From Passive-Optical Observation to High-Power Laser Irradiation - DLR-TP Activities on Space Debris Detection and Mitigation

Kurzfassung

With the strong increase in the number of space debris objects due to spontaneous debris-vs-debris collisions, the highly frequented orbital regime around 800 km has finally arrived at the dawn of the Kessler Syndrome. But it is not only the number of debris objects that can be expected to increase exponentially, the number of newly launched satellites raises in a similar way while, to our knowledge, not a single debris object has ever been actively de-orbited up to now. The related risks of mutual collisions are far from impacting only the orbital environment itself. In fact, the potential economic damage of large-scale satellite failures underlines the necessity of substantial efforts for sustainable operations in space. As an adaptation to the space situation, exhaustive awareness of potential collisions is needed. While more than 35,000 debris objects are tracked and catalogued already, this only constitutes less than 4% of all potentially mission-terminating debris with a size greater than 1 cm. To counteract the large number of untracked space debris in the low Earth orbit, methods for passive-optical debris detection by sunlight reflections in twilight are developed and explored at the DLR Institute of Technical Physics (DLR-TP). With this initial information from the debris, object tracking is undertaken allowing for high-precision laser-based ranging measurements from various facilities of our institute. The recorded data is employed in our numerical models for orbit prediction and serves for conceptual work on ranging station network architectures for reliable orbital data striving to an exhaustive coverage of a multitude of small debris objects down to sizes of only a few centimeters. While our activities on space situational awareness respond to the demand for more comprehensive capabilities in collision avoidance, related maneuvers can only be carried out if at least one of the conjunction partners can actively be maneuvered. For the initially mentioned mutual collisions among different space debris objects, this is not the case – yet. In principle, such objects might be movable remotely from ground using light-matter interaction processes like photon pressure or laser ablation, induced remotely from a high-power/high-energy laser on ground. Conceptual studies on laser-driven collision avoidance are presented which open up the perspective to even de-orbit a multitude of debris fragments using ground-based lasers. Whereas future high-power laser systems for space debris removal still require substantial development efforts, the potential of passive-optical observations for space sustainability should not be underestimated: Temporal intensity fluctuations of the sunlight reflected from debris can already reveal valuable information on its rotational behavior. Hence, these lightcurves are analyzed in order to support in-orbit capture missions – serving as well for space sustainability by active debris removal.