The quantity and length of optical fibers required for the Hobby-Eberly Telescope Dark Energy eXperiment ( create unique fiber handling challenges. For HETDEX, at least 33,600 fibers will transmit light from the focal surface of the telescope to an array of spectrographs making up the Visible Integral-Field Replicable Unit Spectrograph (VIRUS). Up to 96 Integral Field Unit (IFU) bundles, each containing 448 fibers, hang suspended from the telescope’s moving tracker located more than 15 meters above the VIRUS instruments. A specialized mechanical system is being developed to support fiber optic assemblies onboard the telescope. The discrete behavior of 448 fibers within a conduit is also of primary concern. A life cycle test must be conducted to study fiber behavior and measure Focal Ratio Degradation (FRD) as a function of time.

The paper, “Design of the Fiber Optic Support System and Fiber Bundle Accelerated Life Test for VIRUS,” coauthored by Ian Soukup, Joseph Beno, Richard Hayes, James Heisler, Jason Mock, and Nicholas Mollison (UTCEM), John Good, Gary Hill, and Brian Vattiat (UT McDonald Observatory), Jeremy Murphy (UT Astronomy), Seth Anderson (contractor), Svend Bauer, Andreas Kelz, and Martin Roth

(Astrophysikalisches Institute Potsdam), and Eric Fahrenthold (UT Mechanical Engineering) and presented at the SPIE Astronomical Telescopes and Instrumentation 2010, San Diego, California, 27 June-2 July 2010, focuses on the technical requirements and design of the HETDEX fiber optic support system, the electromechanical test apparatus for accelerated life testing of optical fiber assemblies. Results generated from the test will be of great interest to designers of robotic fiber handling systems for major telescopes. There is concern that friction, localized contact, entanglement, and excessive tension will be present within each IFU conduit and contribute to FRD. The test apparatus design utilizes six linear actuators to replicate the movement of the telescope over 65,000 accelerated cycles, simulating five years of actual operation.

For more information please contact Dr. Joe Beno

canfield motion

Six degrees of freedom motion is achieved by the hexapod test device. The two images on the left illustrate the motion required to replicate the fiber system motion without rho rotation. Rho rotation is illustrated in the two images on the right.

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