Battery Current and Temperature Mission Profiles for CubeSats at Low Earth Orbit

CubeSats, a branch of the space industry, has lately received great interest for being an affordable satellite platform. For proper functioning, they are nowadays practically dependent on lithium-ion batteries as a power supply at moments, when there is not enough power generated by solar panels. Thus, batteries have to be thoroughly tested to ensure that they provide sufficient performance, lifetime, and that they are safe. In other industry areas, such as electric vehicles, it is common to use mission profiles (often referred to as driving profiles) for battery testing to closely emulate conditions that are experienced in practice. However, mission profiles reflecting closely CubeSat conditions are not publicly available. Thus, this article proposes a methodology to derive mission profiles, and resulting representative mission profiles, dedicated especially to battery testing. The proposed methodology is based on analyzed telemetry data from three GOMX CubeSats. At first, electrical current characteristics are obtained from the telemetry and are generalized across the satellites, to be subsequently used for the mission profile synthesis. The battery temperature is an important factor for the battery performance and lifetime, and it was identified to be very dynamic in CubeSats. Thus, a model describing battery temperature during their mission is proposed to generate realistic temperature mission profiles. Finally, the current and temperature profiles are synchronized to capture their mutual impact on the batteries, and they are formulated to be suitable for on-ground (laboratory) testing.