NASA's asteroid-deflecting DART spacecraft nears planned impact with its target

The mission's finale will test the ability of a spacecraft to alter an asteroid's trajectory with sheer kinetic force

Ten months after launch, NASA's asteroid-deflecting DART spacecraft neared a planned impact with its target on Monday in a test of the world's first planetary defense system, designed to prevent a doomsday collision with Earth.

The cube-shaped "impactor" vehicle, roughly the size of a vending machine with two rectangular solar arrays, was on course to fly into the asteroid Dimorphos, about as large as a football stadium, and self-destruct around 7 p.m. EDT (2300 GMT) some 6.8 million miles (11 million km) from Earth.

The mission's finale will test the ability of a spacecraft to alter an asteroid's trajectory with sheer kinetic force, plowing into the object at high speed to nudge it astray just enough to keep our planet out of harm's way.

It marks the world's first attempt to change the motion of an asteroid, or any celestial body.

DART, launched by a SpaceX rocket in November 2021, has made most of its voyage under the guidance of NASA's flight directors, with control to be handed over to an autonomous on-board navigation system in the final hours of the journey.

Monday evening's planned impact is to be monitored in real time from the mission operations center at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland.

DART's celestial target is an asteroid "moonlet" about 560 feet (170 meters) in diameter that orbits a parent asteroid five times larger called Didymos as part of a binary pair with the same name, the Greek word for twin.