From this distance—about 20 million miles away from DART—the Didymos system is still very faint, and navigation camera experts were uncertain whether DRACO would be able to spot the asteroid yet. However, once the 243 images DRACO took during this observation sequence were combined, the team was able to enhance it to reveal Didymos and pinpoint its location.
“This first set of images is being used as a test to prove our imaging techniques,” said Elena Adams. She is 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 obtain from ground-based telescopes, but it is important to show that DRACO is working properly and can see its target to make any adjustments needed before we begin using the images to guide the spacecraft into the asteroid autonomously.”
A number of navigation simulations using non-DRACO images of Didymos have already been conducted by the team. However, DART will ultimately depend on its ability to see and process images of Didymos and Dimorphos, once it too can be seen, to guide the spacecraft toward the asteroid, especially in the final four hours before impact. At that point, DART will need to autonomously self-navigate to impact successfully with Dimorphos without any human intervention.
“Seeing the DRACO images of Didymos for the first time allows us to iron out the best parameters for DRACO and fine-tune the software,” said Julie Bellerose, DART navigation manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “In September, we will refine the DART target by obtaining a more precise determination of the location of Didymos.”
Using observations taken every five hours, the DART team will perform three course correction maneuvers over the next three weeks. Each of these will further reduce the margin of error for the required spacecraft trajectory to have an impact. After the final maneuver on September 25, about 24 hours before impact, the navigation team will know the position of the Dimorphos target within a radius of 2 kilometers (1.2 miles). From there, DART will be on its own to guide itself autonomously to intercept the asteroid moon. DART will crash into Dimorphos at 4 miles (7 kilometers) per second.
DRACO then observed Didymos during scheduled sightings on August 12, 13 and 22.
The Johns Hopkins Applied Physics Laboratory (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, intentionally performing a kinetic impact on Dimorphos to slightly alter its motion in space. Although 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 prove it to be a viable technique for deflect an asteroid on a collision course with Earth if one is ever discovered. DART will reach its goal on September 26, 2022.
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