Battery Handling Strategy during Eclipse on Galileo Constellation

The Galileo Control Centre (GCC-D) in Oberpfaffenhofen is one of two control centres responsible of operating the Galileo constellation, managing a fleet of twenty-six spacecraft flying in MEO orbits and consisting of two different satellite families: IOV and FOC. The satellites are placed in three different orbital planes uniformly distributed around the equator at intervals of 120°. Due to the orbit inclination (≈56°) each plane will face two Earth Eclipse season per year. The eclipse time depends on the orientation of the Sun-direction with respect to the orbit plane of the satellites and its inclination. The maximum eclipse duration due to the Earth is 60 min. The S/C can also experience, along its orbit, eclipse event due to the Moon with a total umbra time up to 95min. The batteries of the S/C are designed to provide the power supply to the bus when the Solar Arrays are not illuminated by the Sun. The paper will focus on the operational aspect of the eclipse and on the strategy that has been developed and that is actually used during Routine mission phase. At the beginning, the strategy was developed for FOC S/Cs with the aim of having a unique value of the battery voltage in Solstice and a unique value in Eclipse. A battery fade strategy was performed in order to take into account the degradation of the battery during the S/C lifetime and has been implemented in the strategy. At the same time a similar battery handling approach between Moon and Earth Eclipse has been achieved. Once the strategy was defined and successfully validated, a similar approach has been also developed for IOV S/Cs taking into account the differences in the hardware. This strategy is successfully used in Galileo Routine Operation since 2016.