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 single-pulse-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.
Highlights
The flux of meteoroids onto Earth is the source of the neutral and ion metal layers in the middle atmosphere
Kero et al (2008a) present a method for finding the position of a compact meteor target in the common volume monitored by the three UHF receivers, and how velocity, deceleration, radar cross section (RCS) and meteoroid mass were estimated from the improved tristatic observations
Our initial analysis of Middle and Upper atmosphere (MU) meteor head echoes, before we developed this interpolation, resulted in ripples that were identical to those found in Jicamarca Radio Observatory (JRO) head echo observations by Galindo et al (2011), except for a difference in ripple amplitude due to our oversampling
Summary
The flux of meteoroids onto Earth is the source of the neutral and ion metal layers in the middle atmosphere. HPLA radar systems, have a peak transmitter power of the order of 1 MW and array or dish antenna apertures in the range of about 800– 7 × 104 m2 (Pellinen-Wannberg, 2001), focusing their antenna gain pattern into a narrow main beam with a full-widthat-half-maximum (FWHM) of the order of 1◦ at the VHF and/or UHF operating frequencies This high power density permits numerous head echo detections from faint meteors. Evans maximized the cross-beam detection area of the Geminid, Quadrantid and Perseid meteor showers by pointing the Millstone Hill radar towards the shower radiants at times when the radiants were located at very low elevations above the local horizon This enabled velocity and deceleration determination for meteors belonging to the showers, for which the atmospheric trajectories were aligned with the radar beam
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