OLAF: a Swarm of SmallSats for Active Debris Removal by Space-based Laser Ablation

Small debris objects (1 mm–10 cm) pose a considerable risk to active spacecraft, potentially causing mission-critical damage as they can reach relative impact velocities of 15 km/s in LEO. ESA’s latest Space Environment Report estimates more than 140 million objects in this size range residing in LEO, the majority of which cannot be tracked by ground-based space surveillance systems due to their small size.
OLAF is a proposed mission concept that employs a swarm of 8 small satellites (1 chief and 7 deputies) working together to detect, track, and remove small debris fragments from low Earth orbits using space-based laser ablation. The chief spacecraft is equipped with a wide-FOV 40-cm f/1.2 telescope for debris detection and coarse trajectory estimation. The deputies carry high-resolution, narrow-FOV 60-cm f/3.25 telescopes for precision tracking. In addition, the deputies are equipped with high-power 6.0 kW pulsed Nd:YAG lasers operating at 355 nm, whose combined fluence at the target exceeds the ablation threshold, effectively decelerating approaching debris objects and reducing their orbital lifetime. Laser-debris interactions were simulated for various impact geometries, yielding significant lifetime reductions for fragments approaching from altitude differences of up to 10 km and azimuth angle differences of up to 40 degrees.
The project focused on the autonomous navigation and formation-flying aspects of the mission. The swarm activities are coordinated by the chief spacecraft, which receives GNSS-based PVT and RF ranging data from the deputies via the inter-satellite link, and processes them using an Extended Kalman Filter to estimate the relative states of the swarm. A formation keeping strategy is proposed, with simulations indicating that each deputy requires an annual ΔV between 48 and 187 m/s. The mission’s economic aspects are discussed, with the system capable of deorbiting 130,000 small debris objects over 5 years, at an estimated cost of €3500 per object.