Imagine the vehicle upside down and the camera twisted upside down so the photo is right side up but conflicts with the other sensors. In that situation I would take the rest of the day off.
It wouldn’t be “precise” unless they launched a second one and the same thing happened at the same location. So accurate would be a better word but I would want to see multiple attempts before declaring it accurate or precise. (Thinking about this in terms of target shooting)
Somebody had way too much fun writing the lead paragraph: "Japan's space agency said Thursday that its first lunar mission hit the tiny patch of the moon's surface it was aiming for, in a successful demonstration of its pinpoint landing system—although the probe appears to be lying upside-down."
Maybe I'm saying what you're saying, but that's a sentence, not a paragraph. I find it very annoying when I encounter these and it makes me question the competence of the author. It seems like the complexity of the grammar used reduces with more writing experience.
My opinion is that it should be:
"Japan's space agency said Thursday that its first lunar mission hit the tiny patch of the moon's surface it was aiming for. It was a successful demonstration of its pinpoint landing system although the probe appears to be lying upside-down."
If my kerbel space program has taught me anything it is that being upside down, side ways or whatever after a semi-safe landing, is only an issue if you want to go home.
> But after the landing mishap, the craft's solar panels wound up facing the wrong direction, and it cannot generate power. Officials said there is still hope the probe will be able to recharge when the moon enters its daytime in the coming days.
nitpick - 誤差 is used for numerical deltas, 錯誤 would be more appropriate for boolean errors, or 反転 which is inversion, or transliteration for the English word, エラー also works("ー" is important, エラ without the elongation sign ー is gills on a fish)
The snark is strong in this - but I'll resist and just note that landing on the moon is hard. I reckon they did exceptionally well with nailing the landing site, and hope that next time they'll be completely successful.
I wonder if they had accelerometers recording exactly what happened as it touched down and ended up on it's back?
It was meant to use a rather odd "two-step" landing procedure where it first touches down on the lunar surface on it's rear/primary landing gear, then pivots forward/falls under gravity to also touch down on the front/secondary landing gear.
Presumably this landing procedure was simulated under lunar gravity, but it seems there are multiple potential failure modes:
1) After rear "leg" touchdown, over-rotate forwards over front leg (ending up on back), OR
2) After front "leg" touchdown, bounce/recoil backwards off front leg, flipping onto back, OR
3) Front landing gear hits rock on one side (left or right), thereby flipping it sideways onto back
The whole procedure seems to rely not only on having correctly simulated under lunar gravity (and with correctly simulated stiffness of the vehicle) to avoid scenarios 1) & 2) (which would be different under earth gravity), but also the softness of the landing site being uniform and as simulated - otherwise if landing site surface was harder (rock) or softer than expected, or uneven, then this type of pivot and bounce/not landing would not go as planned.
NASA seems to have done a better job in designing fool-proof landing mechanisms, from the bouncing ball of the first mars rover, to the sky-crane landing of the latest one (which appears over-complicated, but no doubt was chosen at least in part because it is in fact more predictable than the alternatives).
The two-step sounds precisely like how all forward-moving aircraft land: Rear touch first. The alternative (front touch first) is dangerous for reasons any BMX biker could explain: You're much more sensitive to pitching forward from forward-of-gravity friction.
But for a propulsive landing, why would they want to have forward velocity at all, unless by design for this type of landing ? I'd have thought the preference would be to kill forward speed and land vertically.
As an experienced KSP crasher, you never completely cancel horizontal component, so you need a way to dissipate it. And it's easier to dissipate if you know which direction your horizontal component is, which is easier to do when its value isn't so close to 0.
That being said I perfectly see how sub-ms automated command could make what I said wrong.
One of two main engines blew off at ~50m and the craft was essentially in a cross-wind landing, likely without de-crab. Having lateral velocity wasn't a part of the plan.
The engine loss was a detail in the article that I hadn't seen anywhere else in the commentary and speculation on the landing. Even now many commenters don't seem to be taking this into account. Even if there was redundancy built in, an engine loss makes things much more difficult. I can see why they're claiming 100% success despite being upside down.
