Takao Endo, Mitsubishi Electric Corporation; Takuro Tsuchikawa, Mitsubishi Electric Corporation; Takayasu Anada, Mitsubishi Electric Corporation; Hitomi Ono, Mitsubishi Electric Corporation; Hidenobu Tsuji, Mitsubishi Electric Corporation
Keywords: Non-Resolved Object Characterization, GEO Satellite Characterization, photometric light curve, BRDF
Abstract:
We are developing novel methods to analyze space objects using unresolved optical imagery. Our approach involves a 3D computer-aided design (CAD) based ray-tracing system to study the photometric light curve of artificial satellites in geostationary orbit (GEO). Predicting the light curve of an artificial satellite observed on the ground is challenging due to its complexity, which depends not only on the lighting geometry between the illumination source and the observer, but also on the shape of the artificial satellite and its scattering characteristics on the surface. To address this issue, we constructed a simulator that reproduces the illumination conditions on the orbit.
First, we measured the bi-directional reflectance distribution function (BRDF) of the characteristic materials used on satellite surfaces, such as multi-layer insulation (MLI) and solar array panels (SAP), and numerically modeled their scattering properties. Next, we represented the shape of the artificial satellite using publicly available information and assigned scattering properties to each component.
Furthermore, we considered three-dimensional lighting geometry, including direct sunlight and earthshine. We assumed that the solar spectrum, as a light source, was a black body radiation with a temperature of 5800K and an apparent diameter of approximately 30 arc minutes. In normal operation, it is assumed that the front of the satellite SAP always faces towards the Sun, and the satellite bus also points towards the Earth. Finally, we conducted a ray-tracing calculation to determine the brightness observed on the ground by setting the position of the light source, the observer, and the artificial satellite.
In this paper, we present preliminary results obtained using models of the Himawari-8 and QZS-3 satellites, known respectively as a weather and navigation satellite in GEO. The predicted light curves explain the major features observed in actual light curves, although a perfect agreement between the observations and the theoretical models has not yet been achieved. Therefore, we discuss the performance of the ray-tracing calculation and the resulting photometric light curve of satellites in geostationary orbit obtained using ground-based telescopes.
Date of Conference: September 19-22, 2023
Track: Satellite Characterization