Abstract: A reflector antenna assembly for dual linear polarization includes at least two feeds and two reflectors. At least one reflector has a surface which is nominally electrically transparent to linearly polarized radiation in one direction and is located in front of the other reflector so as to be closer to said feeds. At least one of the reflectors is profiled in a manner such as to enable it to generate at least one complex contoured beam while using one of said feeds.

Abstract: A dual reflector antenna system capable of passing radiation to or from a shaped coverage area by means of a single feed, a three dimensional main reflector surface and a three dimensional subreflector surface. Desired levels and/or characteristics of radiation incident upon or received from selected regions of said coverage area are defined, and actual radiation levels and/or characteristics for said regions by modifying both said reflector surfaces are optimized simultaneously. The optimization is achieved by iteratively determining levels and/or characteristics of radiation incident upon or received from each of said regions and obtaining the least favorable value of level and/or characteristic and modifying said reflector surfaces simultaneously to obtain an improved least favorable value of level and/or characteristic.

Abstract: Measurement of flux density at the edges of the footprint of an RF transmission from a spacecraft with a view to determining the spacecraft antenna pointing error is difficult because of atmospheric fading local to the measuring station. Previous proposals to permit determination of pointing error in the face of such effects involve additional hardware on board the craft. Herein, it is proposed to induce a relatively small repetitive scanning motion of the spacecraft hence producing an oscillatory flux density variation at peripheral ground stations and then measuring the oscillatory component relative to the average flux density--frequency analysis equipment operable to discriminate the known frequency of the variation over a plurality of wavelengths can be used giving substantial accuracy improvement. A series of measurements enable the diurnal pointing error pattern to be determined and hence a spacecraft attitude correction command program to be produced.