Dan DeConinck posted:

Why is the mars rover's lifespan 90 days ?

Communication sats last years, even 10+.

Pioneer is 20 years old. Doesn't it have nuclear power ?

The rover is powered by solar panels and has internal batteries. Eventually,
enough dust will collect on the panels and the batteries will stop holding
their charge well enough so that sometime after 90 "sols", there may or may
not be enough power available to keep the lander electronics warm and the
rover completely functioning. The 90-sol lifetime is a "nominal" one (that
is, the rover is designed to last that long), but it may go somewhat longer
(Pathfinder was designed for only 30 days of functionality, but lasted nearly
three times that). Another factor is sun angle, which after 90 days, becomes
less favorable for generating electrical power from the solar panels than it
is now. If the rover was RTG powered (ie: nuclear "batteries"), the power
would not be an issue, but such power generators are expensive, heavy, and not
popular with some environmentalists. Clear skies to you.

David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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