolyn Ernst, DRACO instrument scientist at APL, in a press release.
About three minutes or so after the collision, a CubeSat shoebox developed by the Italian Space Agency, the LCIACube, will be taking 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 captured by the spacecraft will be available on the NASA website starting at 5:30 pm ET on Monday, September 26. The 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 project manager, told reporters Thursday.
Once DART is destroyed in the collision, follow-up observations with ground-based and space-based telescopes will measure the asteroid system to determine how much its orbit has changed.
The mission data will provide astronomers with important information about how well the spacecraft could protect Earth from an incoming asteroid, and will inform any adjustments the probe needs to make.
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 better understand the composition and formation of Dimorphos.
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