Testing technology to deflect asteroid impact with Earth

Researchers will be involved in observing the collision in the first mission to demonstrate technology to deflect an asteroid.


NASA’s Double Asteroid Redirection Test, or DART, is the first mission to demonstrate technology to deflect an asteroid. 

DART will use an autonomous guidance system to aim itself at Dimorphos, a carefully chosen non-threatening asteroid. Dimoprhos is actually a small moon orbiting a larger asteroid called Didymos, and the force of the collision will slightly change the orbit of Dimorphos around Didymos. Because it’s not on a path to collide with Earth, the Didymos system poses no actual impact threat to our planet, yet its relatively close proximity provides an easy way for planetary defence experts to observe and measure the effect of the impact. It is expected that the collision will change the orbital period (which is about 12 hours) by a few minutes.   

The DART spacecraft will launch on a Space-X rocket in late November, and then take slightly less than a year to reach Didymos and Dimorphos, which it will hit in late September or early October 2022.  

Why planetary defence? 

Astronomers estimate that there are approximately 25,000 near-Earth asteroids close to 140 meters or larger in size – big enough to cause regional devastation if they were to hit Earth.  There is therefore a need to track near-Earth asteroids, and better understand what would be required if an asteroid was heading our way and we want to move it away from the Earth.  


Telescopes around the world will be trained on the Didymos system before and after the collision to measure the effects and learn more about the asteroid, its composition, and the effectiveness of the deflection experiment. School of Physics and Astronomy researchers Dr Colin Snodgrass and Dr Cyrielle Opitom are part of the observing team who will study the asteroid from Earth, applying their experience of observing comets and asteroids with some of the world’s best telescopes, including the European Southern Observatory’s ‘Very Large Telescope’. 

Post-impact survey 

After the impact experiment, a related European Space Agency (ESA) mission, Hera, will launch to the same asteroid to study the effects of the collision in detail. Hera will launch in 2024 and arrive in 2026, and will go into orbit around the asteroid, to perform a forensic ‘crash scene investigation’. Combined with the observations from DART and from telescopes on the ground, Hera will give a very detailed picture of the physics of the collision process, which will allow scientists and engineers to design the most effective asteroid deflection mission, if we ever have to do this ‘for real’ on an asteroid that threatens the Earth.