Dart mission to deflect an asteroid. We explain what will happen tonight in space

the first planetary defense exercise in full size is expected for the night of Monday September 26 to Tuesday September 27, 2022. This is the Dart mission, by asteroid Double Redirection Test, in French: redirection test of a double asteroid. We explain what it consists of.

On November 24, 2021, NASA launched the Dart mission with the liftoff of a rocket SpaceX Falcon 9 from the base in Vandenberg, California.

Almost a year later, the probe will reach its target tonight: the asteroid Dimorphos. Its orbit around the Sun passes just seven million kilometers from us at its closest point. Therefore, this does not pose a threat to Earth, but serves as an exercise for NASA. If no asteroid is considered dangerous for the next 100 years, the US space agency wants to be able to deviate from it if necessary.

A speed of more than 20,000 km/h

That’s precisely what the 550kg NASA-designed probe will do. It will collide with the 160 m diameter miniasteroid (half the height of the Eiffel Tower), which orbits its older brother Didymos, at a speed of more than 20,000 km/h. And this to gently push it, without destroying it. The technique is called kinetic impact.

This infographic presents the positions of Dimorphos and Didymos. | JIM WATSON / AFP

To hit such a small target, the spacecraft will steer autonomously for the last four hours before impact. If Dart doesn’t hit her target, she should have enough fuel for another try in two years.

How to follow the event?

Thanks to a camera, called Draco, and located directly on the ship, the event will be visible live on the NASA website from 11:30 p.m. (French time). Little by little we will discover the shape of the asteroid, which is not known, as the ship advances. “It will start with a small point of light, until it fills the entire frame”explained to theAFP Nancy Chabot of the Johns Hopkins University Applied Physics Laboratory. The impact is expected at 01:14 French time (23:14 GMT).

More images are expected a posteriori. the Hubble and James Webb Space Telescopes it should be able to detect a cloud of glowing dust.

Also, three minutes after the impact, a satellite called LiciaCube will pass about 55 km from the asteroid to capture images. Transported by the Dart ship, he was released a few days ago. Their images will be sent back to Earth in the coming weeks and months.

The European probe Hera, which will take off in 2024, will finally observe Dimorphos closely in 2026 to assess the consequences of the impact and calculate, for the first time, the mass of the asteroid.

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