Eagle radiometric calibration investigation

[mggr]

This ticket is spawned from #74 (support ticket for Rachel Gaulton, who found this problem). See that ticket for the initial work, summarised here.

Eagle's calibrated spectral profile on flights appears to differ substantially from CASI in terms of the measured radiance. The shape is the same but the numbers are different by a factor of approximately 4-8, depending on the pixel chosen.

Short history to date:

• 16/Oct Initial problem report from Rachel (2006 dataset)
• 18/Oct AKW recommended investigating on a known dataset
• 22/Oct Picked 166/2007 boresight flight and confirmed we're also seeing this issue
• 29/Oct Demonstrated to Gary and agreed routes for investigation

[mggr]

Routes of investigation:

1. Chris from FSF is visiting in early Dec to calibrate some instruments for 2008. While there, get him to do a quick and dirty calibration on the Specim too, so we have a calibration made in the same conditions as the CASI one to compare against (giving us a ground truth). This will establish if there's a problem with Specim's calibration procedure.
2. As soon as Bill is back from holiday (~10th Nov?), ask him to check on how he handles the Specim calibration in azspec, particularly with non 1-1 binnings (all 2007 Eagle flights are 2-1 or higher and the calibration is 1-1).
3. compare level 0 vs level 1b data to ensure the calibration is being applied
   • done - the level0 looks a bit like a CCD response curve and the level 1b looks like a ground-spectrum and matches the CASI spectra, so this appears to be working, albeit with an offset/factor
4. check the 2007 flights for various binnings to compare against CASI
   • done - no 2007 flights are 1/1, they vary from 2/1 to 8/1 and 8/4
5. compare CASI and Eagle spectra in multiple flights to see if there's a common factor, bearing in mind the binning rates
   • only the 166 boresight and some of the IPY flights have CASI and Eagle run together

[mggr]

Tested L3 vs L1b to ensure it isn't a pixel/sampling size issue (appears it isn't).