NASA’s Double Asteroid Redirection Test (DART) spacecraft recently got its first look at Didymos, the double-asteroid system that includes its target, Dimorphos. On Sept. 26, DART will intentionally crash into Dimorphos, the asteroid moonlet of Didymos. While the asteroid poses no threat to Earth, this is the world’s first test of the kinetic impact technique, using a spacecraft to deflect an asteroid for planetary defense.
This image of the light from asteroid Didymos and its orbiting moonlet Dimorphos is a composite of 243 images taken by the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) on July 27, 2022. Credits: NASA JPL DART Navigation Team
This image of the light from asteroid Didymos and its orbiting moonlet
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 were uncertain whether DRACO
would be able to spot the asteroid yet. But 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, 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.”
Although the team has already conducted 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 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 self-navigate to impact
successfully with Dimorphos without any human intervention.
“Seeing the DRACO images of Didymos for the first time, we can iron out the
best settings for DRACO and fine-tune the software,” said Julie Bellerose, the
DART navigation lead at NASA’s Jet Propulsion Laboratory in Pasadena,
California. “In September, we’ll refine where DART is aiming by getting a more
precise determination of Didymos’ location.”
Using observations taken every five hours, the DART team will execute 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 to
impact. After the final maneuver on Sept. 25, approximately 24 hours before
impact, the navigation team will know the position of the target Dimorphos
within 2 kilometers. From there, DART will be on its own to autonomously guide
itself to its collision with the asteroid moonlet.
DRACO has subsequently observed Didymos during planned observations on Aug.
12, Aug. 13 and Aug. 22.
Johns Hopkins APL manages the DART mission for NASA's Planetary Defense Coordination Office as a project of the agency's Planetary Missions Program Office. DART is the world's first planetary defense test mission, intentionally executing a kinetic impact into Dimorphos to slightly change its motion in space. While the asteroid does not pose any 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 this is a viable technique to deflect an asteroid on a collision course with Earth if one is ever discovered. DART will reach its target on Sept. 26, 2022.
For more information about the DART mission, visit: https://www.nasa.gov/dartmission
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