It’s an incredible image, taken from the surface of the Moon by the tiny Sora-Q rover. The Japanese SLIM lander rests on the regolith, upside down… Worthy of Kerbal Space Program! The national agency delivered its explanations this week, and the least we can say is that the descent was eventful.
On January 19, the arrival of the Japanese lander SLIM (also called Moon Sniper) on the lunar surface was followed by a long suspense. Then a palpable disappointment: despite the success of the entire maneuver, SLIM only had a few hours left to transmit its data before shutting down, because its batteries were no longer charging.
However, the Japanese agency, JAXA, put these 2 hours 37 minutes of communications to good use, and it managed to download as much data as possible, both from the lander to retrace its descent, but also from the instruments at on board and even the two small robots, including the toy Sora-Q, successfully ejected to an altitude of 5 meters above the regolith. They were thus able to discover this extraordinary shot, with SLIM placed on the ground “head first”. And that wasn’t the end of the surprises.
A (relatively) impeccable descent
First, the good news. We knew that SLIM had managed to maneuver from Earth orbit for four months without a hitch. Well, its braking to land on the Moon followed the same pattern! Indeed, from orbit at an altitude of 15 km, the latter descended towards the surface very precisely following its objective, and it set off to land only approximately 3 meters from the coordinates entered into its computer! The on-board computer performed exemplary, consumption was right within the desired window, the image analysis of the navigation using the descent algorithm even made it possible to detect and avoid two potentially dangerous rocks. Everything was going really well, up to 50 meters from the ground, and a few seconds of the feat.
And here is the drama
The teams analyzing the data from the probe had detected unusual readings in the propulsion system logs. But it’s hard to expect an image like the one captured by the navigation camera. The latter in fact photographed one of the two main engines in the process of disintegrating, with pieces and especially a nozzle which was torn from SLIM.
50 meters from the lunar surface, a potential catastrophe (which remains unexplained for the moment, this engine was no more stressed than its neighbor which subsequently remained intact). The vehicle had two identical engines in tandem… If the on-board computer had not reacted immediately, it is a safe bet that SLIM would have crashed with a shock significant enough for it to be seriously damaged. But on the contrary, SLIM did everything to land anyway, using its auxiliary thrusters at full power to try to stabilize. He didn’t quite succeed…
It was by trying to do everything at once that SLIM ended up upside down. Impossible to brake, maintain its orientation, land precisely as planned and jettison the small rovers it was carrying. He therefore drifted about thirty meters while trying to get back on track, and the results were, as we know, mixed. Although it managed to land without damage, the planned final maneuver (arriving vertically and tipping onto its side on the slope) was impossible or poorly executed. Here is SLIM on the head, with one of the most improbable photos of lunar space exploration.
It’s (maybe) not over yet
During its press conference on Thursday, January 25, JAXA showed its data, as well as several images captured on the Moon, including by the SLIM instruments (the spectrometer was still able to function, even if it was at upside down). Apart from its orientation, the entire mission is still a resounding success. And a reminder that the visuals of Kerbal Space Program are not always totally imaginary!
Every day, the agency does not miss a slot to spit its signals at full power towards the lunar surface, in the hope that SLIM has been able to recharge its batteries and can respond. Indeed, the teams confirmed that according to the photos, the Sun must have started to illuminate the panels since Wednesday evening. They even seem confident in the vehicle’s ability to regain strength. The slot lasts a few days, all that remains is to wish them good luck!
Source : Space News
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