Development status of the fast-steering secondary mirror of GMT

Abstract

The Giant Magellan Telescope (GMT) will be equipped with two Gregorian secondary mirrors; a fast-steering secondary mirror (FSM) for seeing-limited operations and an adaptive secondary mirror (ASM) for adaptive optics observing modes. The FSM has an effective diameter of 3.2 m and is comprised of seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary mirror. Each FSM segment has a tip-tilt capability for fast guiding to attenuate telescope wind shake and jitter. The FSM is mounted on a two-stage positioning system; a macrocell that positions the entire FSM segments as an assembly and seven hexapod actuators that position and drive the individual FSM segments. In this paper, we present a technical overview of the FSM development status. More details in each area of development will be presented in other papers by the FSM team.

Design of the fast steering secondary mirror assembly for the Giant Magellan Telescope

“…The allocation of each of the error contributions typically includes fabrication errors in the optics and mirror support, misalignments and distortion due to the mounting of the optics in the mirror cell and dynamic motion of the mirror and thermal effects that contribute to image. Detailed error budget allocations are described in Lee et al [10] . We performed the design optimization based on the Error Budget in Table 1.…”