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Posted by: fredk Sep 18 2006, 04:56 PM

It's been pretty slow in the Spirit forum recently, but hopefully this will reawaken it.

A new thin dark streak is visible in the latest sol 961 rear hazcam, that wasn't visible in the previous shot, from sol 924. It's visible in both L and R hazcam views. It looks remarkably like a dust devil streak, but the scale is very small. Here's the R hazcam from sol 894 subtracted from the 961 image:

The dark streak cuts across more or less from left to right about a third of the frame down from the top. Other differences are visible, mostly around rocks, due to the change in sun angle between the frames.

To demonstrate that the dark streak isn't just an effect due to that change in sun angle, look at these three frames:
http://marsrovers.jpl.nasa.gov/gallery/all/2/r/856/2R202353211EFFAS00P1311R0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all/2/r/961/2R211675465EFFAS00P1398R0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all/2/r/894/2R205729039EFFAS00P1312R0M1.JPG

You can see that the shadows move progressively from the sol 856 to 961 to 894 frames above, as you'd expect from the local times they were taken. But if you flip between the three frames, you can see the dark streak only in the middle (sol 961) frame. If the streak were due to changing sun angle it would be at least as strongly visible in the 856 or 894 frame. Therefore it's not due to sun angle.

As I said, this is way too small for a dust devil streak. And, I don't think we're anywhere near dust devil season. My guess about the origin of this is a small "crumble event" on one of those dark rocks in the upper left, followed by the normal winds blowing some dark dust downwind.

Anyone know if the streak direction is consistent with what the winds should be doing now? Has anyone else noticed changes near Spirit?

Posted by: djellison Sep 18 2006, 05:34 PM

Look at the change in the shadow cast by the aft solar array on the ground - that's quite a lot of solar-angle change - and looking at the three frames - the change you identify would seem to be consistant with a change of illumination more than anything else.

I have - however - been looking hard for changes in lots of images and I've not found anything yet. What WILL be interesting is the changes in tiny ripples upon which the rover is now sat.

Doug

Posted by: helvick Sep 18 2006, 05:42 PM

Interesting. An additional new picture would provide a definite answer. I see your point Doug but it seems to contiguous and localised to just be shadows. It would be great if it did turn out to be a streak.

Posted by: fredk Sep 18 2006, 06:29 PM

Doug, the local time difference between the sol 856 and 961 frames is 14 minutes, which corresponds to a solar angle change of just 3.5 degrees. For sols 961 and 894, the difference is 24 minutes, or 6 degrees. The change in solar panal shadows looks quite large because of the height of the panels above the ground and the closeness of the panel shadows to the hazcam. 3.5 degrees is not a lot of change!

But the strongest argument that the dark streak is not the result of the change in sun angle is in my third from last paragraph in my post above! Any such putative darkening of a patch of soil due to changing solar angle must be monotonic with that angle over such a small range of angles, whereas my three frames show that it clearly is not.

Notice also that the dark streak crosses areas of ground that are at different inclinations, due to ripples etc. Why would differently oriented patches of surface respond to changing solar angle in the same way? Look for example at the largest rock closest to the rover (pixel location 680x375 or so). There are large variations in surface inclination angle in the soil surrounding it, but these do not show up in my difference image - the entire area (except for the rock's shadows) is very close to uniform on the difference image.

Also we don't see any other such darkened (or lightened) patches of soil elsewhere. Just one curiously linear darkened patch. Finally, the dark streak is darkest at the left, near my putative source, and thins to the right.

Altogether, an argument that the streak is an illumination feature necessarily takes on a conspiratorial character: differently oriented patches of soil, coincidentally lined up in a streak, responding in a bizarre non-monotonic way to small changes in solar angle.

Edit: that's conspiratorial in the sense of "contrived", of course no-one's conspiring here!

Actually there is another simple explanation: the feature is the shadow of something off the frame to the upper right. But that's even more conspiratorial!

Posted by: djellison Sep 18 2006, 06:50 PM

Oh crikey - I was looking at something else.....you may have spotted something I was looking in the 800,280 sort of area.... I'll see what I can come up with for anim-difference images

OK - the anim is a work in progress- but this is the difference between the 961 image, and the average of the preceeding three images. Bloody good 'spot' there Fred - nicely found. I'm going to 'phone it in' as it were.

Doug

Posted by: helvick Sep 18 2006, 06:56 PM

Actually the change in solar elevation angles are even less than you indicate because of the change in noon solar elevation as she passed through mid winter. Also there is also a change in solar azimuth that might have been relevant had the solar elevation angle been low enough to cast shadows from landscape features off to the left. It isn't and as you point out anything that could cause such a shadow would be really conspiratorial.

Sol 856 LT 11:07 - Elevation 53.5deg Az 3.9deg
Sol 961 LT 11:21 - Elevation 50.7deg Az 351.7deg
Sol 894 LT 11:45 - Elevation 49.5deg Az 347.0deg

I cannot see how you would get an area of shadow across the entire region in question that would only appear on Sol 961. We still need another photo to be sure but it does look like a clear change to me.

Posted by: dvandorn Sep 18 2006, 07:26 PM

I guess I'm missing something -- except for the minor sun angle changes, I can't see what you're talking about in the three image set. I see what appears to be a dark groove in the very-low-sun-angle image, but I can't identify it in any of the three images. Or any albedo change in them.

Maybe my eyes are just getting too old for this...

-the other Doug

Posted by: djellison Sep 18 2006, 07:30 PM

The attachment that Fred did - and the one I did - are basically the difference between the Sol 961 image, and the other RHAZ images. So that dark streak is something that has changed between the last RHAZ image, and that Sol 961 one. It reminds me of the sort of trail left behind after a DD in Mark's enhanced DD movies.

Doug

Posted by: climber Sep 18 2006, 07:41 PM

Not joking (realy). How far is this? Look prety close though. Any notice of a side effect on power supply (clean up)?

Posted by: djellison Sep 18 2006, 08:00 PM

I'm not sure to be honest - probably best to match these features Nav or Pancam and work the range from that.

