How to watch NASA’s DART spacecraft hit an asteroid tonight

Science reporter Dan Vergano reported for Grid last week that NASA’s Double Asteroid Redirection Test (DART) spacecraft is scheduled to collide with the asteroid Dimorphos tonight about 6.8 million miles from Earth.

It’s all part of a $325 million NASA mission. The 1,325-pound DART spacecraft will hit the asteroid while flying at more than 14,000 mph to test whether intentionally sending a spacecraft to ram into an asteroid could potentially distract it and help us to protect against one approaching earth in the future.

How to watch tonight

The DART spacecraft is scheduled to strike asteroid Dimorphos at 7:14 a.m. ET tonight. You can watch from 6 p.m. on NASA TV or on Space.com.

The Data: Is An Asteroid Likely To Approach Earth?

“Fewer than 1,000 ‘potentially hazardous asteroids’ one kilometer (0.62 miles) or wider – large enough to have continental or planetary effects on impact – orbit near Earth, and none are on a trajectory for our planet,” writes Vergano in its latest report. “Instead, unknown medium-sized ones, about the size of Dimorphos, are the real concern.

“An asteroid like Dimorphos hitting Earth on a typical trajectory of 1 in 12,000 years would leave a crater a mile wide and 1,150 feet deep, according to this fun and scary impact simulator from Purdue University and Imperial College London.”

This is the kind of asteroid with the potential to be a “city buster” – not big enough to threaten the entire planet, but still big enough to devastate any area it hits.

Only in the last decade have scientists really taken seriously the risks of “air bursts” from larger meteors, which streak hundreds of kilometers through the atmosphere before exploding, another potential target for deflections. A 2013 airstrike over a Russian city shattered windows and blew apart with tremendous force, indirectly causing hundreds of injuries.

Science Lens: What do scientists hope to learn from the mission?

The target asteroid, Dimorphos, orbits a larger asteroid called Didymos. By measuring whether and how much the collision changes Dimorphos’ orbit, astronomers can assess the effectiveness of the DART experiment. NASA expects the impact to alter Dimorphos’ orbital velocity by less than 1 percent. While that doesn’t sound like much, small distractions could be enough to nudge future asteroids out of harm’s way.

And the DART results could improve scientists’ overall understanding of space rocks. The internal composition of asteroids, whether they are solid or porous or just loose collections of rock, is difficult to tell without sampling them. DART’s impact should show how solid asteroids like Dimorphos are, a species common near Earth. This in turn tells us how best to deflect them, whether by impact or alternatively by putting satellites into orbit around them, which serve as “gravity tractors” and slowly change their trajectory over time.

Political Objective: Why is NASA cutting the budget for its next asteroid-hunting mission?

NASA in March slashed a proposed $170 million budget for a new infrared space telescope, the Near-Earth Object (NEO) Surveyor, designed to find “city-buster”-sized asteroids buried in the fly near the earth.

Instead, NASA has prioritized other missions with a shorter time window for launch to Mars or deeper into the solar system. While NEO Surveyor can be launched into stable low-Earth orbit at any time, those other missions will have to wait years for a second launch if they miss the window.

NASA’s Lindley Johnson told Grid he was comfortable with the delay in launching NEO Surveyor given the low chance of a dangerous impact if the mission waited until 2028. Outside astronomers like MIT’s Richard Binzel are less confident, saying we have the technology to spot approaching asteroids, so we need to watch out for them in case there’s a rare chance something undiscovered is already coming our way.

Asteroid detection is a mission that NASA only accepted in 2016, and there is no political circle behind its missions like the International Space Station or NASA’s jumbo space rocket, which provides jobs to states with NASA centers.

Congress seems poised to increase NASA’s budget to around $26 billion next year, making planetary defense a small part of its portfolio. DART was a $325 million mission the size of a golf cart, and NEO Surveyor is an upgraded version of the WISE infrared space telescope that NASA launched a decade ago, optimized for asteroid detection. Ironically, this explains some of its difficulties in gaining traction: since it is not a large mission, it lacks political support from major defense contractors.

Thanks to Dave Tepps for editing this article.