Patent ID: 8989586
Filing Date: 2015-03-24
Classification: H04B

Abstract:
1. Optical communications system ( 10 ) for transmission of payload data (PD) from low earth orbit to earth, the optical communications system ( 10 ) comprising: a low earth orbit satellite ( an optical ground terminal ( the low earth orbit satellite ( 20 ) being connectable with the optical ground terminal ( 30 ) via an optical downlink channel (DL), and the optical ground terminal ( 30 ) being connectable with the low earth orbit satellite ( 20 ) via an uplink channel (UC); wherein: said uplink channel (UC) is an acquisition and tracking beacon channel by means of a ground beacon (GB) controlled by said point-acquisition-track subsystem (PAT), the ground beacon (GB) comprising a wide angle beam (W) for acquisition and a guidance beam (G) for tracking; said satellite transceiver (STR) is adjustable so that it can be adjusted with respect to the spatial direction of the ground beacon (GB); said ground beacon (GB) for the uplink channel (UC) is a pulse position modulated PPM channel said point-acquisition-track subsystem (PAT) is configured to perform the following steps when informed of a pass-over of the low earth orbit satellite ( wake the optical ground terminal ( de-activate said uplink channel (UC) once the pass-over of the low earth orbit satellite ( switch the optical ground terminal (