Matthew Ward Agius
Matthew Agius is a science writer for Cosmos Magazine.
The camera on NASA’s Double Asteroid Redirection Test (DART) spacecraft has captured the first image of the spaceship’s target – the asteroid pair Didymos and Dimorphos.
DART is an experiment that will test whether an asteroid can be redirected via a kinetic impact. Simply: NASA wants to see whether crashing a spaceship into an asteroid can alter its path.
Successfully doing so would help inform future development of planetary defences, in case Earth ever had to swat away an asteroid heading for our planet.
The composite image produced by the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) from 243 snaps sent back to NASA shows the Didymos system as a tiny speck against the black backdrop of space.
The image was captured on July 27, when Didymos was around 20 million miles away from the DART spacecraft. It’s now much closer. (Note: The moon is 384,000km from earth.)
By combining the images and enhancing the final composite, DART’s navigations team is able to pinpoint the asteroid’s location.
It’s an important milestone – one of the last – for the project. DART is now fast approaching the asteroid system with impact scheduled for September 26.
As DRACO is responsible for directing DART to its impact point, the ability to see the instrumentation is functional is critical for mission success.
“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), Maryland USA.
“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.”
Refining DART’s position
Completing this test of DRACO’s imaging system will allow NASA to fine-tune the camera for its important job of helping guide the satellite towards its impact point. The mission will further refine the spacecraft’s positioning with follow-up images as September 26 approaches.
Three trajectory corrections will be made prior to impact, with observations made by DRACO every five hours to ensure the lowest possible margin of error for DART’s final course.
The final manoeuvre will be made approximately 24 hours before impact, and navigators will know the position of Dimorphos within two kilometres as the craft autonomously flies itself to the impact site.
Recently, APL scientists completed their final calculations of Dimorphos’ orbit around Didymos. The orbit will be observed after impact to determine whether the collision successfully altered the moonlet’s path around the larger asteroid.