ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-4-621-2004 Radiant measurement accuracy of micrometeors detected by the Arecibo 430 MHz Dual-Beam Radar Janches D. 1 2 Nolan M. C. 1 Sulzer M. 1 Arecibo Observatory, HC3 Box 53995, Arecibo, Puerto Rico 00612 Presently at CIRES, University of Colorado, 216 UCB, Boulder, CO 80309, USA 15 04 2004 4 3 621 626 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/4/621/2004/acp-4-621-2004.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/4/621/2004/acp-4-621-2004.pdf

Precise knowledge of the angle between the meteor vector velocity and the radar beam axis is one of the largest source of errors in the Arecibo Observatory (AO) micrometeor observations. In this paper we study ~250 high signal-to-noise ratio (SNR) meteor head-echoes obtained using the dual-beam 430 MHz AO Radar in Puerto Rico, in order to reveal the distribution of this angle. All of these meteors have been detected first by the radar first side lobe, then by the main beam and finally seen in the side lobe again. Using geometrical arguments to calculate the meteor velocity in the plane perpendicular to the beam axis, we find that most of the meteors are travelling within ~15° with respect to the beam axis, in excellent agreement with previous estimates. These results suggest that meteoroids entering the atmosphere at greater angles may deposit their meteoric material at higher altitudes explaining at some level the missing mass inconsistency raised by the comparisson of meteor fluxes derived from satellite and traditional meteor radar observations. They also may be the source of the observed high altitude ions and metalic layers observed by radars and lidars respectively.