A New Determination of the Solar Parallax by Means of Radar Echoes from Venus

Abstract

DURING the recent close approach of Venus the Jodrell Bank radio telescope has been used to obtain radar echoes from the planet. The radar equipment, which operated at a frequency of 408 Mc./s., had a peak-power of 60 kW. and gave 30-m.sec. pulses at one pulse per second. The transmitter and receiver were operated alternately for periods of approximately five minutes, the light-time to Venus and back. To eliminate fading caused by Faraday rotation of the line of polarization of the signals in the Earth's ionosphere, an aerial system transmitting right circular polarization and receiving left circular was used. This was achieved by means of a feed aerial consisting of crossed coplanar dipoles and reflectors fed in quadrature from a hybrid ring, which also provided 40 db. of isolation between the receiver and transmitter. An electron-beam parametric amplifier (Adler tube) with a noise figure of 2 db. formed the input to the receiver.