NASA is about to try changing the direction of an asteroid

The asteroid Dimorphos is about to have an earthly visitor – a US$300 million spacecraft that NASA will crash into the space rock’s surface in a matter of weeks.

DART – short for Double Asteroid Redirection Test – is a spaceship that has one purpose: to be destroyed in the name of science.

And while the Artemis project is making headlines as the US space agency prepares to send people back to the moon – and eventually to trial humans living on the surface for short periods – DART represents the first test of a technique that could help protect Earthlings from hypothetical asteroid impacts.

While our planet has done well in recent times to avoid catastrophic impacts from celestial objects (it’s only been 65 million years since the dinosaurs forgot to repel an incoming object) DART is a step towards determining whether deflecting an asteroid is possible.

Determining the orbit of twin asteroids

Rather than tumbling through space on its own, Dimorphos is actually a baby, itself orbiting a 780-metre wide parent called Didymos.

Now, NASA has confirmed calculations of Dimorphos’s orbit, ensuring DART’s pathway to collision later this month.

Dimorphos’s orbit was previously determined over a year ago, but recalculating this pathway gives the DART team confidence there are no other variables influencing its course, such as ‘radiation recoil’ from Didymos’s surface which might  push the moonlet further away.

Accounting for potential changes in Dimorphos’s orbit is important.

That ensures that when DART says ‘hello’ to the asteroid’s surface, NASA can be sure that any change in trajectory is caused by the spacecraft, and the spacecraft alone.

Orbit observations to resume after impact

With the Didymos-Dimorphos asteroid system out of telescope range for much of the last two years, NASA used the powerful Lowell Discovery (Arizona, USA) and Magellan telescopes (Atacama, Chile) to make final calculations.

“We really have high confidence now that the asteroid system is well understood and we are set up to understand what happens after impact,” says Nick Moskovitz, an astronomer at the Lowell Observatory. 

The asteroids come within their astronomically closest range of Earth – around 10.8 million kilometres – on September 26. Then, DART will make contact.

NASA’s astronomers will then recommence their observations of Dimorphos’s orbit to determine whether the impact pushed it close to Didymos and shift.