NASA’s Double Asteroid Redirect Test (DART) mission is scheduled to be launched by a SpaceX Falcon 9 from Vandenberg Space Force Base at 06:20 UTC on 2021-11-24 (the evening of the 23rd in California time). The spacecraft will be guided to impact the moon of asteroid 65803 Didymos, named Dimorphos (but often called Didymos B or “Didymoon”). The impact, at a speed of around 6.6 kilometres per second, is expected to change the moon’s orbital velocity by approximately 0.4 millimetres per second (although this depends upon the composition of the asteroid and how it reacts to the impact). Because the moon’s orbital velocity around the asteroid is just 10 centimetres per second, this will cause a substantial change in its orbital period, allowing it to be measured precisely. Ten days before impact, the DART spacecraft will eject a CubeSat which will observe the impact with two cameras and radio the images to Earth.
This is primarily a technology demonstrator mission, testing a new xenon thruster, roll-out solar arrays with optical concentrator cells, a new high gain antenna technology, and autonomous guidance to impact.