Title: A Large Aperture, Solid Surface Deployable Reflector
Author: Robert Taylor
Organization: Composite Technology Development, Inc.
Co-Authors: Dina Turse
The goal of this NASA Advanced Component Technology (ACT) program is to develop a large aperture, solid surface deployable reflector for earth science applications. This type of reflector offers a continuous graphite composite reflector membrane that is formed as a parabolic surface having sufficient accuracy for RF science measurements a high frequencies (ka-band and beyond). By using a continuous membrane, these reflectors also provide a clean aperture for consistent data across the field of view. Over the past year, significant progress has been made towards the validation of this technology through the fabrication and testing of a full-scale Engineering Development Unit (EDU). This paper will describe the EDU hardware and the results of testing. As a parallel effort over the past year, CTD has been working with a team out of The California Institute of Technology's (Caltech) Jet Propulsion Laboratory (JPL) to develop a conceptual design for a deployable reflector for the ACE mission. The results of this conceptual study will also be presented.
CTD’s solid surface deployable reflector technology is applicable to any RF measurements that require an antenna reflector to concentrate the signal. This includes radiometer and radar applications for measurements of sea surface roughness, sea salinity, cloud profiling, atmospheric limb sounding, and snowpack characteristics. The packaging capability of these reflectors allows a larger aperture for higher resolution or higher gain/noise ratios in the same available launch volume. Recent earth science missions including AQUARIUS and ACE have performed trade studies to consider ways to increase the available aperture to meet science goals. However, the cost, complexity and risk of existing deployable reflectors for these missions resulted in the selection of a smaller rigid reflector for the final flight configurations.
While CTD’s deployable reflectors offer significant reductions in complexity and cost over existing deployable reflector technologies, the TRL is not yet high enough for serious consideration in mission trade studies. Therefore, the ACT program has been focused on reducing the risk associated with this technology through testing and validation of a full-scale EDU. This has included the evaluation of deployed surface accuracy and repeatability after multiple gravity off-loaded deployments using photogrammetric measurements. A system-level RF range test was also completed at NASA Glenn Research Center and a thermal distortion test is currently planned for July of 2011.
JPL is currently developing the system design and technology for a dual-frequency radar called ACERAD for cloud and precipitation measurements. ACERAD is a radar instrument within the Aerosol/Cloud/Ecosystem (ACE) mission; a mission which is recommended by the NRC Decadal Survey. CTD has recently designed an antenna reflector system for ACERAD that is largely based on the same technology “building blocks” utilized in the offset-fed reflector configuration; including a flexible solid surface composite membrane and deployable backing structure elements. However, the ACERAD configuration incorporates several novel design features and a different packaging scheme to allow for the extreme surface accuracy required for ACERAD, which will operate at W-band.