[IEEE 2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting - Vancouver, BC, Canada (2015.7.19-2015.7.24)] 2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting - Efficient GPU implementation of SBR for fast computation of composite scattering from electrically large target over a randomly rough surface