 The Landsat 8 operational land imager, OLI, was radiometrically calibrated prior to launch in terms of spectral radiance. The radiance calibration was performed with an uncertainty of 3%, the reflectance calibration to 2%. On orbit, multiple calibration techniques indicate that the sensor has been stable to better than 0.3% to date. This article was offered by Brian Markham, Julia Barsi, Geerke Farron, and others.