[HN Gopher] Japan's precision moon lander has hit its target, bu...
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Japan's precision moon lander has hit its target, but appears to be
upside-down
Author : pseudolus
Score : 142 points
Date : 2024-01-25 12:45 UTC (10 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| j4yav wrote:
| Why appears to be? Is there some doubt?
| braiamp wrote:
| Because it could be a error in the instrumentation.
| world2vec wrote:
| The photo clearly shows it's upside-down.
| n6242 wrote:
| They need more data to verify that the camera isn't also
| upside down.
| j4yav wrote:
| But then how will we prove the planet isn't upside down?
| pi-e-sigma wrote:
| Just ask the Australians.
| chasd00 wrote:
| 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.
| dcuthbertson wrote:
| The author is being coy.
| zem wrote:
| it's just a manner of speaking
| tim333 wrote:
| As mentioned elsewhere it's not actually upside down but seems
| to be tipped over about 90 degrees.
| selimnairb wrote:
| So it's precise, but inaccurate.
| sublinear wrote:
| Accurate but imprecise. It was on target, but not precisely as
| expected.
| iamthepieman wrote:
| Accurate but not reliable. Precision would come into play if
| they launched more than one.
| numpad0 wrote:
| They had an engine anomaly and excess velocity from it, it
| wasn't a failure in intended tipover maneuver
| chasd00 wrote:
| 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)
| samus wrote:
| That would be consistency.
| ryathal wrote:
| Just accurate. Precision is a measure of how close each attempt
| is to the other attempts, you need at least two to get a
| measure of precision.
| the-dude wrote:
| _We choose to go to the moon in this decade and do the other
| things, not because they are easy, but because they are hard ..._
| etc etc.
| whalesalad wrote:
| Put it in reverse, terry!
| matthewfelgate wrote:
| ?uwop-@psdn lla synb noy @ra yYw y@H
| boeingUH60 wrote:
| oko@b llaw a Wa I H
| alenrozac wrote:
| Someone right now at JAXA is performing a dogeza.
| somenameforme wrote:
| 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."
| sublinear wrote:
| 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."
| devjab wrote:
| 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.
| gggmaster wrote:
| Or if you want your solar panel to work.
| plasticchris wrote:
| Nah, kerbal panels are smart enough to pivot around
| yieldcrv wrote:
| but not the Japanese Space Agency's
|
| > 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.
| wozniacki wrote:
| Having said that, is this list of recent robotic moon
| landings, comprehensive? Include this Japanese mission
| should you want to. Robotic Moon
| Landing Missions in 21st Century Chang'e
| 3(2013) Chang'e 4(2019) Beresheet(2019)
| Chandrayaan 2(2019) Chang'e 5(2020)
| Omotenashi(2022) Hakuto-R(2023)
| Luna-25(2023) Chandrayaan-3(2023)
| Peregrine M1(2024) [1]
|
| [1]
|
| https://twitter.com/IndianTechGuide/status/17446149885918
| 046... 2
|
| https://i.postimg.cc/T1Ccxw2X/Robotic-Moon-Landings.png
| BurningFrog wrote:
| Yeah, the panels should get some reflected light, unless
| they're broken off.
| Karellen wrote:
| If the end where fire comes out starts pointing towards
| space, you are having a bad problem and will not go to
| space^W^Whome today.
| VMG wrote:
| is there a Japanese translation for Vorzeichenfehler?
| snickerer wrote:
| Ri Ben noroketsutogaNi samani. Fu Hao Wu Chai toYan uyori, Yue
| noXin shiidansusutairudane!
| numpad0 wrote:
| nitpick - Wu Chai is used for numerical deltas, Cuo Wu
| would be more appropriate for boolean errors, or Fan Zhuan
| which is inversion, or transliteration for the English word,
| era also works("" is important, era without the elongation
| sign is gills on a fish)
| wigster wrote:
| maybe they used nasa code, but forgot that they were starting
| from the other side of the earth
| broeng wrote:
| I think you might have hit the moo^Wnail on the head.
| analognoise wrote:
| One of 5 countries in the world. Amazing accuracy too - within
| 100m^2, and it lost an engine within 50 feet of the lunar
| surface.
|
| That's an incredible result.
| jacknews wrote:
| Goodhart strikes again.
| dcuthbertson wrote:
| SLIM wins the outdoor high dive championship!
| andyjohnson0 wrote:
| 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.
| HarHarVeryFunny wrote:
| 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).
| jvanderbot wrote:
| 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.
