Formation-Flying of Picosatellites using Differential Drag as a Control Methodology

The rise of small satellites offers a cost-effective, faster, and more reliable alternative to traditional large satellites. They have made space missions more accessible, particularly for educational purposes, enabling more frequent launches and hands-on scientific experiments for students and researchers. As space debris continues to pose a global challenge, the Inter-Agency Space Debris Coordination Committee (IADC) published its Space Debris Mitigation Guidelines in 2002 to establish baseline technical standards. The introduction of smaller satellite systems has significantly impacted space traffic. Low Earth Orbit (LEO) has become increasingly crowded due to its higher accessibility, reflecting an exponential growth trend. Very small satellites present challenges in terms of Precise Orbit Determination (POD), necessitating enhanced collision avoidance strategies. The Delfi Program at Delft University of Technology focuses on demonstrating innovative small space technology developed in collaboration with both TU Delft and external partners in the space sector. The program has an educational purpose, preparing students for careers in the space industry by providing hands-on experience and training in cutting-edge space technologies. This thesis builds upon a previous mission analysis, primarily focusing on demonstrating the formation of two satellites in LEO using differential drag to maintain their required relative distance. The new mission draws inspiration from the earlier Delfi-PQ mission, which re-entered the atmosphere in early 2024, continuing the concept of satellite formation. These satellites will be launched together as a single unit and then separated in orbit to function as two independent twin satellites. The TU Delft Astrodynamics Toolbox (Tudat) has facilitated the construction of the proposed scenarios, analyzing different phases of the mission, from detachment to in-orbit control, demonstrating the feasibility of Delfi-Twin in terms of Space Situational Awareness (SSA). Investigations on the mission's lifetime have been fundamental in defining the final mission concept and understanding how differential drag control influences it. The validation of an analytical method used to propagate the relative orbit of one satellite with respect to the other has also allowed for a comparison of two methodologies in terms of processing time, which impacts the mission's safety as well. The last part of this work includes experimentation with a Global Navigation Satellite System (GNSS) receiver to assess the possible errors encountered when using an emulator for small satellites in LEO. The overall research presented will help define not only the mechanical control system that will allow for the relative motion control of the twin satellites but can also serve as a basis for further analysis regarding strategies for Close Proximity Operations (CPO).