Meteor trajectory retrieval from BRAMS data: updates and improvements

BRAMS (Belgian RAdio Meteor Stations) is a Belgian meteor radio forward scatter network using a dedicated transmitter and more than 50 receiving stations located in Belgium and neighboring countries. The transmitter emits a pure sine wave with no modulation at 49.97 MHz with a power of ∼ 340 Watts.

 

The use of continuous wave implies that the total range traveled by the radio wave is unknown and that the only available information are the time delays between the detections of meteor echoes at different receiving stations, due to the specular reflection of the wave off the meteor trail. This makes the inverse problem of inferring meteoroid trajectories from time delays alone ill-posed, yielding high uncertainties — particularly in altitude and inclination, as the BRAMS stations are nearly coplanar. Two additional sources of information have been investigated to better constrain the problem: interferometric data providing the direction of the specular point, and measurements of the pre-t0 phase, constraining the meteoroid velocity.

 

Both methods have independently shown promising results [1,2], but the former will only be available for a limited number of trajectories, while the latter requires very bright echoes, as the pre-t0 phase is highly sensitive to noise.
Other characterization techniques, such as ones based on the Fresnel transform [3] and the analysis of the echo’s spectrum [4], are currently investigated.

Further difficulties arise from the lack of information on range and direction: reflections from airplanes, which, with a radar setup, would be removed based on altitude, often overlap with echoes in both frequency and time, complicating their characterization. Furthermore, determining whether echoes recorded at different stations originate from the same event is non-trivial and is expected to become especially problematic during periods of high activity such as meteor showers.

 

PyBRAMS is a Python package designed for accessing data from the BRAMS network, extracting and characterizing echoes and retrieving meteor trajectories. After successfully demonstrating that accurate trajectory reconstruction was possible [2], the next steps aim at large-scale and autonomous processing of BRAMS data, which requires tackling the aforementioned issues.

 

A fully modular trajectory retrieval scheme has been developed, allowing for the straightforward implementation and coupling of different types of measurements, as well as the use of various trajectory parametrizations: rectilinear or curved geometries, different deceleration models, and prospectively, meteor ablation or ionization curves. Preliminary efforts have also been made towards a Selector algorithm, able to partition echoes into groups likely to originate from the same event and filter out potential outliers.

 

A flexible echo characterization algorithm is under development, using a least-squares approach to model the meteor echoes and the parasitic signals conjointly using progressively more complex models as the signal-to-noise ratio increases.

References

• Balis J., Lamy H., Anciaux M., Jehin E., Radio Science, 2023, Volume 58, Issue 6, https://doi.org/10.1029/2023RS007697.
• Balis J., Lamy H., Anciaux M., Jehin E., De Keyser J., Kastinen D., Brown P. G., Radio Science, 2025, Volume 60, Issue 8, https://doi.org/10.1029/2025RS008305.
• Roy, A., Doherty, J.F. & Mathews, J.D. Analyzing Radar Meteor Trail Echoes using the Fresnel Transform Technique: A Signal Processing Viewpoint. Earth Moon Planet 101, 27–39 (2007). https://doi.org/10.1007/s11038-007-9147-5
• Korotyshkin, D., Radio meteor velocity estimation based on the Fourier transform, Advances in Space Research 74, 4134-4145, 2024. https://doi.org/10.1016/j.asr.2024.06.080