Enhanced Pointing Gimbal Mechanisms for Next Generation Communication Antennas

This paper summarizes the design and the development of a family of high precision Enhanced Pointing Gimbal Assemblies (EPGA) specifically targeting the next generation of satellite communication antenna technologies.The development and qualification of the first two EPGAs started some years ago. The purpose of this project has been to develop a gimbal based on a new rotary actuator technology achieving positioning performance superior to micro-stepping performance, to be used in highly accurate pointing and scanning mechanisms. The design also had to provide high stiffness and high load carrying capacity at the output stage.The design of this new line of gimbals is based on a rotary actuator with a high gear reduction ratio and high load carrying capacity output stage.Analysis of the latest missions, especially those for communication, earth observation and imaging, show that performance requirements for dual axis gimbals used for antenna pointing are becoming more and more demanding. Most recent Ka-band and future generation antenna technologies for smaller spot beams require finer resolutions of less than 0.003 degrees. Considerably larger solid core ( 3.0 meter diameter) and expandable wire-mesh ( 22 meter diameter) require higher load carrying capabilities and moment stiffness to sustain the launch and orbital maneuvering loads. The developed Enhanced Pointing Gimbal Assembly addresses those applications requiring small output step size, high precision pointing, and unpowered holding torque, which challenge the use of gimbals that use conventional rotary actuators.