|
| I wouldn't read too much into that choice.
|
| More likely the velocity was a tad too high.
| HarHarVeryFunny wrote:
| 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.
| phh wrote:
| 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.
| numpad0 wrote:
| 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.
| mutagen wrote:
| 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.
| autoexec wrote:
| > The two-step sounds precisely like how all forward-moving
| aircraft land: Rear touch first. The alternative (front touch
| first) is dangerous
|
| That's why I was never comfortable stopping in rollerskates
| or ice stakes.
| wharvle wrote:
| 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.
| YourDadVPN wrote:
| 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.
| mecsred wrote:
| 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.
| blisterpeanuts wrote:
| Good point, but I wonder if some of the attitudinal jets
| could be employed to push it upright, assuming there's any
| fuel left (and power).
| nerdponx wrote:
| > "An abnormality in the main engine affected the landing
| attitude of the spacecraft," the Japanese space agency Jaxa
| said in a statement. [0] [1]
|
| [0]: https://news.ycombinator.com/item?id=39131130
|
| [1]: https://www.bbc.com/news/science-environment-68091389
| titzer wrote:
| FTA:
|
| > 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.
| NiloCK wrote:
| Remember American Bugs Bunny digging through the earth to find
| himself upside-down in Asia?
|
| Life imitates art. Astonishing.
| mariodiana wrote:
| 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 :-)
| fhars wrote:
| You might enjoy the concept of an earth sandwich https://www.
| popularmechanics.com/science/environment/a306338...
| gnramires wrote:
| So... can they give it a bump? :)
| numpad0 wrote:
| 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.
| maxglute wrote:
| Looks like we need to add upsidedownness to the accuracy-
| precision spectrum.
| smeej wrote:
| > 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."
| bee_rider wrote:
| 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!
| wozniacki wrote:
| 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.
| cesaref wrote:
| If you can walk away from a landing, it's a good landing. If
| you use the airplane the next day, it's an outstanding landing.
|
| Chuck Yeager
| Fatnino wrote:
| Well this one isnt being reused.
|
| But the passenger payloads deployed correctly, so we'll count
| that as walking away.
| numpad0 wrote:
| 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.
| smeej wrote:
| 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.
| numpad0 wrote:
| Yes, it dooooes feel a bit of stretch to call it a perfect
| or successful landing with the head stuck in sand,
| undoubtedly...
| coldpie wrote:
| > 63 points, with 60 for the landing and bonus 1 point each
| for scientific camera and two payload probes
|
| S rank! Play next time for SSS!
| keepamovin wrote:
| Well, _ignoring sign_ the result is still correct. Hahaha! :)
| zem wrote:
| 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.
| csa wrote:
| > 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.
| smeej wrote:
| 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.
| mathrawka wrote:
| Actually Japanese quote from the Project Manager, Sakai-san,
| is:
|
| > ironnaYi Wei deXin shiiFei gaKai ki, Jin Hou ,
| koremadedekinakatsutayounamitsushiyongadekiruyouninarunodeha.
| sokogaYi Fan noYi Yi dehanaika
|
| 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.
| ..
| lmm wrote:
| > 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.
| lallysingh wrote:
| They did lose a thruster on the way down.
| KineticLensman wrote:
| 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.
|
| [0]
| https://en.wikipedia.org/wiki/Apollo_12#Lunar_orbit_and_Moon...
| robertlagrant wrote:
| The operation was a success, but the patient died.
| layer8 wrote:
| 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.
| dylan604 wrote:
| The operation was a success, but the patient died 2 days
| later isn't really much better though.
| layer8 wrote:
| It still remains to be seen whether it won't be revived.
| It's more like a coma at present.
| makeitdouble wrote:
| 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.
| karmakaze wrote:
| > in a successful demonstration of its pinpoint landing system
| --although the probe appears to be lying upside-down.
|
| The problem may have been in their metrics. The KPI should have
| been a successful landing for the full range of 'successful'.
| NoZebra120vClip wrote:
| NASA commentators would call this _nominal_. A nominal
| performance.
| coryfklein wrote:
| 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.
| dylan604 wrote:
| 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
| m3kw9 wrote:
| Wait a sec, who's the camera man?
| dan_hawkins wrote:
| "The image was captured by the small baseball-sized robot
| called Sora-Q that was ejected from Slim moments before
| touchdown last Saturday."
|
| https://www.bbc.com/news/science-environment-68091389
| bluSCALE4 wrote:
| 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.
