Radiometric performance of the Landsat 9 Operational Land Imager over the first 8 months on orbit

The Landsat 9 satellite was launched on September 27, 2021 to continue systematic imaging of the Earth's land surfaces. Together with Landsat 8, it provides coverage of the entire Earth every 8 days. Landsat 9 carries the Operational Land Imager (OLI), which is practically a copy of the Landsat 8 OLI, and the Thermal Infrared Sensor (TIRS). In this paper we demonstrate the excellent radiometric performance of Landsat 9 OLI over its first several months of operations on orbit. On-board calibrator data were used to assess the sensor's radiometric performance characteristics. All spectral bands are radiometrically stable to within 0.1%. The signal-to-noise performance is stable and is 3 to 8% better than Landsat 8. The bias stability is better than 1 DN (Digital Number). The validation of the absolute calibration performed with surface measurements indicated the OLI was calibrated to within 5% in spectral radiance and 3% in reflectance. Still, a comparison between Landsat 9 and Landsat 8 OLI derived top-of-atmosphere reflectance indicated small disagreements between the instruments in all spectral bands, The absolute radiometric calibration of Landsat 9 OLI was adjusted to be in closer agreement with Landsat 8 OLI before products were released to the public.