Radar observations of meteor deceleration

By using a narrow-beam high-power radar operating at 68 cm it has been possible to detect meteors traveling radially toward the radar. In these observations the antenna is directed at the radiant point of an intense meteor shower, and the receiver is tuned to the expected Doppler-shifted signal. Because the actual Doppler shift can be measured with precision, both the velocity and the deceleration of the approaching meteor can be determined. The behavior of the velocity is compared with the theory for a solid particle entering the earth's atmosphere at heights where no air cap is formed. Anomalous behavior was occasionally observed, but the height at which it appears to begin is too great to be accounted for by cap formation. We conclude that errors in the computed height of the meteor may be responsible for the anomalies. A mean value for the effective ablation energy of 15.4 km2/sec2 was obtained, but individual meteors showed wide departures from this value. The mean mass of the meteors is estimated to be in the range 10−2–10−3 gram, corresponding to a visual magnitude of +5.