Development of a Method for Determining Radiant Heat Transfer for Spacecraft Platforms in Near Earth Orbit Flight

External heat fluxes are the main factor affecting spacecraft in near-earth orbits. These fluxes can vary during orbital motion due to the different orientation of the satellite to the Sun. To develop a method for simulating heat fluxes incident on structural elements of the outer surfaces of a spacecraft, taking into account their operating conditions, is an urgent task. The paper introduces a method for a comprehensive analysis of heat fluxes incident on the structural elements of a spacecraft under conditions in near-earth orbit flight. Within the study, we consider direct and reflected from the Earth solar fluxes of thermal radiation, as well as infrared fluxes of radiation from the Earth and "visible" structural elements. To verify the compiled model, we carried out mathematical simulation of the thermal loading of the outer side of the spacecraft platform, located on the illuminated side of the sun-synchronous orbit. The method will be useful when choosing a working orbit in designing a spacecraft at the stage of technical proposals.