However, these actions consume energy, and this resource is scarce in compact, high-tech devices. Computer scientists at Saarland University have now shown how the energy consumption of satellites can be planned so that they always operate optimally without their batteries running out. The results can be transferred to other application areas.

"The core of our current work is the so-called 'planner,'" explains Holger Hermanns, Professor of Computer Science at Saarland University. This planner allows the numerous different activities that modern nanosatellites can perform to be planned continuously in advance and optimized with respect to their energy consumption profile.

The battery model on which the Saarbrücken researchers' planning method is based is noteworthy: "We don't rely on the commonly used linear model, in which the battery charge is simply represented as a value between 100 and 0 percent," says Hermanns. "Our planner uses the kinetic model of the battery, which can also accurately account for the charge fluctuations inherent in each battery." The new method of satellite operation thus enables long-term activity planning and is seamlessly adaptable to entire satellite fleets.

The researchers developed their new activity planning tool using two GOMX-4 satellites from the Danish-Luxembourgish company GOMspace. Each time the satellites pass over the ground station in Denmark, they transmit telemetry data on their battery usage. Based on this data, a new action plan is calculated using the novel scheduler and then uploaded to the satellites. "By optimizing the plan each time the satellites fly over the ground station, we always ensure the best possible battery utilization," explains Hermanns.

The market for so-called LEO (low Earth orbit) satellites is growing rapidly: Today, around 2,500 active miniature satellites orbit our planet. Launches for approximately 50,000 more have already been announced for the next 10 years. However, this innovative approach to battery planning extends beyond this use case and can also be transferred to other application areas, such as e-mobility, drones, and smart home devices.

The researchers published their results under the title "Managing Fleets of LEO Satellites: Non-Linear, Optimal, Efficient, Scalable, Usable, Robust" at one of the largest conferences on embedded software, the International Conference on Embedded Software. In addition to Professor Holger Hermanns, Juan Fraire, Tobias Mömke, and Gregory Stock from Saarland University participated. Fakhri Babayev and Eduardo Cruz participated on behalf of the Luxembourg-based company GOMspace. The project is primarily funded by the European Research Council through the ERC Advanced Grant "POWVER" and the German Research Foundation (DFG) through the Transregional Collaborative Research Centre "CPEC - Center for Perspicuous Computing." The Guangdong Provincial Key Areas Research and Development Programme also participated. in China.

A follow-up project has already been awarded with cooperation partners from Europe, Argentina, and China. The project, which is funded by the EU under the Marie Skłodowska-Curie Actions, is entitled "Models in Space Systems: Integration, Operation, and Networking" and is expected to begin in October 2021.