Precision Measurements of Radar Transverse Scattering Speeds From Meteor Phase Characteristics

Abstract

In this paper, we describe an improved technique for using the backscattered phase from meteor radar echo measurements just prior to the specular point (t 0) to calculate meteor speeds and their uncertainty. Our method, which builds on earlier work of Cervera et al. (1997, https://doi.org/10.1029/ 96RS03638), scans possible speeds in the Fresnel distance-time domain with a dynamic, sliding window and derives a best-speed estimate from the resultant speed distribution. We test the performance of our method, called pre-t 0 speeds by sliding-slopes technique (PSSST), on transverse scattered meteor echoes observed by the Middle Atmosphere Alomar Radar System (MAARSY) and the Canadian Meteor Orbit Radar (CMOR) and compare the results to time-of-flight and Fresnel transform speed estimates. Our novel technique is shown to produce good results when compared to both model and speed measurements using other techniques. We show that our speed precision is ±5% at speeds less than 40 km/s, and we find that more than 90% of all CMOR multistation echoes have PSSST solutions. For CMOR data, PSSST is robust against the selection of critical phase value and poor phase unwrapping. Pick errors of up to ±6 pulses for meteor speeds less than about 50 km/s produce errors of less than ±5% of the meteoroid speed. In addition, the width of the PSSST speed Kernel density estimate (KDE) is used as a natural measure of uncertainty that captures both noise and t 0 pick uncertainties.

Triple-frequency meteor radar full wave scattering Measurements and comparison to theory

“…Details of the hardware, antenna patterns and basic experimental setup for CMOR have been described in detail by Webster et al (2004), , Brown et al (2008), andBrown et al (2010). The detection, analysis and trajectory algorithms and associated software pipeline details are summarized in , Weryk & Brown (2012) and Mazur et al (2020). Here we provide only a brief summary of the main features of CMOR pertinent to the current work; we refer the interested reader to the foregoing references for greater detail.…”

“…The accuracy of echo interferometry, found through comparison with simultaneous optical measurements, is typically of order 0.7 -0.8 • (Weryk & Brown 2012) with the majority of echoes having uncertainties below 1 • . The 29.850 MHz system also has 5 passive remote sites located 5 -20 km from the main site for reception only, enabling measurement of time-of-flight velocities (Taylor 1991;Weryk 2012;Weryk & Brown 2012;Mazur et al 2020). Configuration details for the radar experiment are shown in Table 1.…”

“…However, for the data analysis in this study we use a custom data reduction pipeline optimized to detect meteors of astronomical interest, many of which are unsuitable for wind analysis. The details of the detection pipeline can be found in Weryk (2012); Weryk & Brown (2012) and Mazur et al (2020).…”

“…Events were also rejected if any of the amplitude-time profiles showed multiple maxima after the peak echo power location or unusually slow rise times (indicative of a non-specular echo). Triplet echoes meeting all the foregoing were then examined to determine if their time of flight estimated speeds agreed with the speed estimated from the pre-t 0 technique (Mazur et al 2020) to better than 10% and were retained if this condition was met.…”

“…In addition to their original use in meteor astronomy for such questions as the meteoroid velocity distribution and meteoroid mass influx (Hocking 2000;Elford 2004;Holdsworth et al 2007;Stober et al 2011;Mazur et al 2020), transverse scatter radars have become standard observation systems for mesosphere and lower thermosphere dynamics. These aeronomy measurements provide a useful benchmark for the validation of general circulation models (McCormack et al 2017) at these altitudes including estimates of temperature and winds.…”