What really happened to the software on the Mars Pathfinder spacecraft? • Hacker News Board

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

#21

Post by ErsatzVerkehr » Fri, Jul 05, 2013, 6:25 AM UTC

lisper wrote: post #18

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…

A hardware problem is still a problem, though... Why would it be "written off"?

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

#22

Post by taspeotis » Fri, Jul 05, 2013, 6:27 AM UTC

raverbashing wrote: post #20

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?

Took quite a bit of Googling, but it looks like it's optimistic concurrency control.

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

#23

Post by willvarfar » Fri, Jul 05, 2013, 6:46 AM UTC

mdturnerphys wrote: post #16

Did anyone else notice the "?reposting" in the URL? It looks like someone else submitted this 8 hours earlier ( http://news.ycombinator.com/item?id=5991503 ).

none of us are trawling /new and upvoting anything, sadly. Great posts regularly don't get a single click the first time through the HN mill. To be on the front page an article needs to be 1) clickbait title, 2) good content, 3) lucky, 4) posted when the Americans are awake.

Oh well.

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

#24

Post by pjmlp » Fri, Jul 05, 2013, 6:54 AM UTC

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.))

REPLs are very good for interactive development, regardless of the language.

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

#25

Post by lisper » Fri, Jul 05, 2013, 7:08 AM UTC

ErsatzVerkehr wrote: post #21

lisper wrote: post #18

Earlier quoted context omitted.

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…

A hardware problem is still a problem, though... Why would it be "written off"?

Because it would have appeared to be a problem with the test rig, not the flight hardware.

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

#26

Post by javert » Fri, Jul 05, 2013, 8:12 AM UTC

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…

> Prove its correctness

That's probably an overstatement :P

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

#27

Post by alemhnan » Fri, Jul 05, 2013, 8:23 AM UTC

javert wrote: post #26

kamaal wrote: post #12

Earlier quoted context omitted.

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…

> Prove its correctness That's probably an overstatement :P

well, sure it is right now because we are not able to do so yet. But there is a lot of research in computer science trying to do made that statement less over! :)

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

#28

Post by kotnik » Fri, Jul 05, 2013, 9:45 AM UTC

For a (much) more detailed story, go here: https://www.cs.duke.edu/~carla/mars.html

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

#29

Post by lucaspiller » Fri, Jul 05, 2013, 10:09 AM UTC

willvarfar wrote: post #23

mdturnerphys wrote: post #16

Did anyone else notice the "?reposting" in the URL? It looks like someone else submitted this 8 hours earlier ( http://news.ycombinator.com/item?id=5991503 ).

none of us are trawling /new and upvoting anything, sadly. Great posts regularly don't get a single click the first time through the HN mill. To be on the front page an article needs to be 1) clickbait title, 2) good content, 3) lucky, 4) posted when the Americans are awake. Oh well.

The last bit is the main thing I think. The original has exactly the same title and original poster has a lot higher karma.

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

#30

Post by ghshephard » Fri, Jul 05, 2013, 11:15 AM UTC

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…

A system reset might be easier to overlook than other errors. When we test our gear, something like a 2 dB loss (out of 30 dB initial transmit power) anywhere within our operating range (-40 degrees to +85 degrees) would likely result in another board spin (and a 15-20 day delay in the that particular product), but, a NIC reset during a 72 hour soak (where we cycle the temperature up and down multiple times), isn't something we would get stressed over. That's the entire idea behind having a watchdog - if something looks amiss, start clean.

It may have also been the case in the Pathfinder era that a "Reset" was acceptable behavior.

Also - depending on the nature of the watchdog reset - they may not have been able to capture a core dump - in which case, if there only a few resets - really hard to track down on a tight schedule.