Implementing Ground Station Tracking in the Thermal Analysis of a Mechanically-Steerable Antenna for LEO Data Downlink Applications

Abstract

The calculation of orbital heat fluxes and radiative exchange factors is an essential part of the thermal analysis of spaceborne instrumentation. For instruments which feature kinematic motion, such as robotic arms and mechanically-steerable antennae, there is an additional complexity in this calculation: there are variations in fluxes and radiative exchange factors due to the instrument’s kinematic motion which occur “on top” of the standard flux variations due to orbital motion alone.

The specific kinematic motion associated to the tracking of a ground station by a mechanically-steerable antenna onboard a LEO satellite is well-known and recurrent to many missions, however it is not available as a default pointing law in the ESATAN-TMS thermal analysis software suite. This paper presents a set of user-defined FORTRAN-based algorithms which have been developed to implement the required tracking functionality in ESATAN. The algorithms are simple yet sufficiently accurate for thermal analysis. Algorithm logic, validation approach, and results of in-orbit calculations using the algorithms are presented in the context of the thermal analysis of the KDA MSDDA, a mechanically-steerable antenna developed by Kongsberg Space/ATG/ESA and baselined to fly onboard MetOp-SG satellites A and B.