A meteor head echo analysis algorithm for the lower VHF band

Abstract

Abstract.We have developed an automated analysis scheme for meteor head echo observations by the 46.5 MHz Middle and Upper atmosphere (MU) radar near Shigaraki, Japan (34.85 • N, 136.10 • E). The analysis procedure computes meteoroid range, velocity and deceleration as functions of time with unprecedented accuracy and precision. This is crucial for estimations of meteoroid mass and orbital parameters as well as investigations of the meteoroid-atmosphere interaction processes. In this paper we present this analysis procedure in detail. The algorithms use a combination of singlepulse-Doppler, time-of-flight and pulse-to-pulse phase correlation measurements to determine the radial velocity to within a few tens of metres per second with 3.12 ms time resolution. Equivalently, the precision improvement is at least a factor of 20 compared to previous single-pulse measurements. Such a precision reveals that the deceleration increases significantly during the intense part of a meteoroid's ablation process in the atmosphere. From each received pulse, the target range is determined to within a few tens of meters, or the order of a few hundredths of the 900 m long range gates. This is achieved by transmitting a 13-bit Barker code oversampled by a factor of two at reception and using a novel range interpolation technique. The meteoroid velocity vector is determined from the estimated radial velocity by carefully taking the location of the meteor target and the angle from its trajectory to the radar beam into account. The latter is determined from target range and bore axis offset. We have identified and solved the signal processing issue giving rise to the peculiar signature in signal to noise ratio plots reported by Galindo et al. (2011), and show how to use the range interpolation technique to differentiate the effect of signal processing from physical processes.

Determination of meteor-head echo trajectories using the interferometric capabilities of MAARSY

“…Also planned is the implementation of a Doppler-shifted pulsecoding algorithm to improve the SNR threshold and the range resolution (e.g. Chau and Woodman, 2004;Kero et al, 2012). After cutting out obvious side lobe detections and events with unphysical acceleration curves (meteors with positive accelerations), the calculation of the dynamical meteor masses show the detection of meteoroids in the range of 10 −10 to 10 −3 kg.…”

“…The deceleration of the meteor-head echo is calculated performing a pulse-to-pulse phase correlation (e.g. Chau and Woodman, 2004;Kero et al, 2012) of the signal of receiver Rx1, which provides the radial velocity v r…”

Controlled time integration for the numerical simulation of meteor radar reflections

“…[28]). One reason for this is dierences in the characteristics of the radar systems, e.g., in terms of frequency and antenna geometry, see [29]. According to the observations reported by, e.g., [30] and [31], the head echo can be modeled as over-dense scatter from a plasma layer surrounding the meteoroid, with a specic density distribution.…”

MU head echo observations of the 2010 Geminids: radiant, orbit, and meteor flux observing biases

“…We have developed improved analysis algorithms (Kero et al, 2012c) and collected an extensive set of data (> 500 h) between June 2009 and December 2010. Kero et al (2012b) give an initial overview of the whole data set including radiant density and orbital properties of sporadic meteors.…”

“…The received data were stored as 85 range values from each transmitted pulse, sampled at 6 µs intervals. The sampling corresponds to a range resolution of about 900 m. Nevertheless, using a novel range interpolation technique (Kero et al, 2012c), the ranges of meteor targets are determined with a precision of the order of 10 m, or to within about onehundredth of a range gate.…”