The Large Fiber Array Spectroscopic Telescope: Opto-Mechanical Design and Architecture

This paper describes the preliminary mechanical design and optomechanics of LFAST, the Large Fiber Array Spectroscopic Telescope. The 1,200 m(2) array comprises 132, open air, alt-az tracking mounts, each carrying 20 small co-aligned telescopes in a 5 m square U-shaped space frame about a central, dual-axis worm drive. Each unit telescope has a 0.76 m, f/ 3.5 mirror, a prime focus assembly with field corrector and a guide camera, and feeds a 17um, 1.3 arcsecond optical fiber. LFAST was designed specifically as a fiber fed spectroscopic telescope. By being built from thousands of mass-produced components it will be much cheaper per square meter of collecting area than phased monolithic telescopes currently under construction, like GMT and ELT. Cost effective dome-less operation is made possible by the structural design that maximizes stiffness and active compensation for wind induced jitter. The primary mirrors are protected when not in use by sub-horizon pointing of tracking mount and mirror covers.