Changes at Low Ridge Haven |
Changes at Low Ridge Haven |
Sep 18 2006, 04:56 PM
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Senior Member Group: Members Posts: 4252 Joined: 17-January 05 Member No.: 152 |
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: sol 856, local time 11:07 sol 961, local time 11:21 sol 894, local time 11:45 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? |
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Oct 6 2006, 07:46 AM
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#2
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Senior Member Group: Moderator Posts: 4279 Joined: 19-April 05 From: .br at .es Member No.: 253 |
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". This image was downlinked, among others, and its pointing info is: azimuth=-23.5035deg, elevation=0.0875386. On sol 980 they commanded the same sequence again. This other image 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? This post has been edited by Tesheiner: Oct 6 2006, 11:43 AM |
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