Model and algorithm for calculating the irradiation of a space object by Earth’s radiation

Subject of study. The study focuses on simulating Earth’s radiation to calculate the spectral density of irradiation on a space object represented by a polygonal model as it traverses a trajectory over various regions of Earth’s surface. The model accounts for solar illumination, climatic zones, seasonal variations, cloud cover, and orbital altitude. Aim of study. The objective is to develop an algorithm for calculating the spectral density of irradiation of space objects, offering capabilities comparable with MODTRAN. The algorithm is designed to automatically adapt to changing illumination conditions during the object’s movement in near-Earth space. Method . The study employs mathematical simulation of Earth’s radiation, modeled as a superposition of point sources representing elementary, layered volumetric atmospheric fragments and fragments of Earth’s surface. Engineering calculation methods and numerical estimates of atmospheric optical properties are applied. The model also incorporates contributions from scattered solar radiation and intrinsic thermal radiation. Main results. An iterative algorithm has been developed to calculate the spectral density of irradiation on a surface element (facet) of a space object caused by Earth’s radiation. The algorithm retrieves parameters programmatically from a database required for the calculations. Its functionality is demonstrated through an example of integral energy irradiance computation for a space object at an altitude of 300 km due to Earth’s radiation. Practical significance. The iterative algorithm, supported by a comprehensive database of Earth-related parameters (surface, atmosphere, cloud cover, etc.), provides a valuable tool for simulating the energy reflection-emission characteristics of space objects in near-Earth space.