In-flight interband calibration of AVHRR data by a cloud-viewing technique

A significant degradation in the responsivity of the AVHRR radiometers aboard the NOAA satellite series, affects the index vegetation (NDVI), which is an important source of information for monitoring vegetation conditions on regional and global scales. Many studies have been carried out which use the viewing Earth calibration approach in order to provide accurate calibration correction coefficients for the computation of the vegetation index using the visible and near-infrared spectral channels 1 and 2 of AVHRR. This study deals with the interband calibration of AVHRR visible and near-infrared data by means of an cloud-viewing technique. This technique is simple to implement and can be used in real-time. It is also well-suited to the processing of large time-series of data. Results are presented for various NOAA satellites and are in full agreement with the calibration degradation model proposed by NOAA and various authors.