Super-Hybrid Magnetic Suspensions for Interferometric Scanners

Abstract

NASA maintains the Geosynchronous Operational Environmental Satellite(GOES)fleet for observing severe weather and anomalous atmospheric behavior such as the greenhouse effect. A critical instrument flown on these satellites is the Fourier Transform Infrared(FTIR)interferometer used for atmospheric element detection. An integral part of the FTIR interferometer is the scanning mechanism, which must position a mirror with a high degree of accuracy along its optical axis. Traditional means of controlling the position of this mirror have used flexure-based designs, "porch swing" linkages, or other mechanical actuators. As an alternative mechanism, we have developed a magnetic bearing-based scanner. This scanner uses what we call a super-hybrid magnetic circuit, in which permanent magnets bias both the magnetic bearings and a voice coil actuator. Two designs incorporating this super-hybrid magnetic bearing configuration are presented herein, along with experimental results for the first design. In addition to their use in FTIR interferometers, these magnetic bearing designs may have applications in coordinate measuring machines, lithographic steppers, and other precision motion control devices.