NASA’s Double Asteroid Redirection Test (DART) spacecraft recently took its first look at Didymos, a double asteroid system that includes its target, Dimorphos. On September 26, DART deliberately crashes into Dimorphos, a moon of the asteroid Didymos. Although the asteroid poses no threat to Earth, this is the world’s first test of the kinetic impact technique, where a spacecraft is used to deflect an asteroid for planetary defense. This image of light from the asteroid Didymos and its orbiting moon Dimorphos is a composite of 243 images taken by the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) on July 27, 2022.
From this distance about 20 million miles away from DART the Didymos system is still very faint, and navigation camera experts weren’t sure if DRACO would still be able to spot the asteroid. But once the 243 images DRACO took during this observing sequence were combined, the team was able to refine them to reveal Didymos and pinpoint its location. “This first set of images is being used as a test to validate our imaging techniques,” said Elena Adams, DART mission systems engineer at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. “The image quality is similar to what we could get from ground-based telescopes, but it is important to show that DRACO is working properly and can see its target to make the necessary adjustments before we start using the images to guide the spacecraft.” into an asteroid autonomously.”
Although the team has already performed a number of navigation simulations using non-DRACO images of Didymos, DART will ultimately depend on its ability to see and process images of Didymos and Dimorphos once they are also seen to guide the spacecraft toward the asteroid. , especially in the last four hours before impact. At that point, DART will need to self-navigate to successfully encounter Dimorphos without any human intervention. “When we see the Didymos DRACO images for the first time, we can tweak the best settings for DRACO and fine-tune the software,” said Julie Bellerose, DART navigation lead at NASA’s Jet Propulsion Laboratory in Pasadena, California. “In September, we’ll refine where DART is headed by getting a more accurate position determination of Didymos.”
Using observations made every five hours, the DART team will perform three trajectory correction maneuvers over the next three weeks, each of which will further reduce the margin of error for the spacecraft’s desired impact trajectory. After the final maneuver on September 25, approximately 24 hours before impact, the navigation team will know the position of the Dimorphos target to within 2 kilometers. From there, DART will be on its own to guide itself into collision with the asteroid’s moon. DRACO subsequently observed Didymos during scheduled observations on August 12, August 13, and August 22.
Johns Hopkins APL manages the DART mission for NASA’s Planetary Defense Coordination Office as a project of the agency’s Planetary Mission Program Office. DART is the world’s first planetary defense test mission to intentionally perform a kinetic impact on Dimorphos to slightly alter its motion in space. While the asteroid poses no threat to Earth, the DART mission will demonstrate that a spacecraft can autonomously navigate to a kinetic impact on a relatively small asteroid, and demonstrate that this is a viable technique for deflecting an asteroid into a collision with Earth if it is ever discovered. DART will reach its destination on September 26, 2022.
