Optimization of Narrow-Band Wide-Angle Filtering in a Geostationary Lightning Mapper

Abstract: The author considers problems of narrow-band optical filtering in geostationary lightning mappers. The filtering is designed to isolate the brightest triplet in the optical response of lightning (777.19, 777.42, and 777.54 nm) against a background of sunlight reflected from clouds. Earth’s angle of view is ≈17.5° from the geosynchronous equatorial orbit, and there are considerable differences in the narrow band pass of a Fabry–Pérot filter for different angles of light incidence. The optimum combination of the width and position of the filtering spectrum is found in order to minimize the shift of the central filtering band and the splitting of the filtering spectra of s- and p-polarized light at large angles of filter deflection. New technical solutions based on acousto-optic filters are proposed. © 2022, Allerton Press, Inc.