Improved Satellite Brightness Estimation Techniques

The Visual Magnitude Satellite Catalogue effort [1] presently employs a simple straight-line model for solar phaseand declination-angle dependencies, an approach that, at least for declination angle, lacked any real pedigree. The present attempt to improve the modeling began by investigating several competing gridding techniques that would allow two-parameter brightness dependencies to be displayed visually and selected Universal Kriging as the preferred methodology, as it can be demonstrated to produce minimum estimation error. Brightness histories from the SBV satellite were examined with krigged gridding for two difficult-to-model spacecraft: the HS-376 (cylinder) and HS-601 (cube with panels) geosynchronous satellites; and observed second-degree dependence on declination angle and, less commonly, phase angle suggested the use of a quadric surface fitting function. Quadric surface fits to the krigged gridding compared favorably to similar fits of the actual data while outperforming them in producing reasonable brightness extrapolation to areas of low data density. These results argue for a change of the VM SATCAT model to a quadric surface fit from krigged data, which, while not perhaps the final solution, would be a notable improvement over the present technique.