I never understood why those use front-brakes instead of rear-brakes like the roller blades I had as a kid. The latter I could comfortably use almost instantly, the former, I never got comfortable with.
I assume that you just drag the tip of one skate behind you, rolling on the other until you lose momentum. And having the ability to suddenly stop is akin to ice figure skates, with the pointy bits at front.
Considering they knew these failure modes in advance, would it not have been prudent to put some sort of self-righting mechanism on the lander? Something like the mechanical arms you see in Robot Wars.
Mechanisms weigh a significant amount, long mechanisms like arms even more so. The more mass you spend on contingencies the less science you bring and the less valuable the mission is, even with a flawless touchdown.
Neat idea, I'm not sure how much force those jets produce, maybe it could be enough? It might be risky to fire up jets after a botched landing though. If the nozzle has any material in it I'd be worried about blowing a hole in the lander!
If you can't land reliably, then a lot of the science is wasted. On the other hand, once you reliably solve the landing issue (which was one of the main objectives here, and where they made significant progress in that they successfully deployed the two mini rovers anyway), you can add on as much science as you want.
Also I've said before and will say it again, the moon is not far away. Unlike Mars and other celestial bodies where we have to time launches around orbital positions, gravitational slingshots and such, the moon is really close by, and we should be lofting stuff onto it on a monthly basis.
> One of the lander's main engines lost thrust about 50 meters (54 yards) above the moon surface, causing a harder landing than planned.
When I first heard that they might have landed upside down, a part of me felt a pang of indignation and condescension, for about ten seconds. But I kept my mouth shut and realized these things are hard and something I didn't think of in the ten seconds as an armchair lander-designer might have occurred.
I found the tone of your comment pretty condescending, tbh. Hot landing is hot landing, and you're just speculating as a layman without any insight into their design and decision-making process. "Not simulating lunary gravity correctly." Like c'mon, that's just an insult to their intelligence.
Well, I did also mention stiffness which would relate to how much of a shock absorber effect there would be - preventing a bounce, so if they came in hard, that may indeed have been a factor. Maybe more to the point, it seems to be a fairly unforgiving mode of landing - maybe a NASA "bouncing ball" landing would have absorbed the harder landing without issue ?
It's big vindication for the bouncing ball approach. On the other hand the proximity of the moon makes it much more practical to field crude designs on a more frequent basis, or to put parts in orbit and assemble them into something more ship-like.
>It's big vindication for the bouncing ball approach
Not really, it's only been used for a few Mars missions, and not recently. For lunar missions you don't have the benefit of aerobraking, so you have to use so much fuel to slow down already, the math doesn't work out to use airbags at the last step.
Since I do remember that episode and got curious, I asked ChatGPT. Apparently, the antipodal point on the globe from Hoboken, NJ is somewhere in the Indian Ocean, southeast of Madagascar. From Tokyo, it's in the South Atlantic Ocean, northeast of the Falkland Islands.
Undoubtedly, I'll forget all this by tomorrow morning and remember Asia :-)
Why are you quoting ChatGPT? It's well know to confidently generate incorrect answers. The antipodes in question are very far from Madagascar and the Falkland Islands. Near Brazil and near Australia are much better answers. Blindly quoting ChatGPT just adds noise, you've got to fact check it (at that point, why bother asking ChatGPT?)
Not mentioned in the article but touched in the conference is this is at least third time a 500N-class thruster failed on an ISAS probe. Last time it blew off on Akatsuki/PLANET-C Venus probe, before that was Nozomi/PLANET-B Mars probe, both cut apsis burn shorter than intended and later determined to be from salt buildups due to propellant leaks. Apparently apogee motors has been proving harder to do right than anticipated.
> For the pinpoint landing, Sakai said, he would give SLIM a "perfect score."
I get being really, really proud of what you accomplished here, but...perfect? Really? You can't think of anything that maybe could have gone better?
