Free Space Optical Communications Sy stem Pointer 

Mark E. Rosheim* and Gerald F. Sauter* 

Abstract 

Free Space Optical (FSO) communications pointing problems will be described and a solution presented.  Conventional systems used in sea, land, and space are illustrated. Our integrated approach investigates  three major problems areas: kinemati cs, structure, and dexterity. Their interrelationship will be discussed.  

Introduction 

FSO/RF communication systems o ffer the potential of much higher bandwidth, unencumbered by FCC or  ITU restrictions. FSO/RF communication is also cove rt with low probability of intercept, jam-resistant,  resistant to EMI and co-site interference, low pow er, low weight, small size, and low cost. FSO/RF  communications systems acting as  advanced, next-generation Airborne Communications Nodes also  offer the potential for significant logistics savings. In  Desert Storm, the deploym ent of Army Signal Units  required 40 C-5 sorties and 24 ships. By being largely self-deployable, a UAV-based Airborne  Communications Node could reduce the number of air lift sorties required for communication support by  half or more. 

Office of the Secretary of Defense reports that “The key trend for future com munications system s is  increasing data rates brought on by m igration towards higher RF frequencies and the em erging  dominance of optical over RF system s. Laser-based syst ems will offer data rates two to three orders of  magnitude greater than those of the best future syst ems. The advantages of optical com munication were  demonstrated in 1996 when a ground-based laser com munication system  (lasercom ) provided data rates  of 1.1 terabits/sec at over 80 nm  [nautical m ile] range. Airborne and space borne Tbps lasercom  system s  will certainly be possible by 2025. Although lasercom  will shortly surpass RF in term s of data rate, RF will  continue to dom inate at the lower altitudes for some time into the future because of its better all weather  capability.”  

The Pointer Problem 

A key component of any practical, covert laser comm unication system regardless of space, sea, mobile  or man-portable system will be the advanced, light weight, low cost antenna pointing and tracking  mechanism (Figure 1). The optical community is only beginning to look at this element of the overall  problem of FSO. Such a system requires a mechani sm that is (1) easily m anufacturable and therefore  inexpensive; and that has (2) high slew rate; (3) high accuracy; and (4) wide, singularity-free range of  acquisition. Ross-Hime Designs, Inc. (RHD) believe s that it has developed a new, innovative mechanism  that can meet these demanding r equirements. RHD proposes that a Free Space Communication System  Sensor Pointer be based on the Omni-Wrist III. The Omni -Wrist III is a revolutionary, patented, low-cost,  lightweight, compact, rugged, high-dexterity poi nting device for space, land, and sea-based  communication applications [2-5]. It is a major advanc ement over conventional azimuth/elevation mounts  because it offers 180 degrees of unimpeded (singularity-free), hemispherical movement; low  manufacturing costs; and a streamli ned design integrating pivots into  the body of the device. These  features combine to produce a reliable, high-perfo rmance pointing device capable of greater precision  than existing designs. 

Ross-Hime Des igns has  won a NAVY SBIR Phas e I for "Low Cos t Submarine UAV Communic ation  System and Data Link." According to Mark Ros heim "The key aspect of our approach will be to reduce                                                    * Ross-Hime Designs, Inc., Minneapolis, MN 

Proceedings of the 37th Aerospace Mechanisms Symposium, Johnson Space Center, May 19-21, 2004  171