Perhaps - if we're lucky - they will do another Navcam pan from this position and then we can compare with earlier Navcam pans and vertically project it to see the track.

Doug

Posted by: fredk Sep 18 2006, 08:37 PM

Dvandorn and anyone having trouble seeing this in the original images, here's a 3-frame gif that should help. Frame one is sol 894, unprocessed. Frame two is sol 961, unprocessed. Frame three is frame 2 minus frame 1, and then brightened:

Look for the (subtle!) change between the first two frames at the position of the streak in the difference image (frame 3). It's subtle but I was able to spot it before I made the difference image.

As I said above, I doubt this is a devil. I think small "crumble event" followed by ordinary winds is our best bet. I think we expect some level of steadyish winds all winter?

Posted by: helvick Sep 18 2006, 08:42 PM

Not yet, power has just begun to climb again from the 280whr/sol low point it has been at for the past month or so to 287whr/sol on or about sol 957/958. We've had very regular power reports from Spirit over the past six weeks and there has been no evidence at all of any cleaning (yet).
We'll see if the next power figures show any change but I wouldn't expect it - I think it is very unlikely that this just happened so whatever effect it would have had would already have been seen.

Posted by: dilo Sep 18 2006, 08:48 PM

Fred, your observation is interesting but what disappoint me is that this streak coincide exactly with regions with higher slope (even if with different sign comparing left portion with right). Based on this, I tend to think is a consequence of small illumination differences and/or deposition of some dust layer with slightly different light scattering properties... (not necessarily localized only in this point as for a dust devil track).

Posted by: fredk Sep 18 2006, 09:04 PM

Dilo, the ground here has regions with greatly differing inclinations. Recall what I said in my second post about the area around the big rock. Why don't we see these kind of changes anywhere else?

Obviously a new image (after sol 961) would be great to have. But we've waited over a month since the previous rear hazcam image! Hopefully we won't have to wait as long for the next one...

Posted by: djellison Sep 18 2006, 09:13 PM

That's what I thought dilo - but the change is real imho.

Doug

Posted by: dilo Sep 18 2006, 09:21 PM

ok, let's wait for next images...

Posted by: fredk Sep 19 2006, 04:43 AM

I identified the putative source region of the dark streak in pancam imagery. Since the streak is darkest on the left end, I'm guessing that's near the source. That end is between the red, green, blue, and yellow marked rocks in this crop of the sol 961 hazcam:

Here's a crop from James Canvin's (stunning!) McMurdo pan, where I've identified and marked those same four rocks:


I've circled the area corresponding to the left end of the streak.

It's pretty clear what may have happened here: a piece of the very thinly layered outcrop fell down onto the sand below, kicking up loose dust. There are a number of potential loose pieces, such as the one I've arrowed.

Boy, would I love to see some new pancam imagery of this area!

Posted by: dvandorn Sep 19 2006, 05:59 AM

Yes -- with the flicker gif I can make out the change in albedo. I kept looking in the area of the streak that is apparent in the subtraction image, but by opening each image separately and just moving from one browser window to another, I honestly couldn't see the albedo change. With the flicker gif, I can see the actual albedo change quite clearly, even without the third subtraction frame.

-the other Doug

Posted by: dilo Sep 19 2006, 07:32 AM

Nice hypothesis, Fred.
I was looking for other Pancam images of this region, when I noted a huge DD track not previously visible in the eastern Eldorado!
Original imagese were taken with PanCam L2 filter on Sol 924 and 961 (37 Sols apart), with almost exactly the same pointing and illumination:

(start images are 2P208392405ESFAS00P2411L2M1.JPG and 2P211675276ESFAS00P2411L2M1.JPG).
The track is already evident, anyway I made subtraction and used it also for a elaboration image showing the change over the first image through the hue/sat change:


This story is encouraging, because we aren't yet in the DD season and, with some luck, one of these precursor could hit Spirit soon, making possible anticipated return to full rover activities...

Posted by: climber Sep 19 2006, 09:36 AM

That's something !
I note that, pending the hypothesis of a DD is right, the direction it took would have bring it little bit South of Spirit but not that far. Since the DD desapears in the depression on the other side of the ridge we loose its track. But if it has continued, it should be visible on some images taken in the South direction. Do you agree on this? Do we have such images ?

Posted by: dilo Sep 19 2006, 10:31 AM

Dunno... My impression is that dust devil had effect only on Eldorado dunes, terrain outside wasn't disturbed. If I'm correct, based on prevailing wind direction in old DD movies, devil's direction was toward South (toward Spirit) and the intriguing fact is that terrain in the foreground (the Homeplate, essentially) changed slightly overall hue in the last picture, suggesting a similar (weaker) darkening occurred!
However, if DD invested Spirit, I imagine we should have more whrs now (and a lot less dust on solar panels)...

Posted by: Tesheiner Sep 19 2006, 10:58 AM

Climber & Dilo,

Be careful!
Spirit + DD ==> cleanup-event = Doug jumping off its seat.

Posted by: Bill Harris Sep 19 2006, 11:15 AM

This is not necessarily a dust devil in the usual sense but simply a turbulent swirl in the atmosphere as the wind rounds the Husband Hill obstruction.

--Bill

Posted by: climber Sep 19 2006, 11:20 AM

I know we are walking on eggs here (dunno if the expression works in english, actually, it's a french one )
1-it's not because it didn't happen before that it'll not happen
2-I took some precautions before on a post here above
3-we all know it's a remote possibility
4-the first one to spot such an event will win THE gran price

PS : I'd better like dust jumping off solar panels that Doug out off his seat (don't like " unecessary post deleted")

Edit : you're right Bill, a kind of dd instead of DD.

Posted by: helvick Sep 19 2006, 03:09 PM

I don't want to seem like a spoil sport but I feel the need to reiterate that there has been absolutely no evidence of any dust removal activity at all recently from Spirit's solar panels. Zero, nada, zip. Power output has followed the expected mid winter insolation curve with no additional dust deposition (which is good) but no dust removal either over the past six weeks or so. That was up to Sol 957/958. The next power update might change that but for now any speculation about cleaning is a bit premature.

