Ray paths from a cosmic radio source to a satellite in orbit

A receiver mounted on a satellite in orbit above the maximum of the F 2 layer can receive radiation of frequencies that are totally reflected by the ionosphere. Two effects of reflexion in the upper part of the ionosphere are discussed in this paper; both occur particularly when the satellite enters or leaves a region in which it can receive radiation from a point source. The first of these effects is focusing, which will give a very strong signal at these points, and the second is interference between the two possible rays from the point source to the satellite. The theory of these two effects is discussed and some numerical calculations are described which demonstrate them for a particular model ionosphere.

The Angular Size of the Variable Radio Source Hydra?A

Slee (1955) has shown that the discrete cosmic radio source Hydra-A shows variations in intensity at metre wavelengths. This is the first variable radio source to be found, other than the Sun, although Ryle and Elsmore (1951) investigated about one hundred northerly sources and found no significant variations in their intensities over a period of 18 months. The observations to be described here were undertaken firstly to check the variability of the source, then suspected by Slee, and secondly to measure its angular size and see whether this might also be variable.