An enhanced Earth InfraRed flux and Albedo model based on real data

Within the last years, a larger number of spacecrafts have been launched in Low Earth Orbit (LEO). The current trends show that it is continuously increasing, with a growing part for light CubeSats. Most of the LEO spacecrafts are dedicated to Earth observation, and they can feature relatively large instrument openings and/or low thermal inertia, especially for the CubeSats. This usually makes the payloads or the entire spacecraft thermal behavior particularly sensitive to the Earth environment, for both the albedo and the Earth emitted infrared fluxes. In parallel, the development of numerous Earth climate monitoring missions has provided more accurate and detailed data about the Earth albedo and infrared flux in the last 2 decades. It appeared recently that this data can be used to feed statistical survey of the real thermal environment as viewed from spacecrafts in low orbit depending on their orbital parameters. For this purpose, ESA have developed an internal tool that, for a given orbital position, generates incident infrared and albedo flux values based on real measurements available daily, generating a sizeable number of parametric environmental flux results. A systematic series of simulations have been run with these real data to cover circular orbits ranging from 100 to 800 km altitude and with various inclinations. The emphasis was particularly put on the Sun Synchronous Orbits (SSO) and how their Local Time at Ascendant Node (LTAN) has an impact on the perceived Earth environment. The paper will explain briefly the method of calculation and will present how the worst cold and hot Earth environments were identified for different types of orbits. It will eventually present some ranges of perceived albedo and perceived Earth temperature for the short and long term as a function of the altitude, the inclination and the LTAN for the SSO.