Nasa will crash a spacecraft into an asteroid on purpose later this month – to see what happens next.
The mission, due to take place on 26 September, marks the first step towards a solution – the ability to knock potential doomsday asteroids onto less-threatening flight paths – if an asteroid is hurtling towards Earth.
Nasa's Double Asteroid Redirection Test (DART) spacecraft recently had a first look at its target.
The idea is that the fridge-sized DART spacecraft will hit Didymos, an asteroid with an orbiting moonlet, faster than a bullet – and change its orbit.
The spacecraft will ram the moonlet Didymos B, which orbits around a larger asteroid Didymos A.
It will hit the smaller rock at 3.7 miles per second, and Nasa scientists will monitor to see what effect it has on the 530ft rock's flight path.
From this distance – about 20 million miles away from DART – the Didymos system is still very faint, and navigation camera experts had been uncertain whether the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) would be able to spot the asteroid yet.
But once the 243 images DRACO took during this observation sequence were combined, the team was able to enhance it to reveal Didymos and pinpoint its location.
"This first set of images is being used as a test to prove our imaging techniques," said Elena Adams, the DART mission systems engineer at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland.
"The quality of the image is similar to what we could obtain from ground-based telescopes, but it is important to show that DRACO is working properly and can see its target to make any adjustments needed before we begin using the images to guide the spacecraft into the asteroid autonomously."
Although the team has already conducted a number of navigation simulations using non-DRACO images of Didymos, DART will ultimately depend on its ability to see and process images of Didymos and Dimorphos, once it too can be seen, to guide the spacecraft toward the asteroid, especially in the final four hours before impact.
At that point, DART will need to self-navigate to impact successfully with Dimorphos without any human intervention.
"Seeing the DRACO images of Didymos for the first time, we can iron out the best settings for DRACO and fine-tune the software," said Julie Bellerose, the DART navigation lead at Nasa's Jet Propulsion Laboratory in Pasadena, California.
"In September, we'll refine where DART is aiming by getting a more precise determination of Didymos' location."
Using observations taken every five hours, the DART team will execute three trajectory correction manoeuvres over the next three weeks, each of which will further reduce the margin of error for the spacecraft's required trajectory to impact.
After the final manoeuvre on 25 September, approximately 24 hours before impact, the navigation team will know the position of the target Dimorphos within two kilometres.
From there, DART will be on its own to autonomously guide itself to its collision with the asteroid moonlet.
Watch: Nasa launches mission to test asteroid-deflecting technology