Japan’s Hayabusa2 Spacecraft Drops Off Its Last Robot on Asteroid Ryugu

Japan’s Hayabusa2 spacecraft has been hanging around the asteroid Ryugu for more than a year, dropping off robots and blasting the surface with metal slugs. The Japanese Space Agency (JAXA) hopes to bring Hayabusa2 and its precious cargo of asteroid samples home soon, but first, there’s just one more robot to deploy. 

Hayabusa2 carried several robots with it to Ryugu, and JAXA confirms the spacecraft released its final robotic explorer last night. The Minerva-II2 rover began its descent from an altitude of about 1 kilometer (0.6 miles), but it won’t reach the surface until early next week. After releasing the lander, Hayabusa2 moved back up to a higher orbit to monitor the robot’s progress. 

The first round of robotic explorers consisted of Minerva-II1A and Minerva-II1B, but they weren’t quite rovers. These drum-shaped robots had motors that allowed them to hop along the surface, taking photos and gathering temperature data along the way. This helped JAXA understand the structure of Ryugu, which was much more uneven than they had expected. In late 2018, Hayabusa2 dropped off another robot called MASCOT. This robot used a similar method of moving around the surface, but it was boxy and had no solar panels. It ran just 16 hours on internal battery power before shutting down. 

Minerva-II2 is the third distinct type of robot aboard Hayabusa2. Again, it’s mobile, but calling it a “rover” is a bit misleading. Minerva-II2 is drum-shaped like the previous Minerva explorers, but it’s larger than they were. The image above shows the descent module containing Minerva-II2, and below you can see what the robot actually looks like. 

The Minerva-II2 lander is similar to JAXA’s last Minerva robots, but it’s substantially larger.

JAXA previously reported possible issues with Minerva-II2’s CPU. That might prevent it from relaying data to the spacecraft, but there’s no harm in the attempt at this point. Hayabusa2 has completed its primary mission, using tantalum slugs to launch material from the surface of Ryugu into its sample collection compartment. Even if Minerva-II2 doesn’t work, Hayabusa2 can set course for Earth in the coming weeks with a wealth of data about Ryugu. The sample container should land on Earth in late 2020, allowing scientists to study material from an asteroid that hasn’t been scorched in the atmosphere for the first time.

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