Abstract
The Goddard Laser for Absolute Measurement of Radiance (GLAMR) is a spectral and radiometric calibration facility developed for hyperspectral earth science instruments. A detailed study of the radiometric uncertainty has been conducted as part of our optical calibration of the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission Ocean Color Instrument testing. This instrument has particularly stringent calibration requirements, necessitating a comprehensive set of measurements to characterize sources of radiometric uncertainty. Included in these measurements are the spectrally dependent linearity, repeatability, uniformity, measurement noise, and fluorescence. Uncertainty of the absolute calibration provided by the National Institute of Standards and Technology is also included to establish an overall uncertainty of the radiance.
Improvements and additions to the hardware that have been implemented as part of this study are described, and corrections for linearity and fluorescence are presented. Total radiometric uncertainty at k=1 in the visible and near infrared is 0.2%, in the ultraviolet 0.3%, and in the short-wave infrared 0.4% outside of atmospheric absorption features. Primary contributors to uncertainty are the absolute calibration of the transfer radiometers and the uniformity of the integrating sphere.
Radiometric Uncertainty Analysis of the GLAMR Calibration Facility
The Goddard Laser for Absolute Measurement of Radiance (GLAMR) is a spectral and radiometric calibration facility developed for hyperspectral earth science instruments. A detailed study of the radiometric uncertainty has been conducted as part of our optical calibration of the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission Ocean Color Instrument testing. This instrument has particularly stringent calibration requirements, necessitating a comprehensive set of measurements to characterize sources of radiometric uncertainty. Included in these measurements are the spectrally dependent linearity, repeatability, uniformity, measurement noise, and fluorescence. Uncertainty of the absolute calibration provided by the National Institute of Standards and Technology is also included to establish an overall uncertainty of the radiance.
Improvements and additions to the hardware that have been implemented as part of this study are described, and corrections for linearity and fluorescence are presented. Total radiometric uncertainty at k=1 in the visible and near infrared is 0.2%, in the ultraviolet 0.3%, and in the short-wave infrared 0.4% outside of atmospheric absorption features. Primary contributors to uncertainty are the absolute calibration of the transfer radiometers and the uniformity of the integrating sphere.