Design and analysis of the tracker bridge for the Hobby-Eberly Telescope* wide field upgrade

A large structural weldment has been designed to serve as the new star tracker bridge for the Wide Field Upgrade to the Hobby-Eberly Telescope at McDonald Observatory in support of the Hobby-Eberly Telescope Dark Energy Experiment ‡ . The modeling approach, analysis techniques and design details will be of interest to designers of large structures where stiffness is the primary design driver. The design includes detailed structural analysis using finite element models to maximize natural frequency response and limit deflections and light obscuration. Considerable fabrication challenges are overcome to allow integration of precision hardware required for positioning the corrector optics to a precision of less than 5 microns along the 4-meter travel range. Detailed descriptions of the bridge geometry, analysis results and challenging fabrication issues are discussed.