Radiometric Analysis of Daytime Satellite Detection

A radiometric model for daylight satellite detection is developed and used to evaluate the effects of various parameters on signal-to-noise ratio (SNR). Detection of reflected sunlight from a low-earth orbit, diffuse, planar satellite by a single-pixel infrared photovoltaic detector is considered. Noise considered includes photon noise from the background and signal, as well as thermal noise. Parameters considered include atmospheric conditions, optical parameters, and detector parameters. The Phillips Laboratory Expert-assisted User System, an atmospheric modeling tool that employs the MODTRAN and FASCODE transmission codes, is used to model wavelength-dependent atmospheric transmission and background radiance. The SNR is found to increase when the detector is placed at higher altitudes and when there is lower aerosol content in the atmosphere. The SNR is also found to increase with decreased noise-equivalent bandwidth, detector dark current and field of view (FOV), and with larger optical elements. For a 16” diameter telescope and a FOV no smaller than 70 mrad, optimal bands are found to be between 0.8 μm and 1.7 μm