Version 13 (modified by mggr, 12 years ago) (diff)

--

ATM

Consists of three files patterned as azYYMMDD[ABC].cal, where the last character before the .cal is A for scan speed 12.5, B = 25, C = 50.

The contents of the files are like:

AZ16 bandpairs 10 1 1000 az060306A.cal
87.72727273 24498 6.12019233 24468 2.31661442 24425 5.34458259 24501 2.05878963 24516 2.24453694 24704 1.29384497 24663 3.35342640 24280 0.64997509 24088 0.15410141 24283

Format is 10 pairs of numbers (one each for channels 1-10). The first number is the gain (multiplier), the second number is the dark current level. To compute a real world value, you should compute:

real world value = (sensor_DN - dark_current_level) * multiplier

See also: Processing/RadiometricCalibration/ATM


Specim

Calibration files are produced by Specim when they do maintenance on the instrument. FSF is starting to do this now (first test attempt in Dec 2007).

A brief description of the procedure:

  1. checking wavelength alignment (can be done in imaging mode - 512x?) - this checks that the light is being measured at the correct wavelengths (value unimportant)
    1. pick a suitable calibrated light source (e.g. big lamp) and flood out the CCD evenly
    2. examine the output to see if there are spikes (value unimportant, only position in spectrum counts) in the appropriate emission bands
    3. repeat with a filter and look for troughs (value unimportant, only position in spectrum counts) in the appropriate absorption bands
    4. this method can also be used to verify an existing calibration to some extent
  2. full calibration
    1. switch the instrument to calibration mode (1024x1024 pixels)
    2. point the instrument into a calibrated integrating sphere, at a distance where there won't be too many reflections back into the sphere, but close enough to evenly illuminate the whole CCD
    3. take measurements at the various settings
    4. (post processing) calculate offset and gain constants

Eagle

Files look like:

SN100022_130207_XB.cfg
Lens configuration file - contains calibration date and a few other human-readable items
SN100022_130207_XB.hdr
Header file for the data file..
SN100022_130207_XB.cal
Data file (containing several frames?) of the per-pixel calibrations

Hawk

SN300011_150207_NUC1.cfg
Lens configuration file - contains calibration date and a few other human-readable items
SN300011_150207_NUC1.hdr
Header file for the data file..
SN300011_150207_NUC1.cal
Data file (containing several frames?) of the per-pixel calibrations
SN300011_150207_NUC1.bad
Bad pixel table (text format, unsure of contents)

CASI

Radiometric calibration done by <name of guy> at Environment Agency (or Met Office?) using an integrating sphere at FSF and post-processing at the EA?

Consists of five 700KB files named inXXaA.rad, where X = two digit calibration sequence (up to 36 for 2007) and A = aperature (1-5). The files are binary (guessing pixel array of min/max floats?).

Additionally, there is a file that describes the view angles for each pixel to compensate for (lens?) distortions in the view field. The current version of this file is named NERC253_527tan.txt and looks like:

0 26.311677 0.051465
1 26.221749 0.089928
2 26.131682 0.090067
3 26.041477 0.090205
4 25.951133 0.090344
5 25.860650 0.090483
6 25.770029 0.090621
7 25.679270 0.090759
8 25.588372 0.090898
9 25.497337 0.091036
...
504 -26.131682 0.090205
505 -26.221749 0.090067
506 -26.311677 0.089928
507 -26.401465 0.089789
508 -26.491115 0.089649
509 -26.580625 0.089510
510 -26.669996 0.089371
511 -26.759227 0.089231

I'm guessing CCD column number, X angle, Y angle.