Advancing In-Space Precise Tracking: A Formation-Flying Picosatellites Mission

Abstract

In recent years, the trend towards satellite miniaturization has led to a considerable rise in picosatellite missions in Low Earth Orbit (LEO). Due to their size, identifying and tracking small objects poses significant challenges. While the detectability of individual picosatellites has been proven, the potential implications of clusters flying in formation remain unexplored. Therefore, the Delft University of Technology is starting a pioneering mission involving multiple picosatellites to improve Space Situational Awareness (SSA) by demonstrating the capabilities and limits of both inspace and ground-based tracking means. This paper outlines a high-level mission analysis investigating the feasibility of this formation-flying mission: in the proposed model, the autonomy of each satellite is enhanced by integrating a Global Navigation Satellite System (GNSS) receiver, which enables independent orbital determination and facilitates the validation of satellite position data against other tracking systems. The mission concept involves deploying a cluster of two identical 3P PocketQubes, launched as a single spacecraft into a near-circular orbit. Following deployment, they will be separated using springs, considering factors such as relative velocity, direction, and angle to carefully study the release process. Additionally, their relative distance is controlled using differential drag, i.e. adjusting the satellite drag area by deploying solar panels at varying angles. Through the integrated use of STK and MATLAB, two mission control sequences are defined: the former, characterized by satellite propagation stopping conditions based solely on relative distance, and the latter, in which they are based on both relative distance and relative velocity. Their comparison reveals the latter as the most effective strategy: despite the challenge of controlling satellite distance during close passes (conjunctions), the optimal sequence prioritizes maximizing time in close proximity. This approach reduces the average relative velocity and minimizes the duration of the high drag configuration, resulting in a significant extension of the mission lifetime. The simulations, along with a power budget, support the definition of both mission and GNSS receiver payload requirements. Finally, a suitable candidate is selected from among miniaturized GNSS space receivers and tested through multiple hardware-in-the-loop simulations, using a GNSS signal simulator. These simulations aim at verifying the accuracy of receiver positioning measurements and assessing power consumption. The results of this paper represent the cornerstone of a disruptive mission, providing insights into the future development of satellite control optimization strategies to minimize collision risk. Furthermore, the remarkable payload test results, while reliable, underscore the need to improve testing systems to reduce position errors and achieve higher tracking accuracy for LEO picosatellites equipped with GNSS receivers.