The tiny Minerva-II2 probe is now en route to the surface of the asteroid Ryugu, having been deployed by Japan's Hayabusa2 spacecraft on Thursday. The final phase of this wildly successful mission and the last item on the to-do list before spacecraft makes its journey back to Earth.
Hayabusa2 released the Minerva-II2 probe at 12:57 a.m. Japan time on October 3 (1:57 am AEST) from a distance of about 1 kilometer above the surface of Ryugu, according to the Japan Aerospace Exploration Agency (JAXA).
[MINERVA-II2] Group photo to celebrate the successful separation of the MINERVA-II2! It's well past midnight and are a little tired now … but the operation is ongoing! In the future, we will observe the orbital motion of the MINERVA-II2 after its separation. pic.twitter.com/BLqS9UQB8I
– [email protected] (@ haya2e_jaxa) October 2, 2019
In June 2018, Hayabusa2 arrived at Ryugu – a 1-kilometer-wide asteroid located some 280 million kilometers from Earth. Prior to this week's operation, spacecraft deployed a pair of robotic probes, snapped countless photos of the asteroid, and performed two touchdowns, during which time it collected – we hope – bits of dust and rock from both above and below the surface.
The Minerva-II2 was moving about 13 to 17 centimeters per second at separation, so it took several days for the tiny decahedron to reach the asteroid's surface. But kinda the point; a primary scientific goal of the Minerva-II2 mission is to study and better characterize Ryugu's weak gravitational field and provide an opportunity for engineers to study the navigational challenges of such a small craft toward an object with such a weak gravitational influence. JAXA will collect scientific data from the Minerva-II2 as it delivers its slow descent and will be active on the surface for a short time.
The current mission is quite different from Hayabusa2's previous robotic deployment, when spacecraft deployed the Minerva-II1A and Minerva-II1B probes on September 23, 2019.
JAXA refers to Minerva devices as "rovers," but these tin cans are more accurately described as probes or landers, even if they are capable of making short "hops" on the asteroid's surface. Minerva-II1A and Minerva-II1B were dropped from a height of 50 meters, and once on the surface, the probes took spectacular photos along with a very cool video. By virtue of their hops, the Minerva-II1 were the first mobile devices to explore the surface of an asteroid.
After releasing the Minerva-II2, Hayabusa2 retreated to an altitude of between 8 and 10 kilometers, from where it will continue to monitor the lander. This operation will – perhaps sadly – come to an end on October 9. This marks the final mission for Hayabusa2, which is now set to make its triumphant return to Earth with its precious cargo, with an expected arrival date in late 2020.