NASA's DART spacecraft smashes into asteroid Dimorphous in landmark space maneuver

In the world’s first-of-its-kind planetary defence manoeuvre known as the Double Asteroid Redirection Test (DART), NASA’s spacecraft smashed into an asteroid on Tuesday at 6 p.m. EDT (2200 GMT) or 3:30 am Tuesday, Indian Standard Time (IST). The cosmic collision was carried out more than 6.5 million miles away from Earth and hit the surface of an asteroid called Dimorphos, an asteroid with a diameter of just 560 feet (170 meters). NASA ran live coverage of the event on NASA TV, NASA's website, and NASA's social media channels.

The latter make up what’s called a binary asteroid system and while it does not pose any threat to the Earth, it occasionally passes relatively close to Earth and was chosen as the target for NASA’s Double Asteroid Redirection Test (DART) mission. NASA’s spacecraft hit the asteroid at an estimated speed of over 14,000 miles per hour. Didymos which means "twin" in Greek – was discovered on April 11, 1996, by researcher Joseph Montani of Spacewatch at Kitt Peak National Observatory in Tucson, Arizona.

This image of the light from the asteroid Didymos and its orbiting moonlet Dimorphos is a composite of 243 images taken by the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) . Credit: NASA JPL DART Navigation Team

The goal of the mission was to determine how much DART's impact alters the steroid’s velocity, which scientists estimate may have been by a fraction of one per cent. The mission was managed for NASA by Johns Hopkins University Applied Physics Laboratory (JHUAPL). 

NASA's mission to change asteroid’s orbit

The space agency carried out the historic space collision in the hope that it will change the asteroid’s orbit, speeding it up by small volume. The landmark mission can further be used to deflect hazardous asteroids that pose risks to the Earth. The spacecraft crashed into Dimorphos, at speeds of over 14,000 miles per hour. Didymos spins rapidly – rotating about once every 2.26 hours. The moonlet revolves around the larger body about once every 11.9 hours. The main asteroid and its moonlet orbit each other about 0.62 miles (1 kilometre) apart.

"This is an exciting time, not only for the agency but in space history and in the history of humankind, quite frankly," Lindley Johnson, NASA's planetary defense officer, said in a news conference ahead of the collision test. ”This demonstration is extremely important to our future here on Earth.”

DART was launched atop a SpaceX Falcon 9 rocket earlier on Nov. 23, 2021, and has since been travelling the 7 million miles (11 million kilometres) to Didymos and Dimorphos to smash into it. The collision was recorded on the sole instrument, the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO). DRACO was not able to spot Dimorphos until about an hour before impact. 

At about three minutes prior to impact, two minutes prior to impact, it was 42 pixels in size. DRACO is expected to beam one image per second on the Earth as it approached the Dimorphos at a raging speed of14,760 mph (23,760 kph). Researchers could view the asteroid system up close using images returned from DART’s onboard instrument DRACO which is a high-resolution imager based on the New Horizons spacecraft’s LORRI instrument.

“It’s a difficult job,” JPL’s Julie Bellerose, who leads the DART spacecraft navigation team had said about the test. 

“A big part of what the navigation team is working on is getting DART to a 9-mile-wide (15-kilometer-wide) box in space 24 hours before impact.”

At that point, Bellerose said, the mission’s final trajectory correction manoeuvre (the firing of thrusters to modify the direction of flight) had to be executed by mission controllers back on Earth. From then on, it would be up to DART. During the final hours of its one-way journey, DART utilized the autonomous onboard navigator created by APL to stay on course. JPL’s Center for Near Earth Object Studies (CNEOS), an element of NASA’s Planetary Defense Coordination Office (PDCO), was tasked to determine not only the location of Didymos in space within 16 miles (25 kilometres) but also when Dimorphos would be visible – and accessible – from DART’s direction of approach for the mission to be successful. 

Technicians prepare to move NASA’s Double Asteroid Redirection Test (DART) spacecraft from a shipping container. Credit: NASA

DART consists of a passenger – a small spacecraft contributed by the Italian Space Agency (ASI). The shoebox-sized LICIACube (Light Italian CubeSat for Imaging of Asteroids) had split apart from DART several days before DART’s impact with the moonlet. 

"Dimorphos is a tiny asteroid," Tom Statler, the mission's program scientist at NASA, said during the news conference. "We've never seen it up close, we don't know what it looks like, we don't know what the shape is. And that's just one of the things that leads to the technical challenges of DART. Hitting an asteroid is a tough thing to do.” JPL commentator Samson Reiny had called the mission “history.”