Analysis of Spaceborne VHF Incidental Noise over the Western Hemisphere

Abstract

Computations of the incidental man-made radio noise power existing at geostationary satellite altitudes over the Western Hemisphere have been performed by summing the emissions from those metropolitan areas lying within the intercept pattern of a spaceborne antenna. Area representations of surface man-made radio noise data and the radiation field integral for the observed power at altitude h were used to extend earlier calculations of incidental noise power at aircraft altitudes to Earth-satellite altitudes. Three cases of VHF band coverage from a geostationary satellite positioned over the Western Hemisphere have been analyzed: a) Western Hemisphere coverage by a dipole antenna; b) Western Hemisphere intercept by an Earth-coverage, moderate-gain antenna; and c) North American coverage by a shaped-beam high-gain antenna. It was determined that the increase in antenna noise temperature for frequencies 243 to 260 MHz, attributable to metropolitan incidental man-made radio noise, varied from 1 K for Case A to 54 K for Case C. Analysis of data derived from the LES-5 and -6 satellite test program fixes an upper limit of < 22 K on the Western Hemisphere VHF band incidental man-made noise contribution to satellite-antenna noise temperature during the late evening hours.