EP0325429A2
Expired / Lapsed
EP
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Multiple access communication system
Assignee: BAE Systems PLC
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Filing: 1989-01-18
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Granted: —
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Expires: 2009-01-18
Abstract
Abstract A multiple access communications system comprises a node spacecraft GEO and several user spacecraft LEO₁ tO LEO n . Each user spacecraft LEO₁ to LEO n includes a transmit/receive terminal head 18₁ to 18 n , and the node spacecraft GEO includes n transmit/terminals 22 to 22 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 22₁ to 22 n on the node spacecraft and the transmit/receive terminals 18₁ to 18 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 subsequent 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.
Inventors
- 👤 Michael A. Grant
- 👤 David Robson
- 👤 Nicholas F. Matthews
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 16:07
CPC Classifications
G; G01; G01S; G01S5/00; G01S5/16; G01S5/163; H; H04; H04B; H04B10/00; H04B10/11; H04B10/118; H04B7/00; H04B7/14; H04B7/15; H04B7/185; H04B7/19; H04B7/195; B; B64; B64G; B64G1/00; B64G1/10; B64G1/1007; B64G1/1085
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
87 words
A communications system, comprising a plurality of user stations each having a transmit/receive terminal, a node station having a plurality of transmit/receive terminals associated with respective ones of said user stations, a beacon beam means provided at said node station for initiating respective acquisition phases for linking respective ones of said transmit/receive terminals on said node station with the transmit/receive terminal on the corresponding user station, and means for providing a rigid reference at said node station for the associated transmit/receive terminals and said beacon beam means.
Claim 2
Dependent Claim
87 words
A communications system, comprising a plurality of user stations each having a transmit/receive terminal, a node station having a plurality of transmit/receive terminals associated with respective ones of said user stations, a beacon beam means provided at said node station for initiating respective acquisition phases for linking respective ones of said transmit/receive terminals on said node station with the transmit/receive terminal on the corresponding user station, and means for providing a rigid reference at said node station for the associated transmit/receive terminals and said beacon beam means.
Claim 3
Dependent Claim
50 words
A communications system according to Claim 1, wherein each of said user and node stations is a spacecraft and each of said transmit/receive terminals is operable to pass an optical communications beam of relatively narrow beamwidth and said beacon beam means generates an optical acquisition beam of relatively broad beamwidth.
Claim 4
Dependent Claim
41 words
A communications system according to Claim 1 or Claim 2, wherein each of said transmit/receive terminals has associated therewith acquisition and tracking means for acquiring and tracking a beam incident on the user station associated with said acquisition and tracking means.
Claim 5
Dependent Claim
62 words
A communications system according to any of the preceding claims, wherein said node spacecraft includes an optical bench means which rigidly supports at least the inlet and outlet means of each of said transmit/receive terminals and at least the outlet means of said beacon means, and attitude sensor means is associated with said optical bench means for detecting the angular position thereof.
Claim 6
Dependent Claim
40 words
A communications system according to Claim 4, wherein said beacon beam means includes a laser source located remote from said optical bench means and fibre optic means supplying laser radiation to beam output means located on said optical bench means.
Claim 7
Dependent Claim
147 words
A communications system for communicating between a node station and a plurality of user stations, said system comprising:- a plurality of steerable node transmit/receive terminals at said node station for transmitting or receiving a relatively narrow communications beam to or from a respective user station; a steerable beacon means at said node station for emitting a relatively broad acquisition beam to illuminate any one of said user stations; acquisition control means operable during an acquisition phase for controlling said beacon means and one of said node transmit/receive terminals to follow related scan patterns, and a steerable user transmit/receive terminal provided at each user station for transmitting or receiving a relatively narrow communications beam to or from a transmit/receive terminal at said node station, and each of said user transmit/receive terminals being responsive to illumination by said beacon means to transmit a communications beam to said node station.
Claim 8
Dependent Claim
147 words
A communications system for communicating between a node station and a plurality of user stations, said system comprising:- a plurality of steerable node transmit/receive terminals at said node station for transmitting or receiving a relatively narrow communications beam to or from a respective user station; a steerable beacon means at said node station for emitting a relatively broad acquisition beam to illuminate any one of said user stations; acquisition control means operable during an acquisition phase for controlling said beacon means and one of said node transmit/receive terminals to follow related scan patterns, and a steerable user transmit/receive terminal provided at each user station for transmitting or receiving a relatively narrow communications beam to or from a transmit/receive terminal at said node station, and each of said user transmit/receive terminals being responsive to illumination by said beacon means to transmit a communications beam to said node station.
Claim 9
Independent Claim
116 words
A method of communicating between a node station which includes a plurality of steerable node transmit/receive terminals 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; illuminating a second user station with said acquisition beam and causing the user transmit/receive terminal on said second user station to transmit a communications beam to said node station.
Claim 10
Independent Claim
116 words
A method of communicating between a node station which includes a plurality of steerable node transmit/receive terminals 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; illuminating a second user station with said acquisition beam and causing the user transmit/receive terminal on said second user station to transmit a communications beam to said node station.
Claim 11
Dependent Claim
165 words
In a system including a node station and at least two user stations, wherein the relative positions of the node station and user stations may be determined and wherein the angular attitude of the node stations relative to a reference frame may be 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 may be 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.
Claim 12
Dependent Claim
165 words
In a system including a node station and at least two user stations, wherein the relative positions of the node station and user stations may be determined and wherein the angular attitude of the node stations relative to a reference frame may be 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 may be 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.
Claim 13
Dependent Claim
74 words
A method according to Claim 8, wherein said second user station is caused to transmit a beam back to said node station whereby the angular estimate of the attitude of the node station may be further refined, and thereafter said acquisition beam is caused to follow a third scan pattern on or about an axis connecting said node station with a third of said user stations, the pattern being of correspondingly further reduced extent.
Claim 14
Independent Claim
141 words
A method of directing a beam from a node station towards one of a plurality of user stations, which comprises determining the relative position of one of said user stations with respect to said node station, establishing a communications link generally coincident with the line of sight connecting said node station and said one user station, determining an estimate of the angular attitude of said node station or a part thereof based on the orientation of said line of sight with respect thereto, determining the relative position of a third user station, processing data representing the relative positions of said node station and said third user station and said estimate of the angular attitude to determine an estimate of the orientation with respect to the node station of the line of sight connecting said node station and said third user station.
Claim 15
Independent Claim
141 words
A method of directing a beam from a node station towards one of a plurality of user stations, which comprises determining the relative position of one of said user stations with respect to said node station, establishing a communications link generally coincident with the line of sight connecting said node station and said one user station, determining an estimate of the angular attitude of said node station or a part thereof based on the orientation of said line of sight with respect thereto, determining the relative position of a third user station, processing data representing the relative positions of said node station and said third user station and said estimate of the angular attitude to determine an estimate of the orientation with respect to the node station of the line of sight connecting said node station and said third user station.
References Cited (Backward Citations)
No citation records indexed.
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