Chris H. Lee, Rochester Institute of Technology; Charles M. Bachmann, Rochester Institute of Technology; Patrick Seitzer, University of Michigan, Dept of Astronomy; Heather M. Cowardin, NASA
Keywords: Goniometer, Directional Reflectance Spectroscopy, Imaging Spectroscopy, Polarimetry, Laboratory Measurements
Abstract:
To better characterize the spectral response of common spacecraft materials, the following laboratory measurements are presented to support the Space Situational Awareness community in the analysis of remotely sensed observational data. Of interest is classifying material reflective properties using directional reflectance spectroscopy and spatially resolved polarized imaging spectroscopy, allowing laboratory data to be applicable to ground-based optical telescope observations. The team acquired a typical CubeSat solar panel and a sample of multi-layer insulation (MLI) commonly used on spacecraft for initial measurements. The data were collected at the Goniometer of the Rochester Institute of Technology (GRIT) laboratory with a lab and field goniometer housing two Analytical Spectral Device (ASD) spectrometers, a small Labsphere integrating sphere paired with an ASD spectrometer, and a Headwall micro-Hyperspec E-Series imaging spectrometer with an adjustable linear polarizer. The goniometer measures spectral bi-directional reflectance factor (BRF) data over a broad range from 350-2500 nm at 1 nm spacing with 3 nm spectral resolution in the visible and near infrared and 8 nm in the shortwave infrared. With the same spectral capabilities, the integrating sphere measures directional-hemispherical reflectance (DHR) in a 45 degree -nadir configuration. The Headwall imager covers a spectral range from 400-1000 nm with 1.6 nm spectral resolution. Our initial BRF measurements show interference effects for both materials typically observed with thin films and high infrared reflectivity. In contrast, the interference effects are not present in the DHR measurements of the MLI likely due to the interference effects being averaged out over the reflecting hemisphere. Spatially resolved polarization ratio maps show variability across the materials due to the varying surface structure. We outline a plan for expanding our analysis to a broader range of materials to characterize their directional reflectance spectroscopy.
Date of Conference: September 27-20, 2022
Track: Non-Resolved Object Characterization