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Posted by: slinted Dec 29 2004, 08:23 PM

This seems to be deserving of its own topic, going off of Pando's post in the heatshield thread.

Unfortunetly, the TES mainpage doesn't have daily dust maps anymore, and the latest bolometer images are from Dec 21:


I was looking at the rear haz from Sol 331, wondering what sort of clouds might be responsible, but a dust storm might make more sense.

http://www.lyle.org/mars/imagery/1R157575041EFF40B0P1314R0M1.JPG

Posted by: dot.dk Dec 29 2004, 08:41 PM

This could be real bad news

Can they put the rovers in extended deep sleep to prevent dead batteries?

Posted by: Decepticon Dec 29 2004, 10:25 PM

I see why not?

Just make sure the Batts are fully charged.

Posted by: slinted Dec 29 2004, 10:48 PM

If this is indeed the begining of a global dust storm, its a *very* early one. The "season" for dust storms seems to be generally accepted as Ls 180-360 (southern hemisphere spring and summer), but we're only at Ls 136 now. We're barely out of southern winter. The 2001 superstorm arose around Ls 180 and lasted 3 months.

Posted by: lyford Dec 29 2004, 11:07 PM

I'm no expert, but that looks like a light artifact, not really clouds. A NAVCAM image of the horizon from an hour later than the rear HAZCAM image doesn't seem to show any looming threat....
http://www.lyle.org/mars/imagery/1N157577492EFF40B0P1685R0M1.JPG.html

Posted by: Sunspot Dec 29 2004, 11:08 PM

changed my rather emabarrassing original message lol.......anyway, they should have a good idea of whats going on with MGS Oddyssey and Mars Express

Posted by: akuo Dec 29 2004, 11:12 PM

The MGS used to take dust measurements daily, but looks like this is not currently the case. This site had an updated map of the global dust situation:
http://tes.asu.edu/

Posted by: lyford Dec 29 2004, 11:21 PM

Uh, that would be Dec. 13, 2003, I think.

From the group's homepage:

Posted by: Sunspot Dec 29 2004, 11:24 PM

Forward HazCam shot:

Posted by: alan Dec 29 2004, 11:29 PM

never mind

Posted by: Sunspot Dec 29 2004, 11:34 PM

There is a message in the group dated Dec 12 2004 : "Possible and Probable Dust Storms" When I saw Dec 13 on the image I just linked the two together

Posted by: lyford Dec 30 2004, 12:26 AM

I just read that message - you are right about the date, but I think they are talking about the 2003 storms in that post. I can't see the mysterious "Figure 5" but it is confusing, to say the least. Just joined the yahoo group to look at your linked pic...looks interesting... got more reading to do!

Posted by: Sunspot Dec 30 2004, 12:32 AM

Well.......at least we got to see the heatshield.

Posted by: slinted Dec 30 2004, 09:23 AM

OK, I'm fairly convinced now that Lyford is correct in this being a camera/processing effect, and not an image of an actual feature in the sky. Although the sky in the corresponding left eye of the rear haz taken at the same time shows a similar mottled texture, the actual variation doesn't line up between the two.
It will be definitive once the left image gets fully downlinked, but by comparing the two, I don't believe they show actual differences in brightness between different areas of the sky. Sorry for jumping the gun on this one.
http://www.lyle.org/mars/imagery/1R157575041EFF40B0P1314L0M1.JPG

http://www.lyle.org/mars/imagery/1R157575041EFF40B0P1314R0M1.JPG

Posted by: akuo Dec 30 2004, 11:33 AM

Slinted, I wondered about the rear hazcam images too when I saw them first. When you mentioned the dust storm, my first impression of the images was dust flying close to the hazcam, making it unfocused. If this was the case the effect wouldn't need to line up in the sky.

The effect doesn't appear in the front hazcam images taken at the same time though, so I think this explanation is still unlikely, as the dust in the air would have to be very local.

