PostedSeptember 23, 2022, 07:19
SpaceNasa will rush a kamikaze spacecraft on an asteroid
After ten months of travel, Dart will hit Dimorphos on Tuesday, at a speed of over 20,000 km/h. A life-size test in the event of real danger.
NASA will finally attempt what has never been done before: deviate the trajectory of an asteroid by projecting a kamikaze ship on it. A test of “planetary defense”, which should make it possible to better protect humanity against a possible future threat. The Dart mission (dart, in English) took off in November from California. After ten months of travel, the spacecraft is due to hit the asteroid Dimorphos at 1:14 a.m. Tuesday, at a speed of more than 20,000 km/h.
The ship is no bigger than a car, and its target is about 160 meters in diameter (half the height of the Eiffel Tower). Do not panic, Dimorphos does not represent a threat to the Earth in any way: its orbit around the Sun passes only seven million kilometers from us at its closest. But the mission “is important to get done before we discover a real need,” said NASA mission officer Andrea Riley.
The moment of impact promises to be spectacular and can be followed live on the American agency’s video channel. It is not a question of destroying the asteroid but of pushing it slightly. Dimorphos is actually the satellite of a larger asteroid, Didymos (780 meters in diameter), which it circles in 11 hours and 55 minutes. The goal is to reduce Dimorphos’ orbit around Didymos by about ten minutes.
This change can be measured by telescopes from Earth, by observing the variation in brightness when the small asteroid passes in front of the big one. The objective may seem modest but this demonstration is crucial for the future.
One frame per second
To hit such a small target, the ship will steer autonomously for the last four hours, like a self-guided missile. His camera, called Draco, will take the very first images of the asteroid at the last moment. At a rate of one frame per second, visible live on Earth with a delay of only some 45 seconds. “These images will keep coming, until they don’t,” says Nancy Chabot, of the Applied Physics Laboratory (APL) at Johns Hopkins University, where the control center is located.
Three minutes later, a shoebox-sized satellite, called LICIACube and released by the craft a few days ago, will pass about 55 km from the asteroid to capture images. They will be sent back to Earth in the following weeks and months.
The event will also be observed by the Hubble and James Webb space telescopes, which should be able to detect a bright cloud of dust. Then, the European Hera probe, which is due to take off in 2024, will closely observe Dimorphos in 2026 to assess the consequences of the impact and calculate, for the first time, the mass of the asteroid.