When downloading Lunar Reconnaissance Orbiter LRO NAC images from the website https://pilot.wr.usgs.gov/ a significant portion of them have no useful data -- they have a sort of plaid pattern. Does anyone know what's going on here? Are these some kind of dark image for sensor calibration? Some examples of the affected images:

M159144761RC, M161499633RC, M156784061RC, M156784061LC, M165038842RC, M169754968RC, M167400488LC, M167400488RC, M176828812LC, M176828812RC, M182720706RC, M180361835RC, M1135749148RC, M185079577RC

some LRO images

Example of some "plaid patterns":

some dark LRO images which illustrate "plaid patterns"

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    $\begingroup$ I would guess that these are darks for CCD calibration. But usually data from the PDS is already calibrated. $\endgroup$ – Phiteros Feb 7 '18 at 0:20
  • $\begingroup$ @Phiteros, LRO NAC images start out as Experimental Data Records (EDR), then you spiceinit, calibrate, and echo-remove them to make Calibrated Data Records (CDR). These are the EDR. As far as I know, blank data is kept in SPICE kernels but I don't know the details of how that works. $\endgroup$ – foobarbecue Feb 7 '18 at 2:25
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    $\begingroup$ @uhoh, wow, you went to town on that edit! I'll make all those image numbers into links to .tif files shortly here. $\endgroup$ – foobarbecue Feb 7 '18 at 2:27
  • $\begingroup$ Some of those definitely look like some form of bias calibration. You can see the telltale brighter values in the top right. $\endgroup$ – Phiteros Feb 7 '18 at 2:57
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    $\begingroup$ No worries, it's a 1-minute job in a decent text editor. $\endgroup$ – foobarbecue Feb 7 '18 at 3:44

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