Image stabilization system on SOLAR-B Solar Optical Telescope

摘要

Extremely stable pointing of the telescope is required for images on the CCD cameras to accurately measure the nature of magnetic field on the sun. An image stabilization system is installed to the Solar Optical Telescope onboard SOLAR-B, which stabilizes images on the focal plane CCD detectors in the frequency range lower than about 20Hz. The system consists of a correlation tracker and a piezo-based tip-tilt mirror with servo control electronics. The correlation tracker is a high speed CCD camera with a correlation algorithm on the flight computer, producing a pointing error from series of solar granule images. Servo control electronics drives three piezo actuators in the tip-tilt mirror. A unique function in the servo control electronics can put sine wave form signals in the servo loop, allowing us to diagnose the transfer function of the servo loop even on orbit. The image stabilization system has been jointly developed by collaboration of National Astronomical Observatory of Japan/Mitsubishi Electronic Corp. and Lockheed Martin Advanced Technology Center Solar and Astrophysics Laboratory. Flight model was fabricated in summer 2003, and we measured the system performance of the flight model on a laboratory environment in September 2003, confirming that the servo stability within 0-20 Hz bandwidth is 0.001-0.002 arcsec rms level on the sun.