Technique for estimating uncertainties in top-of-atmosphere radiances derived by vicarious calibration

摘要

Reflectance-based vicarious calibration of satellite sensors is a method by which in-situ radiometric measurements of a surface target and the atmosphere are used to constrain a radiative transfer model for estimating a top-of-atmosphere (TOA) radiance. The procedure provides an at-sensor radiance, independent of the on-board calibrator, that can be used to maintain knowledge of the in-flight calibration performance of the remote sensing system. However, an estimate of the TOA radiance is incomplete unless accompanied with an uncertainty that quantifies the random and systematic errors associated with that estimate. Presented in this paper is a methodology for predicting a TOA radiance with an absolute accuracy estimate derived using an error propagation analysis based principally on validation data recorded by calibrated ground-based radiometer measurements. A vicarious calibration data collect for the airborne sensor ATLAS and the IKONOS satellite on June 30, 2000 at Brookings, South Dakota provides a test case for this technique in the solar reflective spectrum. The results show that using a natural grass covered target under moderate aerosol loading, absolute accuracies between 3% and 5% are achieved for band integrated TOA radiances between 0.4 and 1.6 microns.