Temperature distributions of a communication satellite antenna composed of a horn and a reflector were studied. Antenna temperature is primarily determined by the solar heating, which varies in accordance with the solar incidence angle and its intensity. Monte Carlo method was introduced to calculate the solar heating in order to deal with the self-shading of the antenna and with the mixed specular-diffuse reflection. The spectrum of the reflected light differs from that of the irradiated if the reflectance of the material has spectrum dependence, which mostly holds true in real cases. And since the absorptance is a function of the spectrum of the incident light, this spectrum change after reflection causes a change of the absorptance. In the present ray tracing process of the Monte Carlo method, the spectrum of the light and the absorptance for it are reevaluated at each reflection.
In order to show the effectiveness of this method, temperature distributions were calculated using nodal analysis, and the results were compared with thermal vacuum test data. The solar simulator used is a divergent type powered by Xenon lamps, its characteristics had to be taken into consideration adding to the above-mentioned correction. The calculated results showed good agreement with the measured test data, and also the influence of the diverging light was made clear comparing with the results assuming a parallel solar beam.