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Cluster of CubeSats for Multi-Angle Measurements of Bidirectional Reflectance Distribution Function (BRDF)

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Cluster of CubeSats for Multi-Angle Measurements of Bidirectional Reflectance Distribution Function (BRDF)
Cluster of CubeSats for Multi-Angle Measurements of Bidirectional Reflectance Distribution Function (BRDF) The rapidly advancing capabilities of small satellite systems and instrument miniaturization are increasing the implementation feasibility of distributed missions. In order to analyze the capabilities provided by these new systems for science and military application, we seek to use multi-angular data from a distributed spacecraft mission of 6U CubeSats in order to provide Bidirectional Reflectance Distribution Function (BRDF) measurements. By flying the CubeSats in formation at set distances from each other, the CubeSats will be able to co-point and provide multi-angle measurements of the ground track. These multi-angle measurements can be used to analyze the BRDF signatures and compensate for the anisotropic reflectance of a material, as the directional reflectance or BRDF from an object changes based on illumination and observation geometry (Shell, 2004). Additionally, multiple CubeSats in formation provide varying angular information that is unavailable to a single satellite and can be used to demonstrate the ability of Cubesats to provide 3-D images/videos for both robotic exploration and defense applications. Our research would address the following questions/objectives: BRDF: Can a constellation of CubeSats provide multi-angle measurements that provide useful science data? Hyperspectral imaging detects materials based on spectral reflectance, but not compensating for the directional aspects of reflectance could give inaccurate derivations (Shell, 2004). Previous research has also suggested that a constellation of CubeSats could achieve better BRDF results than a single monolithic spacecraft (Nag, 2015). We propose that multiple 6U CubeSats taking multi-angle measurements could provide BRDF measurements that would improve the accuracy of hyperspectral imaging. ADCS: CanX-4 and CanX-5 successfully demonstrated Attitude Determination and Control (ADCS) formation flight algorithms in flight on November 2014 (Grant Bonin, 2015), and were able to maintain relative position knowledge of better than 10 cm and control accuracy of less than one meter at the range of 50 to 1000 m (Josh Newman, 2015). However, formation flying while pointing at the same target on the ground is a substantially different problem due to slewing requirements and disturbances in Low Earth Orbit (LEO). Our research aims to develop ADCS algorithms that will allow formation flying satellites to successfully co-point while maintaining formation. High Resolution Imagery: Due to the CubeSat's limited size, high resolution imagery can be a challenge because of the requirement to store and download massive amounts of data. However, new technologies such as optical communications offer potential ways to download mass amounts of data much quicker than before, and memory storage on a CubeSat is becoming more capable. Part of our research will study the optimal way to store and download high resolution imagery from a CubeSat. Initial input measurement requirements for science applications will come from science metric values of existing, successful spaceborne instruments (e.g. MISR (Multi-angle Imaging SpectroRadiometer), MODIS (Moderate-resolution Imaging Spectroradiometer)) and airborne (e.g. CAR (Cloud Absorption Radiometer) instrument data. At the conclusion of this research, we will have advanced the technology of formation flying a constellation of CubeSats and will have contributed to analysis of how to improve BRDF measurements from spacecraft. More »

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