100 axis as a flex print design rather than slip rings, roller rings, or conventional cable wraps. These elements  brought together the mechanization aspects of the CPA design.  The mirror units were designe d to exhibit minimum susceptibility towards thermo-mechanical  disturbances. While being of pure Beryllium for weight reason s, the design solution eventually chosen  was a highly optimized mirror shape on an innovative iso-static mounting construct.   The high structural loading capacity while maintaining a mass as low as possible was achieved by using AlBeMet or Titanium for all major structural parts.  In the subsequent sections, first, the main components of the CPA are introduced. Following the description how the ambitious requirements were succ essfully accommodated in the design of the CPA,  some lessons learnt concerning t he implementation of a BAPS and a flex  print cable wrap are discussed  before some of the tested achievements of the CPA are presented.   Background 

A multi-purpose Optical Communi cation Laser Terminal is being developed by TESAT Spacecom,  Backnang, Germany. The terminal – capable of simultaneous data transmission and reception – is  intended for high-bandwidth data transfer between telecommunication satellites operating on different ranges of orbits. The envisaged links (GEO-GEO, GE O-LEO and LEO-LEO, and to ground stations) are  foreseen to be established by laser beams. The entir e terminal is a highly complex system consisting of  tightly interacting subsystems involving mechanical, t hermal, optical, and electro-optical elements. In this  context, RUAG Space supplies the full chain of front end optics, i.e. CPA and telescope. 

Origin of Design-Driving Requirements   The design-driving requirements for the CPA originated from the combination of the wide range of target applications, i.e. operating orbits, as well as the logical need for getting the terminal on the satellite to its in-orbit station. The following points illustrate the origin of the major CPA requirements.  Pointing-Range: For pure GEO-GEO link applications, a much simpler CPA design could be  conceived (Ref. 1) where the required pointing range is much less, especially in elevation. However, if GEO-LEO or LE O-LEO link capability is required, high  pointing range with relatively large rotation speeds and fast acquisition times become necessary.  Pointing Accuracy: When initiating contact betwee n two satellites, the beam is pointed towards the  target terminal based on inertial navigation data provided from the satellite to the CPA drive electronics. In a GEO-GEO sc enario the involved satellites may be as  far as 60’000 km apart, hence directly requiring a high pointing accuracy. For  GEO-LEO or LEO-LEO situations an absolute pointing knowledge is essential. The relative velocities of the involved communication terminals may be quite high. With mutual line of sight contact limited to as little as 20 minutes fast beam acquisition is crucial. This furthermo re, dictates the need for a high-pointing  accuracy even at moderately high-speeds.   Low Jitter: Maximization of the transfer power is essential to maintaining high data  throughput. Therefore, the optical beam has to be kept as stable as possible, hence directly dictating the need for “jitter as  low as possible” at zero velocity as  well as under constant movement. In fact, jitter must therefore be minimized both cross-axis and in plane  NASA/CP-2010-216272