Winter Quarters, at Low Ridge Haven Options

[Tesheiner]

They seems to have corrected that sequence name. It's now written as McMurdo on the tracking web.

BTW, the second row (of 27?) in that sequence is planned for sol 817 (tosol).

CODE

817 p2281.05 52  0   0   52  2   106  pancam_McMurdo_pan_col_2_L234567Rall

Slow pace on both sides of Mars.

[dvandorn]

In re the truly lovely images of Husband Hill from Spirit's winter quarters:

Very nice, but not quite right. The automatic gain compensation of the imaging processes (stretching contrast, etc.) has rendered the extremely relatively dark El Dorado / Ultreya feature to be the same albedo as the surrounding, much brighter, hill and valley.

This would be a *perfect* image if El Dorado / Ultreya appeared as dark, in relation to the surrounding terrain, as it should be.

-the other Doug

[mhoward]

I think it's actually the filter, or perhaps the filter and the lighting. The images are in R1 and R7; I think R1 has been used for the mosaics so far.

[slinted]

I think the lack of contrast in El Dorado / Ultreya is more an issue of filter choice. So far we just have R1 (blue) and R7 (Pancam's furthest IR). As we learned from the close-ups, the sands there are as bright if not brighter than the normal Gusev sands in blue, but dramatically less bright in red. When we get some L2s or R2s, I'll bet the dark sands pop out again.

[mhoward]

Doing an R711 combination seems to work moderately well:



It's hard to get the balance right across multiple images, though.

[climber]

Here we go again on the science side of the pictures!
You're right and I agree and I also say that the lower light the lower contrast. BUT, on this particular case, us, as UMSF'ers as well as as the general public who's paying for this, we've got even more return (ROI ) than we'd expected in our wildest thought.
How poetic I am...

[Phil Stooke]

Regarding the idea of plotting the route on this great new pan:

The route from the hilltop to Eldorado could be mapped very nicely. To the right of Eldorado, the prominent mound is Comanche. Miami is just above and somewhat to the right of it... yes, quite a bit could be plotted. But everything after Eldorado is lost.

But I don't have time to do it.

Phil

[Nix]

Nice to see that R1-7 combo Michael, hadn't taken the time to do it myself.

Individually, the shorter wavelengths will typically render darker areas brighter than they are while the longer (L/R2 for instance), like Slinted states will render the dark areas dark -or rather less reflective than they actually are under Martian lighting.

One can compare this being valid by looking at some radiance data from Opportunity dunefield scenery, while waiting for the 'right' data from Spirit sol 708 from El Dorado..

The reflected glare visible in the scene is also cause for the low contrast in some areas, due to the low sun-altitude. But I don't mind, the effect is indeed a very dramatic scene.

Nico

[Shaka]

They seems to have corrected that sequence name. It's now written as McMurdo on the tracking web.

That's a relief. For a moment I was afraid that global warming had forced a name change.

Individually, the shorter wavelengths will typically render darker areas brighter than they are while the longer (L/R2 for instance), like Slinted states will render the dark areas dark -or rather less reflective than they actually are under Martian lighting.

The discussion by Nix et al. about the albedo variations of Eldorado is one we have touched upon repeatedly in past months. I have tried to contribute my understanding of how incident light is reflected, trapped and scattered by bodies of well-sorted and rounded basaltic sand on Mars. I'm sure that wavelength selectivity of different Pancam images will contribute to how bright or dark the sand looks in an image; ('bluish' sand will look 'blackish' through a red filter). But much of the variation also occurs in Navcam views, with unvarying wavelength biases. These variations conform to a fairly simple dictum: The closer the incident angle of illumination matches the viewing angle, the darker the sand will appear. Orbital midday pictures of Eldorado (and most Martian sand dunes) look black because both light and viewing are from above. From Spirit's present location on the surface of Mars, Eldorado looks bright because there is roughly 90 degrees between illumination and viewing angles, regardless of time of day. From the summit of Husband Hill we were looking down on Eldorado, the angle difference was usually less than 90, and Eldorado looked dark.
The basaltic sands of Mars reflect back very little light; they scatter more to the sides; they absorb and trap a lot. I hope this is helpful.

