Ground-based, daytime modeling and observations in SWIR for satellite custody

摘要

Space Situational Awareness (SSA) can be summarized as the ability to monitor, understand and predict natural and man-made resident space objects. At each ground sensor location, gaps in custody emerge as dim objects fall below detectability thresholds with the rising Sun. The length of the custody-gap for a particular satellite depends on the apparent brightness of that satellite and the brightness of the sky background within the field-of-view at the time of observation. Since daytime skies are slightly darker in the infrared, low-cost, passive SWIR sensors are a viable solution for daytime satellite detection. This research develops and validates models of the daytime sky spectral radiance to compare to custody observations in the near-infrared (NIR) and short-wave infrared (SWIR) wavelengths. Sky radiance model accuracy is quantified via observations from three test campaigns with spectral, temporal, spatial-pointing, and groundsite diversity. Ground-level, in-situ measurements of aerosol particles and meteorological inputs significantly increase the accuracy of sky radiance models. Lastly, the efficacy of SWIR daytime custody is demonstrated via a series of exo-atmospheric target observations in the daytime sky quantifying the performance and limitations of utilizing low-cost, SWIR sensors in accomplishment of the ground-based, daytime custody mission.