Estimation of environmental influence on spacecraft materials radiative properties by inverse problems technique

Abstract

The development of reliable thermal protected covering for optical research and control devices of satellites is a very important scientific and technical problem which demands providing a complex experimental-computational research of the corresponding heat transfer processes. A significant part of this research was based on the results of flight testing, in particular, on the analysis of stability of radiative characteristics of materials. In the interaction processes between space structures, instruments or equipment and the environment, as well as at contact surfaces between these structures, the heat transfer processes play an important role. Very often numerical simulation of these processes drives us to the necessity of using a heat transfer mathematical model with lumped parameters. One of the main difficulties here is how to determine coefficients of the mathematical model, which provide its adequacy to real processes. Direct measurement of most characteristics of heat transfer is usually impossible, and their theoretical estimates are often far from being true and often contradictory. That is why, a problem arises to determine the heat transfer characteristics of structures by means of calculations and experimentally. The practical approval of the suggested technique has been carried out for the estimations of radiative characteristics of the spacecraft thermal control coatings. Of great interest is an experimental determining of the solar radiation integral absorptivity factor As and integral semi-spherical emissivity ε of space surface coating in the conditions of actual operation. The necessity in such research is explained by various events of anomalies, appearing during flight tests of satellites (usually resulted in essential discrepancies between predicted and measured temperatures). These phenomena can be explained by the degradation of the surface of materials: after the increasing of its absorptivity under interaction with the environment. Such tests were executed in particular on spacecraft of the "Cosmos", "Meteor", and "Meteor-Priroda" series [1–3] and corresponded experimental data were used for practical approval of developed method.