I know it's a much more sophisticated problem than this, but my inner child thinks they just forgot "the planet(oid) has to be 'down' on both ends of the trajectory."
You could engineer-ize that kind of problem. Maybe they plugged it into a complicated optimization package (want to minimize stresses from the landing) but forgot to add a crucial orientation related constraint…
Probably, almost certainly, that isn’t what happened. But it could!
I cant help but think the Japanophile contingent on HN are super eager to grade-inflate anything and everything remotely applause-worthy Japan related in general.
FWIW, ISAS Director General(the "faculty" president, also a PM in another probe in the past) Hitoshi Kuninaka scored it at 63 points, with 60 for the landing and bonus 1 point each for scientific camera and two payload probes, you could say he's more based or whatever.
OTOH, in defense of the PM, the lander showed exceptional robustness against loss of an engine, so he'd have a reason to be proud of an explosionless landing.
Oh definitely not saying they shouldn't be proud. I'm intensely impressed, and they should be extremely proud.
It was just the juxtaposition of "perfect" with the picture of the thing upsidedown that made me laugh. "Near-perfect" I'll happily grant. Same with "impressive as all get-out." But "perfect" made me chuckle.
the main point seems to have been the precision with which they could land within a small region, and they did nail that. fta:
While most previous probes have used landing zones about 10 kilometers (six miles) wide, SLIM was aiming at a target of just 100 meters (330 feet). Improved accuracy would give scientists access to more of the moon, since probes could be placed nearer to obstacles.
> but...perfect? Really? You can't think of anything that maybe could have gone better?
The context of the comment in the article referred to the “pinpoint landing” aspect of the landing. They narrowed down the landing range from 10,000m (10k) to 100m… two orders of magnitude.
From the the article,
emphasis mine:
> For the pinpoint landing, Sakai said, he would give SLIM a "perfect score."
> "We demonstrated that we can land where we want," Sakai said. "We opened a door to a new era."
I don’t know if this comment was made in English or Japanese, but I could see how a very specific comment about the pinpoint aspect of the landing in Japanese could be vague when translated into English.
I don’t think anyone is disillusioned enough to think the overall landing was perfect.
I think I was including "landing" in the relevant part of "pinpoint landing," not just the pinpoint element, which was what made it amusing. It did (apparently) "land" and not "crash" (or at least that's what I'm assuming from the fact that it isn't crushed/doesn't look like it made primary impact on some part that was not intended for impact), but "landing and falling over" doesn't normally earns a perfect score in any other common context.
I work in the industry and "pinpoint landing" refers to the accuracy part. If he was talking about landing in general, the sentence would be something like "the landing didn't go as expected, but we achieved a pinpoint landing".
I'm far from a translator... but it is not "We opened a door" but "A door is open to do missions that were not possible before". And he says that might be the most important takeaway from this project.
> I'm far from a translator... but it is not "We opened a door" but "A door is open to do missions that were not possible before".
You're being overly literal. Omitting the subject is normal in Japanese; translating that to a passive-voiced sentence in English is usually misleading.
Again, not a distinction that carries the same nuance that it would in English. The whole animate/inanimate distinction just isn't there in the same way in non-indo-european languages.
が makes the subject the door, not JAXA. Plus it would be very uncharacteristic of a Japanese person in that position making such a bold claim. It goes against Japanese society norms.
>Opening a new door in many senses (or "in different ways" if you want to take some liberty), from now on, missions that couldn't be done until now will become possible. Isn't it the most important (thing)?
As a comparator for the pinpoint landing, the 1969 Apollo 12 landed within walking distance (535 ft) of the Surveyor 3 probe (which had landed two years earlier). It did have a human pilot who flew the descent and managed terrain avoidance.
The patient is alive. The lander still functioned on batteries. The solar panels are facing the wrong way, but they hope that the panels will produce power when the angle of the sun changes.
Other commentors are already pointing out how we went from kilometers of precision to a target of under 100m for this mission. But in practice, the team is confident it landed within 10m, which is pretty darn good.
