British Aerospace Public Limited Company

Nicholas F Matthews

David Robson

Michael A Grant

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.

Multiple access communication system

An Earth orbiting spacecraft (1) is returned to an Earth pointing attitude by means of a star sensor (6), Earth sensor (2), Sun sensor (4) and an angular momentum storage device. With the Sun sensor (4) locked on the Sun (5) the spacecraft is rotated until the star sensor (6) senses a predetermined brighter than magnitude 3 star such as Canopus (7). The angular momentum storage device is operated to preserve an attitude reference and the spacecraft (1) is further rotated by an angle .alpha. such that subsequent rotation around the angular momentum storage axis causes the Earth (3) to enter the view of the Earth sensor (2).

Method of and apparatus for returning an earth orbiting spacecraft to an

A laser beam communication system for spacecraft in which each communication terminal comprises, for steering the beam projected from that terminal, four mirrors, each mounted on a mechanism capable of rotating the mirror about a constant defined axis. The mirrors and their attached mechanisms are arranged in pairs with one pair on either side of a magnifying telescope. All rotating joints in each mechanism are constructed using flexure pivots. Such a pointing element can provide both the range and accuracy required for an important class of free space laser links without introducing any extra friction into the pointing system.

Growing community of inventors

Plainsboro, NJ, United States of America

Nicholas F Matthews