دانلود رایگان مقاله رویکرد جدید مدل سازی بازتاب طیفی فضاپیما

Abstract

Simulated spectrometric observations of unresolved resident space objects are required for the interpretation of quantities measured by optical telescopes. This allows for their characterization as part of regular space surveillance activity. A peer-reviewed spacecraft reflectance model is necessary to help improve the understanding of characterization measurements. With this objective in mind, a novel approach to model spacecraft spectral reflectance as an overall spectral bidirectional reflectance distribution function (sBRDF) is presented. A spacecraft’s overall sBRDF is determined using its triangular-faceted computer-aided design (CAD) model and the empirical sBRDF of its homogeneous materials. The CAD model is used to determine the proportional contribution of each homogeneous material to the overall reflectance. Each empirical sBRDF is contained in look-up tables developed from measurements made over a range of illumination and reflection geometries using simple interpolation and extrapolation techniques. A demonstration of the spacecraft reflectance model is provided through simulation of an optical ground truth characterization using the Canadian Advanced Nanospace eXperiment-1 Engineering Model nanosatellite as the subject. Validation of the reflectance model is achieved through a qualitative comparison of simulated and measured quantities.

5. Conclusion

The validity of modeling a spacecraft’s spectral reflectance as an overall sBRDF, generated using its CAD model and the empirical reflectance of homogeneous samples of its surface materials, has been demonstrated. While the comparison of simulated quantities with those from an actual optical ground truth characterization experiment was only qualitative, it is clear that this approach produces more valid results than the TASAT and DIRSIG systems based on the contents of published literature. The empirical material reflectance database developed as part of this approach is spectral in nature and complete for all illumination and reflection geometries, thus avoiding the dependency on theoretical BRDF models that have demonstrated a limited ability to model the spectral reflectance of different material types. Modeled spacecraft reflectance has also been demonstrated to be a function of illumination and reflection geometry using this approach, which was not consistently exhibited by the TASAT and DIRSIG systems.