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US 5,119,225 AGranted
Multiple access communication system
AssigneeBritish Aerospace Public Limited Company
InventorsMichael A. Grant, David Robson, Nicholas F. Matthews
Life of this patent
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AssigneeBritish Aerospace Public Limited Company
InventorsMichael A. Grant, David Robson, Nicholas F. Matthews
Estimating the term…
A multiple access communications system comprises a node spacecraft GEO and several user spacecraft LEO.sub.1 to LEO.sub.n. Each user spacecraft LEO.sub.1 to LEO.sub.n includes a transmit/receive terminal head 18.sub.1 to 18.sub.n, and the node spacecraft GEO includes n transmit/terminals 22 to 22.sub.n and a single beacon unit 24. The beacon beam may be operated to initiate acquisition phases which allow two-way communication to be established between the transmit/receive terminals 22.sub.1 to 22.sub.n on the node spacecraft and the transmit/receive terminals 18.sub.1 to 18.sub.n on the corresponding user terminals. The acquisition phases include a period during which the beacon scans an uncertainty cone associated with the node spacecraft. This scanning period is reduced for second and subseqeunt acquisitions by using the first and subsequently acquired communication links to provide a more accurate estimate of the angular attitude of the node spacecraft, thus reducing the extent of the uncertainty cone.
A communications system comprising:
A communications system for communicating between a node station and a plurality of user stations, said system comprising:
A method of communicating between a node station which includes a plurality of steerable node transmit/receive terminals optically rigid with respect to each other and two or more user stations each of which includes a steerable user transmit/receive terminal for communicating with a respective node transmit/receive terminal via a relatively narrow communications beam, which method comprises illuminating a first user station with a relatively broad acquisition beam emitted from said node station, causing the user transmit/receive terminal on said first user station to transmit a communications beam to one of said node transmit/receive terminals;
In a system including a node station and at least two user stations, wherein the relative positions of the node station and user stations are determined and wherein the angular attitude of the node station relative to a reference frame estimated subject to an uncertainty factor, a method of establishing communications between said node station and each of said user stations, which comprises causing an acquisition beam associated with said node station to follow a first scan pattern about an axis connecting said node station with one of said user stations, the pattern being of extent dependent on said uncertainty factor, causing said one user station to transmit a beam back to said node station whereby the estimate of the angular attitude of the node station is refined, and thereafter causing said acquisition beam to follow a second scan pattern about an axis connecting said node station with a second of said user stations, the pattern being of correspondingly reduced extent.
A method of directing a beam from a node station towards one of a plurality of user stations, which comprises the steps of:
Dependencies are inferred from the claim text.