A meteor radar under construction in Dourbes

Space Physics
Since 2010, BIRA-IASB has developed the BRAMS (Belgian RAdio Meteor Stations) network in order to detect and characterize meteoroids falling in the Earth’s atmosphere. BRAMS relies on a technique called radio “forward scatter”, meaning that the receivers and the transmitter are not in the same location. This introduces a number of advantages but also complications. In order to compare the BRAMS results to those obtained with a more traditional “backscatter” system, an in-house meteor radar is currently being built at the Geophysical Center in Dourbes. It is expected to emit its first waves in 2019.

Why a meteor radar?

The BRAMS network relies on forward scatter of radio waves off ionized meteoroid trails. With 26 receiving stations spread all over Belgium, it has the ability to detect a large number of meteors thanks to its geometrical extent. It has also the possibility to detect high-speed particles that vaporize at altitudes above ~105 km, for which traditional meteor radars are blind.

On the other hand, reconstructing individual trajectories from multi-station BRAMS observations is a challenging and still on-going task. With a meteor radar, the determination of these trajectories and a comparison of BRAMS results with those from traditional meteor radars will be much easier.

Characteristics of the radar

Traditional meteor radars use a modified version of a commercial weather radar, which has the advantage of providing a ready-to-use system with limited effort to deploy but at a rather expensive cost and with limited possibilities to modify the configuration control and data analysis software. 

Instead, BIRA-IASB has decided to build an “in-house” meteor radar at a much lower cost and with the benefit of developing additional expertise in the Space Physics group. The transmitter and the receiver are located within 100 meters of each other (see Figure 2).

  • The transmitter will emit pulses during only around 10% of the time, with a peak power of the order of 2 kilowatts and a frequency of a few tens of KHz below that of the BRAMS transmitter (49.97 MHz) in order to detect the same meteors.
  • The receiver is made of an interferometric system using 5 Yagi antennas similar to the one built in Humain for the BRAMS network.

Using pulses has the advantage that the total distance traveled by the radio wave is known, and with the interferometric system the direction of the reflection point is known.

With two additional classical BRAMS receiving stations nearby (within 10-15 km of the meteor radar), a time-of-flight technique can be used to determine the trajectory and speed of meteors. We expect the meteor radar to emit its “first wave” later in 2019.  This project is partly funded by the Solar-Terrestrial Center of Excellence (STCE).

Meteor radar in Dourbes
Figure 2: Current state of the meteor radar in Dourbes. In front, the five Yagi antennas from the interferometric receiving system. The transmitter is located in the background, approximately 100 m away. The RF cables are installed in the gutters.
RF cables inside the container in Dourbes
RF cables inside the container in Dourbes. The two upper cables are those going to the transmitter. They have a larger diameter as they will transmit peak powers of 2 kilowatts. The six lower cables are those connected to the five Yagi antennas (one of them is a crossed-Yagi, hence 6 cables).