| NelsonMinar wrote:
| That is an absolutely amazing photograph. It tells the whole
| story in a single picture.
| jnsie wrote:
| I'm curious if it is standard practice to name space-related-
| entities in English ("Smart Lander for Investigating Moon, or
| SLIM"), if this is a translation and in Japan they call it
| something different, or why the named it in English in case this
| is an exceptional case.
| cbracken wrote:
| In Japanese it's called both Xiao Xing Yue Zhao Lu Shi Zheng Ji
| (roughly: small moon lander probe) pronounced "ko-gata tsuki
| chakuriku jisshoki" or surimu (SLIM). It's not uncommon to have
| an English name alongside the Japanese one for some scientific
| projects but not always the case -- e.g. I don't recall hearing
| the Hayabusa probe referred to by any name other than Hayabusa
| (which means falcon) in the news.
| jnsie wrote:
| Lovely insight. Thank you!
| boastful_inaba wrote:
| Well I now have context and explanation for the art I recently
| saw!
|
| See this X thread:
| https://twitter.com/MADOguchimoto/status/1750415013343596786
|
| The artist has anthropomorphized the lander - along with the
| "Sora Q" probe coming to document its misfortune.
| vpribish wrote:
| It's not upside down. The up-side is facing away from the camera.
| This is basic stuff about this mission.
| mckirk wrote:
| Can't help but imagine a passive-agressive lander AI...
|
| 'Ha, they told me a million times exactly _where_ I should land,
| but they never specified _how_ I should land'
| phkahler wrote:
| How could the U.S. get to the moon in the 1960's when it seems
| super difficult to do it today? Humans on board.
| jccooper wrote:
| I suspect Apollo spent a great deal more money in quality
| assurance than this $120 million-ish project.
| pbc wrote:
| Maybe there outsourced the landing firmware to Australia :)
| Aspos wrote:
| Can somebody knowledgeable speculate why they are not using RCS
| to try turning the probe? I am guessing RCS engines can be
| reignited and don't need a certain orientation to work, right?
|
| Is Moon's gravity strong enough to cause damage to solar panels
| or antennas if probe tips?
| numpad0 wrote:
| IIUC, it has 12 strategically arranged RCS and 2(1 broken) main
| thrusters, ALL installed on a back facing mounting plate now
| pointing spaceward. I'm kind of suspecting there could have
| been cool factor involved in the decision leading to this
| design.
| Aspos wrote:
| So, yeah, what prevents them from rolling the probe using
| RCS?
| numpad0 wrote:
| The fact that it's all pointing up!
| Aspos wrote:
| But the roll thrusters are not pointing up, are they?
| numpad0 wrote:
| So, a pair of thrusters tilted 45 degrees up and down
| like ailerons can be called roll thrusters, and anyone
| who says that in deadpan straight face as an actual
| spacecraft engineer is completely insane, right?
|
| 1: https://www.isas.jaxa.jp/home/slim/SLIM/assets/img/SLI
| M_exp....
| Aspos wrote:
| Was hoping a spacecraft engineer would explain why tilted
| thrusters can't create enough angular momentum to roll
| the probe in terms which a humble software engineer would
| understand.
| ziofill wrote:
| the engineers must have put a wrong sign somewhere
| sandworm101 wrote:
| It isnt upside down. It wasnt ever meant to land thrusters-down.
| It should be on its side but is on its nose... 90 out rather than
| 180. The BBC has better renderings of how it should have landed.
|
| https://www.bbc.com/news/science-environment-68091389
| gibolt wrote:
| Here is Scott Manley's great discussion of it:
| https://youtu.be/7bFiJvbKyPs?si=EPXhBYba3XnQN1YB
| FredPret wrote:
| This is exactly the type of thing that happens to my Kerbals.
|
| It's vindicating to learn that even the pros struggle to land on
| a particular spot and end up knocking over their moon lander
| anyway.
|
| Of course, their environment is much more detailed than KSP and
| doesn't have a quick-save button.
|
| Space is hard.
| freeopinion wrote:
| The pinpoint accuracy of the landing is encouraging. As just one
| example of the implications, Japan could now have a mission whose
| purpose was to reach this probe and reposition it. The rescue
| mission could be vastly simplified because they could be
| extremely confident of landing within 100m without accidentally
| landing on the original probe.
| 6R1M0R4CL3 wrote:
| how about turning those engines on the probe ON again and see
| what happens, before its batteries totally go out ?
| wayeq wrote:
| I bet the unit tests all passed though.
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