What is the usefulness of Double Asteroid Redirection Test DART being developed by NASA 1 It will he...........

Explanation:

This is the first-ever mission that will deflect a near-Earth asteroid.
NASA will use kinetic impactor technique to deflect them. This technique involves sending one or more large, high-speed spacecraft into the path of an approaching near-earth object to shift its orbit to defend against future impact. It works by changing the speed of a threatening asteroid by a small fraction of its total velocity. This is done well before the predicted impact so that this small velocity adds up over time to a big shift of the asteroid’s path away from Earth