British Aerospace Plc

Ronald W Young

Simon John Stirland

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.

Investigating and controlling the pointing direction of an antenna on

A satellite orbiting arrangement including an orbiting cluster of co-operative satellites in which inter-satellite communication is to be maintained substantially constantly, the arrangement further including an inter-satellite communication satellite positioned remotely from the cluster in an orbit selected to maintain at least approximate station with the cluster and to enable communication with each satellite of the cluster to be maintained substantially constantly.

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Knebworth, United Kingdom

Ronald W Young