Next Monday, NASA will broadcast its first attempt to alter an asteroid’s orbit, a capability that will be essential if we discover an asteroid that poses a risk of collision with Earth. Planetary defense efforts are focused on a vessel called DART for the Double Asteroid Redirection Test, targeting a small asteroid called Dimorphos orbiting the larger 65803 Didymos, forming a binary system. If all goes according to plan, DART will aim for a head-on collision, slowing Dimorphos and altering its orbit around Didymos. NASA has repeatedly emphasized that neither the asteroid nor the material released by the collision can pose a threat to Earth.
Ars will be present at the Mission Control Center at the Johns Hopkins Applied Physics Laboratory (APL) for the planned collision, which will also be streamed live on NASA’s YouTube channels. Although we will know immediately if the collision happened as planned, it may be several months before we are certain that Dimorphos’ orbit was successfully modified.
To prepare you for Monday’s celebrations, we’ve put together background information on the DART mission and the planned follow-up observations.
DART and its definitive approach
The DART spaceship itself weighs a little over 600 kg and is mainly characterized by the lack of instruments. Its solar panels include an experimental concentrating solar cell that takes up less space to generate the same amount of power as existing space-based hardware, and its main transmitter is testing a new antenna configuration. Its ion engine is also an evolution of the next generation of previous NASA hardware.
But all the action is handled by a single camera, the Didymos Reconnaissance and Asteroid Camera for Optical Navigation, or DRACO, a 2,560 × 2,160 pixel single color camera. DRACO and the transmission hardware are able to send an image back to earth every second. During the final approach to Didymos, DART will be so far away that the round-trip transmission will take more than a minute. Therefore, the asteroid’s final approach and orientation will be handled by an onboard navigation system called SMART Nav (Small-body Maneuvering Autonomous Real Time Navigation).
Right now, Dimorphos is so small that DRACO cannot detach it, and it will remain so until about an hour and a half before impact. As described by Evan Smith, DART Assistant Mission Systems Engineer, the system will switch to onboard navigation about four hours before impact and the SMART Nav will track the larger Didymos and use that for navigation until about 50 minutes before impact. or about half an hour after it can be fixed. 2.5 minutes before the collision, the ion engine is shut down and DART rolls into a collision at about 6 kilometers per second.
Although Dimorphos is only about 120 meters across, it will completely fill DRACO’s view, beginning about two minutes before the collision. “We don’t know what Dimorphos looks like,” said Nancy Chabot, a planetary scientist at the APL. “This will be the first time we’ve even seen what this asteroid looks like.” The final image, sent a second before impact, resolves features as small as four inches, according to Chabot.
And then, if all goes well, the transfers will stop.