A meteor orbit radar

Abstract

A Meteor Orbit Radar, AMOR, has been built near Christchurch, New Zealand. It uses a narrow beam pulsed radar to detect meteors down to a + 12.5 radio-meteor magnitude limit. AMOR measures the relative timelags between the onset of meteor echoes at each of three spaced receiver stations to calculate the meteoroid velocity with an accuracy of ±2.5 km.s-¹ . A 'Luggable' MAC AT is used to run the radar, identify meteor echoes and record raw observation records. A total of 1.3 X 10⁵ meteor velocities have been determined using the new timelag method. For 1.6 X 10⁴ of these observations velocity measurements could be made using Fresnel diffraction patterns and these were in complete agreement with those from the new timelag velocity technique. The diffraction patterns recorded by AMOR allow atmospheric decelerations to be determined by calculating the velocity for overlapping subsections of the patterns. Typically, the atmospheric decelerations found lay between 0 and 40 km.s-². Observed meteor velocities need to be corrected for the presence of the Earth before a heliocentric meteoroid orbit can be calculated. AMOR uses a new vector scheme to make corrections for atmospheric deceleration, the rotation and gravitational acceleration of the Earth, conversion to a heliocentric frame using rotation matrices and a correction for the orbital velocity of the Earth. This new derivation greatly simplifies the theoretical framework for computer based calculation of meteor orbits. The 1990 apparition of the ŋ; Aquarid meteor shower was used as a calibration test for the complete AMOR system. 270 shower meteors were detected giving a mean stream orbit with elements of q = 0.57AU, e = 0.98, i = 165.5°, w = 97°, Ω = 46°. This agrees closely with previous orbits given for the r; Aquarid stream and demonstrates the very large improvement in meteor stream characteristics that can be achieved by AMOR. Orbital elements for individual ŋ; Aquarid meteors can be determined within the following measurement limits: 0.33 < q < 0.76 AU, 0.76 < e < 1.45, 163.0° < i < 167.5°, 62° < w < 126°, 35 < Ω < 49°. Computerised data acquisition, automated reduction to orbital elements and interactive graphical displays were developed and are a significant feature of the system. AMOR is capable of continuous unattended operation producing observation records and reduced orbital elements on site.