Meteoroid trajectory and speed determination using BRAMS data

BRAMS is a Belgian network using reflection of radio waves on ionised meteor trails to detect meteoroids passing through the upper atmosphere. In order to accurately reconstruct the trajectory and speed of meteoroids using BRAMS data, we developed a method using time delays between meteor echoes recorded at various receiving stations. The obtained results were compared with optical observations from the CAMS-BeNeLux network. A second method using complementary data from the radio interferometer in Humain clearly improved the accuracy of the reconstruction.

The BRAMS network comprises a dedicated transmitter and, at the end of 2022, 44 receiving stations in Belgium and neighboring countries.

The reflected signal recorded at a receiving station is called a meteor echo. The reflection of the radio wave is specular, which means that it comes mostly from one point along the meteoroid path, whose position solely depends on the geometry. Hence, different receiving stations will have different reflection points, leading to time delays between the recorded meteor echoes.

Reconstruct accurate trajectory and speed of meteoroids

A long-lasting problem was the ability to reconstruct accurate trajectory and speed of meteoroids using BRAMS data. Indeed, the problem is complex because the BRAMS transmitter emits a continuous wave with no modulation, and hence the distance traveled by the radio wave is unknown.

The only information available are the time delays measured between meteor echoes recorded at various receiving stations. For the first time a method using time delays only has been developed. It provides accurate meteoroid trajectory inclination and speed but is off by a few kilometers in terms of position.

Improved accuracy of reconstruction

A second method using complementary data from the BRAMS interferometer located in Humain improves these accuracies but cannot be applied to the whole BRAMS data set. The accuracy of these reconstructions was assessed by comparing with data from the optical CAMS-BeNeLux network for which BIRA-IASB contributes by running 8 cameras.

These two methods pave the way to fully exploit the capabilities of BRAMS for future applications such as the determination of meteoroid fluxes or sounding of the upper atmosphere (e.g. wind-speed measurements).

 

Reference

Balis, J.; Lamy, H.; Anciaux, M.; Jehin, E. (2022). Reconstructing meteoroid trajectories using forward scatter radio observations and the interferometer from the BRAMS network. , Europlanet Science Congress 2022, Granada, Spain, 18-23 September 2022, Vol. 16, EPSC2022-227, DOI: 10.5194/epsc2022-227.

Illustration time delays between meteor echoes
Illustration of the origin of the time delays between meteor echoes recorded at two different stations Rx0 and Rxi due to the specularity condition. The specular point P0 of the reference station Rx0 is created before the specular point Pi of the station Rxi. The blue arrow indicates the meteor path, travelling at a speed V. The two radio wave paths Tx − P0 − Rx0 and Tx − Pi − Rxi are in general not coplanar.
Reconstruction trajectory using BRAMS data
Example of result showing the reconstruction of the trajectory using BRAMS data and compared with a CAMS trajectory: a) Projected view in the horizontal plane. b) 3D view. The green line is the CAMS trajectory. The blue cross is the reference station (Humain). The red plus is the transmitter (Dourbes). The light green diamonds are the stations used for the BRAMS reconstruction. The orange and light blue line represent respectively the radio wave path from the transmitter to Humain specular point, and the radio wave path from this specular point to the receiver in Humain. The purple line is the reconstructed trajectory with the BRAMS data.