On-orbit calibration of an ocean color sensor with an underflight of the airborne visible/infrared imaging spectrometer (AVIRIS)

Abstract

Abstract Accurate calibration of ocean color sensors in the orbital environment is essential to achieve the objectives for which these sensors were proposed, developed, and launched. However, the trauma of launch and the orbital environment may cause changes in sensor calibration. An innovative approach to calibrating ocean color sensors uses the simultaneous underflight of the spaceborne ocean color sensor by a calibrated airborne imaging spectrometer. On May 20, 1997, the high-altitude Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) underflew the Ocean Color and Temperature Scanner (OCTS) onboard the Advanced Earth Observing System (ADEOS) satellite. AVIRIS measures the total upwelling spectral radiance from 400 to 2500 nm at 10-nm intervals at high radiometric and spatial resolution. This spectral range includes the eight ocean bands of OCTS. The spectral, radiometric, and spatial calibrations of AVIRIS are determined in the laboratory and validated in flight. The AVIRIS underflight was designed to match the observation geometry of OCTS. An ocean surface calibration target was determined based on common azimuth and zenith observation. The AVIRIS spectra of the calibration target were corrected to the top of the atmosphere radiance and convolved to the OCTS spectral, radiometric, and spatial characteristics. These AVIRIS data were then used in conjunction with the OCTS data to calculate an on-orbit calibration for OCTS with uncertainty analysis.