NASA will smash its DART spacecraft into an asteroid on Monday. Here's how to watch.

NASA's Double Asteroid Redirection Test (DART) spacecraft is set to slam into an asteroid on Monday (Sept. 26), in the first ever test of humanity's ability to deflect life-threatening space rocks before they collide with Earth. 

The 1,210-pound (550 kilograms) DART craft, a squat cube-shaped probe consisting of sensors, an antenna, an ion thruster and two 28-foot-long (8.5 meters) solar arrays, will smash into the asteroid Dimorphos while traveling at roughly 13,420 mph (21,160 km/h). 

The goal of the probe's test is to slow the orbit of the 525-feet-wide (160 m) Dimorphos around its larger partner — the 1,280-feet-wide (390 m) asteroid Didymos. Neither asteroid poses a threat to Earth, as they will be more than 7 million miles (11 million kilometers) from our planet at the time of DART's impact, but NASA scientists want to use the test to study how a more dangerous asteroid might one day be nudged from its deadly collision course. DART will collide with Dimorphos at 7:14 p.m. ET on Monday, with live coverage set to begin at 6 p.m. ET on NASA TV. 

Related: What happened when the dinosaur-killing asteroid slammed into Earth?

"Our DART spacecraft is going to impact an asteroid in humanity's first attempt to change the motion of a natural celestial body," Tom Statler, a scientist working at NASA's planetary defense team, said at a Sept. 12 news briefing about the mission. "It will be a truly historic moment for the entire world." 

DART began its journey to Didymos and Dimorphos 10 months ago, launched aboard a SpaceX Falcon 9 rocket that blasted off from Vandenberg Space Force Base in California, but its roots can be traced back further. In the early 2000s, scientists at the European Space Agency (ESA) proposed another asteroid-bumping test named after Don Quixote, Miguel de Cervantes' 16th-century literary knight renowned for charging pointlessly at windmills, which he mistook for giants. The quixotic mission was never finalized. Then, in 2011, the ESA agreed to work with NASA on a joint deflection mission: the Asteroid Impact Mission (AIM). AIM was later split into NASA's DART and the ESA's Hera missions; the first to collide with Dimorphos on Monday, and the second to launch in 2026 to study the crash's aftermath. 

Scientists expect the test to slow Dimorphos' orbit down by around 1% and bring it into closer orbit with Didymos. The mission will be considered a success if it slows Dimorphos' 12 hour orbit down by 73 seconds, but the real change could be by as much as 10 minutes. 

As the DART craft will be destroyed on impact, its onboard Didymos Reconnaissance and Asteroid Camera for Optical Navigation (DRACO) will only be able to snap second-by-second images of the orbiter's last moments before it smashes into Dimorphos. To get a better immediate picture of the outcome, the scientists will turn to the Italian Space Agency's LICIACube — a smaller "cubesat" spacecraft that split from DART on Sept. 11. Orbiting the aftermath of the collision at a distance of 34 miles (55 km), the LICIACube will beam photos back to Earth of the trajectory-altering impact and the plume of material thrown out by the crash. 

"There will be an impact that will change the trajectory; there will be a crater formed; and after that there will be ejecta that will propagate through space, and LICIACube will photograph this," Stavro Ivanovski, a researcher at Italy's Institute for Space Astrophysics and Planetology and a member of the LICIACube team, said during a Sept. 19 news briefing.

Also witnessing the impact will be some observatories on the ground; NASA's James Webb Space Telescope and Hubble Space Telescope; and the agency's Lucy spacecraft. Their observations will be vitally important to scientists looking to understand how much force is needed to successfully divert an asteroid.

NASA isn't the only space agency looking to develop its asteroid redirection capabilities; China's National Space Administration is also in the early planning stages of an asteroid-redirect mission. China says that in 2026, it will slam 23 of its 992-ton (900 metric tons) Long March 5 rockets into the asteroid Bennu.

Bennu is not as benign as Didymos and Dimorphos (though the threat of a potential impact is more than 150 years in the future). Between 2175 and 2199, the 85.5-million-ton (77.5 million metric tons) space rock is on track to swoop within 4.6 million miles (7.5 million km) of Earth's orbit. Although Bennu's chances of striking Earth are slim — just 1 in 2,700 — the space rock is as wide as the Empire State Building is tall, meaning that any collision with the Earth would have a cataclysmic impact, causing gigantic tsunamis if it landed in the ocean, and killing millions if it landed in a populated area.

The estimated kinetic energy of Bennu's impact with Earth is 1,200 megatons, which is roughly 80,000 times greater than the energy of the bomb dropped on Hiroshima. By comparison, the space rock that wiped out the dinosaurs delivered about 100 million megatons of energy, Live Science previously reported.

"[A] half-kilometer-sized object is going to create a crater that's at least five kilometers in diameter, and it can be as much as 10 kilometers in diameter," Lindley Johnson, the Director of NASA's Planetary Defense Coordination Office told the New York Times. "But the area of devastation is going to be much, much broader than that, as much as 100 times the size of the crater. An object [of] Bennu's size impacting on the Eastern Seaboard states would pretty much devastate things up and down the coast."

Originally published on Live Science.