In one month, the European Space Agency's Hera mission will make history. Moving at 12 kilometers per second relative to Earth, the spacecraft is about to rendezvous with the binary Dimorphos-Didymos asteroid pair. NASA's Double Asteroid Redirection Test (DART) slammed into Dimorphos in 2022, and Hera will now provide a follow-up view of the resulting damage. Launched on a SpaceX Falcon-9 rocket from Cape Canaveral, Florida, on 7 October 2024, Hera is ESA's first Space Safety Programme-class mission. It took just over two years to reach its destination. Even now, the pair of asteroids is little more than a few pixels across in Hera's view.
Didymos is 780 meters in diameter and orbits the Sun once every 2.1 years. In 2003, scientists discovered that it has a small moonlet, a 151-meter rock named Dimorphos. Like our Moon, the pair are dark and silicon-rich. The encounter occurs 1.5 astronomical units from the Sun, which makes for a dimmer view, though Hera's two 5-meter solar panels still generate enough power. DART saw Dimorphos as a rubble pile asteroid shortly before impact. DART's 6.6 km/s impact shortened the original 11-hour, 55-minute orbit by about 32 minutes, and a debris stream was seen in the weeks after impact.
Standing on the boulder-strewn surface of either asteroid would offer an alien vista of a spinning sky dominated by the other companion. Gravity there is so feeble that a would-be astronaut could fall to the surface at a days-long, leisurely rate. Hera's two CubeSats, Juventas and Milani, will test this kind of detail. Built by GomSpace in Luxembourg and Tyvak International in Turin, Italy, they will separate from Hera shortly after rendezvous. Milani will analyze the dust field and spectral composition, while Juventas will study the asteroids' internal structure and may come to rest on Dimorphos.
After its nominal mission ends in 2027, controllers may extend Hera's life as a technology demonstrator to test autonomous spacecraft control. The mission offers a rare chance to observe the Didymos-Dimorphos system again, bringing these alien worlds into close view through Hera's eyes.
Source: Hacker News · Summarized by HeadlinesBriefing