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#1 Re: Unmanned probes » Spirit & Opportunity 2 - Continued from original thread » 2004-01-28 05:40:41

I would think that a 15 watt drain is *very* serious.  I believe that the rover's solar panels are supposed to generate 750watt-hours per day (at the start of the mission. This will decrease over time due to dust of course)
Also, Sprit was generating less than that at the start if its mission, due to the atmosphere being more dusty. I don't know the figures for Opportunity, since Nasa prefers to give us pretty pictures instead of telemetery.

Anyway, if we assume that the 15watt thermostatically controlled heater is on half the time (12 hours, at night when it's coldest), thats a daily power requirment of 12*15, i.e 180watt-hours. That's 25% of the power budget, not allowing for charge/discharge losses in the batteries.

This will get much worse, as the solar illumination decreases, the panels get dusty, the batteries age, and average temperatures drop due to seasonal changes on Mars.

Still, 15watts seems quite large for a simple joint heater. Perhaps that figure is not accurate, or the units given are wrong (i.e. 15watt-hours instead of watts?)

Anyone got more information on this issue?

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