Initial Cross-Calibration of Landsat 8 and Landsat 9 Using the Simultaneous Underfly Event

With the launch of Landsat 9 in September 2021, an optimal opportunity for in-flight cross-calibration occurred when flew underneath 8 while being moved into its final orbit. Since two instruments host nearly identical imaging systems, underfly event offered ideal conditions. The purpose this work was to use imagery collected by estimate parameters a calibration update scheduled at end on-orbit initial verification (OIV) period. Three types uncertainty were considered: geometric, spectral, and angular (bidirectional reflectance distribution function—BRDF). Differences caused geometric found be negligible application. Spectral minimal except green band viewing vegetative targets. BRDF models derived from MODIS product indicated substantial error could occur required development mitigating methodology. these three contributions properly addressed, it estimated that total data kept under 1%. during filtered remove outliers based on analysis. These used calculate TOA radiance values each spectral taking ratio average pixel 9. Initial results approach may as accurate 0.5% space 1.0% space. developed study refine OIV