Opportunity has scored a noticable (~20%) power benefit from something recently, presumably a cleaning event or events but that is not yet clear.

Posted by: fredk Sep 19 2006, 05:53 PM

Nice find, Dilo!

I have to wonder like Bill Harris if this isn't a dust devil proper. The thing is, we know that there's something unique about the topography associated with Eldorado, since we have the rippled sands there. Could we have captured here a step in the normal buildup of Eldorado?

It's also interesting that the track ends (or starts!) at the edge of Eldorado.

But still, remember we're seeing Eldorado quite foreshortened here, so the track is actually quite long and thin (and probably longer still - we can't see the other end of it). That to this non-expert sounds like a devil or something very close.

Posted by: ustrax Sep 22 2006, 10:47 AM

Returning to this places makes me shiver...
dilo, do you remember http://i16.photobucket.com/albums/b14/ustrax3/ultreyadd.jpg?

It looks to be (in the image above) the same area you are making reference to, seems like this is a previliged DD corridor...

Posted by: dvandorn Sep 22 2006, 02:33 PM

The darkening in El Dorado isn't very long -- it likely was caused not be a dust devil, but by a seasonal change in the direction and speed of the local winds. At least, that's what I would suggest, barring any evidence that dust devils actually occur during mid-winter here in Gusev.

-the other Doug

Posted by: dilo Sep 22 2006, 07:05 PM

Eh, Ustrax, not only I remember these images... in fact, I was inspired by them in searching changes inside Eldorado! I remember also our wild theories about these features (cracks in a lake made of lava or something else...).
About other Doug's explaination, the absence of any trace outside the dune field is suspect, but also a seasonal wind change impacting a so delimited region is a little hard to accept, IMHO...

Posted by: slinted Sep 22 2006, 09:53 PM

Is there a second image to confirm the darkening? This seems *very* early in the season for there to be dust devils (the shape of the ground track seems wrong too). Strong gusts could be responsible, but I wanted to throw out another possibility.

Given that Opportunity has recently http://www.unmannedspaceflight.com/index.php?s=&showtopic=3205&view=findpost&p=69002, could this darkening be a cloud shadow projected on the ground?

edit: So, the changes are real and lasting, as evidenced by http://nasa.exploratorium.edu/mars/spirit/pancam/2006-09-24/2P212384718EFFAS00P2269L1M1.JPG taken on sol 969.

Posted by: jamescanvin Sep 25 2006, 12:18 AM

Tosol we have a pancam of this area (360 L1 albedo pan) - the little bit you point to is just off the bottom but the rest of the outcrop looks undamaged (by eye).

Personally, I don't buy the 'bit falling off' theory I think it's much more likely that as a small gust of wind blew over the ledge and the vortex created in its wake produced a 'mini dust devil'.

http://nasa.exploratorium.edu/mars/spirit/pancam/2006-09-24/2P212384500EFFAS00P2269L1M1.JPG

Posted by: alan Sep 25 2006, 12:26 AM

Another streak has appeared at El Dorado, also a couple of narrow streaks to the left on the hillside (arrowed) look like they were caused by rocks rolling down the side of the hill.

Posted by: slinted Sep 25 2006, 02:23 AM

The newest streak is darker than the previous, and much wider and longer.

Here's a 3 frame animation, comparing the L2 images from sol 924, L2 from sol 961 and L1 from 969 showing the 2 new dark streaks:
http://www.lyle.org/~markoff/collections/eldorado_924_961_969.gif

Posted by: dilo Sep 25 2006, 02:35 AM

Very good, Alan/Slinted!
I noticed too a couple hours ago, but this time you beat me in posting it!
Not only this streake is darker and longer... it is clearly visible outside the field of dunes, ant this reinforce idea that dust devil season started, at least in this point! probably, the South side of Husband hill is a good place for local atmospheric warming which cause this phenomenon...
Correct me if I'm wrong, but Spirit didn't yet activated the new navigation software implementing the smarter DD catcher. If so, at this point they should do asap!

Posted by: CosmicRocker Sep 25 2006, 02:57 AM

Fine work catching and displaying those streaks, dilo, alan, and slinted! I think I've said it before, but the collaboration that takes place in the UMSF community is becoming legendary, and this is yet another wonderful example. That animated gif is sweet.

Posted by: dvandorn Sep 25 2006, 04:25 AM

I dunno -- I'm not necessarily convinced that you have to invoke a dust devil to get these changes. Surely an unusual set of straight-line winds could have caused the same type of track? I mean, wouldn't it all depend on where, when and how straight-line winds blow as to what effect it might have on the ground? And this *is* the leeward, "protected" side of Husband Hill, which has allowed the dust to settle into El Dorado in the first place... you'd think that any straight-line wind events would be fairly rare, and thus a lot more noticeable here than elsewhere around the hills.

It just seems awfully soon past the winter solstice to be seeing actual dust devils. For all of me, I could be wrong, though.

-the other Doug

Posted by: Jeff7 Sep 25 2006, 08:46 PM

Hopefully this means that we'll start seeing some stronger winds, which might kindly come by to clean up Spirit.

Posted by: fredk Sep 26 2006, 12:15 AM

You certainly may be right about this being just due to wind - the recent streaks on Eldorado support that.

What intrigued me about this from the start was the narrowness of the dark streak I found. That's what led me to the localized "crumble event" idea. It's still possible there's something just below the sol 969 pancam frame.

However, I did a difference image between the sol 969 L1 and sol 859 L2 images (not the same bandpass, of course):

You can make out the left end of my dark streak, in the lower right part of the frame, just to the right of the jaggedy outcrop. With this high resolution, there's clearly no single point source for the darkening. Also, there appears to be more darkening farther away, in areas not visible to the hazcam. This all starts to sound like wind gusts affected by small scale local topography.

Posted by: dot.dk Oct 3 2006, 04:10 PM

Has anyone 'in the knows' commented on these changes? And what may have caused them?

