NASA to crash a spacecraft into an asteroid, ESA to follow up

Source: nasa.gov

The European Space Agency's (ESA's) Hera mission is set to become the first ever Spacecraft to explore the binary system of Didymos asteroid. The moon that orbits the Didymos (named didymoon and is almost the size of great pyramid with 160m diameter) will be the smallest asteroid ever explored.

However, the Hera mission won't be the first to reach the binary asteroid. NASA is planning to launch its Double Asteroid Redirect Test (DART) between 2020 and 2021, which will target Didymoon as a part of its planetary defence program.

Credit: NASA

The program aims to protect earth from dangerous comets and asteroid impact.
The DART Spacecraft will crash into Didymoon at a speed of 6 km/s when it reaches it in 2022. It will be controlled by an onboard camera and an autonomous navigation system. As a result of this collision, the orbital speed of Didymoon around Didymos shall be changed.

Credit: ESA 

After this collision, the Hera mission will explore the asteroid when it reaches there in 2026. It will check the impact and deflection created by DART.
According to Hera project scientist Michael Kuppers, who made a note on ESA website, "This will give us a good estimate of the momentum transfer of the impact and hence its efficiency as a deflection technique".

Didymoon was chosen due to its size and proximity to earth. "However, this isn't the first time a spacecraft is chosen for impact on a planetary body. Back in 2005, NASA's deep impact crashed into comet temple 1. It didn't try and deflect it, rather its aim was to expose the subsurface material. The comet was much larger in size with 6 km diameter. Didymoon is small enough in size and its orbital period can be altered significantly with such an impact. It currently orbits around its parent asteroid with a period of 12 hours", as said by Hera's lead scientist Patrick Michel in a note released on February 4, 2019.