A Precision Deployable Aperture System Facility

Abstract

Precision deployment is an enabling technology for future NASA large aperture missions. Possible concept missions include optical, infrared, sub-millimeter, or microwave apertures too large to fit unfolded in a launch shroud. Dimensional stability is the overriding structural design driver for these large deployable apertures. The stability is driven by constraints derived from the system's mass and structural stability and to thermal and dynamical loads. As the aperture size increases, and the systems mass density is correspondingly decreased, the ability to test the performance of these apertures in a 1-g environment requires both a unique facility and special testing methodologies. This talk will describe a facility under development that includes an enclosure with extreme environmental control, a metrology systems for measuring deployment precision and aspects of an integrated modeling system that will be validated in the facility. Though built to the demanding specifications of deployed optical systems, this talk will focus on components of the facility specific to space-based microwave and millimeter wave antenna systems. The first component of the facility is an enclosure with 10 m times 5 m times 3 m (L times W times H) usable volume that is controlled under ambient temperature to thermal stability of <0.01 Cdeg/Hr, acoustic control of <35 dBA and seismic control of <10 mugs. The enclosure includes a gravity offload system and allows development of single and multi-petal test articles. Instrumentation in the facility includes three-dimensional videogrammetry system capable of absolute measurement accuracy less than 1 millimeter, and a laser vibrometer system for modal testing. The second component of the facility is the development of an optical metrology system for aligning and monitoring large, deployable structures and telescopes to a fraction of a wavelength. A six beam 'optical hexapod' metrology gauge is being built that will measure to 1 micron absolute accuracy with 1 nanometer relative accuracy over a 10 m range. The final component of the facility is comprised of system architecture and modeling components using integrated modeling tools for predictive simulations of aperture systems under orbital loads. These models are being compared to controlled experiments completed in the facility.