[HN Gopher] Japan's Moon lander makes it through another lunar n...
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Japan's Moon lander makes it through another lunar night
Author : LorenDB
Score : 168 points
Date : 2024-04-25 16:27 UTC (3 days ago)
(HTM) web link (www.theregister.com)
(TXT) w3m dump (www.theregister.com)
| p1mrx wrote:
| Here's a paper about the batteries they used, but I don't see any
| mention of temperature testing below 0degC:
|
| https://www.jstage.jst.go.jp/article/tjsass/66/6/66_T-22-48/...
| Woovie wrote:
| They seem to reference a paper at "19)"[0] which goes into much
| further detail. It's odd though reading where they reference
| it, they talk about nothing below 0 C at all.
|
| [0] https://ieeexplore.ieee.org/document/1145732
| dylan604 wrote:
| Is that because that's the limit of the sensor or an actual
| reading. It's something that happened with dosimeters at
| Chernobyl where people didn't realize the levels were so bad
| until someone pointed out that the sensors were maxed out
| because the levels were higher than the range the units were
| designed to display. I would hope that's not the reason, but
| it has happened in the past
| icegreentea2 wrote:
| JAXA said that the mission design for the lander was one lunar
| day, which generally doesn't involve dropping much below 0C
| (https://space.stackexchange.com/a/37374)
|
| So ya, they probably didn't do any significant testing below
| 0C.
| inamberclad wrote:
| Man, that thing keeps chugging! Great news for JAXA, I wonder
| what additional science they're getting out of it. I know that we
| would have used any extra time for further downlink. So much
| data, such little bandwidth!
| konschubert wrote:
| Genuine question: What kind of relevant data is this thing
| collecting?
|
| I would guess the main value is in practicing the technological
| skills of sending a thing to the moon and maintaining
| connection with it.
| inamberclad wrote:
| I took a look at the press releases and I can't see a lot of
| information about payloads, but if they're operations were
| anything like Nova-C (which I worked on), then they generated
| lots more data on landing than they could downlink at the
| time.
| dotnet00 wrote:
| Probably environmental data, mainly temperature, and of
| course, they get to see how it progressively fails. They're
| starting to see some temperature sensor and battery issues
| for instance.
| zoom6628 wrote:
| I would suggest main value is in seeing how this thing still
| lives! It was designed for one lunar day and has survived 3. So
| for learning about what still works and what doesn't this is
| invaluable for future reliability engineering.
| chasil wrote:
| Why can't they just put the electronics in a refrigerator
| that can drop to these temperatures?
|
| Are we able to also simulate the radiation in a laboratory?
|
| I will wager that this was done prior to launch, and current
| longevity is not a complete surprise.
| dotnet00 wrote:
| In this case there does not appear to be any public
| evidence that they did much testing in below freezing
| temperatures. This isn't to say that they couldn't do the
| testing, just that they didn't do it because the mission
| parameters did not require it. There don't seem to have
| been many "ongoing experiment" type sensors on the lander
| which would be significantly useful to keep going longer
| than the initial mission.
|
| As for radiation, I attended a lecture series last year
| about the various kinds of radiation testing involved in
| designing hardware for satellites, they probably did do
| similar things to those for satellite electronics (stuff
| like firing beams of IIRC electrons over the PCBs to see
| what parts might need reinforcement/redundancy against
| random charged particle strikes).
| yencabulator wrote:
| Part of the unknown is likely what temperatures, how much
| radiation, of what kinds. The SLIM lander can land in
| places previous automatic landing systems couldn't, so it's
| very possible this area has never had such measurements
| done. There's still much we don't know about the moon,
| including how cold the lunar night actually is in different
| areas.
|
| Also, the _point_ of SLIM was to test the new automatic
| landing system, a combination of camera-based navigation
| and a new landing strut system meant to handle inclines.
| 100 meter precision instead of previous 20 km. Everything
| that comes after that is near-free extra data.
| jordz wrote:
| Does anyone else find it strange that craters on the moon can
| reach a temperature lower than absolute zero, according this
| article anyway? =)
| qwertox wrote:
| > The surface temperature on the Moon can drop below -150degC,
| and the temperature in some craters can get as low as -247degC.
|
| -273,15degC < -247degC.
| mongol wrote:
| Crazy cold.
| asah wrote:
| 26 Kelvin!
| jordz wrote:
| It was edited. It definitely had -274 (:
| tzot wrote:
| Perhaps you misread -247degC as -274degC?
| ryan_j_naughton wrote:
| Can someone help me understand - besides batteries, why does
| extreme cold negatively impact other electronics?
| Mkengine wrote:
| Most materials contract when they cool down. For example,
| differential contraction between metal contacts and
| semiconductor materials can cause them to detach or break,
| disrupting electrical connections. Also extremely low
| temperatures can lead to changes in semiconductor properties
| such as carrier mobility, which affects how efficiently
| electronic signals are processed.
| user_7832 wrote:
| Couldn't all connectors be made with some kind of expansion
| joint, like how infrastructure (bridges etc) are made? Given
| how they use older nodes, this may perhaps even be possible
| for transistors (Assuming they also have such expansions)?
| dotnet00 wrote:
| Of course you can do all sorts of things to make the
| electronics able to survive, but ultimately that supposedly
| just wasn't part of the initial design requirements they
| settled on.
| yencabulator wrote:
| It's good to remember that the total lifetime budget of
| this lander is only $121.5 million, and that includes all
| the staff still receiving data. It was always intended to
| be a technology demonstrator, not an ongoing science lab.
| Tade0 wrote:
| Normally materials in chips are selected so that they have
| similar thermal expansion coefficients - otherwise they
| would fall apart just from reaching normal work
| temperatures.
|
| There's another problem here: below a certain temperature
| semiconductors become insulators. You're running the risk
| of your chip shutting down in a disorderly manner.
| liampulles wrote:
| I recently watched a documentary about the ongoing Voyager
| missions[1], and this same tactic (turning instrument heaters off
| to save power, hoping the instruments still produce useful data)
| continues to be used with success.
|
| In that documentary, it was remarked by one of the engineers that
| scientists often designed these instruments to be more robust
| than what was expected.
|
| [1]: https://www.itsquieterfilm.com/
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