Hello Doug,

QUOTE (djellison @ Feb 28 2006, 07:44 PM)

To paraphrase Steve, they will die eventually, I'm sure of that.

I started reading this thread with no recollection at all of hills Grisson, Chaffee and White, and with about as much expectation that Spirit could get that far. Then I started thinking about probabilities. Granted that (as you say) they'll both die one day, but taking into account also the much longer than expected lifespan so far, the cleaning events and so on... surely there

*is* a finite (but small) chance that Spirit could live long enough to reach Grissom. Just to pick a random number, let's say there's a 1% probability. Is that enough to warrant torturing ourselves dreaming of the unattainable? Engineering decisions are surely driven by probabilities. To pull another random example... bridges are built to withstand 100, 200, 400 year storms, (assuming that figure's been correctly calculated by the people with the pulsating frontal lobes and access to the the data & tools needed to work it out...) My local suspension bridge* has a design limit of (IIRC) 100mph winds. Well, 120mph winds are not inconceivable here... but very unlikely;once every four hundred years, IIRC. 80mph, OTOH, happens every other year. So, given that faster enough winds will result in it falling into the river

that's probably a risk worth addressing, either reducing the probability of it happening, or reducing the consequences of it happening.

Looking at the rovers' lifespans from the inverse point of view... if there's a 1 in 400 chance of Spirit reaching Grissom, and assuming she survives the winter and finishes surveying HP,.. is that a high enough probability to merit spending time thinking about consequences? If OTOH JPL decide to continue puttering around the Columbia Hills, and

*then* we find she's still alive after travelling a distance equivalent to Grissom... there's an opportunity cost.

Anyway... I'm happy that, to me, this is purely idle speculation rather than a decision I have to take

*

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