A new method for the measurement of meteor speeds: The pre-to phase technique

Abstract

In this paper we describe a new technique for measuring the speeds of individual meteors based upon the variation of the phase received in specular reflections from the meteor train prior to the meteoroid reaching the point of closest approach to the observation site. The technique is characterized by high precision, high yield, and is less subject to selection effects than the techniques used heretofore. About 75% of observed meteors are able to have a speed determined, compared with only 10% previously. It has application to the measurement of the velocities of meteoroid streams and the distribution of speeds of sporadic meteors. The latter is vital to the modeling of the response of HF/VHF radars to meteor backscatter [Elford, 1964; Thomas et al., 1988], as well as having astronomical implications. Results of observations with our narrow-beam VHF radar are presented. Data collection carried out during the epoch of the θ Ophiuchid meteor shower, whose radiant passes through the response function of the VHF radar, renders speeds which are in accord with the previously known speed for that shower. The speed distribution of sporadic meteors is determined and compared with the distributions obtained in previous radar and optical programs.