In English, Art means dart. And on Tuesday, September 27, at 1:14 am (Paris time), NASA’s dart hit the target: the suicide mission DART (Double Asteroid Redirection Test) crashed into the small asteroid Dimorphos, 160 meters in diameter, a larger satellite. asteroid, Didymus. All 11 million kilometers from Earth.
During the hour before the collision, we were able to follow the approach of the double asteroid on the NASA channel thanks to Draco, the camera installed on DART. Although the film was more like a slideshow, since it was only streaming one frame per second, you could almost feel transported into a spaceship. Fifty minutes before impact, when Dimorphos was still a pale blur, the target was announced to be “locked”like a fighter plane attacked by a missile.
Two trajectory corrections later, made by the autonomous navigation software, we were able to clearly distinguish Didymos and its diamond shape. It wasn’t until the final minutes that Dimorphos’s oval, whose shape scientists were previously unaware of, began to take shape on screen. In the final seconds, when there was no doubt that DART would hit, Draco sent more and more detail from a rocky surface. He took up the entire field of vision, then nothing. When he died, the probe signed the success of its mission.
Next step, Hera’s mission
The objective of DART, which hit Dimorphos at a speed of 22,000 km/h, is to slightly modify the trajectory of its target, in order to learn how to deflect a potentially dangerous asteroid for Earthlings. An army of telescopes points to the Didymos-Dimorphos pair to measure how long the period of revolution of the second around the first will change. The results of these observations are not expected for several days or even weeks. It is also the time it will take for the retransmission of the images taken by LiciaCube, an Italian nanosatellite that accompanies DART, which, keeping cautiously at a distance so as not to risk being destroyed by the rocks ejected during the impact, filmed the scene and its result. .
That said, the DART suicide mission is only Act I of the story. In 2027, the European Space Agency’s Hera mission (which will take off in October 2024) will examine Dimorphos from all angles to analyze in depth the consequences of the collision. As explained by Patrick Michel, director of research for the CNRS at the Côte d’Azur Observatory and scientific director of Hera, the latter “It will give two sets of crucial information: the final result of the impact and all the internal properties of the target thanks to a radar. We will know if it is an aggregate or a monolith, its mineralogy, its geological properties, its mass…” All of this information is crucial to modeling what happened on Tuesday and helping to understand how effective a spacecraft impact is in knocking an asteroid off course. In order to prepare the right dart for the day when the threat of a great rock-killer, from the hypothetical, becomes real.