The DART (Double Asteroid Redirection Test) mission launched a space probe weighing around 600 kg to crash into Dimorphos in 2022.
The objective is to evaluate the effects of a kinetic impact (6 km/s) by a spacecraft on the trajectory of a small asteroid because it is possible that in the future we will need to deviate the trajectory of a potentially dangerous asteroid.
The choice to target Dimorphos, the satellite of Didymos, makes it possible to accurately measure the change in trajectory of a small asteroid. Given the mass ratio and despite the very high speed of the spacecraft, the change in trajectory of Dimorphos should modify its orbital period only very slightly (about 1%). Moreover, the scientists do not want to modify the trajectory of Didymos because it could become dangerous whereas it is not today.
Even if the mission works as planned, it is not at all sure that the trajectory of Dimorphos will be modified because we do not know its composition and its internal structure.
If the ground is soft the impact will be null, if the object is compact, tons of ejecta will be sprayed, a crater will appear and its trajectory should be slightly modified.
The shoebox-sized LICIACube nano-satellite, attached to the probe during the journey to the target, will separate from the probe before impact so as to fly over Dimorphos three minutes after impact and transmit the images. .
In 2022, more than ten of the most powerful telescopes on the planet will be mobilized for several nights to observe the effect of the impact on Dimorphos.
In 2027, the consequences of the impact will be filmed by the Hera mission, which is to place a probe in orbit around Didymos. Thus we will have a perfectly documented real experience which will allow to validate the numerical simulations of impacts.