Yoshinori Suematsu

A coronal condensation observed at the total solar eclipse of June 11, 1983 and a related transient prominence

A coronal condensation was observed simultaneously with Fexiv λ5303, Fex λ6374, Fe xi λ7892, and Hα filtergraphs. The size and shape of the condensation in λ5303 are different from those in other filtergrams. Hα filtergrams taken around the eclipse time show that a small transient prominence exists in close proximity to the condensation core and behaves like a post-flare loop system, though the appearance is quite different and no flare-report exists. A small-scale energetic phenomenon seems to have occurred at the top of magnetic loops.

Wave-Front Error Measurements and Alignment of CLASP2 Telescope with a Dual-Band Pass Cold Mirror Coated Primary Mirror [STUB]

“Chromospheric LAyer Spectro-Polarimeter (CLASP2)” is the next sounding rocket experiment of the “Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)” that succeeded in observing for the first time the linear polarization spectra in the hydrogen Lyman-α line (121.6 nm) and is scheduled to be launched in 2019. In CLASP2, we will carry out full Stokes-vector spectropolarimetric observations in the Mg ii h and k lines near 280 nm with the spectro-polarimeter (SP), while imaging observations in the Lyman-α line will be conducted with the slitjaw optics (SJ). For the wavelength selection of CLASP2, the primary mirror of the telescope uses a new dual-band pass cold mirror coating targeting both at 121.6 nm and 280 nm. Therefore, we have to perform again the alignment of the telescope after the installation of the recoated primary mirror. Before unmounting the primary mirror from the telescope structure, we measured the wave-front error (WFE) of the telescope. The measured WFE map was consistent with what we had before the CLASP flight, clearly indicating that the telescope alignment has been maintained even after the flight. After the re-coated primary mirror was installed the WFE was measured, and coma aberration was found to be larger. Finally, the secondary mirror shim adjustments were carried out based on the WFE measurements. In CLASP2 telescope, we improved a fitting method of WFE map (applying 8th terms circular Zernike polynomial fitting instead of 37th terms circular Zernike fitting) and the improved method enables to achieve better performance than CLASP telescope. Indeed, WFE map obtained after the final shim adjustment indicated that the required specification (< 5.5 μm RMS spot radius) that is more stringent than CLASP telescope was met.

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.

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

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.