Characterization of Earth observing satellite instruments for response to spectrally and spatially variable scenes

Earth-observing satellite sensors are calibrated in the laboratory against blackbody and lamp-based uniform optical radiation standards. These sources and additional characterization tests fail to approximate the spatially, spectrally, and temporally complex scenes viewed on-orbit by these sensors. The lack of appropriate diagnostic tools limits the ability of researchers to fully characterize and understand the radiometric performance of sensors before deployment. The consequences of these limitations are that problems in a sensor’s performance, e.g. optical crosstalk, scattered light, earth-shine, are often first observed on-orbit. Advanced radiometric characterization artifacts, able to produce realistic spectral distributions and spatial scenes in the laboratory, would enable more complete instrument characterization, with the resulting potential benefit of improved on-orbit performance. In this work, we present a radiometric platform for the development of application-specific metrics to quantify the performance of sensors and systems viewing realistic spectral and spatial scenes. There are two components to the platform, both based on Digital Micromirror Device (DMD) technology. The first component is a spectrally programmable light source. This source can reproduce, with high fidelity, the spectral distributions of targets observed on-orbit, for example, the water-leaving radiances for various phytoplankton chlorophyll-a concentrations and atmospheric conditions. The second component is a spatially programmable projection system. This system uses the programmable spectral distributions from the light source as basis functions to generate complex spatial scenes with true spectral content. Using this platform, sensor and system performance may be quantified in terms of the accuracy of measurements of standardized sets of complex source distributions. In essence, the programmable source will be a radiometric platform for advanced sensor characterization, enabling a pre-flight validation of the pre-flight calibration. The same platform can also serve as a basis for algorithm testing and instrument comparison. With the same fundamental technology, platforms can be developed to cover the full reflected solar region; similar platforms can in principle be developed for the thermal IR region as well.