The Air Force Research Laboratory has observed the color photometric signatures of geosynchronous (GEO) satellites since 1996. Recently, we have constructed models and a radiometric simulation in order to aid in understanding the physics of satellite radiometric signatures. We report on the results of the construction of models of GEOs and the comparison of the resulting simulated photometric signature from the models to empirical photometric data obtained of these satellites using CCD technology. We regard these models to be of "first order" in that they employ accurate basic sizes and shapes along with excellent reflectivity functions for typical spacecraft materials. However, they do not yet attempt to represent specular glints nor do we have ground truth knowledge of materials. They also do not include fine structure on the satellite. The models are basically made of three facets: solar panels, main bus structure, and large antennae. The observed signatures are defined as the brightness and colors as functions of phase angle. The brightness and colors are referred to the magnitude systems based on visible Johnson filters, SILC filters (a specialized set of filters for satellite discrimination), and near-IR extension of the Johnson filters. The simulated signatures are calculated in this same magnitude system. The satellites that we have modeled include: AMSC1, Msat M1, Telstar 7, DTV 2, DTV1R, Solidaridad 1 and 2, and Anik F1. We have varying degrees of success matching the empirical data for which examples will be shown. This effort includes the conduction of a joint observation/modeling program in which we have attempted to measure the reflectance of solar panel materials near the condition of zero phase angles, which is a condition that is difficult to duplicate in the laboratory. Application of these observations has dramatically improved the agreement of our simulated signatures with observed color photometric signatures. The importance of these modeling efforts lies in several regimes including simulating anomalous signatures for the purpose of resolution, maximizing the efficiency of observing strategies, and improving understanding of the ability of color photometric observations to distinguish spacecraft materials and structures in the absence of spatial-resolved imagery.
Electro-optical signatures comparisons of geosynchronous satellites
2006 IEEE Aerospace Conference ; 6 pp.
2006-01-01
294176 byte
Conference paper
Electronic Resource
English
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