Posted by: helvick Oct 3 2006, 07:28 PM

I haven't noticed any official statement indicating any cleaning but the last reported power level , 296 whr sometime between Sol 969 and 976 is 10-15whr higher than I'd expected and is the second notable up tick in power in a fortnight following two months of flat power output. That is well within the error in my estimates so you can't read too much into and the most likely explanation is simply clearer skies but it might indicate some cleaning is actually happening.

Posted by: alan Oct 6 2006, 04:58 AM

Another streak on El Dorado this time at the south (left) edge.
http://qt.exploratorium.edu/mars/spirit/pancam/2006-10-05/2P213361480ESFAS00P2411L2M1.JPG
I think they show up better at El Dorado because the sand is bluer and provides more contrast when the dust is removed. How many more are we not seeing in the areas where the contrast is subtler?

Posted by: dilo Oct 6 2006, 05:57 AM

Yes, Alan... I noticed too! Look to this animation from Sol 969 and 980 (filter is not the same, L1 vs L2, but this do not introduce big difference here):

(...hey, Spirit changed orientation! )
Even tough the streak direction doesn't seems toward the rover position, could be related to the power level increase highlighted by Helvick...?

Posted by: alan Oct 6 2006, 07:27 AM

Damn, when did that happen? I haven't seen any recent hazcams.

Posted by: Tesheiner Oct 6 2006, 07:46 AM

It didn't move, at least by commanding; current site/drive id is still AS00.
The reason for that effect might be related to a different pancam heading on the two shots. Remember that the image from sol 980 is not a full frame (EFF) but a sub-frame (ESF).

Edited: I cheched the camera pointings an the offset between both of them is about 3º. On the other hand, the rotation which can be seen on Dilo's animated gif is about 0.5º and it's too big to be related to the 3 degrees offset. Spirit should be on a quite steep side-slope in order to account this image rotation to a change in camera heading. Therefore, the "mistery" is still alive.

Edited again: I searched for previous shots like the one taken on sol 980 and found that on sol 924 they commanded a sequence named "pancam_ElDoradoChange_L27". http://marsrovers.jpl.nasa.gov/gallery/all/2/p/924/2P208392344ESFAS00P2411L2M1.JPG was downlinked, among others, and its pointing info is: azimuth=-23.5035deg, elevation=0.0875386. On sol 980 they commanded the same sequence again. http://qt.exploratorium.edu/mars/spirit/pancam/2006-10-05/2P213361480ESFAS00P2411L2M1.JPG was downlinked, among others, and its pointing info is: azimuth=-23.5013deg, elevation=0.048464. Those two pictures were taken pointing to virtually the same position and if you open the following animated gif the new streaks can be seen and a small displacement between the two shots, but no rotation at all.
Man! I changed my mind three times in the last few hours.

Edited once again and hopefully for the last time! I calculated the pancam mast tilt (deviation from the absolute vertical) hence the rover's tilt needed to create a 0.5 degree image rotation effect as a consequence of a 3 degree pointing offset. If I did my math correctly the rover should be on a 10 degree east-west slope to account for that effect. Spirit is on a north-facing slope, but does this slope has an east-west component too?

Posted by: slinted Oct 6 2006, 04:12 PM

Here's an enhanced-by-difference-image version of the changes from sol 924 and the most recent images on sol 980



The movie showing all 4 panoramas taken over the last 60 sols is http://www.lyle.org/~markoff/collections/eldorado_924_961_969_980.gif

Posted by: dilo Oct 6 2006, 09:19 PM

Great movie, slinted! looking to it, I have impression that events intensity is going to increase...
At this point, I think they should absolutely install the new smarter DD-catach SW because spectacle should be fantastic!

Posted by: dilo Oct 8 2006, 10:12 PM

An attempt to understand if a DD really hit Spirit is this movie of the sundial in the last 40 days:

I do not see any significative change in the dust level, however... . And you?

Posted by: alan Oct 8 2006, 10:49 PM

I've been checking the sundial images myself since the changes started appearing at El Dorado. I haven't seen anything yet either. Nice movie, I like watching the shadows of the rock behind the sundial dance.

Posted by: jvandriel Oct 30 2006, 11:44 AM

Movement at Low Ridge Haven but now on the solar deck

of Spirit. Not only the shadow but look at the wire in front

of the mast.

jvandriel

Posted by: djellison Oct 30 2006, 12:49 PM

That thing's been ratting around that little pocket for aaagess.. (well, more than 1000 sols anyway) I think RM mentioned it in another thread at one point.

Doug

Posted by: jvandriel Oct 30 2006, 01:24 PM

Doug,

I know, that wire is there for 1000 Sols ( from the arrival on Mars ) but,

as far as I know, this is the first animation of that wire moving.

jvandriel

Posted by: ElkGroveDan Oct 30 2006, 03:37 PM

Indeed. Not sure what the elapsed time between images is, but I would expect that with Spirit sitting there in the same spot all this time, the question is: What caused it to move?

Posted by: djellison Oct 30 2006, 03:42 PM

Posted by: Nix Oct 30 2006, 04:42 PM

Either that or a D...nah,.. the joke is getting rather old..

Nico

Posted by: rogelio Oct 30 2006, 06:21 PM

A minor point (and perhaps one that has elicited comment already): Since the sun has a smaller angular diameter as seen from Mars (by about 40-65% depending on the season), shadows cast there would have noticeably sharper margins... I would like to believe that this is evident in the sharpness of the shadow cast by Spirit’s landing mast...

Posted by: jvandriel Oct 30 2006, 06:49 PM

ElkGroveDan,

here are the numbers of the 2 images of the moving wire:

image nr 1:
2N202270255EFFAS00P1988L0M1.JPG ( Sol 834 )

image nr 2:
2N208124777EFFAS00P1988L0M1.jpg ( Sol 900 )

It must have been the wind which has moved the wire.
It is even easier because Spirit is tilted on 1 side.

jvandriel

Posted by: djellison Oct 30 2006, 07:17 PM

Oh - I distinctly remember the '99 total eclipse here in the UK - I was in Bidford-on-Avon, we got about 95% eclipse, and I was at a gliding competition - I remember the shadows the gliders were casting on the ground were very very sharp.

