JAXA SLIM 's Moon Landing was a near crash, space craft rolled onto moon, ending on side

JAXA | Outcome for the Smart Lander for Investigating Moon (SLIM) 's Moon Landing: 

global.jaxa.jp

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January 25, 2024 (JST)

Japan Aerospace Exploration Agency

 The Japan Aerospace Exploration Agency (JAXA) Smart Lander for Investigating Moon (SLIM) landed on the lunar surface on January 20, 2024 at 0:20 am JST, and communication was established with the Earth.

 However, due to the spacecraft not being at the planned attitude upon landing, power generation was not possible from the solar cells, and the spacecraft was shutdown with a command from the ground at 2:57 am JST.

 Analysis of the data acquired before shutting down the power confirmed that SLIM had reached the Moon’s surface approximately 55m east of the original target landing site. The positional accuracy before the commencement of the obstacle avoidance maneuver (at around a 50m altitude) which indicates the pinpoint landing performance, was evaluated to be at approximately 10m or less, possibly about 3 - 4m. While more detailed evaluation continues, it is reasonable to mention that the technology demonstration of pinpoint landing within an accuracy of 100m, which has been declared to be the main mission of SLIM, has been achieved.

 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, was obtained from the spacecraft. The small probes (LEV-1 and LEV-2) were successfully separated just prior to landing in this contingency situation. The multi-band spectroscopic camera (MBC) onboard SLIM was also operated on a trial basis and captured images until the power was turned off.

 Regarding the circumstances of how SLIM became stationary on the lunar surface at an attitude that could not generate power from the solar cells, the acquired technical data revealed that at an altitude of 50m just prior to the start of the obstacle avoidance maneuver, the thrust from one of the two main engines was most likely lost. Under these circumstances, the SLIM onboard software autonomously identifies 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. The descent velocity at the time of contact with the ground was approximately 1.4 m/s or less, which was below the design range., but 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, including consideration of external factors aside from the engine itself, with the plan to determine the detailed cause. We will provide further information as the investigation progresses.

 Regarding future activities, further analysis of the acquired technical and scientific data, as well as analysis of the cause of the anomalies that occurred, will proceed. Analysis of the data 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. Although SLIM’s activities on the Moon were originally expected to last only a few days, the necessary preparations for recovery will continue in order to acquire further technical and scientific data.

 We will continue to keep you updated on the status of the project.

■ Image of the lunar surface captured by the SLIM onboard navigation camera after landing (credit: JAXA)

Note: the image is rotated to align with the direction of gravity.

■ Estimation of SLIM’s current location and the target landing site (credit: Chandrayaan-2:ISRO/SLIM:JAXA)

Note: 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 50m. The two blue frames are images acquired during the obstacle detection at HV2. As the spacecraft subsequently enters the obstacle avoidance operation, the performance of the pinpoint landing is evaluated based on the positional accuracy at this point. The positional accuracy at the time of the first and second obstacle detection was respectively about 3 - 4m and 10m. Note that it is highly likely that the main engine was already affected by the loss of function when the second obstacle detection occurred. The SLIM footprint in the red frame is the safe landing zone set autonomously by SLIM based on the obstacle detection during HV2.

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JAXA SLIM spacecraft overturns and lies upside down during lunar landing • Mezha.Media

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As it turned out, the soft landing of the JAXA SLIM spacecraft on the Moon was not so soft. During the descent, the vehicle tipped over and is now lying upside down.

This became known thanks to the images of the miniature lunar rover LEV-2, which took SLIM from the side. The images were posted on Twitter/X by the JAXA Institute of Space and Astronautics.

The unscheduled landing occurred because one of SLIM’s two engines collapsed while hovering near the lunar surface, and its nozzle fell off. According to JAXA representatives, it was allegedly due to some external causes. That’s why the spacecraft “steered” and overturned.

The LEV-1 and LEV-2 rovers fired off the SLIM during the hover and worked normally. LEV-2 deployed from the sphere state to the uniaxial rover state, took a picture of SLIM lying upside down, and transmitted the photo to Earth via LEV-1.

JAXA is still hoping that the sun will illuminate the SLIM solar panels and provide enough energy to charge the vehicle’s batteries. Although there is a possibility that the panels were damaged during the landing.

Of course, Japanese social media reacted to the event with a bunch of drawings depicting the SLIM device as a girl who has lost her shoe and really doesn’t want to wake up.

Last Minute Problems on Apollo 11 Moon Landing

 Japan's achievement is significant. Despite the last minute problems, the control system managed to get SLIM down in mostly one piece. When the sun comes up in 2 weeks, if the batteries can restart, the mission could still be salvaged. Landing on the moon is not easy, and making the achievement of the NASA Apollo program even greater, but they had Neal Armstrong on the spot to deal with problems. And they had problems.

The final descent and landing of Apollo 11 on the Moon was indeed a tense and critical phase, with several challenges arising in the last 50 meters:

1. Fuel Warning: The lunar module, Eagle, was burning fuel at a higher rate than anticipated due to its descent trajectory and the uneven lunar terrain. This triggered repeated fuel quantity warnings from the onboard computer, raising concerns about whether they had enough fuel to complete the landing and return to the command module.
2. Computer Overload: Adding to the tension, the computer also threw up several "1202" alarms, indicating a potential overload. While the cause was unclear and deemed low risk by Mission Control, it added another layer of uncertainty to the already critical situation.
3. Terrain Hazards: As they descended closer, the astronauts encountered unexpected terrain features, with craters and boulders appearing larger than expected. Armstrong had to manually pilot the Eagle to avoid these obstacles, requiring quick thinking and precise maneuvering.
4. Landing Spot: The intended landing zone, close to the planned rendezvous point with the command module, proved too rough. Armstrong had to search for a suitable landing site while fuel levels dwindled, eventually settling on a precarious area with boulders and slopes.
5. Landing Gear Contact: During the final descent, one of the landing gear legs made contact with the lunar surface briefly before fully extending. While this didn't cause any immediate damage, it added another element of uncertainty and stress to the landing.

Despite these challenges, Armstrong managed to land the Eagle safely with just seconds of fuel remaining. This remarkable feat of skill and composure under pressure is a testament to the training and capabilities of the Apollo 11 astronauts.

It's important to note that these problems were anticipated and accounted for to some extent in the mission planning. However, the actual experience of landing on the Moon presented unforeseen challenges that required the astronauts to adapt and make critical decisions in real-time. Their success in overcoming these obstacles is a key part of the Apollo 11 story and a reminder of the incredible human ingenuity and courage that made this historic mission possible.