Spectrum of the Galactic Radio Emission between 1.5 and 10 Mc/s as observed from a Satellite

Abstract

THE Alouette satellite (1962 β α 1) carries an ionospheric sounder in a nearly-circular orbit at a height of about 1,000 km. This experiment provides data on the electron number density at and below the satellite, and on the local magnetic field strength¹. In addition, since the automatic-gain control voltage of the sweep frequency receiver is telemetered to the ground, simultaneous measurements are also made of the background radio noise. (The receiver is inactive during the pulse transmission, and the included integration circuit essentially removes any effects of the echo pulses from the recordings of the automatic-gain control voltage.) Accordingly, for frequencies below those which can penetrate the ionosphere, these background noise data contain information on extra-terrestrial radio sources; the accompanying ionosonde data help to describe the propagation and reception of such cosmic radio waves by the satellite. In this communication the results of the galactic noise measurements as a function of frequency are outlined; they will be discussed in more detail elsewhere, as will the observations of other extra-terrestrial sources.