The Storm, Dust storm of 2007 |
The Storm, Dust storm of 2007 |
Jul 5 2007, 05:57 PM
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#1
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Member Group: Members Posts: 710 Joined: 28-September 04 Member No.: 99 |
Oh no...This is getting bad:
The new and potentially bleak outlook is a stark shift from the prognosis earlier this week. The dusty squall has reduced direct sunlight to Mars' surface by nearly 99 percent, an unprecedented threat for the solar-powered robotic explorers. If the storm keeps up and thickens with even more dust, officials fear the rovers' batteries may empty and silence the robotic explorers forever. Opportunity's energy-gathering ability has been slashed to a dangerous 280 watt-hours-enough power to light only three 90-watt light bulbs. "The worst-case scenario is that enough dust in the sky decreases solar energy to the point that we have to shut down too many things to save power," Lemmon said. "The rovers keep their battery alive by keeping their electronics alive." "The reality of the situation is that we're limited as to what we can do from the ground by cutting power use," Callas said. "If it continues to worsen and stay that way, it's a survivability issue for Opportunity. If Mars wants to kill the rovers, it can." http://www.space.com/news/070705_dusty_rovers.html |
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Jul 10 2007, 10:12 PM
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#2
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
That 255 whr figure for Sol 1225 is bugging me (Sorry Astr0 - feel free to object right back )
I calculate that at a Tau of 4.1 on Sol 1225 for Opportunity she should have generated around 310Whr. All of the other numbers that I've seen recently indicate that the insolation model I'm using underestimates the real values by 10% or so ( e.g. on sol 1221 @ Tau=3.3 the MER team have published a value of 402 Whr when I estimated about 360 Whr ). That would make me expect a real value of about 340 Whr if the Tau value of 4.1 is correct. Furthermore I really suspect that there was at least one small (5% or so) cleaning event sometime between Sol 1211 and 1220 which would put the number closer to 355Whr. The most likely reason for this is that the diffuse Insolation model I'm using becomes increasingly unreliable as Tau rises past ~3 but it is also possible that the 255 Whr number isn't accurate. I'm also very surprised at Opportunity being able to function at all at that level, my understanding all along has been that 270-280Whr is extremely marginal for her given her stuck heater. Very much looking forward to published numbers from the team. |
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Jul 11 2007, 12:06 AM
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#3
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Senior Member Group: Members Posts: 4260 Joined: 17-January 05 Member No.: 152 |
That 255 whr figure for Sol 1225 is bugging me Well, we had that report that began this thread that the direct sun was attenuated by "nearly 99%" (tau = 4.6), with power at 280 Whr. The report was dated the 5th (sol 1225), though the sol is not mentioned in the article. Does that fit your model better?The more recent data show a peak at 4.1, so 4.6 seems to have been an error. I suppose at times like this with everyone wanting tau values, numbers get out that aren't very accurate. Let's hope the clearing trend continues! |
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