Near space has over the last 70 years evolved from a frontier to a vital part of our modern society, and today, we are highly dependent on space for applications like telecommunications, navigation and remote sensing. The significant increase in near space utilization has led to a large increase in space debris, stemming from old satellites, rocket stages, collision and breakup fragments, and anti-satellite weapon tests. This debris threatens satellites in orbit, resulting in costly avoidance operations or in worst case loss of satellites or personnel.
The larger pieces of debris in low Earth orbit (LEO, orbits lower than 1000 km) are rather well known, as they are possible to track using ground-based radars. The ESA Space Debris Office currently estimates that there are 130 million objects between 1 mm and 10 mm, and one million objects larger than 1 cm. Currently they only track 32 290 objects of any size. The modeling for the smaller space debris particles is based on studies of impact craters on returned space hardware like shuttle windows, radiators, and solar panels. However, debris particles smaller than 3.2 mm are currently not observed from ground, which leaves a gap in space debris models used by scientists to predict and avoid collisions in space.
The QBDebris project aims to help fill this gap by developing and deploying two CubeSats, where the first is 10x10x10 cm in size, while the second is 10x10x20 cm. The satellites will be coordinated in their operation and carry modified automotive radars. The scientific goals of the mission are to show that commercial radars can indeed be used to detect space debris particles in the millimeter size range and demonstrate the possibility of advanced coordinated control and synchronized operation of satellites in LEO orbits. Radar measurements will also give us a significantly increased understanding of the orbits and behavior of space debris, which may be used to improve current space debris models.
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.