Some radar observations of meteors and aurorae at 300 and 500 Mc/s using a large radio telescope—I Observations of meteors

Abstract

Abstract The characteristics of radar echoes from meteor trails have been studied at 500 and 300 Mc/s with a high power transmitter used in conjunction with a large radio telescope. At the higher frequency the sporadic meteor rate varied between one every few hours up to about two per hour depending on the elevation of the beam, the time of year and the time of day. During the Perseid meteor shower the average rate increased to about three times the sporadic rate. At the lower frequency the sporadic rate was about twenty times that at 500 Mc/s. It is concluded that the echoes arose from meteor trails having initial linear densities in the region 10 13 –10 14 electrons per cm. A class of echoes has been identified in which the specular condition for reflection is relaxed. The echoes were characterized by a symmetrical rise and fall of amplitude in time. It is believed that these echoes were obtained from short lengths of highly ionized trail moving immediately behind the larger meteors and that the amplitude variation arose from either the reradiating polar diagrams of the short trail or the main beam of the aerial.