Doug

Posted by: JRehling Oct 30 2006, 07:28 PM

What does gliding during a total eclipse do to your insurance rates?

Posted by: djellison Oct 30 2006, 07:33 PM

Actually - the Civil Aviation Authority declared the time from first contact to fourth contact as aviation darkness - so the flying for the day started AFTER the eclipse. Also - because of the sun getting stolen for the morning - it was a poor day for gliding, very few good thermals around.

Doug

Posted by: climber Oct 30 2006, 08:34 PM

Two notes :
1- I saw the eclipse 100% from a site in France, it was, it was, whow...If somebody here never see a full eclipse, please run, run, there's nothing like this. It has a big effect on the crowd too : people start to talk together, sharing something big. An eclipse IS something big.
2- The last 4 posts (including this one) are wayyyyy out of topic

Posted by: ElkGroveDan Oct 30 2006, 10:33 PM

For those who haven't seen one yet, here's your http://sunearth.gsfc.nasa.gov/eclipse/SEatlas/SEatlas3/SEatlas2001.GIF:

Posted by: Jeff7 Oct 31 2006, 12:47 AM

You're right.



Tornado!!

Posted by: monty python Oct 31 2006, 08:19 AM

Has anyone suggested that a future rover have strings or wires intentionally attached to the solar array deck so as to swing around and wipe the deck of some accumulated dust? Maybe around the circumfrence to push it off the deck sides? These wouldn't be powered, just loose but tied down at one end.

Posted by: djellison Oct 31 2006, 08:34 AM

You would end up depending on wind strong enough to blow around a piece of string, but at the same time not strong enough to blow off dust that would be removed by that piece of string....AND somehow get the string to not just hang of the sides of the rover like corks on the side of an Aussie farmers hat. I can see why one might see the little 'scratches' in the dust that that little cable tie has made at the base of the PCMA - but I just can't see it working as a means to actively clean dust off a solar array. There are far better methods in development at the moment ( electrostatics being one...excellent paper at the IAC about that, with cool videos to match )

Easy solution.....RTG.

Doug

Posted by: Oersted Oct 31 2006, 08:36 AM

Thanks, very useful! - Hmmm, China 2009 looks like an interesting trip...

- Intriguing and nicely low-tech idea about the strings swiping the solar arrays!

Posted by: ustrax Oct 31 2006, 04:28 PM

How on Mars have I been missing this?!...
El Dorado and it's olivine marbles still have a story to tell...

Posted by: jvandriel Nov 3 2006, 10:00 AM

I have added 1 image and now the movement

is even greater.

jvandriel

Posted by: Ant103 Nov 3 2006, 10:06 AM

I think that the moove of the wire is due to thermal differences. Light side is more heater than the dark side. This make a sort of dilatation in the wire and twist it : it moove. The wind can't make this sort of displacement because if it is the contrary, sans between solar cell will be blown away.

Posted by: MahFL Nov 3 2006, 11:12 AM

All of the dust would not be blown away if it was electrostatically stuck to the rover deck, that peice of string is proberly very very light weight. Also it does seem to have scratched some dust away.

Posted by: Tesheiner Nov 3 2006, 11:58 AM

Mmm, is that consistent with the current power levels?

Posted by: djellison Nov 3 2006, 12:29 PM

We know there are winds on Mars. We've seen flaping heatshield material, we've seen moving DD's. We also know that it takes particularly strong winds to clean the dust off the arrays. The 'normal' weather on Mars could thus be inferred to perhaps be enough to blow around a tie wrap, but not enough to blow off the dust.

Doug

Posted by: fredk Nov 3 2006, 05:46 PM

Returning to what got me to start this thread, we have a http://marsrovers.jpl.nasa.gov/gallery/all/2/r/992/2R214427072EFFAS00P1399L0M1.JPG for sol 992. In the first post in this thread I presented a difference image that showed a dark streak had appeared in the rear hazcam view sometime between sol 924 and 961. The new sol 992 view confirms that the dark streak is still there - here's the difference between the sol 992 and 924 images:

This next image shows the difference between the sol 992 and 961 images - you can't see the streak, so that means there's been no noticable change between sols 961 and 992, in other words, again, the streak is still there:


My best current guess is that this is due to strong winds that blew through and removed dust, darkening the streak, but affected by local topography to give such a localized streak.

Posted by: jvandriel Nov 4 2006, 08:59 PM

Spirit still working at Low Ridge Haven.

jvandriel

Posted by: elakdawalla Nov 6 2006, 07:23 PM

When the Athena payload was part of the 2001 Mars Surveyor lander, a more ambitious plan for the Red Rover Goes to Mars DVD assembly included a little "windsock" -- a very short vertical standard with a wispy piece of Mylar or some similar material attached, which would be able to show the wind direction and speed. Once Athena got put on a rover that would drive away from the assembly, however, this experiment didn't make much sense.

--Emily

Posted by: CosmicRocker Nov 8 2006, 04:26 AM

It would have made sense if it was put on the rover. In retrospect, it would have been so simple for someone to tie a short length of thread to some part of the rover visible to a camera...much like the telltales used by sailors to trim their sails. The post on the color target would have been a logical choice, since it is imaged once or twice each sol. A thread of variable linear density would be even better for observing a wider range of wind speeds. It would have provided a lot of valuable information about wind, it would have been inconsequential to the mass budget, and it surely could have been easily designed to not interfere with other experiments. Such an experiment could have probably been designed and implemented for a cost that was orders of magnitude below most others.

A simple "telltale" experiment could have been included for almost no cost, and no negative impact on other aspects of the mission. I hope something like this could be included in some future mission.

Posted by: remcook Nov 8 2006, 10:03 AM

I think both MSL and Exomars plan to have windsensors on them. Maybe MPL? Not sure...

Imaging a string or windsock is actually a very inefficient way of measuring wind as data rates are concerned. Also, I guess you want to have your sensor some distance away from the rover, otherwise it would tell more about the thermal emission from the rover than the 'normal' wind on Mars. This may require a boom.

