Monitoring the yearly sporadic Micrometeor Flux into the upper Atmosphere Using
the Arecibo Dual-Beam 430 MHz Radar

Diego Janches Arecibo Observatory and Penn State University

We discuss results from a year long program of observations and study of the
micrometeor flux into the upper atmosphere using the dual-beam 430 MHz Arecibo
radar (AO) in Puerto Rico.  The AO radar detects decelerating particles in the
size range 0.5-100 microns for which precise altitude; instantaneous Doppler
velocity (rms errors of the order of 10-100 m/sec) and (constant) deceleration
are obtained.  This provides a tool for the study of a mass-region of the
interplanetary dust distribution that was previously inaccessible to
ground-based instruments and helps bridge the gap between spacecraft dust
measurements and traditional meteor radar capabilities.  The AO radar sees over
9000 events daily inside the 300 m radar beam in the 80-140 km altitude region
and with the addition of the dual-beam capabilities two separate regions of the
sky can be observed at the same time.  Results from the first months of
observations are presented and discussed.  These include meteor dynamical
parameter distributions, mass flux estimates and meteor orbits.