JAXA’s SLIM is Back To Work on the Moon

JAXA’s Smart Lander for Investigating Moon, or SLIM, has resumed operations on the lunar surface. SLIM landed upside down because of an engine failure leaving the solar cells pointing in the wrong direction. But the sun’s angle has changed over the past several days and the solar cells are now recharging the battery.

JAXA’s Institute for Space and Astronautical Science (ISAS) excitedly reported restoring contact with SLIM.

SLIM Project members never give up ????! Communication with #SLIM has been resumed ????????‼️ We are extremely proud of the team who continued operations day and night to reach SLIM again. https://t.co/iJbFeQoC4X

— JAXA Institute of Space and Astronautical Science (@ISAS_JAXA_EN) January 29, 2024

The lander was able to send back data and images for about two-and-a-half hours on January 19 Eastern Standard Time (January 20 in Japan) before mission controllers deliberately disconnected the battery when it reached 12 percent to preserve this opportunity to start back up again.

SLIM ejected two tiny rovers just before landing, Lunar Excursion Vehicle-1 (LEV-1) and Lunar Excursion Vehicle-2 (LEV-2). LEV-1 can communicate directly with Earth and is a relay for LEV-2, a baseball-sized “transformer” rover built by Japan’s Takara Tomy toy company. LEV-2 took a picture showing SLIM with its nose in the lunar dirt. The image also confirmed that one of SLIM’s two engine nozzles is missing. The engine failure led to the bad landing.

The solar cells are mostly on top of the lander so sunlight could not reach them until the sun’s angle shifted.

SLIM’s main purpose is demonstrating pinpoint landing accuracy. The theme of the mission is moving from “the era of ‘landing where we can’ to ‘landing where we want'” according to a January 25 JAXA press conference.  Despite everything, it landed well within 100 meters of the designated location — 55 meters east of that spot. The accuracy was even better at 50 meters above the surface before obstacle avoidance maneuvers began, perhaps as good as 3-4 meters, JAXA said.

Based on JAXA’s pre-established criteria for “minimal,” “full” and “extra” success, SLIM already could claim full success based on landing accuracy. Now it’s working on “extra.”

Images from SLIM’s Multi-Band Camera (MBC) already are coming back, adding to the partial image received the first day.  JAXA’s scientists are naming the rocks and today’s image was of “Toy Poodle.”

SLIM is one of a new class of lunar landers that are much less expensive — and much less robust — than those sent in the 1960s and 1970s by the Soviet Union and the United States and more recently by China. Their electronics are not designed to survive the bitter cold and darkness of lunar night. Every part of the Moon, except the poles, experiences 14 days of sunlight and 14 days of darkness. (There is no “dark side” of the Moon in permanent darkness.) Temperatures fall to minus 208ºF (minus 130ºC) at night.

SLIM is in the Shioli Crater in the Sea of Nectar (Mare Nectaris) and night soon will fall there, but a couple more days of operations may be possible.

Japan is the fifth country to successfully soft land on the Moon, joining the Soviet Union, United States, China, and India.

In the past decade, only government-built spacecraft have landed successfully: China’s Chang’e-3/Yutu lander/rover in 2013, Chang’e-4/Yutu-2 far-side lander/rover in 2019 and Chang’e-5 sample return mission in 2020; and India’s Chandrayaan-3 in 2023.

Attempts by others, both governments and private entities, have failed: an Israeli non-profit, SpaceIL, with its Beresheet lander in 2019; India’s first attempt with Chandrayaan-2 in 2019; JAXA’s first attempt with the OMOTENASHI cubesat launched on the Artemis I test flight in 2022; a Japanese commercial company, ispace, with HAKUTO-R M1 in May 2023; the Russian government’s Luna-25 in August 2023; and the U.S. commercial company Astrobotic’s Peregrine last month.

Another U.S. commercial attempt is coming up in February with Intuitive Machines’ Nova-C.

Astrobotic and Intuitive Machines are two of several companies developing lunar landers through Commercial Lunar Payload Services (CLPS) partnerships with NASA. NASA pays them to deliver NASA payloads to the lunar surface and they are expected to find non-NASA customers to close the business case. Like SLIM, Peregrine and Nova-C are not designed to survive the lunar night.