An overview:
http://www.atm.ox.ac.uk/main/research/posters2005/2005cw.pdf

Posted by: Gray Nov 8 2006, 05:43 PM

The scientific value of a windsock on the sundial may have been minimal, but he PR value might have been huge. I'm thinking science education of school kids. It could be a great lead-in for lots of science projects. Which was is the wind blowing on Mars? First you have to figure out which way the rover is facing, then measure the bearing of the wind-sock. If observations are made over a long time, it could lead to discussions of the seasons, prevailing winds and dunes etc, etc.

Posted by: helvick Nov 8 2006, 07:26 PM

I think you mean Phoenix not MPL. In any case Phoenix will have a MET instrumentation package that does lots of meteorological science but interestingly does not include any direct wind speed sensor. There is some talk of using one (or more) or the mast mounted atmospheric temperature sensors as a hot wire anemometer. Deborah Bass mentioned on http://phoenix.lpl.arizona.edu/features/weblogs/deborah_bass.phpthat they had decided to add a telltale to one of the masts so they could detect really low wind speeds.

Posted by: alan Nov 8 2006, 08:38 PM

Another streak formed on El Dorado, this one running left to right.
http://qt.exploratorium.edu/mars/spirit/navcam/2006-11-08/2N216030159EFFAS07P1765L0M1.JPG

Posted by: slinted Nov 9 2006, 03:44 AM

Alan, good eyes!

To back up a bit, the pancams that came down today show 2 new streaks on El Dorado that formed sometime between sol 980 and 992. Here are the relevant frames for comparison in L2:
980 http://marsrovers.jpl.nasa.gov/gallery/all/2/p/980/2P213361480ESFAS00P2411L2M1.JPG http://marsrovers.jpl.nasa.gov/gallery/all/2/p/980/2P213361542ESFAS00P2411L2M1.JPG
992 http://nasa.exploratorium.edu/mars/spirit/pancam/2006-11-08/2P214426796ESFAS00P2415L2M1.JPG http://nasa.exploratorium.edu/mars/spirit/pancam/2006-11-08/2P214426858ESFAS00P2415L2M1.JPG

Here's an difference-enhanced view of cumulative changes between sol 924 and 992:


The movie of the changes (not enhanced) is http://www.lyle.org/~markoff/collections/eldorado_924_961_969_980_992.gif.

That being said, the much newer navcam image Alan pointed out shows even more activity. I'm looking forward to seeing more recent the pancam coverage of that spot in the sols to come.

Posted by: CosmicRocker Nov 9 2006, 05:49 AM

Wow, it's really amazing how much activity you guys are catching at El Dorado.

Helvick: Thanks for mentioning the telltale comment on the Deborah Bass blog. It is interesting to note that she spent a few lines talking about who would pay for the threads. I guess the reality of the situation is that they could never simply tie a few threads onto a spacecraft as an ad hoc experiment designed to simply provide qualitative data, as I was suggesting. It sounds like a good opportunity for someone to create a high-tech startup company that manufactures telltales calibrated to the planetary conditions of your choice.

Posted by: dilo Nov 9 2006, 06:51 AM

Is a streak invasion, guys!

If you look carefully, in the last frame there is also another weak strike on the right, at the margin of ElDorado!

Posted by: Burmese Nov 9 2006, 07:32 AM

One wonders if this 'activity' is occuring everywhere but that El Dorado, with it's 'finely sorted' material, is simply able to record a footprint of the activity better than elsewhere in the area.

Posted by: Tesheiner Nov 9 2006, 09:40 AM

Yeah, this place is very dynamic.
I would say these streaks are part of cycle repeating year after year (mars year off course). Remember when we got the first views of the whole El Dorado area right before arriving at Home Plate (mmm, it was about sol 740) and no streaks were visible; now, we can see them. My 2c hypotesis is that once this windy season comes to an end the streaks will slowly disappear due to dust deposition, so by sol 1500 they won't be visible any more.

Posted by: climber Nov 9 2006, 05:58 PM

It's strange to see such a dynamic place where Steve Squyres on last Q-nA mentioned a place where sand is trapped and stay there (If I undestood it correctly). Mars is telling us something again... I'd better say "Mars is writing something to us". Nice draw and choregraphy on an aesthetic point of view.

Posted by: Burmese Nov 10 2006, 02:49 AM

Particles of a certain size stay there, smaller ones don't, apparently. The thin coating of dust there seems to come off more readily then elsewhere and thus such a change is more visible in that area. Perhaps El Dorado is a sort of 'canary in the mine' indicator of wind activity due to its' composition and location.

Posted by: ustrax Nov 10 2006, 02:29 PM

Now that the exhile it's over it is time to see what Spirit has been doing all this time...
http://www.youtube.com/watch?v=IrvZmHcd240

Posted by: fredk Nov 10 2006, 04:48 PM

New dark streak visible between sols 1010 and 1013 near feature Oberth on McCool Hill, so far just in the front hazcams. Here's a difference image, 1010 minus 1013, so the dark streak appears light here:

You can see the streak in other images from sol 1013. I hope we get navcams of this area!

Posted by: alan Nov 18 2006, 03:58 PM

Another new streak at El Dorado, running from the to center to the right. Won't be long before El Dorado is all dark.
http://qt.exploratorium.edu/mars/spirit/navcam/2006-11-18/2N217096131EFFAS20P0740L0M1.JPG

Posted by: dilo Nov 19 2006, 07:18 AM

Yes, Alan... In reality, there are two new streaks, crossing each other:

someone is writing a msg... perhaps Mel Gibson or Ustrax knows the meaning!

Posted by: dilo Nov 21 2006, 08:54 PM

Perhaps I'm going crazy, but I see another weak streak added to the picture:

Herebelow the updated sentence, do we have some Mars language expert?

Posted by: lyford Nov 21 2006, 09:15 PM

I can't be sure, but I think it's trying to tell us something....

