Frequency dependence of radar meteor echo rates.

Observations of the radar meteor echo rates obtained using a steerable HF radar located near Alice Springs are examined. Consideration is given to the radio meteor ceiling selection effects and Hughes's 'missing mass'. A computer model of the response of HF radar to meteor echoes is constructed. The effect of echo ceiling detected from the observations and the effect predicted by the computer model are compared. The relationship between echo rate and frequency is studied. It is concluded that the radar meteor 'missing mass' may be attributed to the echo signal attenuation resulting from finite trail initial radius and trail diffusion. The data suggest that the majority of echoes originate from altitudes above 100 km.