By 
January 25th, 2024
Image credit: JAXA/Inside Outer Space screengrab
New details regarding the successful landing of Japan’s Smart Lander for Investigating Moon (SLIM) have been released at a January 25 press briefing held by the Japan Aerospace Exploration Agency (JAXA).
It has been confirmed that on January 20, the Lunar Excursion Vehicle (LEV-1), a small robot deployed from SLIM did carry out activities on the lunar surface. Telemetry data was sent directly to Earth from the small robot.
SLIM team members spotlight results.
Image credit: JAXA/Inside Outer Space screengrab
That data indicates that, after deployment from SLIM, the LEV-1 executed planned leaping movements and direct communication with ground stations, including inter-robot test radio wave data transmission from the Transformable Lunar Robot (LEV-2, nicknamed “SORA-Q”).
Standby state
Currently, LEV-1 has completed its planned operational period on the lunar surface, depleted its designated power, and is in a standby state on the lunar surface.
While the capability to resume activity exists contingent on solar power generation from changes in the direction of the sun, efforts will be maintained to continue receiving signals from LEV-1.
SLIM’s multi-band spectroscopic camera took this lunar landscape image created by synthesizing 257 low-resolution monochrome pictures. Based on this landscape image, the team is sorting out rocks of interest, assigning a nickname to each of them, with intent of communicating their relative sizes smoothly by the names.
Image credit: JAXA/Inside Outer Space screengrab
Both LEV-1 and LEV-2 have become Japan’s first lunar exploration robots.
JAXA stated that LEV-1’s leaping movements on the lunar surface, inter-robot communication between LEV-1 and LEV-2, and fully autonomous operations “represent groundbreaking achievement.”
Attitude of SLIM
Regarding the SLIM spacecraft, due to it not being at the planned attitude upon landing, power generation was not possible from the solar cells.
Subsequently, SLIM was shut down with a command from the ground. The multi-band spectroscopic camera (MBC) onboard SLIM was operated on a trial basis and captured images until the power was turned off, JAXA announced.
Lunar topography captured by the Indian spacecraft Chandrayaan-2, overlaid with images acquired by the SLIM navigation camera during the HV2 (second hovering) at an altitude of about 50 meters. The two blue frames are images acquired during the obstacle detection at HV2. The SLIM footprint in the red frame is the safe landing zone set autonomously by SLIM based on the obstacle detection during HV2.
Image credit: JAXA/ISRO
Analysis of the data acquired before shutting down the power confirmed that SLIM had reached the Moon’s surface approximately 180 feet (55 meters) east of the original target landing site.
Pinpoint landing achieved
“While more detailed evaluation continues, it is reasonable to mention that the technology demonstration of pinpoint landing within an accuracy of 328 feet (100 meters), which has been declared to be the main mission of SLIM, has been achieved,” JAXA said.
All technical data on the navigation guidance leading to the landing, and navigation camera image data captured during the descent and on the lunar surface that is necessary for future pinpoint landing technology were obtained from the spacecraft.
Engine issue
Regarding SLIM’s attitude on the lunar surface after touchdown, it is a position that could not generate power from the solar cells.
Analysis of technical data revealed that at an altitude of 50 meters — just prior to the start of the obstacle avoidance maneuver — the thrust from one of the two main engines was most likely lost.
Image credit: JAXA/ISAS
The SLIM onboard software autonomously identified the anomaly, and while controlling the horizontal position as much as possible, SLIM continued the descent with the other engine and moved gradually towards the east.
SLIM landed “upside down” with the thruster up. No two-step landing was performed.
Below design range
The descent velocity at the time of contact with the ground was approximately 1.4 meters per second or less, which was below the design range.
Conditions such as the lateral velocity and attitude were outside the design range, and this is thought to have resulted in a different attitude than planned.
The cause of the loss of the main engine functionality is now being investigated.
As for future activities, JAXA said that further analysis has shown that SLIM’s solar cells are currently facing west, suggesting that there is the possibility for power generation and thus recovery of SLIM as the sunlight illumination condition improves with time.
Japan has become the 5th country to successfully soft land a spacecraft on the surface of the Moon.
The SLIM project is led by members of the JAXA Institute of Space and Astronautical Science (ISAS), and researchers from universities and other institutions across the country.
SLIM was launched last year on September 7, departing Earth atop an H-IIA launch vehicle from the Yoshinobu Launch Complex at JAXA’s Tanegashima Space Center.
Go to this informative video showcasing the Transformable Lunar Robot (LEV-2), nicknamed “SORA-Q.”
https://youtu.be/PupLqwt4d2o?si=Z8V4poXC2Tvx2zPG
Image credit: JAXA/ISAS
Lunar surface mosaic image captured by the SLIM-mounted Multi-Band Camera (MBC). The grey area on the right of the mosaic lacks data due to the discontinuation of scanning operation.
Image credit: JAXA/University of Aizu/Ritsumeikan University
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