Posted by: Nix Nov 21 2006, 09:36 PM

You got it nailed lyford...good one.

Nico

Posted by: Stu Nov 22 2006, 12:05 AM

Love that Ultrayan grafitti...!

Just a quickie... how I imagine Spirit saw the sunset from Low Ridge Haven at least once... with the grafitti on the hillside, and Earth shiniing in the dusk glow too...

Posted by: ustrax Nov 22 2006, 11:13 AM

Me too...

And, Stu...that is my favourite from your images so far...

Posted by: dilo Nov 24 2006, 06:31 AM

Agree with you, really nice composition and colors, Stuart.

Posted by: Ant103 Nov 24 2006, 05:55 PM

Maybe you will think that this image is the same as the beautiful Stu's picture but not. This pic was taken on sol 1024 with a low sun angle and colorized by me from McMurdo's colors.

Posted by: fredk Nov 24 2006, 05:59 PM

Another new dark streak on McCool Hill (white arrow):

This showed up between sols 1022 and 1027 (this image is the difference between hazcams from those sols). The image also shows nice detail in the sol 1022 clouds.

We need someone to spot a dust devil in the act!

Posted by: centsworth_II Nov 24 2006, 06:11 PM

When will they put Spirit's new DD detecting software to use?

Posted by: mhoward Nov 25 2006, 03:29 PM

http://homepage.mac.com/michaelhoward/.Movies/SpiritSol1024-1029Sun.mov

This is actually just one camera pointing of a 4x1 downsampled Navcam mosaic that they've shot four times now at different times of the day. It would be fun to put the mosaic together and animate the whole thing... maybe some other time.

Posted by: mwolff Nov 26 2006, 05:33 PM

The software was used last week to detect a faint cloud. The atmospheric group is still climbing the learning curve...but key is that it still requires "resources" to run; so one has to "trade" potential detections for other
observations.

Posted by: djellison Nov 26 2006, 05:55 PM

I've tried bribary with a poster, but still not sky hemisphere (LOCO, obviously) from Jim



Doug

Posted by: jvandriel Dec 10 2006, 05:33 PM

Movement.

Look at the 2 tracks just right of center of this image.

Taken by Spirit on Sol 1006 with the Mi camera.

jvandriel

Posted by: Nix Dec 10 2006, 06:54 PM

Uuuh... ?

Nico

Posted by: Floyd Dec 10 2006, 09:41 PM

Mini rover tracks

Posted by: ElkGroveDan Dec 10 2006, 09:45 PM

At last, something new to keep the anomalists busy.

Posted by: slinted Dec 11 2006, 11:32 AM

Here's a newly updated version of the http://www.lyle.org/~markoff/el_dorado/el_dorado_streaks.gif as seen by Pancam, through sol 1023

Posted by: bgarlick Dec 11 2006, 11:18 PM

Since this is an MI image of a capture magnet, maybe the tracks were caused by the large particle landing on the magnet and then getting pulled/dragged by the magnetic field towards the center where the field is strongest. This would imply this big particle is quite strongly attracted by the magnetic field.
Actually if you look at the bottom of that MI you will also see a number of very narrow tracks left by smaller particles that slid closer to the magnetic attractor.

http://www.unmannedspaceflight.com/index.php?act=Attach&type=post&id=8685

Posted by: Sunspot Dec 12 2006, 07:21 PM

One rear hazcam image at exploratorium:

http://qt.exploratorium.edu/mars/spirit/rear_hazcam/2006-12-12/2R218779702EFFAS81P1312L0M1.JPG

Posted by: alan Dec 12 2006, 07:41 PM

I'll take a guess and say the rock to the left of the data dropout in this image is now in Spirit's work volume
http://qt.exploratorium.edu/mars/spirit/rear_hazcam/2006-12-05/2R218602658EFFAS52P1312R0M1.JPG

Posted by: slinted Jan 20 2007, 04:13 AM

Here's the latest http://www.lyle.org/~markoff/el_dorado/el_dorado_streaks.gif, updated to include 2 new frames: sol 1042 and 1081. The co-registration is getting more difficult since Spirit is now driving. Since the sol 1042 and 1081 images didn't quite lineup or stitch properly to the previous stack, I've also put up a http://www.lyle.org/~markoff/el_dorado/el_dorado_streaks1042+.gif between just those 2 sols with better lineup.

That being said, I am at a loss to explain what happens between 1042 and 1081. The streaks that were there on 1042 are still visible on 1081, but are muted in appearance, with the newest S-shaped streak across the middle showing a much darker tone than the rest. Did the recent dust storm drop fresh dust, covering over the older streaks? Or is this all an effect of the lighting changes that comes with higher tau?

Posted by: nprev Jan 20 2007, 04:32 AM

Interesting. Just a guess here, but might these be the effects of not-quite-dust devils, i.e small, very short-lived ones unlike the behemoths that Spirit captured in action? (To coin a term: dust gremlins.) That might explain the apparently odd dust distribution; the brighter (and presumably lighter/finer) material may have been picked up quite briefly by them and then dropped on the dark streaks.

Posted by: Floyd Jan 20 2007, 01:05 PM

I would think that extremely fine dust coming out of the atmosphere would cover everything with a really thin layer—which would partially erase the dark tracks. We were essentially track free when we first observed new tracks, so the ones from the previous active season were gone. I assume the last active season was Martian fall, and now we are going into spring. The erasure of dark features on a ¼ to ½ Martian year basis would agree fairly well with disappearance of rover tracks (the color/albedo difference going much sooner than imprint which could take years?).

Posted by: dilo Jan 23 2007, 07:32 AM

There was a change detected by new software on Sol1086:

My first impression is that a small dust devil shadow passed very close to Spirit
The following image is a composition with one B/W frame with color based on differences between 3dh and 5th frames:

The shape is incredibly thin and regular, with a clear bending... some alternative explaination?
(unfortunately, lates sundial image was taken before this event, so I cannot verify any effect on Spirit dust cover for the moment...)

