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Japan's Moon lander makes it through another lunar night
- p1mrx 3y agoHere's a paper about the batteries they used, but I don't see any mention of temperature testing below 0°C: https://www.jstage.jst.go.jp/article/tjsass/66/6/66_T-22-48/_pdf https://www.jstage.jst.go.jp/article/tjsass/66/6/66_T-22-48/...
- Woovie 3y agoThey 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 https://ieeexplore.ieee.org/document/1145732
- dylan604 3y agoIs 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 3y agoJAXA 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 https://space.stackexchange.com/a/37374) So ya, they probably didn't do any significant testing below 0C.
- inamberclad 3y agoMan, 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 3y agoGenuine 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 3y agoI 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 3y agoProbably 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 3y agoI 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 3y agoWhy 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 3y agoIn 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).
- jordz 3y agoDoes anyone else find it strange that craters on the moon can reach a temperature lower than absolute zero, according this article anyway? =)
- ryan_j_naughton 3y agoCan someone help me understand - besides batteries, why does extreme cold negatively impact other electronics?
- Mkengine 3y agoMost 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 3y agoCouldn'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)?
- deleted 3y ago[deleted]
- dotnet00 3y agoOf 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 3y agoIt'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 3y agoNormally 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 3y agoI 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/ https://www.itsquieterfilm.com/