NASA, the US space agency, gave details about its Double Asteroid Redirection Test (DART)’s plan to hit a small moonlet target in a double asteroid system with a spacecraft in 2022, its first mission to demonstrate a planetary defence technique. The asteroid, called Didymoon or Didymos B, is a moon asteroid around 150 meters tall orbiting a larger body Didymos A, the most accessible asteroid of its size from the Earth, the Xinhua news agency reported.
The asteroid poses no threat to Earth and is an ideal test target: measuring the change in how the smaller asteroid orbits about the larger asteroid in a binary system is much easier than observing the change in a single asteroid's orbit around the Sun. Work is ramping up at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, and other locations across the country, as the mission heads toward its summer 2021 launch – and attempts to pull off a feat so far seen only in science fiction films.
“The Didymos system is too small and too far to be seen as anything more than a point of light, but we can get the data we need by measuring the brightness of that point of light, which changes as Didymos A rotates and Didymos B orbits,” said APL’s Andy Rivkin, DART investigation team co-lead, who participated in the observations.
The brightness changes indicate when the smaller moon, Didymos B, passes in front of or is hidden behind Didymos A from our point of view. These observations will help scientists determine the location of Didymos B about Didymos A and inform the exact timing of DART’s impact to maximize the deflection.
The investigation team will observe Didymos again from late 2020 into the spring of 2021. Final ground-based observations will occur as the spacecraft travels toward the asteroid, as well as after impact occurs.
But the NASA team will eventually see the asteroid system close-up thanks to an Italian-made imager. The shoebox-sized cube satellite will record the spacecraft's impact and its aftermath.
DART will carry an optical navigation system to capture images that help the spacecraft reach its target.
In its latest design, DART spacecraft will be able to move by relying on small hydrazine thrusters while utilising the electric propulsion system, which will push the start of the primary launch window to July of 2021, shortening the mission flight time. Its previous planned launch time was December 2020.
The DART spacecraft will crash itself into the asteroid at a speed of approximately six kilometer per second and the collision will change the speed of the moonlet in its orbit around the main body by a fraction of one per cent, enough to be measured using telescopes on the Earth, according to the NASA.
(With agency inputs)