A golf cart-sized spacecraft will deliberately slam into a small asteroid at about 24,000 miles per hour on Sept. 26. It’s humanity’s first test of our ability to deflect dangerous incoming space rocks.
NASA currently knows the location and orbits of about 28,000 nearby asteroids. To be clear, scientists have not found an asteroid that poses an immediate threat to human civilization. But experts say it’s a matter of when — not if — the Earth is on track to be hit by it.
NASA’s Double Asteroid Redirection Test (DART) mission launched atop a SpaceX Falcon 9 in November 2021, with the goal of pushing a space rock into a slightly tighter orbit around its companion asteroid. It’s a test of whether such a nudge one day could distract a rogue space rock on its way to Earth. The $308 million spacecraft traveled 6.8 million miles from Earth to Dimorphos, a small asteroid orbiting the asteroid Didymos.
“I am confident that we will strike on Monday and that there will be a complete success,” Lindley Johnson, NASA’s first planetary defense officer, told reporters at a news conference Thursday.
On Monday, September 26, four hours before impact, DART switches to autonomous mode and steers itself toward its 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 Dimorphos’ speed 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 that.)
Dimorphos is about 525 feet in diameter and orbits another, larger asteroid – the 2650 foot wide Didymos.
According to Elena Adams, a DART mission system engineer, the team will know that DART successfully smashed into Dimorphos when they lose the spacecraft’s signal. “We will all celebrate,” Adams told reporters on Thursday.
The asteroid system poses no threat to Earth, according to NASA, making it the perfect target to test our ability to smash into asteroids, change their orbit and move them out of Earth’s way.
While the spacecraft will not survive the encounter, its only scientific instrument – the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) – will be turned on for the deadly dive, taking one frame 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 the impact,” said Carolyn Ernst, DRACO instrument scientist at APL, in a press release.
About three minutes after the collision, a shoebox-sized CubeSat developed by the Italian space agency LICIACube will capture high-resolution images of the event. On September 11, the CubeSat left the spacecraft and is now a safe distance of about 54 miles from the surface of Dimorphos.
A live stream of images captured by the spacecraft will be available on NASA’s website beginning Monday, Sept. 26 at 5:30 p.m. ET. The impact is expected to occur around 7:14 PM ET.
“Even after DART is gone, images traveling through space keep coming back for about eight seconds,” Ed Reynolds, DART’s project manager, told reporters on Thursday.
Once DART is destroyed in the collision, follow-up observations with telescopes on the ground and in space will evaluate the asteroid system to see how much its orbit has changed.
The data from the mission will provide astronomers with important information about how well spacecraft can protect Earth from an incoming asteroid, as well as inform about any adjustments that need to be made to the probe.
Two years after DART’s collision with Dimorphos, the European Space Agency is launching 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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