JAXA MINERVA-II1 Rovers Achieve Asteroid Landing, Autonomy, Image and Data Capture

September 24, 2018

Courtney E. Howard

Image captured by Rover-1B on September 21 at around 13:07 JST. This color image was taken immediately after separation from the spacecraft. The surface of Ryugu is in the lower right. The coloured blur in the top left is due to the reflection of sunlight when the image was taken. (Image credit: JAXA)

Japan Aerospace Exploration Agency (JAXA) officials have released the first images from two unmanned rovers that landed safely on the surface of asteroid Ryugu just days ago.

Image captured by Rover-1A on September 22 at around 11:44 JST. Color image captured while moving (during a hop) on the surface of Ryugu. The left-half of the image is the asteroid surface. The bright white region is due to sunlight. (Image credit: JAXA).

Image captured by Rover-1A on September 21 at around 13:08 JST. It is a color image taken immediately after separation from the spacecraft. Hayabusa2 is at the top and the surface of Ryugu is bottom. The image is blurred because the shot was taken while the rover was rotating. (Image credit: JAXA)

The bottom of the Hayabusa2 spacecraft. (Image credit: JAXA)

The compact MINERVA-II1 rovers, Rover-1A and Rover-1B, separated from the Hayabusa2 spacecraft on Sept. 21 at 13:06 Japan Standard Time (JST) and landed on Ryugu with a bounce. The two rovers are in good condition and are transmitting images and data, JAXA officials reveal. At least one of the two rovers is moving on the asteroid surface, the data confirms.

MINERVA-II1 is already credited with two milestones: the first mobile exploration robot to land on the surface of an asteroid and achieving the first autonomous movement and image capture on an asteroid surface.

MINERVA-II1 is being called “the world’s first manmade object to explore movement on an asteroid surface,” JAXA officials say.

The two MINERVA-II1 rovers (Rover-1A, 1B) are hexagonal in shape with a diameter of 18 cm, height of 7 cm, and weight of roughly 1.1 kg each. The pair were developed at the JAXA Institute of Space and Astronautical Sciences in collaboration with the following manufacturers, universities, and organizations: Aichi University of Technology, University of Aizu, Addnics Corp., Antenna Giken Co. Ltd, ELNA, CesiaTechno, University of Tokyo, Tokyo Denki University, Digital Spice Corp, Nittoh Inc., Maxon Japan, DLR, and ZARM.

Rover-1A has four cameras, and Rover-1B has three cameras, with which to produce a stereo image of the surface of Ryugu. Projections from the rover edge that look like thorns are temperature sensors to measure the surface temperature of Ryugu. Additional instruments on the rovers include optical sensors, an accelerometer, and a gyroscope.

The rovers communicate with Hayabusa2 using the repeater (OME-E) installed on the main spacecraft. The maximum communication speed is 32 kbps. Data received by Hayabusa is then transferred to the Earth. The OME-E will also be used for communication with the German/French lander, MASCOT, scheduled for deployment in October.

The main feature of MINERVA-II1 is the ability for the rovers to move on the surface of Ryugu by utilizing a hopping mechanism. Within the rover is a motor that rotates and causes the rover to “hop” (jump up) during the rebound, enabling the rovers to move across the asteroid surface and explore multiple areas. On Ryugu, MINERVA-II1 moves autonomously, determining what should be done for the exploration by itself.

The small rovers, MINERVA-II1. Rover-1A is on the left and Rover-1B is on the right. Behind the rovers is the cover in which they are stored. (Image credit: JAXA).

Gravity on the surface of Ryugu is very weak, so a rover propelled by normal wheels or crawlers would float upwards as soon as it started to move. The hopping mechanism was adopted for moving across the surface of such small celestial bodies. The rover is expected to remain in the air for up to 15 minutes after a single hop before landing, and to move up to 15 m horizontally.

Courtney E. Howard is editorial director and content strategist at SAE International, Aerospace Products Group. Contact her by e-mail at This email address is being protected from spambots. You need JavaScript enabled to view it. .