Abstract: A communication system employing an optical beam 17 suitable for transmission of data between a first terminal 12 and a second terminal 22. The apparatus transmits beam 17 from terminal 12 with two different scan patterns, a rosette pattern 625 or 650 for the central part of the scan, and a spiral pattern 600 for the remainder of the scan.

Abstract: A communication system employing an optical beam 16 suitable for transmission of data between a first terminal 12 and a second terminal 22. The apparatus aligns beam 16 from terminal 22 with a beam receptor 92 located in terminal 12 within a first uncertainty region TU which enables tracking of data with beam 16. Optics 50 enables receipt of beam 16 and transmission of the beam along a path 58. A positioning mechanism 150 points the optics 50 to the location of the terminal 22 within a second uncertainty region TU. An acquisition sensor 96 receives at least a portion of beam 16 and locates the terminal 22 within a third uncertainty region, such as the region represented by detector quadrant AQ1, which is larger than region TU but smaller than region RU1. A controller 200 responsive to locating of terminal 22 causes positioning mechanism 150 to move at least a portion of optics 50 to successively adjust the position of the beam path relative to acquisition sensor 96.