Recording Radio Signals from Earth Satellites

Abstract

SYSTEMATIC recordings of radio transmissions from an Earth satellite for examination of the ionosphere can be used for providing also, for that particular observing site, the orbit data necessary for the prediction of transit times and the computation of ionospheric influences. For this purpose Doppler frequency shift measurements are particularly useful, and a system has been developed in this Laboratory whereby, with relatively simple equipment, the necessary information from 1958 δ 2 (Sputnik III) can be recorded simultaneously with the intensity variations which were previously reported¹. The intensity variations and frequency samplings are displayed on adjacent cathode-ray tubes and photographed on 35-mm. film moving vertically at a speed of 6 in. per min. A beat-frequency oscillator is used in the receiver and the audio output applied to the horizontal deflexion plates of a cathode-ray tube without a time-base to give a record of the intensity variations as shown at A in Fig. 1. The pulse modulation of the transmission is clearly denned, but the ‘fading pattern’ is also well delineated.