Posted by: akuo Dec 30 2004, 12:52 PM

Ok, the effect is again visible in today's rear hazcam images. I think its crud on the hazcam lenses now, maybe related to the possible dust storm. The spots on the lens also stay put even though the lighting changes.

Posted by: Sunspot Dec 30 2004, 01:14 PM

How much of a power drop did Opportunity experience? For Spirit this could be quite a problem.

Posted by: lyford Dec 30 2004, 06:55 PM

well, the same shmutz is on the rear hazcam images wherever they face:




I thinks it's dust or something in the optics... but not a storm.

BTW - posting these 1024x1024 images in the forum forces me to scroll sideways to read - anyone else have that problem?

Posted by: slinted Dec 30 2004, 07:15 PM

Why is it that Opportunity is the one always having "events" happen to it? We're looking at something which altered both rear haz's sometime after midafternoon sol 330 and before the same time on sol 331. As you mentioned akuo, these "spots" are constant. Below are 2 frame animations of Sol 331 and 332 from both ccds, the mottled pattern is identical.

http://www.lyle.org/~markoff/collections/opp_rear_haz_left.gif
http://www.lyle.org/~markoff/collections/opp_rear_haz_right.gif

If Opportunity did get hit with dust coming from whichever direction the rear haz's were facing, maybe the panels are now covered as well leading to the worsening power situitation? It would be very easy to tell by comparing some new panel navs / MI's to the ones taken within the last couple weeks.

I'm trying to think of what else other than dust on the lenses might be responsible. If it isn't on the lens then its part of the flat field for the ccds, could there be something electronic that could have happened to alter both ccds?

Posted by: Sunspot Dec 30 2004, 07:17 PM

Is it just me or do the shadows ast by the pancam calibration target look paler that they used to be?

SOL 331, L4



SOL 324, L4

Posted by: slinted Dec 30 2004, 07:31 PM

I don't think its you, the shadowed area is brighter in comparison to direct light (a change in the ratio between solar brightness and sky brightness?). I hope we're not being fooled by the auto-contrast-stretched raw images.
Sol 328

Sol 331

Posted by: Sunspot Dec 30 2004, 07:36 PM

Well we should find out whats happening at Mondays press briefing....

Posted by: Pando Dec 31 2004, 05:40 AM

Thanks Slinted I was merely trying to keep a low profile

Posted by: Pando Dec 31 2004, 06:22 AM

To give you an idea what's going on, the atmospheric opacity was at around 0.9 during Oppy landing and the dust storm then was subsiding. It continually improved until the opacity was about 0.5 at Sol 327. On Sol 328 it went up to 0.6, then on Sol 329 to 0.8, Sol 330 to 1.2, and on Sol 331 to 1.25! It is currently at 1.2 and dropping. MGS has confirmed small dust storms in the region. Energy intake has decreased close to 30% since Sol 327, but there is still a comfortable margin to continue normal plan of heat shield analysis. Nevertheless it has caused some worry and sent the rover engineers scambling during uptrend. For Spirit the opacity jumped from around 0.2 to 0.4 on Sol 351, but the following Sol it went back down to 0.3.

Assuming the dust storm doesn't pose further problems, Oppy should be done investigating the heat shield at around Sol 350 and starting to drive 1.2km South toward Vostok crater, about 50-Sol trip about 1/5th of the way to Victoria crater.

Posted by: Pando Dec 31 2004, 08:27 AM

Oppy had more than 180 W/Hr drop in 2 Sols.

Posted by: lyford Dec 31 2004, 07:45 PM

Again, thanks Pando for the inside scoop!

Posted by: mhoward Jan 5 2005, 11:48 PM

Pando has already filled us in, but the duststorm is finally mentioned in the latest http://www.jpl.nasa.gov/missions/mer/daily.cfm. Needless to say, I hope we're done with duststorms now, unless they're of the miraculous solar panel *cleaning* variety... (I know, I know, the cleaning events were probably something else)

Posted by: Pando Jan 6 2005, 12:08 AM

Eh! took them a while...