On the context of the "perfect score", they initially gave themselves a 60 out of 100 score during their first press conference after the landing, and today a member of the audience explicitely asked them to revise that score knowing what we know now.
The speaker made the point that achieving that much of precision is just ground breaking and will completely change how we frame the "where do we land" question from now on,so giving it a perfect score is I think legit.
It's possible that the "minimum success criteria" or "primary objective" of the mission was to touch down intact within a radius. If that was achieved, then I think even in English it is reasonable to call the landing "perfect" in that it achieved all of the mission goals.
But that all depends on whether, "land upright and measure things with the expensive instruments we sent it with" was originally included as a primary objective and whether they've just moved the goal posts to minimize the appearance of the failure.
We seem to be losing the definition of words. From "perfect phone calls" to "perfect landings" just feels like moving the goal posts. Let's tone down the rhetoric a bit. A very successful landing. sure. Met all of the necessary goals even if wasn't as designed. sure. Perfect landing. Let's not be silly
I can see talking yourself into that definition, but any 4-year-old can look at that picture and tell you it didn't land perfectly. "No, silly! It's upsidedown!"
I think this is a best-worst case scenario. Pretty embarrassing if you ask me. I'm imagining the Star Trek teleporting thing and one guy appearing upside down, at an angle. Argh must be the Japanese teleporter.
158 comments
[ 3.3 ms ] story [ 218 ms ] threadMy opinion is that it should be: "Japan's space agency said Thursday that its first lunar mission hit the tiny patch of the moon's surface it was aiming for. It was a successful demonstration of its pinpoint landing system although the probe appears to be lying upside-down."
> But after the landing mishap, the craft's solar panels wound up facing the wrong direction, and it cannot generate power. Officials said there is still hope the probe will be able to recharge when the moon enters its daytime in the coming days.
https://twitter.com/IndianTechGuide/status/17446149885918046... 2
https://i.postimg.cc/T1Ccxw2X/Robotic-Moon-Landings.png
That’s an incredible result.
It was meant to use a rather odd "two-step" landing procedure where it first touches down on the lunar surface on it's rear/primary landing gear, then pivots forward/falls under gravity to also touch down on the front/secondary landing gear.
Presumably this landing procedure was simulated under lunar gravity, but it seems there are multiple potential failure modes:
1) After rear "leg" touchdown, over-rotate forwards over front leg (ending up on back), OR
2) After front "leg" touchdown, bounce/recoil backwards off front leg, flipping onto back, OR
3) Front landing gear hits rock on one side (left or right), thereby flipping it sideways onto back
The whole procedure seems to rely not only on having correctly simulated under lunar gravity (and with correctly simulated stiffness of the vehicle) to avoid scenarios 1) & 2) (which would be different under earth gravity), but also the softness of the landing site being uniform and as simulated - otherwise if landing site surface was harder (rock) or softer than expected, or uneven, then this type of pivot and bounce/not landing would not go as planned.
NASA seems to have done a better job in designing fool-proof landing mechanisms, from the bouncing ball of the first mars rover, to the sky-crane landing of the latest one (which appears over-complicated, but no doubt was chosen at least in part because it is in fact more predictable than the alternatives).
I wouldn't read too much into that choice.
More likely the velocity was a tad too high.
That being said I perfectly see how sub-ms automated command could make what I said wrong.
That's why I was never comfortable stopping in rollerskates or ice stakes.
Also I've said before and will say it again, the moon is not far away. Unlike Mars and other celestial bodies where we have to time launches around orbital positions, gravitational slingshots and such, the moon is really close by, and we should be lofting stuff onto it on a monthly basis.
[0]: https://news.ycombinator.com/item?id=39131130
[1]: https://www.bbc.com/news/science-environment-68091389
> One of the lander's main engines lost thrust about 50 meters (54 yards) above the moon surface, causing a harder landing than planned.
