A new method for determining meteoroid mass from head echo data

Abstract

A head echo is the radar reflection from the plasma immediately surrounding a meteoroid upon its entry into the Earth's atmosphere; analysis of these plasmas can help determine a parent meteoroid's inherent properties, such as mass. In the past, meteoroid mass was calculated using head echo velocity and deceleration data by assuming momentum conservation between the meteoroid and air molecule. We refer to such masses as “dynamical masses.” This method, however, can only be used to determine meteoroid mass if either the meteoroid radius or density is assumed. In this paper, we expound upon a new method for determining a meteoroid's mass by utilizing our new spherical scattering theory. This theory allows us to use head echo measurements to calculate head echo plasma density. Then, by using the plasma density in an established formula that estimates the ratio of unionized to ionized material produced by an ablating meteoroid, we can determine a meteoroid's mass. We refer to such masses as “scattering masses.” We show that our new mass determination method applies to head echoes detected simultaneously at VHF and UHF and verify that the meteoroid mass is the same at both frequencies. We conclude with a comparison between dynamical and scattering masses and show that in general, these methods agree to within an order of magnitude.