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new THEMIS color releases, Images showing color variations.
edstrick
post Jun 29 2006, 08:13 AM
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I stand corrected. My understanding remains that the HiRes cam does cross-CCD integration, but I'd have to recheck the specs.
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djellison
post Jun 29 2006, 08:58 AM
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Yes - HiRISE does TDI - (128 lines I think)

Essentially as eash row 'dwells' on the target, it adds the photons, then passes the count onto the next row of the 128 rows....thus increasing SNR by, in theory, 128 times. Of course there is noise and some losses within the process - but that's the theory as I understand it.

MOC NA, MOC WA, HRSC and CTX are, as I understand it, single line Pushbrooms. HiRISE a Pushbroom-with-TDI, and MARCI / THEMIS a Pushframe design. Discreet framing cameras were on board the Vikings, Mariners, and the crap SRC channel on HRSC smile.gif

Doug
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edstrick
post Jun 29 2006, 09:23 AM
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The absolutely critical thing with a camera like HiRISE is the image must smear nearly perfectly across the detector parallel to the cross-frame rows of pixels and the camera must step the "bucket" of electrons along the column in near perfect time with the image motion, and nothing can jiggle during the imaging. "Nearly perfectly" is probably somewhat better than 1/4 pixel or so. That would be measurable but not obviously degrade the image.

That HiRISE did so well from a grossly non-nominal elliptical orbit under low to extremely low sun illumination angles and did so with "first try" image aquisition software and decalibration files and software says that barring hardware failure, we've got ourselves a winner.

The only sad thing is that the "phace-phreaks" will still be able to "discover" untold signs of archaeological wonders at and well beyond the resolution limits of the images, no matter how high the resolution is. Hoaxland would be able to discover signs of artificial intelligence in the artifacts of an image of a single electron, I'd swear!
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