QUOTE (djellison @ Sep 7 2008, 10:34 AM)
I'd also add that the compact, well insulated WEB of the rovers probably performs a far better job of insulating itself than the Phoenix design.
Not my specialty, but I imagine so. The PHX EBs were originally spec'd for an equatorial mission, and they have no RHUs. They're beefed up enough that energy dissipation into the EBs occasionally affected operations due to the need to avoid being too hot (as with the MERs). But of course the PHX payload could dump more energy into the boxes than the MERs could. Spirit demonstrates another difference--the rovers can sleep 23.9 h /sol if needed. PHX requires periodic, brief housekeeping wakeups like Mars Polar Lander would have needed. The way PHX works is suited to one of the goals, getting diurnal coverage of the atmospheric state.
So on the face it is shocking to see that PHX survival energy is comparable to the best days of Spirit's life ... but that is just the difference between the missions. The PHX panels were designed for PHX (OK, M'01, but for the way the lander uses energy) -- lots of area, no worries about mobility. But the MER's of course would need much more energy per day with no RHU and a peak temperature of -30 or so, even ignoring the other considerations.