The modifications to the instrument calibration between Reprocessing 4.1 and Reprocessing 5 are as follows:
- the exponential fits were performed using the 85 lunar calibrations obtained through the end of the SeaWiFS mission; the fits for Reprocessing 4.1 were based on 76 calibrations.
- the long period time constant in the exponential fits was changed from 1600 days to 2500 days; the short period time constant remains at 200 days.
- only band 4 is now fit by a single long-period exponential; for Reprocessign 4.1, band 3 was also fit by a single exponential.
|Changes in SeaWiFS Gains, Reprocessing 4.1 to Reprocessing 5|
The gains for the new calibration increase after day 1500 because the
calibration for Reprocessing 4.1 no longer tracked the response of the
instrument and because of the change in the long-period time constant. The
early gain increase centered around day 400 because the relative contributions
of the short-period exponential and the long-period exponential to the
simultaneous fit changes as a result of the change in the long-period time
constant. The relative contributions of the short-period and long-period
exponentials to the fit are shown
The changes in the calibration are the most significant for bands 7 and 8, which are the atmospheric correction bands. Consequently, the gain ratios for bands 7 and 8 are evident in the comparisons of normalized water-leaving radiances in the the test results for Reprocessing 5 ( Effect of updated lunar cal & switch to Thuillier).