Abstract
The Operational Land Imager (OLI) 2 is the visible, near-infrared and short-wave infrared sensor to be flown on Landsat 9. It is nearly identical to the OLI on Landsat 8. Several improvements to the pre-launch characterization program were implemented for OLI 2, including a revised instrument level spectral response test. This characterization used the NASA Goddard Laser for Absolute Measurement of Radiance (GLAMR), in lieu of the traditional monochromatorbased system used for the Landsat 8 OLI. GLAMR, like the system on which it was based, the NIST Spectral Irradiance and Radiance responsivity Calibrations using Uniform Sources (SIRCUS), uses tunable lasers coupled into an integrating sphere with a large exit port. The GLAMR based test provided characterization of 100% of the OLI 2 detectors spectral response with the OLI 2 full aperture and about 5° of the field illuminated as opposed to about 10% of the OLI detectors using partial aperture illumination of about 0.15° of the field illuminated with the monochromator-based system. Testing was performed across the full spectral range of the sensitivity of the OLI 2 detectors, approximately 350 to 2500 nm. This enhanced testing captured some variation in the spectral response within individual focal plane modules related to spectral filter transmission variations and expected variations in spectral response across the focal plane due to angle of incidence and different filter wafers used for the focal plane modules. In addition, with illumination of adjacent focal plane modules, most cross talk effects were appropriately captured. The measured spectral responses met the requirements in the vast majority of cases with a few minor deviations.
Spectral Response Characterization of the Landsat 9 Operational Land Imager 2 using the Goddard Laser for Absolute Measurement of Radiance (GLAMR)
The Operational Land Imager (OLI) 2 is the visible, near-infrared and short-wave infrared sensor to be flown on Landsat 9. It is nearly identical to the OLI on Landsat 8. Several improvements to the pre-launch characterization program were implemented for OLI 2, including a revised instrument level spectral response test. This characterization used the NASA Goddard Laser for Absolute Measurement of Radiance (GLAMR), in lieu of the traditional monochromatorbased system used for the Landsat 8 OLI. GLAMR, like the system on which it was based, the NIST Spectral Irradiance and Radiance responsivity Calibrations using Uniform Sources (SIRCUS), uses tunable lasers coupled into an integrating sphere with a large exit port. The GLAMR based test provided characterization of 100% of the OLI 2 detectors spectral response with the OLI 2 full aperture and about 5° of the field illuminated as opposed to about 10% of the OLI detectors using partial aperture illumination of about 0.15° of the field illuminated with the monochromator-based system. Testing was performed across the full spectral range of the sensitivity of the OLI 2 detectors, approximately 350 to 2500 nm. This enhanced testing captured some variation in the spectral response within individual focal plane modules related to spectral filter transmission variations and expected variations in spectral response across the focal plane due to angle of incidence and different filter wafers used for the focal plane modules. In addition, with illumination of adjacent focal plane modules, most cross talk effects were appropriately captured. The measured spectral responses met the requirements in the vast majority of cases with a few minor deviations.