Mood at the news conference that's going on now is decidedly more upbeat with the lander's "medical" condition being raised from critical to serious. They believe they have a handle on what is wrong (something to do with computer memory) and expressed confidence that they can work around the problem. However, it may take "about 3 weeks" to work it all out. Of particular interest to me was news that they were able to successfully command the computer to shut down. They have not been able to do that since the problem started which meant that the batteries have been discharging much faster than normal. While power from the solar panels will operate the craft during the day, without battery power the heaters will not operate at night subjecting certain critical systems to huge temperature swings which could cause things to physically break. Now that the computer can be shut down again the rover can again recharge batteries by day and temperatures can be maintained at night. Landing of the second MER is set for 10:05 pm MST tonight (Saturday). Patrick
I was plodding away on the treadmill watching the news conference when Pete Theisinger described the problem such as they know it. The embedded software guy in me yelled 'address line' and sure enough he mentioned that possibility a few minutes later. There's a lot of analysis left, but this is quite interesting. The magnitude of the problem would depend very much on which address line it might be. If it's a fairly high-order line, then it might be possible to work around it with a reasonable amount of functionality. I remember one of the large planetary probes (perhaps one of the Voyagers) had some bad memory that they programmed around. That was pretty slick. I've debugged an awful lot of flaky hardware and software, but it's always been sitting right in front of me. I've never had to analyze a piece of gear 100 million miles away. I've always had an awful lot of respect for those engineers at JPL. Good luck to them this time around. Michael
Mood at the news conference that's going on now is decidedly more upbeat with the lander's "medical" condition being raised from critical to serious.
Thanks for that lucid explanation, Michael. Does this mean that Opportunity has the same problem? C. --- Michael Carnes <moogiebird@earthlink.net> wrote:
I was plodding away on the treadmill watching the news conference when Pete Theisinger described the problem such as they know it.
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Not necessarily. If a bad address line had been in the design, that should have turned up long ago when testing the boards. Missing that sort of problem would be on a par with the metric/english snafu that doomed the Polar Lander a few years ago. Taking a generalist approach (since I've never seen any of these boards), I might speculate that a connector had broken or a cable had been pinched. There are more esoteric things that might cause an address problem, but I'd have to have some idea of the system architecture and I don't. But over the last few days, the engineers have doubtless been going through a type of brainstorming that I know very well. Someone proposes a "what if" and it usually gets shot full of holes. But every now and then, someone describes a scenario that would result in all the evidence at hand. That's the "working hypothesis" as described by Pete Theisinger. It's not always right, but good engineers can get really seriously engaged by the process. It's fun and it makes you crazy when you look up and realize you're four hours late for supper. We'll just have to sit on the sidelines and see what happens. I'm glad that NASA's being open about this--it's nice seeing them not playing the stuffy beaurocracy they sometimes are--and giving us a chance to see the analysis unfold. I hope that it gives people a chance to see how engineering works, since the typical TV portrayal of engineers is pretty dismal. Hey, fingers crossed for tonight! Michael
Thanks for that lucid explanation, Michael. Does this mean that Opportunity has the same problem?
C.
--- Michael Carnes <moogiebird@earthlink.net> wrote:
I was plodding away on the treadmill watching the news conference when Pete Theisinger described the problem such as they know it.
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participants (3)
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Chuck Hards -
Michael Carnes -
Patrick Wiggins