Ultra Light Self-Motorized Mechanism for Deployment   of Light Weight Spacecraft Appendages  C. Boesch*, C. Pereira *, R. John **, T. Schmidt **, K. Seifart **, H. Sparr **, J. M. Lautier +, T. Pyttel++ Abstract A mechanism to deploy satellite reflector antennas was developed to provide a rotation angle of up to 90  degrees. The energy necessary for deployment is stored within curved tape springs, which are buckled and thereafter folded into stowed position. The release at the hold down points and stored energy of the buckled tapes triggers the deployment. New characteristics with respect to similar mechanisms are a complete guidance without friction  combined with a high pointing stability (0.01° half cone). No additional latching elements are needed.   The presented hinge integrates several functions (deployment motorization, guidance, latching and  pointing stability) in a compact design weighing less than 0.6 kg (1.3 lb). This paper reports the development process from concept to finished product including material characterization, simulation, verification approach and lessons learned. The design of The Ultra Light Mechanism for Advanced Antenna Systems (ULMAAS) is not exclusively intended for deployment of reflector antennas. The concept is scaleable for different appendages, e.g., solar generators or masts.  Introduction The Ultra Light Mechanism for Advanced Antenna Systems (ULMAAS) focuses on a new generation of  lightweight reflector antennas requiring compact and accurate deployment systems with no motorization and high pointing stability. An ultra light reflector of Astrium [1] was selected as reference application. This allowed specifying requirements more precisely and establishing a representative test program. The development started with a survey covering comparable deployable mechanisms of the last 40  years. A simple design emerged from this survey and a patent application covering its unique features was submitted. The concept aimed for a device with low mass, high reliability and high pointing accuracy. A major characteristic is its completely frictionless deployment. The next steps were the trade-off on materials and geometry, simulations, and functional testing.  Verification of the mechanism performance was done using a dummy antenna in a qualification process  that includes multiple deployments after thermal cycling in order to gauge repeatability of deployment kinematics and reliability of end position.  Requirement Specifications  A performance specification was written with the help of Astrium in Toulouse and other antenna  manufacturers in order to guide the development of the mechanism. The specification was a general catalog of requirements not specifically tied to a particular design. Some of the key parameters and requirements are listed below:  - Antenna payload with 2.2-m (7.5-ft) diameter and a mass density of 2.2 kg/m 2 shall be deployed  - Mass should not exceed 0.5 kg (1.1 lb) including interfaces to the spacecraft and deployable  appendage *  RUAG Aerospace, Wallisellen, Switzerland  ** HTS GmbH, Coswig, Germany  +  ESA-ESTEC, Noordwijk, The Netherlands  ++ University of Applied Sciences, Friedberg, Germany  Proceedings of the 39th Aerospace Mechanisms Symposium, NASA Marshall Space Flight Center, May 7-9, 2008.  221