Georgia Tech Research Institute Goniometer (GT-RIG): A Commercial Off the Shelf (COTS) Bidirectional Reflectance Distribution Function (BRDF) Characterization System for Spacecraft Materials

Abstract Accurate characterization of the spectral Bidirectional Reflectance Distribution Function (BRDF) of spacecraft materials is critical for a wide-range Space Situational Awareness (SSA) tasks ranging from assessing the pose of spacecraft to modeling solar radiation influences on trajectories. Unfortunately, many goniometer systems that are used to measure the BRDF of materials are highly specialized, bulky, and costly to repair. These limitations mean that performing BRDF measurements within a small and potentially damaging space-weathering chamber is prohibitive in terms of both the cost-to-repair goniometer damage and overall volume-allowance. This is a major gap for BRDF characterization of spacecraft materials, as recent experiments have shown that BRDF can substantially differ when characterized in Earth's atmosphere relative to when characterized under the influence of space weather factors such as Ultraviolet (UV) radiation and Atomic Oxygen (AO). To meet this need, we present the development of a Commercial Off The Shelf (COTS) goniometer system that enables broadband characterization of the BRDF of spacecraft material samples: the Georgia Tech Research Institute Goniometer (GT-RIG). This system has a volume-constrained design with easily swappable COTS components, enabling future BRDF characterization within space-weathering chambers. In this paper, we present a characterization of the prototype system, a modeling of the uncertainties of resultant BRDF measurements, and an initial set of BRDF measurements acquired by the system on Kapton material samples.