[X] My Assistant

[djellison]

Expect a quiet few sols - http://www.lpl.arizona.edu/~lemmon/mars-tau-b.html
SOL TAU
5097 0.65
5098 0.64
5099 0.67
5100 0.64
5101 0.60
5102 0.60
5103 0.61
5104 1.55
5105 ****
5106 2.12

[scalbers]

How severe is this dust storm compared with others weathered by Opportunity? Estimating the total solar radiation in heavy dust conditions is an interesting exercise and the scattered light will be the main contributor when the direct radiation diminishes. I'm trying to model all this with my simulated weather imagery package. A key factor would be how much light gets absorbed for each scattering event (a single scattering albedo of about .90 in green light and .97 in the IR see figure 8). A tau of around 10 would only cut the light down about 50% if absorption wasn't a factor. I can note a Titan analog with a tau of around 8 and estimates of 10% of the visible band light getting through when absorption is factored in. Deimos' formulation in post #28 is reasonable. As mentioned more light in the IR will help for the solar panels. Serpens' YouTube video is pretty impressive.

[mcaplinger]

How severe is this dust storm compared with others weathered by Opportunity?

The worst previous was back in 2007: "Due to extensive dust storms in Mars' southern hemisphere causing record atmospheric opacity levels, Opportunity is currently experiencing its lowest power levels to date. The tau measurement as of sol 1225 is 4.12, resulting in a mere 280 watt-hours of array energy. A tau measurement of 5.0 would result in approximately 150 watt-hours."

https://mars.nasa.gov/mer/mission/status_op...07.html#sol1382

Keep in mind that we have two competing measurements, the tau determined by analysis from Pancam images, and the actual solar production. From an engineering perspective, only the second one is of direct interest. I'm sure they have a model to go from the first to the second, but once you have an actual number for the second you should use it. And of course for any model, you not only have to know the irradiance but also how much dust is on the panels.