The selection and analysis of the thermal worst cases is one of the critical points in the thermal design of a spacecraft. Typically, a limited number of scenarios are sufficient to cover the configuration of the mission and the orientations and orbit conditions when they are simple but in some cases, more specific configuration is needed.
In the case of Proba-3 ESA’s IOD mission, the possible scenarios are much more complex because the mission is composed of two spacecraft that perform formation flying maneuvers. During each orbit are performed more maneuvers than other missions perform in their entire lifetime. In addition, a very precise definition of the pointing and relative position of the spacecraft at specific moments of the orbit is needed to represent correctly the shadow of one spacecraft over the other.
Additionally to the complex maneuvering scenario and the pointing changes, has been checked that ESATAN is not able to change the Sun’s Declination during the simulation, not representing the correct Sun position, impacting directly the generation of the correct shadows.
In order to generate the adequate inputs to perform the Thermal analysis in an automated way to cover the different scenarios, a MATLAB/Simulink tool has been implemented. This tool also takes into account this ESATAN’s limitation in the Sun positioning and generate the correct ephemeris to model the shadows in an accurate way.
The generated ephemeris and pointing angles have been introduced in an ESATAN-TMS 2017 radiative case and checked by means of shadow maps. The correct definition and implementation has been possible thanks to a close cooperation between the Mission/System Engineering team and the Thermal Engineering team.
In addition to the ephemeris, the thermal dissipations of all the units and the relative position of units’ moving parts have been also introduced in thermal analysis. Moving parts analysis is especially important in the case of the Proba-3 primary payload, designed to open the door only at specific times during the orbit to operate in the umbra conditions generated by the shadow of the other spacecraft.
The presented process has been carried out to generate all the thermal use cases needed for the definition of the thermal control subsystem of a very challenging mission as Proba-3 ESA’s IOD mission.