THE DART MISSION

NASA’S DART spacecraft was launched on 24 November 2021 en route to the asteroid Didymos and its smaller companion Dimorphos, which orbits around the larger body like a tiny moon. DART is the first space mission designed to test a method that might be needed to protect our planet from a potentially disastrous asteroid impact at some point in the future. It will achieve this with the simple action of crashing into Dimorphos in the hope that this will slightly alter its orbit around Didymos.

DART, which stands for Double Asteroid Redirection Test, is expected to reach Didymos in late September 2022 at a distance of 6.8 million miles from Earth. That’s too far away for mission controllers to operate the spacecraft in real time, so it will have to carry out the impact manoeuvre autonomously. DART’S main onboard instrument is the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO), which it will use both for scientific imaging of the asteroid and for navigation, ensuring it crashes into Dimorphos and not the much larger Didymos.

Around ten days before the encounter, DART will deploy a smaller companion spacecraft built by the Italian space agency, LICIACUBE. It’s hoped this will capture images of the impact, as well as the resulting dust cloud and possibly even the impact crater on Dimorphos. But the effects of the collision are unlikely to be very dramatic – even though DART will be travelling at the high speed of 15,000 miles per hour – because it’s so tiny in comparison to its asteroid target.

The impact is expected to change Dimorphos’s orbit around Didymos by around one per cent – a difference that should be large enough to be measured by telescopes on Earth.

Didymos is the Greek word for twin

1 BIG BROTHER

This is the larger of the two asteroids in the binary system.

2 LITTLE SISTER

The actual target of the DART spacecraft is the smaller asteroid orbiting around Didymos.

2 3 COLLISION

The main function of the spacecraft is to crash virtually head-on with Dimorphos.

3 1 4 OBSERVER

This small spacecraft will be deployed by DART to take photos of the impact and its effects.

6 5 ORIGINAL ORBIT

The orbit of Dimorphos around Didymos would remain constant in the absence of an impact.

5 4 6 NEW ORBIT

The impact is expected to alter the orbit of Dimorphos, probably making it slightly smaller.