Here's some future plans:

333 - 336: Close-in remote sensing of Flank portion of heat shield, including microscopic images.

337: Drive to East Point, image debris field from there.

338 - 343: Drive to North Point. Do IDD work on a rock at that location.

344 - 34x: Approach main portion of heat shield debris and impact divot for possible close-in observations.

34x - 39x: Leave heat shield and drive towards the crater Vostok which is 1.2km to the South. Stop at smaller craters and targets of interest along the way. Vostok is the first major objective on the long road to the etched terrain and the crater Victoria at South.

Posted by: Sunspot Jan 6 2005, 12:32 AM

Cool..... I was hoping they would take a look at that rock

Posted by: djellison Jan 18 2005, 07:10 PM

This is quite an interesting issue. Something specific happened between end of drive Sol 330, and end of drive Sol 331 - only to the read hazcams, but to both of them and no other camera - and has remained consistant and in place ever since.

I cant figure out what it might be - perhaps a local dust laden wind feature. The rover was parked just west of the impact crater at the time

Doug

Posted by: BruceMoomaw Jan 22 2005, 03:26 PM

A nicely detailed new Planetary Society article on the recent activites of both rovers ( http://planetary.org/news/2005/mer-update_0121.html ) confirms that, yes indeed, that mottling on the rear Hazcams is due to the recent dust storms.

Posted by: akuo Jan 26 2005, 03:38 PM

JPL has released dust comparison images between the rovers on their marsrovers site
http://marsrovers.jpl.nasa.gov/home/index.html

Here are the images, I didn't realise Spirit was that badly covered in the stuff!

Posted by: remcook Jan 26 2005, 05:35 PM

so, what do they use to calibrate the pictures now? Or do they just use experience from previous pictures when there was less dust?

Posted by: djellison Jan 26 2005, 07:49 PM

You kind of have to trust Pancam I guess. You calibrate it when you land - and then you can use housekeeping data and darkfields to calculate how it's performing thereafter

D

Posted by: akuo Jan 26 2005, 09:36 PM

There is also one almost clean spot on the rovers. The middle of that little dust magnet next to the calibration target! I'm not sure if they do this, but they should be able to subtract the dust's effects using that neutral grey colour.

Posted by: sjdprods Jan 26 2005, 11:10 PM

If dust accumulation on the cells got to a point of desperation, would it be even possible to consider "brushing" sections of the panel with the RAT brush, or is that either 1) mechanically impossible -- not in the physcially possible work space, 2) practically impossible -- just too risky to damage important components, or 3) practically impossible, because the 'brush" would destroy the solar cells?

Posted by: djellison Jan 26 2005, 11:47 PM

It's barely possible kinematically ( i..e the IDD could reach perhaps 5% of the cells I'd guess ), and the 'brush' is, I believe, made of something like steel So it would scratch the hell out of the solar cell cover plates and possibly crack them

Reach back over your head with the inside of your elbow against your nose - the wrist just about on top of your head - and your hand probably just reaching over the back of your head. Now try and scratch your back No mobility left to do it

We see about as much as the IDD can do when it uses the MI, APXS and Mossbauer on the magnets on the front of the rover - and they used the MI on a few of the solar cells right near the front as well - but it just cant reach much further than that.

I spoke to Colin Pillinger on this very issue once - at an Open University Open Day - we were talking next to a Beagle 2 model - and a passer by said "couldnt you brush the solar panels clear of dust", and as Colin thought of a sensible way to answer, I simply replied "better to have dusty solar arrays than broken ones"

Doug

Posted by: Marcel Jan 28 2005, 01:28 PM

I would say the same (there's obviously a big difference in dust load now, compared to a year ago), because there not much reason to believe that calibration of the camera would change the images that much, BUT:

there's some aspects that makes me suspicious about fully relying on the appearance of (especially) Spirit's callibration target at sol 357, compared to sol 9:

- the angle (and direction) of illumination with respect to the target and the camera is completely different in the two frames. Compare the appearance of shiny objects in sunlight at photographs between morning, noon and evening, and between summer and winter and we all know what i am talking about
- optical depth (tau) and thus the relative part of scattered sunlight is of great influence considering the contrast of an image and it's "crispness" (compare pictures taken in direct sunlight to clouded circumstances: often it just appears more "dull").
- the distribution of brownish coloration of the black pole in the middle is homogenous. The ball atop is evenly covered on the horizontal AND vertical surface of it. Even the shaft under the ball is just as brown as the rest, while we know, that horizontal surfaces should build up dust much more than vertical ones.

