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A NASA spacecraft that will crash into an asteroid on purpose is approaching its target.
The DART mission, or Double Asteroid Redirect Test, will rendezvous with the space rock on September 26 after launching 10 months ago.
The spacecraft will crash into an asteroid’s moon to see how it affects an asteroid’s motion in space. A live stream of images taken by the spacecraft will be available on NASA’s website beginning at 5:30 p.m. that day. Impact is expected to occur around 7:14 p.m.
The mission goes to Dimorphos, a small moon orbiting the near-Earth asteroid Didymos. NASA officials said the asteroid system poses no threat to Earth and is an ideal target for kinetic impact testing, which may be necessary if an asteroid is on its way to hitting Earth.
The event will be the agency’s first full-scale demonstration of diversion technology that could protect the planet.
“For the first time, we will measurably change the orbit of a celestial body in the universe,” said Robert Braun, head of the Space Exploration Sector at Johns Hopkins University’s Applied Physics Laboratory.
Near-Earth objects are asteroids and comets, with orbits that place them within 30 million miles (48.3 million kilometers) of Earth. Detecting the threat of near-Earth objects, or NEOs, that could cause serious damage is a primary focus of NASA and other space agencies around the world.
Astronomers discovered Didymos more than two decades ago. It means “twin” in Greek, a nod to the asteroid forming a binary system with a smaller asteroid or moon. Didymos is almost half a mile (0.8 kilometers) wide.
Meanwhile, Dimorphos is 525 feet (160 meters) in diameter, and its name means “two forms.”
The spacecraft recently spotted Didymos for the first time using an instrument called the Didymos Reconnaissance and Asteroid Camera for Optical Navigation, or DRACO. It was about 20 million miles (32 million kilometers) from the binary asteroid system when it took the images in July.
On the day of impact, images taken by DRACO will not only provide the first look at Dimorphos, but will also use the spacecraft to autonomously guide itself to rendezvous with the tiny moon.
During the event, these images will be beamed back to Earth at a rate of about one per second, providing a “pretty amazing” look at the moon, said Nancy Chabot, DART coordination officer at the Applied Physics Laboratory.
At the time of impact, Didymos and Dimorphos will be relatively close to Earth, within 6.8 million miles (11 million kilometers).
The spacecraft will accelerate to about 15,000 miles per hour (24,140 kilometers per hour) when it collides with Dimorphos.
It aims to collide with Dimorphos to alter the asteroid’s motion in space, according to NASA. This collision will be recorded by LICIACube, or Light Italian CubeSat for Imaging of Asteroids, an auxiliary cube satellite provided by the Italian Space Agency.
The CubeSat-sized briefcase carried him into space with DART. It has recently been deployed from the spaceship and is traveling behind it to record what is happening.
Three minutes after impact, the CubeSat will fly in Dimorphos to capture images and video. The video, while not immediately available, will return to Earth in the weeks and months following the collision.
Dimorphos was chosen for this mission because of its size relative to asteroids that could pose a threat to Earth. The spacecraft is 100 times smaller than Dimorphos, so it won’t obliterate the asteroid.
The fast impact will only change Dimorphos’ speed by 1% as it orbits Didymos, which doesn’t seem like much, but it will change the moon’s orbital period.
“Sometimes we describe driving a golf cart into a great pyramid or something like that,” Chabot said. “But for Dimorphos, this is really about asteroid deflection, not disruption. This is not going to explode the asteroid; it’s not going to break into lots of pieces.”
The push will slightly alter Dimorphos and bind Didymos more gravitationally, so the collision won’t change the binary system’s path around Earth or increase its chances of becoming a threat to our planet, Chabot said.
Dimorphos completes an orbit around Didymos every 11 hours and 55 minutes. After impact, this may change to 11 hours and 45 minutes, but follow-up observations will determine how much change has occurred.
Astronomers will use ground-based telescopes to observe the binary asteroid system and see how much Dimorphos’ orbital period has changed, which will determine whether DART was a success.
Space-based telescopes such as Hubble, Webb and NASA’s Lucy mission will also observe the event.
In four years, the European Space Agency’s Hera mission will arrive to study Dimorphos, measuring the moon’s physical properties, and to study the DART impact and the moon’s orbit.
There are currently no asteroids directly impacting Earth, but there are over 27,000 near-Earth asteroids of all shapes and sizes.
The valuable data collected by DART and Hera will help in planetary defense strategies, especially in understanding what forces might change the orbit of a near-Earth asteroid that could collide with our planet.