In-orbit calibration (TOTAL channel) V space -V IBB Raw Earth V (counts) Raw IBB V (counts) =

In-orbit calibration B : ground calibration measurement of G(SW source) / G(LW source) L F IBB : ground calibration measurement of the filtered internal black body radiance

In-orbit calibration monitoring SW response monitored via CALMON solar diffuser sphere Quartz filter transmission: [V sw (light) – V sw (dark)]/ [V TOT (light) – V TOT (dark)] SW response: [V CALMON (light) – V CALMON (dark)] / G TOT

In-orbit calibration monitoring Internal black body behavior monitored as by temperature variation

Calibration table updates 1: spectral response Updated reprocessed visible ( µm) 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)

Reprocessed Average Detector Spectral Response and witness sample data

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

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.

Variation of black body and detector temperatures Detector temp. variation 0.4  C Implies G(TOT) variation ~ (0.04%)

Gain variations 28/4/03 – 03/03/04 Pixel 123 (noisy)

Gain variations Scan means 28/4/03 – 03/03/04