NASA DART mission: why was a spacecraft flown into an asteroid and was the mission a success?

The mission was the first attempt at a planetary defence test

NASA has successfully flown its Double Asteroid Redirection Test (DART) into its asteroid target, in what was the agency’s first attempt to move an asteroid in space.

The target was the asteroid moonlet Dimorphos, a small body just 530 feet (160 metres) in diameter. It orbits a larger, 2,560-foot (780-metre) asteroid called Didymos.

NASA confirmed that neither asteroid poses a threat to Earth.

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    Mission control at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, announced the successful impact at 7:14 p.m. EDT, roughly 12.14am UK time.

    Following the successful mission, NASA Administrator Bill Nelson said: “At its core, DART represents an unprecedented success for planetary defence, but it is also a mission of unity with a real benefit for all humanity.

    “As NASA studies the cosmos and our home planet, we’re also working to protect that home, and this international collaboration turned science fiction into science fact, demonstrating one way to protect Earth.”

    How long was DART in space?

    Asteroid moonlet Dimorphos as seen by the DART spacecraft 11 seconds before impact (Credits: NASA/Johns Hopkins APL)

    DART was directed into its asteroid target after 10 months in space.

    The mission’s one-way trip confirmed NASA can successfully navigate a spacecraft to intentionally collide with an asteroid to deflect it, a technique known as kinetic impact.

    How did DART reach its target?

    NASA has released information on how DART was guided towards its asteroid target, and also how it was able to distinguish between the asteroid and asteroid moonlet.

    A spokesperson for the agency said: “The spacecraft’s sole instrument, the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO), together with a sophisticated guidance, navigation and control system that works in tandem with Small-body Manoeuvring Autonomous Real Time Navigation (SMART Nav) algorithms, enabled DART to identify and distinguish between the two asteroids, targeting the smaller body.

    “These systems guided the 1,260-pound (570-kilogram) box-shaped spacecraft through the final 56,000 miles (90,000 kilometres) of space into Dimorphos, intentionally crashing into it at roughly 14,000 miles (22,530 kilometres) per hour to slightly slow the asteroid’s orbital speed.”

    What will NASA do now?

    Following the successful mission, NASA will now observe Dimorphos using ground-based telescopes to confirm that DART’s impact altered the asteroid’s orbit around Didymos.

    It is estimated that the impact to shorten Dimorphos’ orbit by about one per cent, or roughly 10 minutes; precisely measuring how much the asteroid was deflected is one of the primary purposes of the full-scale test.