In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =
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Transcript of In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =
![Page 1: In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649dc95503460f94abee26/html5/thumbnails/1.jpg)
In-orbit calibration (TOTAL channel)
Vspace-VIBB
Raw Earth V (counts) Raw IBB V (counts)
=
)(tL
VVG
FIBB
IBBspace
1)()(spaceIBB
IBBsceneFIBB
FIBB
IBBsceneFscence VV
VVtLtL
G
VVL
![Page 2: In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649dc95503460f94abee26/html5/thumbnails/2.jpg)
In-orbit calibration
1()(
)()()()(
TOTVTOTV
TOTVTOTVTOTLTOTL
spaceIBB
IBBsceneFIBB
Fscence
)(
)(
)()(
)()()(
SWLVV
VV
B
TOTL
SWLTOTBG
SWVSWVSWL
FIBB
spaceIBB
IBBsceneFIBB
FIBB
IBBsceneFscence
B : ground calibration measurement of G(SW source) / G(LW source)
LFIBB : ground calibration measurement of the filtered internal black body radiance
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In-orbit calibration monitoring
• SW response monitored via CALMON solar diffuser sphere
Quartz filter transmission: [Vsw(light) – Vsw(dark)]/ [VTOT(light) – VTOT(dark)]
SW response: [VCALMON(light) – VCALMON(dark)] / GTOT
![Page 4: In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649dc95503460f94abee26/html5/thumbnails/4.jpg)
In-orbit calibration monitoring
• Internal black body behaviormonitored as by temperature variation
![Page 5: In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649dc95503460f94abee26/html5/thumbnails/5.jpg)
Calibration table updates 1: spectral response
• Updated reprocessed visible (0.4-2.5µm) detector spectral response received
• In the absence of infrared data this was ‘stitched’ to the witness sample infrared data (starting at 2.5µm)
• Updated calibration parameters have been produced from this (B, A, T)
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Reprocessed Average Detector Spectral Response
and witness sample data
Reprocessed measured average detector and witness sample response
250
270
290
310
330
350
370
390
410
430
450
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7
wavelength (um)
No
rmal
ize
d r
es
po
ns
e
`
![Page 7: In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649dc95503460f94abee26/html5/thumbnails/7.jpg)
Reprocessed Average Detector Spectral Response
and witness sample data
Reprocessed measured average detector and witness sample response
250
270
290
310
330
350
370
390
410
430
450
0 2 4 6 8 10 12 14 16
wavelength (um)
No
rmal
ize
d r
es
po
ns
e
`
![Page 8: In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649dc95503460f94abee26/html5/thumbnails/8.jpg)
Effect of reprocessed data on calibration
Ratio of Gain calculated from a SW source to that calculated from a LW source
Would be 1 for perfect knowledge of spectral response and instrument linearity
Green: old SR, Red: reprocessed SR
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Calibration table updates 2: internal black body table
• Pixel to pixel variability in the filtered internal black body radiances determined from ground calibration has been found to be due to pixel offset drift during the calibration measurements
• This drift can and has been illuminated for the central pixels, a decision needs to be made about how the issue is dealt with for the other pixels in the array
• An update to the internal black body table will result after such a decision.
![Page 10: In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649dc95503460f94abee26/html5/thumbnails/10.jpg)
Variation of black body and detector temperatures
Detector temp. variation 0.4C
Implies G(TOT) variation ~ 0.008 (0.04%)
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Gain variations 28/4/03 – 03/03/04
Pixel 123 (noisy)
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Gain variations Scan means 28/4/03 – 03/03/04