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What really happened to the software on the Mars Pathfinder spacecraft?

rapitasystems.com

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Re: What really happened to the software on the Mars Pathfinder spacecraft?

#11

Post by ams6110 »

gizmo686 wrote: post #6
ams6110 wrote: post #4

Engineers later confessed that system resets had occurred during pre-flight tests. They put these down to a hardware glitch This doesn't really ring true to me. Sounds like the sort of programmers who are inclined to blame "cosmic rays" for odd behavior that they don't understand. I would think on a mission as expensive as the pathfinder, and knowing that once the hardware is launched you will never have physical acc…

>\Sounds like the sort of programmers who are inclined to blame "cosmic rays" for odd behavior that they don't understand. In fairness, they go out of their way to harden they computers against cosmic rays. I am sure that they make a decision about what an acceptable amount of cosmic ray induced error is, and design the system knowing that it will happen. Having said that, I agree that having unexplained problems on…

I didn't mean they were blaming cosmic rays. I've worked with completely terrestrial programmers who are prone to blaming "cosmic rays" or "compiler bugs" for their own mistakes... and the claim that the Pathfinder engineers chalked up the reset to a "hardware glitch" reminded me of those sorts of rationalizations.

Re: What really happened to the software on the Mars Pathfinder spacecraft?

#12

Post by kamaal »

ams6110 wrote: post #4

Engineers later confessed that system resets had occurred during pre-flight tests. They put these down to a hardware glitch This doesn't really ring true to me. Sounds like the sort of programmers who are inclined to blame "cosmic rays" for odd behavior that they don't understand. I would think on a mission as expensive as the pathfinder, and knowing that once the hardware is launched you will never have physical acc…

It was the same thought I had too.

I remember reading it in a article some time back. Software for this sort of systems isn't written like we do. Come to office, fire up IDE and code. Rather by and large software is first written on paper and the possible side effects and correctness is first verified thoroughly.

I know of a embedded programmer from 80's/90's era. He has done embedded programming both in assembly and C heavily. I recently happen to run into his journals/notes at his home. Turns out even for things as simple as a telephone answering machine or a ECG machine. They would heavily work things out on the paper first. Prove its correctness, once they've got it all figured out then they go out and do it on an editor. I mean it was so well organized on paper, he had all the tests figured out to there most extreme edge cases and he had everything on paper.

I did a small project with him and it was fun to watch him work. It felt like bulk of the work happened on paper first and then on the real tool. There was hardly any room for error, bugs were very minimal. And beyond all, working on paper has its biggest benefit. There is no dangerous distraction called the 'web browser'.

Re: What really happened to the software on the Mars Pathfinder spacecraft?

#13

Post by Sami_Lehtinen »

I've been using OCC to avoid this problem with my apps, and I couldn't be more happy. It mostly voids issues with priority inversion. (Not exactly, if using pre-emtive scheduling and long running high priority tasks.) It doesn't matter if something is stuck, looping, crashes or so, it still won't bring down the whole system. + Offers great parallel performance as long as resources aren't too widely shared. I got sick'n'tired administering (and creating) systems as DevOp, when I were using traditional locks and all the problems which those caused, even on top of poor performance.

Re: What really happened to the software on the Mars Pathfinder spacecraft?

#14

Post by jon2512chua »

taspeotis wrote: post #2

Seeing this article reminds me of http://www.fastcompany.com/28121/they-write-right-stuff

Interesting read.

Though correct me if I'm wrong, but I find the article rather biased against iterative/agile way of writing software. Don't get me wrong, I believe there's a time and place for over-2500-pages-of-specs-for-6000-LoC kinda process, but the article seems to be saying that quick iterations are of the stone age/how little children do it and that the way the on-board shuttle group software team wrote their software is the "perfect" way.

Re: What really happened to the software on the Mars Pathfinder spacecraft?

#15

Post by taspeotis »

jon2512chua wrote: post #14
taspeotis wrote: post #2

Seeing this article reminds me of http://www.fastcompany.com/28121/they-write-right-stuff

Interesting read. Though correct me if I'm wrong, but I find the article rather biased against iterative/agile way of writing software. Don't get me wrong, I believe there's a time and place for over-2500-pages-of-specs-for-6000-LoC kinda process, but the article seems to be saying that quick iterations are of the stone age/how little children do it and that the way the on-board shuttle group software team wrote thei…

It's been a while since I've read the article, but I skimmed over it and didn't really get that vibe from it.

I felt it was more "these guys are extreme outliers in terms of software quality, but also extreme outliers in terms of process."

Re: What really happened to the software on the Mars Pathfinder spacecraft?

#17

Post by DigitalJack »

kamaal wrote: post #12
ams6110 wrote: post #4

Engineers later confessed that system resets had occurred during pre-flight tests. They put these down to a hardware glitch This doesn't really ring true to me. Sounds like the sort of programmers who are inclined to blame "cosmic rays" for odd behavior that they don't understand. I would think on a mission as expensive as the pathfinder, and knowing that once the hardware is launched you will never have physical acc…

It was the same thought I had too. I remember reading it in a article some time back. Software for this sort of systems isn't written like we do. Come to office, fire up IDE and code. Rather by and large software is first written on paper and the possible side effects and correctness is first verified thoroughly. I know of a embedded programmer from 80's/90's era. He has done embedded programming both in assembly and…

That fricken web browser. I had to resort to sticking hacker news and a few others in my hosts file pointing back to 127.0.0.1. (On xp)

Re: What really happened to the software on the Mars Pathfinder spacecraft?

#18

Post by lisper »

ams6110 wrote: post #4

Engineers later confessed that system resets had occurred during pre-flight tests. They put these down to a hardware glitch This doesn't really ring true to me. Sounds like the sort of programmers who are inclined to blame "cosmic rays" for odd behavior that they don't understand. I would think on a mission as expensive as the pathfinder, and knowing that once the hardware is launched you will never have physical acc…

Pathfinder was not all that expensive by space mission standards. The total budget was only about $200M or so, which was an order of magnitude less than typical prior missions.

Also, while I was not personally involved in Pathfinder, I was in the research program that led up to it. We were doing things that had never been done before, including the first use of an off-the-shelf commercial operating system on a space vehicle. We were under tremendous time and budget pressure, and so was Pathfinder. The idea that an intermittent system reset could be written off as a hardware problem is entirely plausible.

Re: What really happened to the software on the Mars Pathfinder spacecraft?

#19

Post by lisper »

dandrews wrote: post #10
dschiptsov wrote: post #9

There were rumors that older generations of spacecrafts fly on lisp systems. Nevertheless, you see, they had C-interpreter (REPL) there.))

You're likely thinking of this essay: http://www.flownet.com/gat/jpl-lisp.html

Or this: http://www.youtube.com/watch?v=_gZK0tW8EhQ

Re: What really happened to the software on the Mars Pathfinder spacecraft?

#20

Post by raverbashing »

Sami_Lehtinen wrote: post #13

I've been using OCC to avoid this problem with my apps, and I couldn't be more happy. It mostly voids issues with priority inversion. (Not exactly, if using pre-emtive scheduling and long running high priority tasks.) It doesn't matter if something is stuck, looping, crashes or so, it still won't bring down the whole system. + Offers great parallel performance as long as resources aren't too widely shared. I got sick…

What's OCC?
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