Instrument design and on-orbit performance of the solar optical telescope aboard hinode (Solar-B)

Abstract

The Solar Optical Telescope (SOT) aboard Solar-B satellite (Hinode) is designed to perform high-precision photometric and polarimetric observations of the solar lower atmosphere in visible light spectra (388--668 nm) with a spatial resolution of 0.2 to 0.3 arcsec. The SOT consists of two components; the optical telescope assembly (OTA) consisting of a 50-cm aperture Gregorian telescope with a collimating lens unit and an active tip-tilt mirror for an image-stabilization and an accompanying focal plane package (FPP) housing two filtergraphs and a spectro-polarimeter. Since its first-light observation on 25 Oct. 2006, the image-stabilization system has been working with performance better than 0.01 arcsec rms and the SOT has been continuously providing unprecedented solar data of high spatial resolution. Since the opto-mechanical and -thermal performance of the OTA is crucial to attain unprecedented high-quality solar observations, we here describe in detail the instrument design and on-orbit diffraction-limit performance of the OTA, the largest state-of-the-art solar telescope yet flown in space.