New Concepts for Spacecraft Antennas and Radar Structures Based on Ultra-thin Composites

This paper presents a new deployable reflector concept for an Earth observation mission that requires a low-cost L-band Synthetic Aperture Radar (SAR) instrument with a large aperture. A novel “hollow solid” structural concept is proposed that comprises curved surfaces formed from thin sheets of carbon-fiber-reinforced-plastic connected by flexible hinges along the edges. The front surface of the hollow solid provides the reflective surface. This proposed structure has very high stiffness-to-mass-ratio, because of its thin-walled box-type construction. A detailed study of a half-scale technology demonstrator, including design, manufacture and testing, is presented in the paper. INTRODUCTION This paper presents a novel deployable reflector structure for a mission requiring a lowcost L-band Synthetic Aperture Radar (SAR) instrument. This comprises an offset parabolic cylinder with a linear feed array. The satellite in its flight configuration and SAR imaging orientation is shown in the schematic diagram of Figure 1. This configuration provides some of the advantages of phased arrays (like low loss and elevation beam steering), at much reduced cost. The required reflector shape is an offset parabolic cylinder with an arc-length of 7.9 m and width of 3.2 m. The reflector structure is connected to the spacecraft bus by a truss structure, which would be deployed before the reflector structure; this structure will not be discussed in the paper. Figure 1: Flight configuration (courtesy of EADS Astrium).