抄録
A meteor is a phenomenon in which extraterrestrial material, generally known as a meteoroid, enters the Earth’s atmosphere, ionizing the surrounding components and/or emitting light. The surface of a meteoroid moving at high speed reflects very high frequency (VHF) radio waves by melting itself and ionizing the components of the surrounding atmosphere. The radio wave reflected from the head of a meteor is called a meteor head echo and results in a Doppler shift. Since the early 2000s, some researchers have made multi-static measurements of head echoes using high-power large-aperture pulse radars. Meanwhile, the authors have attempted to observe meteor head echoes with Doppler shifts using traditional low-cost and low-power ham radio devices for over a year. Moreover, by setting the transmitter and the receiver in close proximity, it became clear that the Doppler shift shows a value that follows the meteor velocity component in the line-of-sight direction. This implies that any observer who is involved in amateur radio operations can make observations similar to those obtained from a large-scale pulse meteor radar. Using this technique, the authors recorded two remarkable Eta Aquarids meteor head echoes in a location very close to the transmitting station, in May 2021. The Doppler shift calculated from the meteor head echo agreed well with the data obtained from the position of the meteor’s actual path using the known physical parameters of the Eta Aquarids meteors. We propose that this method facilitates the observation of meteor head echoes at multiple points simultaneously, enabling the estimation of the position and ground velocity of a meteor. This system will help us find the path of a meteorite during daytime hours or on cloudy days.
