Minimize Mission Performance

The OLCI-A and OLCI-B instrument health is excellent. The sensors temperatures are perfectly well controlled. The nominal radiometric diffusers ageing show the expected magnitude and spectral behaviours: around 0.35% after 3 years for OLCI-A at 400 nm (Oa01), down to 0.06% at 510 nm (Oa05) and undetectable above; below 0.15% for OLCI-B.

The instrument sensitivity evolution so far is limited to less than 2% (OLCI-A) and no evidence of degradation can be demonstrated: the variation of the instrument sensitivity seems more correlated with a potential spectral evolution of the correcting filters – inside the spectrometers – than to darkening of the optics or loss of sensitivity of the CCD sensors. Sensitivity evolution of OLCI-B is similar to that of OLCI-A, but shows higher magnitudes that are still to be confirmed: the time series starts with an earlier orbit than for OLCI-A and the in-flight BRDF modelis not yet implemented, limiting the accuracy of the evolution assessment. The regularly monitored instrument SNR performance is well within requirement.

Spectral Calibration is monitored thanks to dedicated acquisition campaigns. The in-flight spectral campaigns reveal a high agreement of the in-flight characterisation with the pre-flight spectral calibration for both A and B sensors, with differences of the OLCI channels centre smaller than 0.1nm, except for channels Oa01 (400 nm) and Oa21 (1020 nm), with up to 0.2nm. A small temporal evolution is observed, different for each camera.