Cross calibration Thaichote & Landsat 8 over Libya4 using pseudo invariant calibration sites (PICS)

Thaichote, Thailand earth observation satellite, has been in orbit since October 2008 serving satellite data for numerous applications to users community. It requires a satellite system to show a high degree of radiometric stability. Thus, it is essential to monitor the radiometric performance of a satellite in order to accurately identify changes on the surface without confusing them with changes occurring due to the sensor. Landsat 8 Operational Land Imager (OLI) has been in orbit since 2013. It is a well-known and well calibrated satellite with its calibration uncertainty of 3% for all bands, This paper presents a radiometric comparison of these sensors from analysis of image data and radiometric characterization results obtained from the Libya 4 Pseudo-Invariant Calibration Site (PICS) using Thaichote lifetime data and Landsat 8's 3.5 years in orbit. Cross-calibration between Thaichote and Landsat 8, using their lifetime data, showed differences on the order of 8% for blue band, 3% for green and red bands, and 6% for nir band, after application of a spectral band adjustment factor (SBAF) and performing BRDF Solar Zenith Angle and BRDF Viewing Zenith Angle correction to the Thaichote image data. These cross-calibration results suggest there is a need to apply Absolute Gain Scale Factor (AGSF) in the processing system for all four spectral bands.