Abstract
The pursuit of highly accurate remote sensing instrumentation has driven the need for an improved, SI-traceable radiometric calibration (RadCal) methodology. A notable example of this necessity is the calibration of the Hyperspectral Imager for Climate Science (HySICS) instrument under the CLARREO pathfinder project, with a stringent calibration requirement of 0.3% (k=1), which is much lower than the existing state-of-the-art instruments. Detector-based absolute RadCal in the solar reflective region has become possible with the implementation of the tunable laser source. One such system is the GLAMR system developed at NASA Goddard that can scan the spectral range of 340-2500 nm. RadCal using GLAMR as the light source has been performed on several major operational instruments, often as part of their spectral characterization to measure the relative spectral response (RSR). Absolute detector responsivities (ASRs) are measured during the process, leading to simultaneous absolute RadCal.
In this presentation, the GLAMR RadCal data for the Landsat-9 Operational Land Imager (OLI)-2 channels are processed and analyzed. The measured detector ASRs are integrated in the spectral domain to calculate the integrated responsivities to validate the values characterized from the separate absolute RadCal using a broadband light source. The results reveal a spectrally dependent agreement within the combined uncertainty margins of GLAMR and Landsat RadCal. The major sources of uncertainties that lead to these deviations are discussed. These results can demonstrate the capabilities of GLAMR absolute RadCal and can be referenced to estimate the overall uncertainty associated to the GLAMR RadCal of HySICS, which is a key phase of CPF’s independent calibration.
GLAMR Calibration as an Absolute Radiometric Calibration Approach
The pursuit of highly accurate remote sensing instrumentation has driven the need for an improved, SI-traceable radiometric calibration (RadCal) methodology. A notable example of this necessity is the calibration of the Hyperspectral Imager for Climate Science (HySICS) instrument under the CLARREO pathfinder project, with a stringent calibration requirement of 0.3% (k=1), which is much lower than the existing state-of-the-art instruments. Detector-based absolute RadCal in the solar reflective region has become possible with the implementation of the tunable laser source. One such system is the GLAMR system developed at NASA Goddard that can scan the spectral range of 340-2500 nm. RadCal using GLAMR as the light source has been performed on several major operational instruments, often as part of their spectral characterization to measure the relative spectral response (RSR). Absolute detector responsivities (ASRs) are measured during the process, leading to simultaneous absolute RadCal.
In this presentation, the GLAMR RadCal data for the Landsat-9 Operational Land Imager (OLI)-2 channels are processed and analyzed. The measured detector ASRs are integrated in the spectral domain to calculate the integrated responsivities to validate the values characterized from the separate absolute RadCal using a broadband light source. The results reveal a spectrally dependent agreement within the combined uncertainty margins of GLAMR and Landsat RadCal. The major sources of uncertainties that lead to these deviations are discussed. These results can demonstrate the capabilities of GLAMR absolute RadCal and can be referenced to estimate the overall uncertainty associated to the GLAMR RadCal of HySICS, which is a key phase of CPF’s independent calibration.