DART takes aim at an asteroid target

NASA’s DART (Double Asteroid Redirection Test) spacecraft recently got its first glimpse of Didymos, the binary asteroid system that contains its target Dimorphos. On September 26th, DART will intentionally crash into Dimorphos, the asteroid moon of Didymos. While the asteroid poses no threat to Earth, this is the world’s first test of the kinetic impact technique, which uses a spacecraft 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 acquired on July 27, 2022 by the Didymos Reconnaissance and Asteroid Camera for Optical Navigation (DRACO).

At this distance – about 20 million miles from DART – the Didymos system is still very faint, and navigation camera experts weren’t sure if DRACO could spot the asteroid yet. But once the 243 images DRACO captured during this observation sequence were combined, the team was able to enhance them to reveal Didymos and pinpoint his location.

“This first set of images will be used as a test to prove our imaging techniques,” said Elena Adams, the DART mission systems engineer at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. “The quality of the image is similar to what we could get from ground-based telescopes, but it’s important to show that DRACO is functioning properly and can see its target in order to make any necessary adjustments before we start using the images to guide the spacecraft.” fly into the 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 visible in order to navigate the spacecraft to the asteroids, especially in the last four hours before impact. At this point, DART must navigate itself to successfully interact with Dimorphos without human intervention.

“Once we see the DRACO images from Didymos for the first time, we can iron out the best settings for DRACO and tweak the software,” said Julie Bellerose, the DART navigation director at NASA’s Jet Propulsion Laboratory in Pasadena, California. “In September we will refine what DART is targeting by getting a more accurate fix on the location of Didymos.”

Using observations conducted 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 required trajectory. After the last maneuver on September 25, about 24 hours before impact, the navigation team will know the position of the target Dimorphos within 2 kilometers. From there, DART will autonomously guide itself to its collision with the asteroid moon.

DRACO subsequently observed Didymos during scheduled observations on August 12, August 13, and August 22.