A precision cryogenic positioning stage for detector dithering and flexure compensation

This paper presents the design and technical progress of a precision X-Y stage for detector dithering and flexure compensation being developed for the Magellan InfraRed Multi-Object Spectrograph, MIRMOS. Designed to operate at 80 K, the stage will accurately control detector position in two orthogonal degrees of freedom. The piezo-driven flexure stage is very compact providing high-resolution backlash-free motion of the detector. A magneto resistive bridge provides position feedback in each degree of freedom, greatly reducing hysteresis, which is common in piezoelectric actuators. The system is designed to operate in open loop using a lookup table keyed to the Nasmyth rotator angle for flexure control. Here, the optomechanical design of the stage, electrical control system, and performance results from early prototype efforts are presented and discussed.