It's only fitting that since I did a good night post to India's lunar lander Vikram and rover Pragyan when they turned off for the lunar night (and actually turned off for good), I should do one for JAXA's SLIM lander and it's two miniature Lunar Excursion Vehicles. (Again, with apologies to Margaret Wise Brown)
As predicted, SLIM shut down as the sun set on Mare Nectaris January 31, here on EST.
Japan's historic SLIM moon lander has powered down ahead of a likely mission-ending cold lunar nighttime — but not before grabbing some final images and loads of science data.
JAXA's SLIM account on X, formerly Twitter, posted a final image taken by SLIM's navigation camera on Jan. 31 Japan time, while stating that the agency confirmed the spacecraft had entered a dormant state as expected.
There's no denying that SLIM's accomplishments were limited by landing upside down, apparently caused by the failure of one of the two engines that were used for landing. It's reasonable to call it a partial success, but JAXA is talking bigger than that.
But whether or not SLIM wakes up, the spacecraft has hit its full and extended mission goals by achieving a precision landing, deploying a pair of small rovers and demonstrating their interoperability, and obtaining a wealth of science data.
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"Based on the large amount of data we have obtained, we are proceeding with analyses to identify rocks and estimate the chemical composition of minerals, which will help solve the mystery of the origin of the moon," a Google machine translation of a Feb. 1 JAXA statement read.
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"We will announce scientific results as soon as they are obtained," the statement added.
Much like India's Vikram and Pragyan, we can't confidently state the SLIM is done, but neither vehicle was designed to survive the brutally cold lunar night. All we can say is that the probe will stay "asleep" until sunrise in just about another 14 or 15 days.
As a tribute, the crew that kept monitoring and working to get what they could out of the lander.
JAXA team from their X (Twitter) posts.
How hard is it to design a probe that will go into standby for 14 days? All that work for something to last, at most, 14 days if it landed correctly.
ReplyDeleteCrazy inefficiency.
Beans, have you ever considered the thermal environment that batteries would have to endure during the long, cold Lunar night? The batteries and other electronics have to be kept "warm", and that takes energy. They didn't/couldn't provide the necessary energy storage (batteries or TNG's) to stay warm. so the craft had a limited life even if things had gone swimmingly.
ReplyDeleteWelcome to the wonderful world of remote sensing. Really, really remote sensing...
Yes I have considered the thermal environment. One of the joys of one of my job at Gates Battery Plant north of Gainesville, FL back in the day was I got to sit down with some of the brains at Gates Aerospace who were working on batteries for Space Station Freedom and various other space programs. They knew in the late 80's how to build small to medium battery packs that handle thermal extremes, even to having batteries with batteries so the secondary batteries only handle thermal lows.
DeleteYes, it's difficult engineering but it's a known known issue. It's not a known unknown issue, nor are any unknown unknowns having to be dealt with, as, so far, there are no weird energy/battery eating moon thingies... yet, as far as we know...
Seriously though, it's more an issue with experiment/instrument space vs infrastructure space. Batteries and batteries within batteries to keep the main batteries warm for 14 days are infrastructure. JAXA chose to scrimp on infrastructure vs instruments and it shows, sadly, in that they got, what, 4 days of telemetry.
Though if the whole reason for the mission was to test out the weird landing system and everything else was extraneous, then the mission was... not a success. Did not stick the landing. Landed in a way that was non-viable for instrument success.
Pretty much a soft failure of a mission no matter how you see it.
I went to bed before all this conversation last night, and this is much of what I was going to say, but there's one thing I was going to say.
DeleteI think the only issue is the batteries. Semiconductors and passive components aren't going to be damaged by sitting at lunar night temperatures. They typically don't even fail to operate at temperatures below their rated operating temperatures (I'll guess -55C), they just operate differently and don't meet their specifications. When they're warmed back up to their rated temperatures, they'll meet their specs again. Wires, solder joints, interconnects, and all are designed for that.
BTW, Beans: the little I know about batteries originally came from the Gates applications engineering manual, for a box I was designing for the Space Station, back around 1990. I have no idea if it ever really flew, and if it flew, I think it would have been obsoleted by now.
No, the stopping of Space Station Freedom killed Gates Aerospace. Dead. And led to the selling of the whole Gates (non-car battery) Energy to Energizer, which refused to push Li-Ion batteries and to making positive changes with the NiCd and NiMetal Hydride battery lines.
DeleteWhich led to the Alachua County plant going tits-up by 1995. All those jobs, all that money in our county, all that research and development, all of it hinged on Space Station Freedom and the aerospace battery contracts and other contracts based upon developments from SSF.
One of the things that Gates Aerospace had achieved was survival of the batteries due to 'rapid' thermal cycling from the batteries being exposed to sunlight and darkness. The same survival due to orbital cycling would also be useful on the Moon or on spaceprobes. All due to their research and development of batteries within batteries to keep the main battery warm (or warm it up.)
Sad, so much promise gone. Kind of like Sierra Space having to basically do all that research for inflatable habitats after Bigalow had already done all that research and then went belly-up thanks to the Covidiocracy (yeah, they were in trouble but the Cough pushed them over the edge, actions by the Federal Government and Nevada's government being the death-knell.)
It's not "hard", Beans, but you have some pretty severe mass restrictions with the launcher they used. Another pound of batteries, or a pound of insulation?
ReplyDeletePersonally, I wouldn't be so fast on the switch when the Sun rises. I'd give it some time to warm-up a bit, and let the battery warm a bit, before I attempted to power it up.
Yep. As I said in response to Igor above, it's an infrastructure vs instruments balance. JAXA chose... poorly from a long-endurance viewpoint.
DeleteAnd, you know, all of this wasn't new in the early 70's. We knew all of this by the beginning of the Surveyor probes, which were launched using Atlas-cargo rockets. The H-II has similar characteristics to the Atlas used to launch said Surveyors, including payload, so...
Seriously, this shouldn't be this hard. Surveyor used a more energetic path to the Moon, while SLIM used a low-energy method which should have allowed for more 'cargo' vs fuel.
As to letting the electronics and the battery warm in the sunlight, that's a serious 'duh' of which I think most engineers don't think about.
Hard-won knowledge based on Field Service experience and a dash of common sense.
DeleteJapan chose even MORE poorly from a mission success viewpoint. If your vehicle is not sufficiently redundant to survive a single failure, well...
DeleteAnd "engine out" is a single failure!
Beans, why not put your questions to JAXA?
ReplyDeletehttps://global.jaxa.jp/activity/pr/inquiries/index.html