New phase function development and complete spectral radiative properties measurements of aerogel infused fibrous blanket based on simulated annealing algorithm

Aerogel infused fibrous blankets have been regarded as one the most promising superinsulation materials for application of thermal subsystems with severe limitations in weight, volume, and thermal insulation efficiency in space missions. Aiming at accurate description of radiation transport within such multiscale, multicomponent composites with absorbing, emitting, and anisotropic scattering features, this research is interested in experimental characterization of complete series of spectral radiative parameters on basis of theoretical solution and optical measurements for the composites. To overcome the convergence difficulty in ill-posed problem, simulated annealing algorithm was employed for inverse identification of multiple radiative parameters of the aerogel-based samples. A new phase function with two Henyey-Greenstein (HG) and Rayleigh scattering functions was proposed to describe the radiation scattering distribution inside the composites. It was found that the developed method successfully achieved high precision measurements of radiative parameters of anisotropic scattering medium. The proposed phase function gives more exact expression of angular distribution behavior of scattering occurring inside the multiscale composites, in comparison with the commonly-used phase functions. The information collected from sensitivity analysis of Bidirectional Reflectance Distribution Function (BRDF) and Bidirectional Transmittance Distribution Function (BTDF) facilitated highly accurate and more efficient identification and optimization of experimental tests in measurements of complete radiative parameters of aerogel infused fibrous blankets for space applications.