Izumi Mikami

The Solar Optical Telescope onboard the Solar-B

The solar optical telescope onboard the Solar-B is aimed to perform a high precision polarization measurements of the solar spectral lines in visible wavelengths to obtain, for the first time, continuous sets of high spatial resolution (~0.2arcsec) and high accuracy vector-magnetic-field map of the sun for studying the mechanisms driving the fascinating activity phenomena occurring in the solar atmosphere. The optical telescope assembly (OTA) is a diffraction limited, aplanatic Gregorian telescope with an aperture of Φ500mm. With a collimating lens unit and an active folding mirror, the OTA provides a pointing-stabilized parallel beam to the focal plane package (FPP) with a field of view of about 360x200arcsec. In this paper we identify the key technical issues of OTA for achieving the mission goal and describe the basic concepts in its optical, mechanical and thermal designs. The strategy to verify the in-orbit performance of the telescope is also discussed.

High precision composite pipes for SOLAR-B optical structures

Abstract The authors have been developing new high thermal conductivity and low moisture absorption composite pipes for high precision space optics applications on the Japanese Institute of Space and Astronautical Science (ISAS) SOLAR-B satellite. Pitch based K13C (Mitsubishi Chemical) high modulus and high conductivity graphite fiber, and EX1515 (Bryte Technology) low moisture absorption cyanate resin, were applied to the pipes. Thermal expansion of the composite pipes was designed to be zero and more uniform in the longitudinal direction in order to obtain long term dimensional stability in the space environment. Model pipes whose length was 500 mm were fabricated and evaluated for thermal and hygroscopic deformation in a new testing apparatus. Equivalent coefficient of thermal expansion of the model pipes was essentially zero (less than 0.1 ppm/°C) and standard deviation of these coefficients was 0.05 ppm/°C. Hygroscopic deformation of the model pipes was under representative conditions 7 ppm over 3 month. The excellent thermal and hygroscopic stability were verified. In addition, thermal conductivity of the model pipes was more than 200 W/(m · K).

Mechanical structure of JNLT: analysis of mirror deflection due to wind loading

The Japanese National Large Telescope (JNLT) will use a thin meniscus mirror of 7.5 m diameter and 0.2 m thickness as a primary mirror. One of the biggest concerns is mirror deflection due to dome-inside wind loading, which varies with time not only in its pressure amplitude but also in its pressure profile on the mirror surface. To analyze such mirror deflection, a method combining modal analysis and random vibration analysis was introduced. From the rms mirror deflection obtained by this method, the image quality degradation is considered to be better than that budgeted as wind loading degradation. Information about the method and typical result of the analysis are presented.

Mechanical Structure of JNLT

The Japanese National Large Telescope (JNLT) requires mechanical performance of high tracking accuracy to achieve good image quality and a mechanical configuration to provide several kinds of focus modes. Under these requirements, a conceptual design for the JNLT mechanical structure has been performed. This paper presents the results of the conceptual design currently under consideration.

Dome Design of JNLT

In recent years, it has become increasingly clear that the dome is often itself a major source of seeing degradation, due to its adverse thermal properties. In order to enable the Japanese National Large Telescope (JNLT) to attain the highest image quality as a ground-based telescope, 0.1″ r.m.s. on 80% light energy diameter basis is budgeted to the dome-induced seeing degradation as a design goal. Feasibility of this goal has been studied, using the latest design concept of the dome, in the following manner. Model the JNLT dome on the latest design plan for dynamic thermal analysis. Perform the dynamic thermal analysis to attain temperature distribution in the dome. Predict the seeing degradation induced by the dome using the thermal analysis result.

Power Beaming Technology Demonstration Satellite for Solarbird(R) Space Solar Power System

To meet future electrical power requirements with reduced environmental impact, Mitsubishi Electric Corporation envisions development of a space-based system for utilization of solar power. The Solarbird® system comprises a constellation of satellites for power generation and transmission to Earth. Early demonstration of critical power transmission technology using multiple satellites in low Earth orbit is planned. The demonstrator design and planned transmission experiment are described.

Thermal design concept of JNLT

The seeing degradation in the Japanese National Large Telescope (JNLT) caused by its hemispherical dome is investigated. A possible plan of the JNLT site layout and the thermal control concept are introduced in order to attempt to reduce the seeing degradation induced by the dome to the 0.1 arcsec FWHM range budgeted. A three-dimensioal compressible fluid analysis of the inside and outside the dome, including heat transfer effect, is developed and used to understand the seeing degradation mechanism as well as the wind buffet effect on the telescope and the primary mirror.