Seems to me there's more to it than just dust. What, i don't know, but there's something else influencing the look i would say.

But, if Spirit is really as dusty as it looks, it makes me want to cry....

Marcel.

Posted by: djellison Jan 28 2005, 01:38 PM

Really? The air on mars may be thin - but it's there, and has wind - and the dust it carries is quite 'clingy' - and imho, it is the side of things that should get dustier first as the dust doesnt 'fall' out the sky, it drifts with the air flow. Infact, you could tell the prevailing wind at Gusev by the side of the sundial the dust stuck to after the first dozen days on the lander If the horez. surfaces should be dustier than the sides of surfaces - then how can you explain the rocks on the ground at gusev - many have a dusty upwind side and a less dusty downwind side. The same is true of pathfinder - infact Yogi is a prime example - v.dusty on the left - much darker on the right. You can see it on the earliest pictures of the black mast - dust up one side much faster than it gathers on the top.

Put it this way - when its raining, you windows get wet as WELL as the floor, and in a blizzard, the snow hits your windows and melts a lot quicker than it lands on the floor.

The colours demonstrated in those images are not exagerated - and imho, instead of being sadened by the state of Spirit - it's grounds to celebrate and rejoice in the fact that DESPITE all that dust, the damn thing's still working And imagine how long Opportuinty would have to spend at Meridiani to get that dirty Those images say to me - look - despite all this, they still work, so you can expect a whole lot more to come yet

Doug

PS - to celebrate, the wheel emoticon now rotates

Posted by: Marcel Jan 28 2005, 03:35 PM

About the deposition of dust: one the huge advantages of solar arrays in vertical (or at least, not horizontal) configuration is the fact that they adhere less dust:

gltrs.grc.nasa.gov/reports/2004/TM-2004-213367.pdf

But you're probably right that this effect is not as strong as i thought it was. Vertical surfaces do actually get dusty also. But it must be a little bit less than pure horizontal ones. At least, that's what the quoted article claims.....

Considering my depressed state about all this dust: you're right. Much more to come. .....but i got addicted to "news from Mars" so much, that the idea that it might stop soon sometimes gets to me. But I'm better now. Thanks.

I'm still working on an idea to keep the arrays clean though......for future missions. Compressed air to blow it off ? Sheets of foil (like the ones you sometimes see on toiletseats in hotels) ? Electrostatic ways ?

Any reaction on the illumination/scattering influence on the contrast/color ?

Posted by: djellison Jan 28 2005, 04:27 PM

"For a rover vertical solar
array, the dust obscuration rate was assumed to be much smaller than that for a horizontal array." (Thank you GL )

Assumed....not measured fwiw, looking at the sundial, I'm fairly sure that a vertical array would collect as much dust as a flat one - but a vertical array may be more condusive to 'shaking' the dust off over rough terrain

Compressed air = heavy system of tank and thus expendable, or a heavy compressor and thus you sand-blast the arrays with fines.

iirc - Polar Lander (or perhaps it was the orig '01 design) had a small array on the side that was configured to reject dust electrostatically.

The long term answer to using solar arrays on mars is very simple.. Use RTG's

As for the comparative images - yeah - scattering might be different - but, the shadows are roughtly the same intensity, the azimuth of the illumination may be different, but the elevation's about the same - I think it's fair to say that the images are a valid before and after comparison. What would be interesting is seing if driving over rockier terrain on a slope might dislodge some of this.


D