[atomoid]

the incident angle shouldt matter too much sine the sandfield is not flat but wavy that vaiation should override and make somewhat insignifficant any change incident angle. otherwise ultreya would be very mottled looking based on its topography.

after cancelling out the effects of the filter used, i thought the 'lightening' of ultreya had more to do with the dynamic range of the exposure compressing the contrast between the soil values when a signifficant portion of the image is the sky, causing the white set point to hog the higher end of the dynamic range and robbing the darker portion of it contrast range.

[Shaka]

the incident angle shouldt matter too much sine the sandfield is not flat but wavy that vaiation should override and make somewhat insignifficant any change incident angle. otherwise ultreya would be very mottled looking based on its topography.

But of course Eldorado and all dune fields do look "mottled", with the mottles comprising mostly bands of albedo gradients parallel to the ripple crests and troughs. That's how we see the ripple patterns at all. If we're going to get into the small scale variations within a ripple, other minutia regarding the degree of sorting and rounding and the mean particle size can also make contributions, as well as the mineral composition and albedo of individual grains.
It would be nice if one of our rockhounds could supply the URL of a good discussion of these principles with suitable illustrations. I don't know of one offhand. I could make this clearer if I had a blackboard.

after cancelling out the effects of the filter used, i thought the 'lightening' of ultreya had more to do with the dynamic range of the exposure compressing the contrast between the soil values when a signifficant portion of the image is the sky, causing the white set point to hog the higher end of the dynamic range and robbing the darker portion of it contrast range.

It's interesting that we have a component of our membership who prefer to explain albedo patterns as an artifact of the imaging technology rather than as 'real' light patterns that we would all see if we were standing on Mars 'in the flesh'. I wonder if they are primarily photographers who are fixated on the foibles of their machinery, rather than the natural world. As a biologist, my fixation is on the latter, but clearly we can both make a contribution to this discussion.

[aldo12xu]

The rift between artistic license and what's "real" can be a distant one. Here's my revised attempt to bridge the gap:



http://www.marsgeo.com/Photos/Spirit/BestC..._HP_HHill_c.jpg

[Shaka]

The rift between artistic license what's "real" can be a distant one.

You're right about that, Aldo! Over the years since the MER landings we have all developed our own 'personal' mental images of the 'reality' of Mars. That is the MIRACLE of the MER missions! We aren't really there on Mars, using our own eyes, but the extraordinary imaging systems of Spirit and Opportunity have given us a sense of Martian reality. (Personally, I have gained nothing more valuable from the NASA programs since I watched Buzz Aldrin 'skip' across the Moon.)
None of us has really stood and watched a sunset on Mars. We have all felt the magic that can accompany that moment on Earth. The MER cameras know nothing about those moments. They are programmed to 'optimize' each frame in terms of brightness and contrast. What Dilo's interpretation of their panorama has done is to remove the imaging machine from our experience, and to give us a real Martian sunset - as real as anything we can know until we stand there.

[lyford]

well spoken, shaka!

[Nix]

Concerning artifacts in the imagery, we all know by now not to make wild assumptions based on raw images.
Still, some rough comparisons can be made IMO if the time-interval is short enough. That's why I referred to comparing some calibrated Oppy-scenery through L2/L5/L7/R1 until we get to see some calibrated data for El Dorado.

Here's the L1 pan shot on sol 799.
[Radiometrically calibrated L1 images are used to produce estimates of the albedo (bolometric albedo; see page 23 of Bell et al.: Pancam In-Flight Calibration) for those interested in the technical stuff.]



while a 'raw' pan, this should provide a somewhat more realistic perception of the scene since L1 is centered at 739 nm with 338 nm bandpass (~largest wavelength coverage amongst the Pancam filters)

Nico