Hayabusa2 Rehearses Landings on Asteroid Ryugu

Figure 2: Image of the surface of Ryugu captured with the ONC-W1 at an altitude of about 47m. The image was taken on October 15, 2018 at 22:45 JST. The red circle indicates the candidate point for touchdown, L08-B. (Credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST)

Japan’s Hayabusa2 spacecraft spent the last several weeks rehearsing for a landing on asteroid Ryugu scheduled for early next year. JAXA’s status reports for the last three weeks are reproduced below.

Hayabusa2 Status

Week of Oct. 22, 2018

Making maximum use of the data obtained during TD1-R1-A, the TD1-R3 operation ran from October 23 – 25. This was a rehearsal that covered the operation sequence until the point just before touchdown.

The spacecraft descended to the same region at TD1-R1-A using the LRF (Laser Range Finder); a short-range laser sensors with four beams that measures the distance to the asteroid surface. Using this measurement, the spacecraft automatically kept the altitude constant and hovered above Ryugu, and then dropped a TM (Target Marker).

The spacecraft was able to recognise the image of the TM when lit by the FLA strobe light (FLAsh lamp), moving to just above the TM position and continuing to hover. Finally the spacecraft ascended. This result was a huge success! Everyone is feeling relieved as we move into next year.

Week of Oct. 29, 2018

Our second “BOX-C” operation began on 10/27, immediately after returning to the 20km altitude home position from the “TD1-R3” operation. This time was a special operation in two steps; BOX-C1 where the spacecraft descended to an altitude of about 5.1km and BOX-C2, with descent to about 2.2 km.

Arrival at BOX-C1 occurred as scheduled on 10/30 and we completed observations using the laser altimeter and optical cameras. We arrived at BOX-C2 on 11/1 with the objective of photographing the TM (Target Marker) that was successfully dropped during TD1-R3, and to accurately identify its position.

The spacecraft descended over the sub-solar point where the spacecraft, Sun and TM on the surface of Ryugu all line up. The spacecraft captured an image at an altitude of about 2.5km with the Optical Navigation Camera – Telescopic (ONC-T), and then withdrew after descending to an altitude of about 2.2 km. The result was a huge success!

The retroreflective material of the TM reflected sunlight and made the TM glow in the image. This is another step forward for the TD1 operation at the beginning of next year. The spacecraft then slowly rose to save fuel and returned to the home position on 11/5.

Week of November 5, 2018

After completing important operations such as TD1-R3 and BOX-C2, the spacecraft returned to the home position at an altitude of 20km. This week, we performed a health check for the optical navigation cameras (ONC), the thermal infrared imager (TIR) and the near infrared spectrometer (NIRS3).

Although we normally image Ryugu, for these tests we changed the spacecraft attitude to intentionally remove the asteroid from the field of view and image deep space (a so-called ‘dark observation’). Observing dark deep space allows us to investigate the level of noise in the observation equipment. This will be the third dark observation after arriving at Ryugu.

Week of Oct. 29, 2018

Our second “BOX-C” operation began on 10/27, immediately after returning to the 20km altitude home position from the “TD1-R3” operation. This time was a special operation in two steps; BOX-C1 where the spacecraft descended to an altitude of about 5.1km and BOX-C2, with descent to about 2.2 km.

Arrival at BOX-C1 occurred as scheduled on 10/30 and we completed observations using the laser altimeter and optical cameras. We arrived at BOX-C2 on 11/1 with the objective of photographing the TM (Target Marker) that was successfully dropped during TD1-R3, and to accurately identify its position.

The spacecraft descended over the sub-solar point where the spacecraft, Sun and TM on the surface of Ryugu all line up. The spacecraft captured an image at an altitude of about 2.5km with the Optical Navigation Camera – Telescopic (ONC-T), and then withdrew after descending to an altitude of about 2.2 km. The result was a huge success!

The retroreflective material of the TM reflected sunlight and made the TM glow in the image. This is another step forward for the TD1 operation at the beginning of next year. The spacecraft then slowly rose to save fuel and returned to the home position on 11/5.