A CubeSat formation for space debris characterisation

The QBDebris project aims to demonstrate the successful operation of a formation of two CubeSats capable of characterising space debris in situ. Once operational, the satellites will characterise and record the orbital elements of space debris smaller than the ground detection limit (3.2mm) using of the shelf commercial radars. On completion, the project will have demonstrated characterisation of small pieces of space debris in situ using off the shelf radars, and that it is possible to coordinate orientation and maintain the relative position between satellites using differential drag control. The project is running in parallel with the UNICube project, where students at UiT are developing a student satellite with a similar payload as intended for QBDebris. The main objective for the project is to develop advanced scientific and technological solutions for measuring space debris in situ with commercial radars using a formation of CubeSats under coordinated control. WP1: Deployment strategy (July 2023 – December 2024) We have performed the mission design study with specifications of satellites as well as the mechanical design for satellite separation. An official tender process for the satellite build was performed in the spring of 2024, with the outcome of one company giving a non-binding offer which was significantly higher than stipulated costs. This is mainly due to a shift in the market for satellite suppliers, increased costs for satellites in general and worsened NOK/EUR currency rates. We are currently considering the next steps to handle the situation, either through downscaling of the operational part of the project or a possible collaboration with UiO/CENSSS to develop a joint satellite. Two bachelor thesis projects were performed in the spring of 2024; 1) development of an ADCS testbench for satellite control, and 2) mechanical design, prototyping and testing of an in-orbit separation mechanism for CubeSats. The separation mechanism and ADCS control will be tested in a suborbital flight in the GHOST mission (Andøya Space), planned for launch in November 2025. WP2: Attitude coordination (January 2024 – March 2026) WP2 has the objective to develop robust and reliable attitude control subsystems for the satellites. We have initiated the work towards the attitude control subsystem, focusing on developing an attitude control solution for single satellites which ensures that the satellite has the desired effective surface in the direction of relative velocity. This effective surface is in turn what will provide the necessary drag to allow for relative positioning and orbital corrections of the two satellites. The approach utilizes the integrator backstepping framework to design an attitude controller that ensures reliability and high precision. As a part of this work package, one student has completed his master project at NTNU with a thesis entitled “Satellite Formation Flying Using Attitude-Controlled Differential Drag” in June 2024, which presents two approaches for relative orbit control of two satellites in formation. We have also initiated a second master project with the working title “Efficient attitude-based algorithms for effective surface tracking”, which further explores the problem of tracking effective surfaces to provide desired drag profiles. WP3: Radar payload (July 2023 – December 2025) The objective of WP3 is to develop and implement an off the shelf radar payload capable of measuring space debris. The radar has been developed and tested in the laboratory. To facilitate better experimental testing in a controlled environment, a bachelor thesis project was completed in spring 2024 to develop a lab setup capable of firing projectiles at 300+ m/s for particles in several different millimeter sizes. We have also conducted two tests at the shooting range, yielding velocities close to 800 m/s. All tests have resulted in radar detections, supporting our hypotheses that the radar is indeed capable of detection space debris. Development of the radar payload has started. Some challenges are still to be overcome on how the amplify the output power, but work is progressing. The PhD in the associated UNICube project started in August 2024, which supports radar development. We expect a paper on the radar to be published next year (deliverable D3.1). A commercialisation process for the radar has also been started, which will be followed up with an RCN application by Norinnova. An upgraded version with a test on ISS will be applied for through the EIC Pathfinder Challenges call on Space debris in October 2024. WP4: In-orbit operation (March 2026 – March 2027, with possible extension to December 2027) The last of the technical WPs will be initiated with the planned launch of the satellites, with the objectives of operating the satellites in orbit, demonstrating coordinated control of the satellites and the capability of detecting space debris.

In this project, we aim to demonstrate the successful operation of a formation of two CubeSats capable of characterising space debris in situ. Once operational, the satellites will characterise and record the orbital elements of space debris smaller than the ground detection limit of a few millimeters. Very little is known about these objects, even though there are millions of them in orbit, and they pose a significant risk for both astronauts and satellites. The satellite formation will be able to simultaneously measure the same volume as using off the shelf commercial radars. The satellites will be joined together to a size of 3U at launch, and once in orbit, split into two satellites which will maintain relative distance and orientation using novel control strategies. The CubeSats will be designed with actuators for reorientation (reaction wheels, magnetorquers), to be able to synchronize their attitudes to satisfy mission requirements. Orbital adjustments will be made by utilising differences in drag, depending on the spacecraft orientation, providing significant challenges to flight coordination. The main objective in this project is to develop advanced scientific and technological solutions for measuring space debris in situ with commercial radars using a formation of CubeSats under coordinated control. On completion, the project will have shown that it is possible to characterise small pieces of space debris in situ using off the shelf radars. The project will have then generated statistics of the orbital elements and density of debris, which will be very useful as input to space debris models, satellite operations and planing of future satellites. In addition, the project will have shown that it is possible to coordinate the orientation and maintain the relative position between the satellites using a leader-follower scheme with attitude control actuators only.