Mars Rover Spirit Reaches Winter Tilt

An anonymous reader writes "The Mars rover Spirit has been inching carefully down the north slope of the feature 'Home Plate' to tilt its solar panels into the sun to survive the long Martian winter. On Friday, it reached a tilt of 29.9 degrees, probably the final tilt it will reach for the winter. Although it's used the tilt strategy to increase power over the Martian winter twice before, this year it's especially critical, since a global dust storm last summer has left the solar-powered rover covered with dust and starved for power. Geoffrey Landis, one of the MER scientists, commemorated Spirit's trek to the winter haven with a sonnet on his blog. (The second of the two rovers, Opportunity, is at a landing site that's not as far into the southern hemisphere, and hence has less need to find a tilted surface.) OSU has a website explaining some of the software used to visualize the terrain to optimize the tilt, and for the latest news, the ongoing log of the rover status is updated weekly."

Comments

Re:Stupid but obvious

[jasonwea]

A quick Google isn't turning up anything authoritative, but from memory:

For the original 90 day mission length, running out of juice due to dusty panels would not have been a concern. It would have just been another thing to break and would have added to the mass of the rover, quite possibly costing valuable capacity for other scientific tools.

[insert rant about how some of that war budget could do wonders for NASA]

Re:Stupid but obvious

[splutty]

- More Moving Parts
- Weight
- Dust too fine to be brushed off easilly
- Chance to actually reduce power generation on failure by blocking the solar panels
- Needs power itself

And all this aside from the fact that asking someone to make a solar panel wiper for Mars is going to be an enormously expensive and involved operation. Windspeeds, airpressure, particle count, gravity, temperature all play a part in this. And anyone using windshield wipers on their car knows how unreliable they are to begin with.

"I disagree" != "Troll"

[pla]

Dear mods - Please learn the difference between "I do not agree, you have offended my delicate sensitivities", from "Troll" and "Flamebait".

Though confusingly similar to the untrained eye, people can legitimately disagree with your personal worldview without trolling.


Although metamoderation almost always vindicates me, and I couldn't care less about my karma ("excellent", BTW) I do find it somewhat discouraging that zealots (whether religious, political, or Apple) manage to silence any discussion on topics they don't like by modding to below the default visible threshold.

If you disagree with me, say so. You might even convince me of the error of my ways. Modding me down just reinforces the view that those who silently disagree with me really have no rational arguments worth hearing.

Dust removal, hard but possible

[Geoffrey.landis]

We actually had built a dust experiment to test out some methods of removing dust. It had been scheduled to fly on the Mars-2001 Surveyor Lander, but the 2001 lander mission was cancelled after the failure of the 1999 Polar Lander (which used the same basic spacecraft design). In fact, we talked about dust removal technology for the MER, but it simply turned out that the most reliable solution was to increase the size of the panels so that they would still be at nominal power after 90 days worth of calculated dust accumulation. (My Pathfinder data showed about a quarter of a percent loss of power due to dust per (Martian) day, for what it's worth, but the longer term data looked hint that it was leveling out with time). There's just a lot of reliability in the no-moving-parts solution, and as a bonus, it gave the rover quite a bit of power margin at landing (and, in fact, after landing too-- the dust-related power loss in fact does tail off.)

With that said, let me note that dust removal is probably a bit harder than you realize. The optical data showed that suspended dust is extremely fine-- the cross-section weighted average particle radius is about 2.5 microns, so these particles are about the size of the particles in tobacco smoke. Particles this fine are predicted to adhere extremely well, by van der Waals and electrostatic forces. Picture trying to use your windshield wipers to clean the dust off your windshield, without using the wiper fluid. (and wiper fluid is tricky on Mars, too; you need it to stay liquid for long enough to run the wiper, and neither evaporate or freeze before it hits the panel). And blowing dust off is very tricky-- the atmospheric pressure is less than 1% that of Earth's. We could carry fluid, or compressed gas, but those would be consumables-- and if we had designed the mission and budgeted consumables for a 90 sol lifetime, we'd have run out of them years ago anyway, so we'd be in the same position we're in now anyway.

A feather duster might work, but feathers almost certainly violate the planetary protection policy :)