Posted by: alan Jan 23 2007, 01:48 PM

I see a series of three images in which a dark arc with a bright area inside it appears to move away from Spirit. My first thought was an internal reflection in the camera although I think the motion should have been in the opposite direction if that was the case.

Posted by: Pertinax Jan 23 2007, 01:52 PM

This is a bit of a crazy (or better, unverifiable) thought: my first impression was that of a faint cloud shadow approaching and passing over the site. [Oh for even a lowres all sky camera!]


-- Pertinax

Posted by: climber Jan 23 2007, 05:03 PM

It seams to me that it afect the whole scenary : what about eclipse ???

Posted by: fredk Jan 23 2007, 06:02 PM

A dilo wrote, this pattern is an extremely well defined and near-circular, but it covers quite a range of distances from the rover. Also it is a brightening rather than darkening, so it can't be a shadow. So my first guess was also internal lens reflection. But the images were taken near noon, and the camera is pointing at the horizon, so this seems very unlikely.

I think what it must be is a specular reflection of sunlight off of the rover onto the ground, which would explain the well-defined shape. Perhaps someone more familiar with the configuration of the rover could identify what part of the rover could cause such a reflection from an overhead sun?

Posted by: dilo Jan 23 2007, 07:53 PM

Very intriguing explaination, fredk. However, I think is not realistic because the images were taken very few minutes apart.
About cloud or satellite shadow, I think size and borders are too shallow...

Posted by: fredk Jan 23 2007, 08:14 PM

I agree the feature has way to sharp edges to be a shadow - plus it's a brightening anyway.

Are you saying you'd expect a sunlight reflection to move more slowly? That's not necessary; if the reflection is from a curved surface the solar motion can be magnified.

Another similar idea is a reflection from the rover, specular or diffuse, but partly shadowed by another part of the rover. The edge of this shadow could move quickly.

Posted by: Pertinax Jan 23 2007, 08:21 PM

While taking a better look at the series of images, I noted a decent gust / dust devil moving near the horizon on the right side of the image. The image is a chronological stacking ( R-G-B ) of the first three images in the series which was then saturation enhanced ~300%.

More on topic: the change in brightness does not seem to be from any quick variations in atmospheric optical depth (dust / water clouds). It is strange.


-- Pertinax

Posted by: jvandriel Jan 23 2007, 08:23 PM

Dilo,

did you anti-vignet the images before making

the gif animation ?

jvandriel

Posted by: dilo Jan 23 2007, 10:30 PM

No... it was a very quick/dirt process before going to work!
Pertinax, thanks. I missed the first DD of the season in the sequence I made!
Addendum: prehaps I should thank Mizar who first saw it!

Posted by: slinted Jan 24 2007, 02:26 AM

From http://www.lpl.arizona.edu/~lemmon/mer_dd.html :

"New, sol 1086: Definite dust devil near the north horizon in the first couple frames. The bright halo looks like an artifact related to the Sun shining on the NCAM optics after it gets past the Sun shade (not how the halo moves on the ground, and how it slowly develops in the image thumbnails)."

This make sense looking at the thumbnails on his page. The 'halo' develops gradually across the full span of images, as opposed to other DD tracks we've seen that show up dramatically and completely from one frame to the next. But we do have confirmation of that first visible DD on the horizon, so that's good. I'm looking forward to the rest of the frames from this one.

Posted by: ElkGroveDan Jan 24 2007, 03:21 AM

Anyone know how Spirit's doing on power? That track in the foreground of Marco's image looks real close. Perhaps a little stray whooosh nudged her up a bit.

Posted by: jamescanvin Jan 24 2007, 03:51 AM

Dan, I think the consensus now is that that 'track' is an artifact not a real DD track.

Posted by: ElkGroveDan Jan 24 2007, 04:30 AM

Darn. Then I guess the artifact's impact on the power levels would have been minimal

Posted by: edstrick Jan 24 2007, 11:32 AM

Somehow, I don't think it was a sunglint off a UFO floating over the rover with an air-jet dust-brush being used to clean off the solar panels. But boy, are we wishing for a good cleaning.

Posted by: Nix Jan 24 2007, 11:36 AM

I noticed the dd too, didn't know it was the first one! Yay

Nico

Posted by: fredk Jan 24 2007, 05:08 PM

A beautifully defined DD track at the base of McCool Hill appeared between sols 1080 and 1082:

Perhaps we will get lucky down here in the basin with a cleaning event!

Posted by: fredk Feb 1 2007, 11:15 PM

A different kind of change this time. Sol 1093 navcams gave us a nice view of roughly half martian year old tracks from the dragging wheel next to brand new tracks:

Time passes on another planet.

Posted by: hortonheardawho Feb 6 2007, 01:07 AM

Spirit sol 1099 (!!!) MI pan of old dribbled salt track:

http://www.flickr.com/photos/hortonheardawho/380560864/

with links to 3D pairs and location image.

Too bad it's kind'a out-of-focus...

Posted by: ustrax Feb 7 2007, 11:14 AM

I don't know if someone already made reference to this but there is a http://marsrovers.nasa.gov/gallery/press/spirit/20070205a/McMurdo_labeled_br2.jpg back at http://marsrovers.nasa.gov/home/.

Posted by: Tesheiner Feb 7 2007, 11:17 AM

http://www.unmannedspaceflight.com/index.php?s=&showtopic=44&view=findpost&p=82863.

Posted by: ustrax Feb 7 2007, 11:44 AM

Thanks Tesheiner.

Posted by: hortonheardawho Feb 11 2007, 03:22 AM

3D location of several recent MI images with Flickr image note links to the colorized pans
and links to 3D colorized pairs from the panoramas:

http://www.flickr.com/photos/hortonheardawho/384055280/

Maybe I should start hyperlinking everything.

Posted by: slinted Feb 14 2007, 03:00 AM

A couple new streaks have shown up across El Dorado, sometime between sol 1103 and 1107. Since all we have from that period is navcam, this animation just compares the two sols. It's also an interesting look at the recent drive, since Home Plate comes much closer into view.

http://www.lyle.org/~markoff/el_dorado/el_dorado_1103_1107.gif