As DART moves closer to slam into asteroid, ESA explains its follow-up Hera mission

In less than four weeks, NASA’s DART (Double Asteroid Redirection Test) spacecraft will ram into a moonlet of a binary asteroid system. Named Didymos, it has a relatively smaller orbiting asteroid named Dimorphos which actually is DART’s target. 

According to NASA, Dimorphos measures 160 metres across and will be roughly 10.8 million kilometres from Earth at the time of the impact. DART’s estimated collision will take place at 4:44 am IST on September 27 (7:14 EDT on Sept 26). 

After the collision takes place, the European Space Agency will send a follow-up mission named Hera to perform a close-up inspection of DART’s impact. The DART mission intends to test the ‘kinetic impactor’ planetary defence technique which involves artificially changing an asteroid’s path. If successful, this technology could save Earth from potentially hazardous asteroids in case one hurtles toward us in the future. 

(Dimorphos size comparison with Rome's Colosseum; Image: ESA)

The Hera mission

According to ESA, the Hera spacecraft is currently being developed at facilities of aerospace companies OHB and Avio in Germany and Italy, respectively, and is due to launch in 2024. ESA says that the spacecraft will carry two shoebox-sized CubeSats-- Milani and Juventas-- which will be deployed after it reaches the vandalised asteroid. Milani will carry out spectral measurements of Dimorphos's dust whereas Juventas will perform the first radar probe of an asteroid. 

(Propulsion Module flight model of Hera. Propellant tanks, thrusters and associated pipes and valves will be integrated; Image: ESA)

One of the main objectives of Hera is to gather key information such as the size of DART’s crater, the mass of Dimorphos and its make-up and internal structure. ESA says that Hera's data might turn the DART deflection experiment into a well-understood, repeatable technique. The agency also revealed that the mission is currently in midst of the Critical Design Review (CDR) following which the engineers will begin assembling the spacecraft. 

"Successful completion of the CDR brings us a step nearer to space", Karim Mellab, Hera’s Assembly, Integration and Test manager said in an official statement. "At the same time, the Hera team will be watching closely as DART approaches Dimorphos. Its impact is a moment that we have been looking forward to for many years– our two missions were originally conceived together".