[X] My Assistant

[Harkeppler]

Combination of the infrared images of Sol 616 with R4 (red), R5 (green) and R6 (blue) give as a pseudocolor photo after some color enhancement an interesting result:

the blue-gray sharpe edged small stones (probably some vulcanic material) found strawn around the Erebus site look quite different in infrared but not in the visual band. There are at least three destinct infrared signatures giving probably a hint on their origin and chemical composition.

Here, on the left an R2 (red), R1 (blue)-picture is shown with synthetic green chanal according to the visual color taken from an L4L5L6 image and on the right the R4R5R6 picture.

The original Opportunity photos were normalized using a circular mask to reduce the radial loss of brightness to the edges.

This pair can be seen on the right (I am wondering that the thumbnails are not shown in the correct sequence).

The second image couple shows Bounce at Sol 68 in L4L5L6, L2L7 and R2R1 (from left to right with synthetic green in L2L7 and R2R1) for comparison: There is a possibility to make nearly natural looking color composites using the R2 and R1 channels.

This image triple is shown on the left.

(Image processing was done by collegue Mr. Norbert Gasch)

The interesting question is now: Does anyone have an idea what sorts of material this can be at the Erebus site?

Best wishes: Harald

Attached thumbnail(s)

 

[CosmicRocker]

Doug: I'm guessing you are saying that because we have no idea of the exposure times used for the various fiters, and will not know until the PDS release of these images. Is there something else going on in the conversion to jpeg?

Because the individual exposures are unknown, we sure can't say much about the spectral properties, but it seems that within the confines of this particular set of images we can detect relative differences between the spectral properties of the various pebbles.

Harald's image from Erebus is interesting in that it seems to show several different types of pebbles, where they all are very similar in color, looking at the visual bands. I previously thought we were seeing only two different kinds of pebbles; the blueberries and the dark cobbles. But this false color composite seems to strongly suggest several distinct mineralogies/lithologies.

Harald: A long time ago, before I understood that the individual filters were imaged with different exposures, I tried to determine the mineralogy of the blueberries by sampling their luminance in all the filters, correcting them according to the quantum efficiency curve for the pancam CCDs and their predicted exposure times, as published in the Bell paper, and then comparing the derived spectra to published spectra of various minerals. It was a lot of work, and my results were inconclusive. After the announcement that the blueberries were hematite I could see some crude similarities between my spectra and those released by JPL in an early press conference, but nothing one could be confident about.

Thanks for sharing that image with us. I have to imagine you are seeing a real difference between the pebbles in that image, but I think we would need additional information to identify the minerals. But to be honest, I am not an expert in spectral analysis.

[djellison]

Doug:  I'm guessing you are saying that because we have no idea of the exposure times used for the various fiters, and will not know until the PDS release of these images.  Is there something else going on in the conversion to jpeg?

Yes - they all get stretched to hell and back. Basically, it's like the 'auto-levels' function in photoshop - and once you have an image, you have no means whatsoever of converting it back. Not to mention the conversion from 12 bit to 8 bit, and heavy JPG compression.

It's not just exposure and stretching, it's all the other calibration that goes on ( flatfield, dark field, exposure, temperature etc etc etc ) that we only get with the PDS releases as well.

Doug

[helvick]

Yes - they all get stretched to hell and back.

The problem item is the stretching\auto levelling because we have absolutely no idea what the conversion was doing at the time. The use of the jpg format also affects the usability of the data, I suspect that we could compensate somewhat for it but I would not trust a spectral interpretation from an image that had been jpg'ed.

The other conversions could be compensated for to some degree:
8->12bit. We have the look up tables for these so that's straightforward.
Exposure. This is slightly tricky but with the regular sun shots and fairly precise knowledge of the light model at any point in time it is be possible to get a fairly accurate estimate of the exposure duration of an image.
Temperature. This is harder to deal with but once again it can be estimated albeit with a fairly high error margin based on already published data.
The Flatfield\darkcurrent removal and other calibration steps seem to be sufficiently well documented to allow amateurs to carry them out if they had unmodified raw image data.

IF we had temperature, exposure and (all of) the unmodified raw image data then we could do the rest. But since we don't have that it can't be done.

[djellison]

IF we had temperature, exposure and (all of) the unmodified raw image data then we could do the rest. But since we don't have that it can't be done.

All we actually need is an l/p to the recent data on the workbook

Doug