Spirit cleaner? Options

[Ant103]

Hum... I don't know if the rover takes the pictures at the same time. I hope so because I've remarked that they take the exactly same portion of the sky with Grissom Hil at the left. To reveal colors, I apply exacctly the same processing to have a regular following, but I'm aware that ambiant light have an influence on the exposure. And this is one of the parameter that I can control to have a quite perfect series of pictures and compare them.
But, I hope that this board show -partially- the evolution of dust level in the martian air.

[mhoward]

I'm aware that ambiant light have an influence on the exposure

There's more than that going on: the raw JPGs are automatically brightness-stretched before they get to us, so the brightness levels in the individual images are more or less unpredictable. If you are using the raw JPGs, you can't reliably conclude anything about the brightness levels. Still, it's an interesting series of images.

[fredk]

I should add that although the autostretching means you can't trust the overall brightness and colour of the images, you can trust the change in relative brightness across individual images. So that "inversion" effect, where in the early sols the sky is brighter near the horizon, but more recently and especially during the storm the sky is darker near the horizon, is real. Also we can probably trust the increased haziness of the distant peak at later sols.

[Ant103]

Okay

Two other board who show Oppy's and Spirit's panels. To the left, many time before the storm. To the right, just after the maximum level of it :


We can se quickly that solar panels are more clean than the others sols ago.

[mhoward]

True, you can make some very broad qualitative observations; but probably not much, and not very reliably. And even then, you must be careful to take other variables into account, like time of day, to say nothing of filter choice (for Pancam).

[helvick]

I'm sure I heard 3x (i.e. 270 sols for MER )

I heard that somewhere too but it always depends on what you mean by "margin".
The solar panel requirements for the rovers specified that they had to deal with a predicted dust loss rate of 0.18% per Sol which left them at around 700Whr after 90 sols, 600 after 180 sols and 500 after 270 sols. If that rate had been seen consistently throughout the mission with no cleaning Spirit could have lasted until somewhere between sol 750 and 800. You might read that as a 7 or 8x margin.

However the initial power requirement was to be able to deliver a minimum of around 350-400 Whr/sol at 90 Sols so the initial design really only gave about a 2x margin after 90 sols and given that a single storm like the one we are seeing right now would reduced that to zero, you could argue that there was no margin at all.

[climber]

I'm sure I heard 3x (i.e. 270 sols for MER )
Doug

So it'll be 1800 Sols for MSL. Well, they may be have to think about a way to protect lenses for that long afterall.
BTW, for a launching date in summer 2009, MSL would be around by summer 2015 with only 3 times is scheduled life... you'll have a new shed by them

[ElkGroveDan]

... you'll have a new shed by then

Then we will have to start calling him Doug "Two-Sheds" Ellison.

[djellison]

THREE sheds. Technically I had a little brick one at the end of the garage, the woodern office one...and then I'll probably get a small JCB in and go for some sort of large basement in the garden

Doug

[fredk]

Dramatic changes on the ground, too. Compare these pairs of navcams from sols 1239 and 1250:

http://marsrovers.jpl.nasa.gov/gallery/all...ATP0755R0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all...CMP0765R0M1.JPG

http://marsrovers.jpl.nasa.gov/gallery/all...ATP0755R0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all...CMP0765R0M1.JPG

http://marsrovers.jpl.nasa.gov/gallery/all...ATP0755R0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all...CMP0765R0M1.JPG

The local times of these pairs are only about 15 minutes apart, so the solar incidence angle is essentially the same, although there is a bit of movement of the rover between sols.

The rover tracks are much less prominent now - it seems to be mostly due to albedo effects. Exposed light areas have been covered in darker dust. And generally, the whole ground has taken on a "mottled" look, which I recall from after the previous big cleaning event near Larry's Lookout. That mottling seems to do a great job of hiding the older tracks - some of them are almost invisible now.

I can think of a couple explanations for the mottling - perhaps the thickness of the lighter dust varies like the mottling pattern, so when the wind removes light dust the pattern is exposed. Or it may be that the wind generates eddies or turbulence that actually remove dust in the mottled pattern.

[Ant103]

Hum... Interesting. At many places around the rocks, the ground has darken, and in the same time, at local elevation of the ground (top of ripples), the ground has lighten. And, I don't know if is it my eyes who play me a trick, but, I see very faint dark trails.

[Pertinax]

The recently windswept areas look (to me at least) to be areas where the lighter sulfate (and silica?) rich soil is now much less covered by / peaking through the darker fines (which themselves accumulated in crevasses and in the lee of objects).

-- Pertinax

[alan]

I wonder how much of the apparent change in albedo is due to changes in lighting. Although the local time is similar the lighting has been changed due to the increase in tau, which according to Doug's graph has more than doubled at Spirit's location during the two weeks.

More diffuse lighting, caused by the light being scattered by dust in the atmosphere, could increase the importance of albedo vs. the slope of the ground or dust drifts relative to the sun.

[fredk]

Good point, Alan. Still, there are plenty of very smooth areas, where the slope is more or less constant, which have become mottled. But definitely the more diffuse lighting would make relief features like the tracks less noticible.

[slinted]

I'm glad we keep having good reason to come back to this thread. Spirit cleaner? Cleaner yet as of sol 1252!

Here's the sweep magnet sol 1251->1252, in L7, showing the strength of the winds (this one probable rivaled the big cleaning back on sol 421) picking up dust from one side very well, and dumping/spreading it down onto the other side...like an arrow, pointing in the direction of the winds.



The area around Spirit shows some effects from the wind as well (even the dust mottling on the front haz's changed):