Low Noise High Dynamic Range Sky Characterization System

The development of tactical IR imaging equipment requires calibrated night sky spectral radiance measurements from the visible (VIS) through the shortwave infrared (SWIR). Measuring the dark moonless night sky spectra at the required resolution is challenging due to the background noise produced from external thermal emissions. Spectral Sciences, Inc. is building a low noise spectrometer via an innovative use of waveband-dependent cold filters to eliminate out-of-band thermal noise. We propose developing the Sky Spectrometer and Radiometer (SkySR), a rugged and compact optical instrument for measuring spectral radiance and atmospheric temperature. SkySR combines an extremely low noise spectrometer with high dynamic range, enabling both daytime and nighttime spectral measurements with 8 nm or greater resolution in the VIS to SWIR wavebands. To fully characterize the observed radiance, SkySR measures apparent atmospheric temperature in the midwave and longwave for estimating the radiance contributions from atmospheric thermal emissions. A lightweight fieldable instrument for characterizing spectral sky backgrounds is well suited to support development of tactical equipment and other military and commercial needs such as supporting remote sensing simulations and field measurement campaigns.