Stray light characterization in a high-resolution imaging spectrometer designed for solar-induced fluorescence

摘要

New commercial-off-the-shelf imaging spectrometers promise the combination of high spatial and spectral resolutionneeded to retrieve solar induced fluorescence (SIF). Imaging at multiple wavelengths for individual plants and evenindividual leaves from low-altitude airborne or ground-based platforms has applications in agriculture and carbon-cyclescience. Data from these instruments could provide insight into the status of the photosynthetic apparatus at scales of spaceand time not observable with tools based on gas exchange, and could support the calibration and validation activities ofcurrent and forthcoming space missions to quantify SIF. High-spectral resolution enables SIF retrieval from regions ofstrong telluric absorption by molecular oxygen, and also within numerous solar Fraunhofer lines in atmospheric windowsnot obscured by oxygen or water absorptions. Because the SIF signal can be < 5 % of background reflectance, rigorousinstrument characterization and reduction of systematic error is necessary. Here we develop a spectral stray-light correctionalgorithm for a commercial off-the-shelf imaging spectrometer designed to quantify SIF. We use measurements from anoptical parametric oscillator laser at 44 wavelengths to generate the spectral line-spread function and develop a spectralstray-light correction matrix using a novel exposure-bracketing method. The magnitude of spectral stray light in thisinstrument is small, but spectral stray light is detectable at all measured wavelengths. Examination of corrected line-spreadfunctions indicates that the correction algorithm reduced spectral stray-light by 1 to 2 orders of magnitude.