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I have just downloaded t0902_mrrsu_05s138_0256_1.img covering Gale crater, and just have some general questions:

- Is the coverage for all mrrsu* products typically about 40% of a tile? I wasn't expecting such a large amount of missing data.

- Is there any reason why each image strip seems to be individually normalised, but only in some products? For example, the IRAC product seems to have consistent values across the mosaic (I can clearly see the crater from the image), however, other products (mainly single band images, eg R440) appear to have each image strip with different ranges across the mosaic, as do the mrrif* images.



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As you may know, the tiles are created by compiling multiple, independent observations. Each of the long strips across a tile is a separate observation.)


Some tiles have more coverage that others, and the one you are looking at is more sparse than most. That may be due in part to limitations on CRISM's ability to get coverage over Gale crater, since MRO is frequently conducting relay for MSL there. That prevents CRISM observations to reduce radio interference with the relay. Also, it's fairly low latitude where orbits crossing a given point are less frequent than at higher latitudes.


The browse products for the MRDR images are all generated from each observation, and go into the tile without adjustment. Some products that may be sensitive to seasonal, atmospheric, or photometric variability can show significant variation between observations, and that will show in the tile display as strip-to-strip inconsistency. Some products may not be as sensitive to such variability and might seem more consistent. For example, the blue wavelengths that go into R440 are probably more sensitive to atmospheric scattering than the IR, so dust aerosol variation between observations might explain some of the difference between R440 and IRAC.

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Ah I see. Thank you.


One more question, relating to TRDRs - do you know the approximate number of images that have been studied so far, or perhaps how many images are available? I know that Carter et al. (2014) submitted an abstract to the LPSC this year in which they conducted a survey of 2900 images (http://www.hou.usra.edu/meetings/lpsc2014/pdf/2364.pdf), and I wondered why this number was chosen as I read elsewhere that about 10000 images were taken in MROs PSP.

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CRISM is getting close to 100,000 total observations of all types. We've acquired close to 16,000 FRT (plus roughly 2000 HRS and 4000 HRL) and a bunch of FRS and ATO that I haven't counted yet. So, I don't know why the number 2900 came up. Probably has something to do with their study area or target.



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