Large SAR Membrane Antennas with Lightweight Deployable Booms

Abstract

At the DLR Institute of Composite Structures and Adaptive Systems and the company Kayser-Threde extremely lightweight and stiff deployable carbon fibre-reinforced plastics (CFRP) booms and deployment mechanisms have been developed. The main target application is to develop an ultra-light weight solar sail for deep space satellite propulsion. Based on the successful development and ground-testing of a 20m x 20m deployable solar sail structure the in-orbit verification of the deployment principle and mechanisms is now being planned for launch in 2007. Kayser-Threde in collaboration with DLR has most recently completed a phase-B study of the solar sail project under ESA/ESTEC contract. In addition, mission and design studies have been performed at Kayser-Threde for ultra-light weight structures which can reach 100m x 100m in free space where a reflective, thin polyimide membrane is unfolded using DLR's advanced CFRP booms. Synthetic Aperture Radar (SAR) satellites require large and long antennas which in turn require a large satellite bus as well as a launcher with a large fairing. This is especially true for lower frequency SARs such as L-Band, where antenna sizes of typically 12m x 3m are required. The cost for such a SAR mission could be reduced significantly if the antenna and its deployment and support structure would be lightweight and could be folded during launch. The membrane antenna concept has been demonstrated in Canada by the CSA and EMS Technologies, and in the US by JPL. Receive only antennas are of interest for micro satellites which fly in a formation with a large active SAR satellite in order to perform SAR interferometry in a "Cartwheel" configuration. However, research has also been done for active phased array membrane antennas. The paper provides a first concept for a deployment and support structure for a L-Band SAR membrane antenna. Estimates for the mass and the achievable stiffness are provided.