Wouter,

On Sat, 14 Apr 2007 21:46:53 +0200, wouter van ooijen wrote:

> > How Mars Global Surveyor was lost:
> > 
> > http://planetary.org/news/2007/0413_Human_and_Spacecraft_Error
> > s_Together.html
> > 
> > in light of the recent postings on how to create bug-free software, I 
> > thought this might be of interest.
> 
> The bold text that starts the article is IMHO misleading: "resulted from
> mistakes made by both the human operators and the spacecraft's onboard
> fault protection software." The rest of the text does not mention any
> error in the on-board software, only errouneous parameters upload from
> earth. Pure human operator errors.

Well *all* errors are human in origin - the machine didn't write its own software!  :-)  But they did say that the 
onboard software made a couple of mistakes,  one in trying to orient the spacecraft in a way that faced a battery to 
the Sun (implying that the battery orientation wasn't a parameter it took notice of, or even had), and one in 
misinterpreting high battery temperature as due to overcharging.  Possibly also misinterpreting the "stuck" motor as a 
hardware fault, rather than a parameter error.  Maybe there should have been a set of fallback "absolute limit" 
parameters that are hardwired - appropriate for physical parameters such as the end-point of a jack-screw or 
whatever - which the onboard software checks against the live parameters its using.

Cheers,


Howard Winter
St.Albans, England


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