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Ticket Resolution Summary Owner Reporter
#249 invalid Rescaling dark frames causes calibration errors benj benj

Processing data in azspec and using the -dIc option to rescale dark frames seems to cause the data to be incorrectly radiometrically calibrated.

I've attached three screenshots. dIc_ex1.png shows spectral profiles for the rescaled flightline from both azspec (top) and CaliGeo (bottom). You can see that the azspec spectrum goes up at both ends, where the CaliGeo spectrum doesn't. The azspec spectrum also has values that are consistently about 600 higher than CaliGeo (discounting the edges of the spectrum, which as mentioned are much higher).

dIc_ex2.png shows spectral profiles from the second flightline, which did not require the dark frames to be rescaled. Azspec and CaliGeo are in very close agreement for this line.

odd_one_out.png is just for illustration - it shows all of the Eagle lines from that flight (as processed through azspec) overlaid. The first flightline (with the rescaled dark frames) is clearly visible as different - much whiter than the other lines.

This may affect any datasets from 2006, and some VOCALS data.

Related tickets: #218 #250

#250 invalid Create program to rescale dark file benj benj

We need a program that will read in a dark frame file, rescale it to mimic that for a different integration time and then output the new file.

Basic level: Read in data file, multiply by a user-specified scaling factor (except pixels 1 & 2 on band 1 for each line), output new data file.

What we really want: Same, but calculate scaling factor from differential of integration times - check relative data values for existing dark files to try and work out if the result of changing the integration time is just a linear scaling (hopefully) or something more complicated, then implement appropriate algorithm. The user should also be able to specify a scaling factor as above if they prefer.

Gold-plated: Same, but also account for changes in framerate and in spectral/spatial binning. May be worth spending half an hour to check whether the effects of altering these are also just linear scaling, but if they're not then don't include them (assume constant).

Related tickets: #218 #249

#256 fixed Hawk contains dark stripes benj benj

Hawk imagery since the start of 2009 contain dark stripes running along-track. Initially there was just one stripe but following the instrument's return to Specim in April there has been a number.

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