Abstract
In order to deliver high quality, traceable, multi-sensor optical Earth Observation measurements and fused data products, there is a need for common reference sources and dedicated intercalibration and bias assessment activities. The goal of the Ground to Space CALibration Experiment (G-SCALE) was to demonstrate the use of convex mirrors as a radiometric and spatial calibration and validation (cal/val) technology for Earth Observation (EO) assets operating at multiple altitudes and spatial scales. Specifically, to generate a point source with NIST-traceable absolute radiance signal for simultaneous vicarious calibration of multi- and hyperspectral sensors in the VNIR/SWIR range, aboard Unmanned Aerial Vehicles (UAVs), aircraft, and satellites. The experiment was carried out at the Rochester Institute of Technology’s 177-acre Tait Preserve in Penfield, NY, USA on July 23, 2021. The G-SCALE represents a unique, international collaboration between commercial, academic, and government entities for the purpose of evaluating a novel method to improve vicarious cal/val for EO, in direct comparison to traditional diffuse reflectance techniques. We will provide an overview of the experiment and acquired data sets, with an intercomparison of signature retrievals using both traditional and mirror-based calibration techniques.
Furthermore, we will present updates to the FLARE Network, an on-demand automated commercial cal/val network utilizing the mirror technology employed in G-SCALE. Extensive validation efforts have shown stable performance against commercial and agency missions, with radiometric uncertainties below 3.5% across most of the solar reflective spectrum (350 – 2500 nm). In addition to high dynamic range fixed nodes, newly developed semi-mobile stations have been developed which can be quickly and inexpensively deployed to provide targeted references suitable for cal/val. The first of these units was commissioned to validate Sentinel 2 surface reflectance products. Finally, we present the upcoming Mauna Loa node, created in partnership with the NOAA Mauna Loa Observatory. This high-altitude, atmospherically stable site provides multiple radiometric and spatial calibration points. The Mauna Loa FLARE node has the potential to achieve < 1.5% radiometric uncertainty for multi- and hyperspectral Earth Observation missions.
The Ground to Space CALibration Experiment (G-SCALE): SI-traceable Intercalibration of Multiscale Earth Observation Platforms using Mirror-based Targets
In order to deliver high quality, traceable, multi-sensor optical Earth Observation measurements and fused data products, there is a need for common reference sources and dedicated intercalibration and bias assessment activities. The goal of the Ground to Space CALibration Experiment (G-SCALE) was to demonstrate the use of convex mirrors as a radiometric and spatial calibration and validation (cal/val) technology for Earth Observation (EO) assets operating at multiple altitudes and spatial scales. Specifically, to generate a point source with NIST-traceable absolute radiance signal for simultaneous vicarious calibration of multi- and hyperspectral sensors in the VNIR/SWIR range, aboard Unmanned Aerial Vehicles (UAVs), aircraft, and satellites. The experiment was carried out at the Rochester Institute of Technology’s 177-acre Tait Preserve in Penfield, NY, USA on July 23, 2021. The G-SCALE represents a unique, international collaboration between commercial, academic, and government entities for the purpose of evaluating a novel method to improve vicarious cal/val for EO, in direct comparison to traditional diffuse reflectance techniques. We will provide an overview of the experiment and acquired data sets, with an intercomparison of signature retrievals using both traditional and mirror-based calibration techniques.
Furthermore, we will present updates to the FLARE Network, an on-demand automated commercial cal/val network utilizing the mirror technology employed in G-SCALE. Extensive validation efforts have shown stable performance against commercial and agency missions, with radiometric uncertainties below 3.5% across most of the solar reflective spectrum (350 – 2500 nm). In addition to high dynamic range fixed nodes, newly developed semi-mobile stations have been developed which can be quickly and inexpensively deployed to provide targeted references suitable for cal/val. The first of these units was commissioned to validate Sentinel 2 surface reflectance products. Finally, we present the upcoming Mauna Loa node, created in partnership with the NOAA Mauna Loa Observatory. This high-altitude, atmospherically stable site provides multiple radiometric and spatial calibration points. The Mauna Loa FLARE node has the potential to achieve < 1.5% radiometric uncertainty for multi- and hyperspectral Earth Observation missions.