It sounds like something out of a science fiction script: The dart probe, which starts in July 2021, is supposed to throw an asteroid off course through its targeted impact. The mission is to test whether it would be possible in this way to deflect an asteroid heading for Earth in time.

Try to deflect an asteroid moving at 17 kilometers per second by colliding with a probe the speed change is likely to be only a few millimeters per second. That can hardly be measured with telescopes on earth. Technology Review reports in its current issue how the researchers on the darts mission are solving the problem.

Premium Part of the solution lies in the objective of the mission: Andy Cheng of Johns Hopkins University, now the chief scientist of the Darts Mission, discovered 2011 a specialty: Dimorphos is the little companion of Didymos, an asteroid with a diameter of about 800 meters. “The orbit of Dimorphos around Didymos is like a ticking clock,” says Tom Statler, scientist of the Dart Mission Program at NASA headquarters. “It turns in circles every twelve hours. What we do with darts is hit that clock. ”

The measurements are supposed to determine the momentum transfer efficiency, typically denoted by the Greek letter β. It is a measure of how much of the probe’s momentum is transmitted to the asteroid. So far, this value can only be roughly estimated, as asteroids have different compositions and not much is known about their internal structure.

Targeted Thirty days before the planned impact, the spaceship will begin collecting visual navigation images. The autonomous navigation system SmartNav “identifies Didymos and starts looking for Dimorphos that we are trying to meet,” says Elena Adams, chief engineer of the Dart Mission.

This article comes from issue 1 / 2020 of the Technology Review. The booklet is from 17. 12. 2020 in the trade as well as directly in the heise shop available. Highlights from the magazine:

“After figuring out that it is in the right place and that it makes sense, it switches from facing the main asteroid to facing its moon.” Only two minutes before impact does Smart Nav stop performing maneuvers, and that Spaceship slides into the asteroid. “And then – boom!” Says Adams. If everything goes according to plan, darts will be on 30. September 2022 cease to exist.

Small companion To ensure that the scientists receive data after the impact, a small cube called the LiciaCube will separate from the dart ten days beforehand. LiciaCube will observe the ejection plume and also photograph the back of Dimorphos as it flies by. But LiciaCube will have no way to slow down its flight – and race past Dimorphos into the depths of space.

Until 2027 the asteroid has its rest for now. 2024 the European Space Agency Eva wants to start its mission called Hera. The probe should visit Dimorphos again at the beginning 2027 in order to measure it more precisely, to examine its composition and to determine β even more precisely. Hera will have two observation cubes of her own and will travel the Didymos-Dimorphos system for three to six months. (wst)