All-sky interferometric meteor radar meteoroid speed estimation using the Fresnel transform

D. A. Holdsworth,W. Singer,D. J. Murphy,R. A. Vincent,I. M. Reid,W. G. Elford

doi:10.5194/angeo-25-385-2007

Abstract

Abstract. Fresnel transform meteor speed estimation is investigated. A spectral based technique is developed allowing the transform to be applied at low temporal sampling rates. Simulations are used to compare meteoroid speeds determined using the Fresnel transform and alternative techniques, confirming that the Fresnel transform produces the most accurate meteoroid speed estimates for high effective pulse repetition frequencies (PRFs). The Fresnel transform is applied to high effective PRF data collected during Leonid meteor showers, producing speed estimates in good agreement with the theoretical pre-atmospheric speed of the 71 kms−1. Further simulations for the standard low effective PRF sampling parameters used for Buckland Park meteor radar (BPMR) observations suggests that the Fresnel transform can successfully estimate meteor speeds up to 80 kms−1. Fresnel transform speed estimation is applied using the BPMR, producing speed distributions similar to those obtained in previous studies. The technique is also applied to data collected using the BPMR sampling parameters during Southern delta-Aquarid and Geminid meteor showers, producing speeds in very good agreement with the theoretical pre-atmospheric speeds of these showers (41 kms−1 and 35 kms−1, respectively). However, application of the Fresnel transform to high speed showers suggests that the practical upper limit for accurate speed estimation using the BPMR sampling parameters is around 50 kms−1. This limit allows speed accurate estimates to be made for about 70% of known meteor showers, and around 70% of sporadic echoes.

Highlights

Radar techniques have been used for meteor observations for over 50 years
Recent advances in personal computers and digitization technology have resulted in a suite of instruments used for online meteor observations (e.g. Hocking et al, 2001), such as the Buckland Park Meteor Radar (BPMR) (e.g. Holdsworth et al, 2004)
The Buckland Park VHF ST (BPST) radar results suggest that the Fresnel transform is capable of determining meteoroid speeds up to the maximum entry speed of 72 km s−1, with an accuracy of better than 1%, while the application using the Advanced Meteor Orbit Radar (AMOR) radar suggests the Fresnel transform is capable of determining meteoroid speeds with an accuracy of 0.1 km s−1

Summary

Introduction

Radar techniques have been used for meteor observations for over 50 years. Atmospheric observations were later made by measuring the radial drift speed of the ionized trail for investigation of mesospheric and lower thermospheric dynamics Hocking et al, 2001), such as the Buckland Park Meteor Radar (BPMR) Holdsworth et al, 2004) These radars are capable of estimating count rates of up to twenty thousand underdense meteor echoes per day, which has allowed the development of new techniques for estimating atmospheric parameters, such as those for used to estimate absolute temperature (e.g., Hocking, 1999; Holdsworth et al, 2006). Meteoroid speeds provide essential data in the calculation of meteoroid orbits, which are important for predicting and removing the dust foreground emission from the infrared observations of remote astrophysical objects Meteoroid speeds provide essential data in the calculation of meteoroid orbits, which are important for predicting and removing the dust foreground emission from the infrared observations of remote astrophysical objects (e.g. Kelsall et al, 1998)

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Discussion

Conclusion