RETRAM: A network of passive radars to detect and track meteors

When a high speed meteoroid enters atmosphere, its ablation produced by friction with the air molecules ionizes the surrounding gas into a plasma reflecting electromagnetic waves. This phenomenon is well known for radars where the plasma creates a moving target reflecting back the transmitted pulses. This reflection mechanism is also the key for point to point communications where specific wireless systems are designed to use these opportunistic reflectors to open obstructed channels. Most meteoroids fully ablate during their atmospheric entry, from which micrometeorites will eventually reach the ground. For more massive objects which can survive to their atmospheric entry, it is of high interest for scientists and astronomers to collect fallen meteorites. Meteor detection and tracking is the core research work done in the RETRAM group. Conversely to most of the published work on the topic, this project uses passive radar techniques and continuous processing to detect falling objects and to try to estimate their trajectory. Experiment started in the vicinity of Paris, France. This paper describes the underlying physics and architecture of the system, the different illuminators of opportunity used and gives some results for the main showers since 2012.