Optical Filter Selection for the Detection of Light Pollution from Low Earth Orbit

Light pollution is defined as excessive, misdirected, or obtrusive artificially produced outdoor lighting. It disrupts ecosystems and wastes energy, besides interfering with astronomic research. Light pollution is currently growing at a rate of almost 10% annually, and is an active area of research and monitoring. This paper describes a design step in the development of a single-pixel monitoring payload to perform light-source identification from low-Earth orbit. Public light sources emit signature light spectra in the visible and near-infrared range. This spectrum is captured in eight or fewer spectral segments using optical bandpass filters thus achieving two orders of magnitude data reduction relative to state-of-the-art mini spectrometers. The challenge is to select the center wavelengths and full width at half maximum (FWHM) of the optical filters to achieve highest accuracy in identifying the light sources in the light mixtures captured from a low Earth orbit (LEO).We describe the optimization procedure used to select filter characteristics for monitoring light pollution from orbit using an eight-detector characterization payload.