When I first heard that they might have landed upside down, a part of me felt a pang of indignation and condescension, for about ten seconds. But I kept my mouth shut and realized these things are hard and something I didn't think of in the ten seconds as an armchair lander-designer might have occurred.
I found the tone of your comment pretty condescending, tbh. Hot landing is hot landing, and you're just speculating as a layman without any insight into their design and decision-making process. "Not simulating lunary gravity correctly." Like c'mon, that's just an insult to their intelligence.
Not really, it's only been used for a few Mars missions, and not recently. For lunar missions you don't have the benefit of aerobraking, so you have to use so much fuel to slow down already, the math doesn't work out to use airbags at the last step.
The purpose of this landing design was explicitly to allow landing in areas that wouldn't previously be considered acceptable: slopes.
Life imitates art. Astonishing.
Undoubtedly, I'll forget all this by tomorrow morning and remember Asia :-)
https://www.geodatos.net/en/antipodes/united-states/hoboken
https://www.geodatos.net/en/antipodes/japan/tokyo
I get being really, really proud of what you accomplished here, but...perfect? Really? You can't think of anything that maybe could have gone better?
I know it's a much more sophisticated problem than this, but my inner child thinks they just forgot "the planet(oid) has to be 'down' on both ends of the trajectory."
Probably, almost certainly, that isn’t what happened. But it could!
Chuck Yeager
But the passenger payloads deployed correctly, so we'll count that as walking away.
OTOH, in defense of the PM, the lander showed exceptional robustness against loss of an engine, so he'd have a reason to be proud of an explosionless landing.
It was just the juxtaposition of "perfect" with the picture of the thing upsidedown that made me laugh. "Near-perfect" I'll happily grant. Same with "impressive as all get-out." But "perfect" made me chuckle.
S rank! Play next time for SSS!
While most previous probes have used landing zones about 10 kilometers (six miles) wide, SLIM was aiming at a target of just 100 meters (330 feet). Improved accuracy would give scientists access to more of the moon, since probes could be placed nearer to obstacles.
The context of the comment in the article referred to the “pinpoint landing” aspect of the landing. They narrowed down the landing range from 10,000m (10k) to 100m… two orders of magnitude.
From the the article, emphasis mine:
> For the pinpoint landing, Sakai said, he would give SLIM a "perfect score."
> "We demonstrated that we can land where we want," Sakai said. "We opened a door to a new era."
I don’t know if this comment was made in English or Japanese, but I could see how a very specific comment about the pinpoint aspect of the landing in Japanese could be vague when translated into English.
I don’t think anyone is disillusioned enough to think the overall landing was perfect.
> いろんな意味で新しい扉が開き、今後、これまでできなかったようなミッションができるようになるのでは。そこが一番の意義ではないか
I'm far from a translator... but it is not "We opened a door" but "A door is open to do missions that were not possible before". And he says that might be the most important takeaway from this project.
https://news.yahoo.co.jp/articles/08a8bfdd7a41486140a97a8570...
You're being overly literal. Omitting the subject is normal in Japanese; translating that to a passive-voiced sentence in English is usually misleading.
が makes the subject the door, not JAXA. Plus it would be very uncharacteristic of a Japanese person in that position making such a bold claim. It goes against Japanese society norms.
Translation for those wondering.
[0] https://en.wikipedia.org/wiki/Apollo_12#Lunar_orbit_and_Moon...
On the context of the "perfect score", they initially gave themselves a 60 out of 100 score during their first press conference after the landing, and today a member of the audience explicitely asked them to revise that score knowing what we know now.
The speaker made the point that achieving that much of precision is just ground breaking and will completely change how we frame the "where do we land" question from now on,so giving it a perfect score is I think legit.
The problem may have been in their metrics. The KPI should have been a successful landing for the full range of 'successful'.
But that all depends on whether, "land upright and measure things with the expensive instruments we sent it with" was originally included as a primary objective and whether they've just moved the goal posts to minimize the appearance of the failure.
https://www.bbc.com/news/science-environment-68091389