Thermal force effects on satellites

Abstract

Thermal force effects due to the Earth infrared radiation acting on artificial satellites can explain most of the residual orbit decay observed on high altitude satellites. In this work, we propose an improved thermal model that presents the total thermal effect as a sum of the summer-winter and the "generalized" day-night effects. We show that a unified model may take into account the sin theta' term (where theta' is the co-latitude of the thermal energy source) for the day-night force component and the cos theta' term for the summer-winter force component. These terms are associated with temperature variations on the satellite's surface due to its movement around the thermal energy source and allow the simultaneous application of these two forces resulting in a unified total thermal force that has two components: the Summer-Winter force, in the satellite spin axis direction (z), and the generalized Day-Night force, in the satellite equatorial plane (xy). We calculate the along-track accelerations for a test-satellite (parameters based on the LAGEOS satellite data) and obtain the average along-track acceleration <S> = -3.46 x 10-13 ms-2, for the day-night effect, and <S> = -2.85 x 10-12 ms-2, for the summer-winter effect, that leads to a residual orbit decay of nearly 1.08 mmd-1. Finally, we analyze the behavior of the average radial and along-track accelerations, and the thermal lag angle, as a function of the satellite's altitude, and show that there is a "selective law" that associates the maximum thermal effect to the radius and altitude of the satellite, and control the satellite orbit decay.