Instrument design of 1.5-m aperture solar optical telescope for the Solar-C Mission

A 1.5 m aperture optical telescope is planned for the next Japanese solar mission SOLAR-C as one of major three observing instruments. The optical telescope is designed to provide high-angular-resolution investigation of lower atmosphere from the photosphere to the uppermost chromosphere with enhanced spectroscopic and spectropolarimetric capability covering a wide wavelength region from 280 nm to 1100 nm. The opto-mechanical and -thermal performance of the telescope is crucial to attain high-quality solar observations and we present a study of optical and structural design of the large aperture space solar telescope, together with conceptual design of its accompanying focal plane instruments: wide-band and narrow-band filtergraphs and a spectro-polarimeter for high spatial and temporal observations in the solar photospheric and chromospheric lines useful for sounding physical condition of dynamical phenomena.