Calibration of AVHRR-2 data for retrieving sea surface temperature.

The response of the sensors of the AVHRR on board the NOAA-7 satellite, measuring the radiance in the 11 micrometer window region, is not linear. The in-flight two-point calibration obtained can be optimized for the error due to the non-linearity of the sensors response. The NOAA Users' Guide gives the optimization of the calibration in the range 225 to 310 K. This range is too large with respect to sea temperature variations. A better optimization is possible if a smaller range of temperature is considered. The 225-310 K range is reduced to 285-295 K, chosen so that the coefficients of the linear approximation, which best fit the non-linear calibration, can be arranged according to the characteristics of the target. Results show that a difference of as much as 0.4 K can be observed between the standard and the new optimized calibration proposed. -Authors