Characterization of Leonid meteor head echo data collected using the VHF‐UHF Advanced Research Projects Agency Long‐Range Tracking and Instrumentation Radar (ALTAIR)

Abstract

The Leonid meteor shower, which was predicted to hit storm‐like activity on 17 November 1998, was observed using radar and optical sensors at the Kwajalein Missile Range in order to study potential threats to orbiting spacecraft. Meteor head echo data were collected during the predicted peak of the “storm” primarily using the Advanced Research Projects Agency Long‐Range Tracking and Instrumentation Radar (ALTAIR). ALTAIR is a dual‐frequency radar at VHF (160 MHz) and UHF (422 MHz) that is uniquely suited for detecting meteor head echoes due to high sensitivity, precise calibration, and the ability to record radar data at a high rate (Gb/min). ALTAIR transmits right‐circular (RC) polarized energy and records left‐circular (LC) sum, RC sum, LC azimuth angle difference, and LC elevation angle difference channels; these four measurements facilitate the determination of three‐dimensional target position and velocity as a function of radar cross section and time. During the predicted peak of the storm, ALTAIR detected 734 VHF head echoes in 29 min of data and 472 UHF head echoes in 17 min of data, as well as numerous specular and nonspecular ionization trails. This paper contains analysis on the head echo data, including dual‐frequency statistics and the variability of head echo decelerations. We also include results from the analysis of the radius‐density parameter, which shows a strong correlation with deceleration.