Simultaneous dual-frequency observations of meteor head echoes using ALTAIR

We present a sample of radar meteors detected during the November 1998 Leonid shower that were collected using the ARPA Long Range Tracking and Instrumentation Radar (ALTAIR) at 160 and 422 MHz. A total of 900 VHF and 500 UHF head echoes were collected near the peak of the shower; these data produced a detection rate of approximately 1 VHF head echo every 2 seconds, which is the highest rate recorded by any sensor. These data were analyzed to determine frequency-dependent radar cross-section (RCS) and true 3-D velocity, as well as altitude and aspect angle trends. These data are the first to reveal that the shape and strength of the head echo varies as a function of detection angle. In addition, the azimuth and elevation data were used to compute the deceleration as a function of time, which can be utilized to compute the radius/density of the meteoroid itself. The majority of these meteoroids had mass ranges between 10^-6 and 10^-3 grams and diameters less than 2 mm.