Victor Bucklew, L3Harris; Joe Dodd, L3Harris; Jim Drakes, L3Harris; Donna Kocak, L3Harris
Keywords: Space debris, sensors, plasma, precursor solitons, debris detection technique
Abstract:
The persistent growth of sub-centimeter debris in Earth’s orbit poses a significant threat to spacecraft, satellites, and astronauts due to the potential for catastrophic collisions. This paper introduces a novel debris detection method, Plasma Detection and Ranging (PLADAR), which utilizes the interactions between plasma waves to detect and characterize space debris. PLADAR aims to expand the detection capabilities for a broader range of debris sizes and at greater distances than current proposed soliton-based direct detection techniques.
Sub-centimeter debris includes various particulates, such as paint flecks, erosion byproducts, and satellite fragments, which are challenging to track with existing ground-based systems. To address this, our study explores the interaction between orbital debris and the plasma environment in low Earth orbit (LEO), where debris can induce ion density perturbations in the plasma. These perturbations can generate self-sustaining waves which propagate as ion-acoustic solitary waves—coherent disturbances that maintain their shape while traveling through the plasma at high speeds.
PLADAR operates on the principle of detecting the phase shifts caused by collisions between user-generated precursor solitons and debris-generated waves. Precursor solitons, which travel ahead of the debris, and pinned solitary waves, which move at the same velocity as larger debris, are key to this detection method. Our numerical analysis investigates how debris size influences the properties of precursor solitons, with larger debris producing solitons with higher amplitudes and shorter periods. We also demonstrate a key result showing that the phase shifts resulting from soliton-soliton collisions provide measurable data that correlates with the properties of the interacting waves, and subsequently offers insights into the debris’ size and trajectory.
The PLADAR approach involves several steps:
Wave Generation: A solitary wave transmitter, comprised of a small metallic sphere for instance, aboard a spacecraft emits a series of precursor solitary waves aimed at another spacecraft. These waves are generated by applying a voltage to small metallic objects tethered to the spacecraft, inducing a charged state that acts as a forcing function on the surrounding plasma.
Wave Propagation: The generated precursor waves propagate through the plasma until they encounter waves produced by debris particles.
Wave Interaction: When precursor solitons collide with debris-generated waves, a phase shift occurs. This shift is a direct result of the conservation of momentum and energy during the collision, with the individual waveforms retaining their shape and energy.
Wave Detection: The altered precursor wave, now containing information about the debris, is detected by a sensor aboard a secondary spacecraft. This sensor, such as a high-speed Langmuir probe, measures changes in the plasma potential to identify the phase shift or other alterations to the wave resulting from the soliton-soliton collision.
Data Analysis: By analyzing the detected phase shifts and synchronizing timing signals across multiple transceivers, detailed information about the debris, including its size and trajectory, can be deduced.
Our simulations reveal that solitons generated by a 1 mm forcing function can propagate approximately 10 km, indicating the potential range of the PLADAR technique. The method’s line-of-sight nature does impose limitations on the field of view, which is confined to the cross-sectional path of the transmitter’s waves. Nevertheless, employing an array of transmitters can slightly extend this field, allowing for the detection of debris intersecting the line-of-sight at various angles.
In summary, PLADAR presents a potential pathway to advance detection of sub-centimeter orbital debris onboard a spacecraft, offering a new tool for enhancing space situational awareness. Our initial numerical findings demonstrate proof of principle of the key result of phase shifts from precursor soliton-soliton interactions, laying the foundation for further research to refine the technique and explore its practical deployment in space. The continued development of PLADAR could play a crucial role in safeguarding space assets against the ever-increasing hazard of orbital debris.
Date of Conference: September 16-19, 2025
Track: Space Debris