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Comment by scohesc | Hacker News Reader

The telemetry screen showed that the craft might have flipped over, doesn't look good for a landing unfortunately...

You got this next time, Japan! :)

It was supposed to flip over, so that in itself doesn't mean anything. See this picture: https://cdn.arstechnica.net/wp-content/uploads/2024/01/SLIM_... (from https://arstechnica.com/space/2024/01/japans-moon-sniper-mis...)

But it seems likely that it has not flipped over in the way that it was supposed to. It going below zero altitude in the end, and the "waiting for confirmation of a good landing", don't give me much hope.

Animated SLIM mission (labels in English), https://www.youtube.com/watch?v=57hS8uLU7v4

From JAXA's talk, https://www.youtube.com/watch?v=Ej4ZMp4a2xw&t=4695s

I don't know why, but that lander and its two robots seem adorable to me.

Japanese design always seems adorable to me.

Seems the last telemetry was flipped. My bet is that the last final burn before contact with the surface caused it to flip. It also looked like it carried too much velocity as the very end, again I think that's because it was doing the last hard burn in a direction not toward the surface.

Given how many failures there have been in the final process of contacting with the moon, I would be tempted to just embrace the velocity. One idea would be to use an anchor shot into the lunar surface.

Assuming it did flip over would Japan still be on the list of countries to have successfully landed? There's a big difference between what we presumably witnessed and an out of control craft smashing into the surface.

In the vein of "any landing you can walk away from", between it (a) successfully deploying the sub-rovers (though maybe that happens slightly before contact?) (b) it communicating enough post-landing telemetry that they can diagnose things, I think that should count as "successfully landing". (One of the actual mission goals was ending up on the ground within meters of where they intended, and it sounds like they nailed that too?)

Note that my comment was written when they were still trying to regain contact with the lander.

If your main goal was to land and go forward with tests, but your landing started the soon to be demise of the cargo, I cant really say it's successful.

It deployed the rovers similar to how injured pilots might still exist an aircraft after a crash. If they soon die due to solar panel issues from the crash, they didn't really walk away to live another day.

https://www.theregister.com/2024/01/29/japan_lander_wakes_up... we didn't know this at posting time, but the solar panels weren't damaged, just pointed the wrong way, and when they finally got sunlight again, they were able to properly start the science mission. (Shortened, because it's not designed to survive the lunar night, but lots of neat "first time seen" data.)

Also, I thought I read that at least one of the robots actually communicates directly with earth even if the lander is toast? Honestly I'm a little surprised that our first step at investigating a moon or planet in this century isn't "deploy a microsat version of GPS + TDRSS to simplify the landers" so that the first task of every mission is just "pop a gopro" :-)

IIRC, it should have flipped, that's how it lands. Unusual, but why not.

It also looked like it went below 0 altitude? I had it muted so not sure if that was expected or not, but seemed like it might have touched down too fast.

> It also looked like it went below 0 altitude?

"Lithobraking"[1]

[1]: https://en.wikipedia.org/wiki/Lithobraking

That would be consistent with it rolling down the slope.

That makes sense. I was thinking that its altitude sensor might have been miscalibrated or confused, so it hadn't yet reached the ground when it thought it had.

Perhaps an improved design would not matter which orientation it came to rest in. It could extend a rod to right itself, or simply work regardless of its orientation.

It would be a fun engineering challenge to built such.

There's a fair amount of prior art in battlebots hardware, recovering from flipping over - nothing quite as weight-constrained as an actual lander, but at least there are worked examples...

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