Joseph Hughes, Research Scientist
Space debris presents a growing challenge for satellite missions, and even small pieces of debris pose significant risks to operational spacecraft. However, tracking these small objects, particularly those smaller than 10 cm, has proven difficult. At Orion, we are exploring innovative methods to tackle this issue, focusing on disturbances in the very low frequency (VLF) electric field as a potential solution through our Space Debris Identification and Tracking (SINTRA) program.
The problem of space debris detection
While larger pieces of space debris (greater than 10 cm) can be tracked, smaller objects are harder to detect with traditional radar or optical systems. However, these tiny objects still have the potential to cause mission-ending damage, so finding a way to detect them has become a critical focus in the field of space safety. As we become more of spacefaring society, tracking and mitigating this debris will be essential to ensuring the safety and sustainability of future space travel and exploration.
A novel approach: Disturbances in the electric field
To address this, we investigated the potential of using plasma waves excited by "generator" objects in low Earth orbit (LEO) to detect disturbances in the VLF electric field. The idea is that certain objects, particularly those with unique electromagnetic signatures, could cause measurable perturbations in the electric field that could be detected by nearby spacecraft with appropriate instruments.
In our study, we leveraged data from the Plasma Wave Experiment (PWE) onboard the Japanese Aerospace Exploration Agency (JAXA)’s Arase spacecraft. The PWE instrument, which includes an Onboard Frequency Analyzer (OFA), measures VLF electric field power in space, providing valuable insights into plasma waves and disturbances caused by nearby objects.
Analyzing the data
To comprehensively analyze the conditions that lead to these electric field perturbations, we examined five months of data from the Arase spacecraft. During this period, we identified conjunctions—instances when Arase came within 300 km of objects in the Space-Track database1. These conjunctions were particularly valuable as they occurred during Arase’s highly elliptical orbit, where it spends approximately 15 minutes per orbit at altitudes below 1,000 km (the “perigee passes”).
For each perigee pass, we collected detailed information on the geometry of the conjunctions, the Earth’s magnetic field (using IGRF data), electron density (using IRI data), and the corresponding VLF E field measurements from Arase’s instruments.
Results: Disturbances and plasma waves
Through the analysis of hundreds of perigee passes, we observed frequent plasma wave occurrences that exhibited characteristics consistent with different wave types. We focused on testing three hypotheses related to the electric field power and its correlation with nearby space debris:
Arase measures higher E field power when near a generator object
Arase measures higher E field power when in the wake of a generator object
Arase measures higher E field power when along the same magnetic field line as a generator object
Our results strongly supported the first and third hypotheses, with a significant correlation (p ~ 0.0001) observed for both. This means that when Arase passed near a generator object or along the same magnetic field line, we saw a measurable increase in E field power, indicating the presence of disturbances that may be linked to nearby space debris.
Implications for space debris detection
These findings provide promising evidence that disturbances in the VLF electric field could serve as an effective method for detecting small space debris. By monitoring plasma wave activity during spacecraft orbits, we could potentially track objects that are too small to be detected by traditional means. This approach opens up new possibilities for space safety, allowing for earlier detection of debris and better protection for active spacecraft. Space debris poses significant challenges for the future of space exploration and satellite operations. Innovative approaches, such as detecting VLF electric field disturbances, offer promising pathways for improving debris detection and mitigation strategies. This research contributes to a deeper understanding of the space environment and helps advance efforts to ensure the long-term sustainability of space activities.
This work was previously presented at the American Geophysical Union’s Fall Meeting for 2024. Click the link below to view the poster.
1 Space-Track.org promotes spaceflight safety, protection of the space environment and the peaceful use of space worldwide by sharing space situational awareness services and information.
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