Set a calendar alert: NASA to broadcast first asteroid redirect on Monday - Ars Technica
The planetary defense effort is focused on a craft called DART, for Double Asteroid Redirection Test, which will target a small asteroid called Dimorphos that orbits the larger 65803 Didymos, forming a binary system.
If all goes according to plan, DART will direct itself to a head-on collision that slows Dimorphos, altering its orbit around Didymos.
But all of the action is handled through a single camera, the Didymos Reconnaissance and Asteroid Camera for Optical navigation, or DRACO, a 2,560×2,160-pixel single-color camera.As such, the final approach and targeting of the asteroid will be handled by an on-board navigation system called SMART Nav (Small-body Maneuvering Autonomous Real Time Navigation).
As described by Evan Smith, DART's deputy mission system engineer, the system will shift over to on-board navigation at about four hours before impact, and the SMART Nav will track the larger Didymos and use that for navigation until about 50 minutes before collision, or about a half-hour after it can be resolved.
At 2.5 minutes prior to the collision, the ion engine will be shut off, and DART will coast into a collision at about 6 kilometers a second.
Even though Dimorphos is only about 120 meters across, it will completely fill the view from DRACO starting about two minutes before collision.