Measurement of vibration environment of 6m-diameter radiometer thermal vacuum chamber in JAXA

Abstract

Space-borne large optics will be required in future missions for astronomy and earth observations. In order to realize large-optics missions, JAXA has started the study of the ground measurement techniques of large optics. The 6m diameter radiometer thermal vacuum chamber (6m chamber) at Tsukuba Space Center will be used for tests of JAXA's future large-optics missions like Space Infrared Telescope for Cosmology and Astrophysics (SPICA). We measured the vibration environment of the 6m chamber for the feasibility study of precise optical measurement. We placed a test mirror inside the chamber and measured the surface figures of the mirror from outside the chamber with a high-speed interferometer, while the chamber was being vacuum-pumped and cooled by liquid nitrogen; we also directly measured the vibrational levels with accelerometers concurrently. The measurements were performed for each phase of the chamber system operation including pumping and cooling processes. This paper presents the results about optical measurement under the vibration environment on the 6m chamber. We confirm that the vibrations from pumps and shroud have negligible effects on optical measurements owing to a vibration isolation system in the 6m chamber.

Optical testing of lightweight large all-C/SiC optics

“…The optical systems should be aligned in a horizontal lightaxis configuration within the facility limit to handle a 3.5-m aperture telescope like SPICA. A Twyman-Green interferometer with dynamic phase shift, produced by 4D Technology, was used and vibrations from the pumps and shroud of the chamber were confirmed to be negligible for optical measurement [7]. To avoid considerable facility modification, the interferometer was operated in an aluminum and titan pressure vessel, which was mounted on the five-axis stage in the chamber.…”

Evaluation of Spaceborne SiC Mirror Materials Using Samples Cut from the Periphery of a Mirror Body

“…The research team examined the manufacturability of a large-scale, lightweight mirror body, a quality assurance process, and cryogenic mirror-surface testing technology by manufacturing and evaluating a prototype optical system with a primary mirror of 800 mm in diameter constructed entirely of HBCesic Ò (Ref [5][6][7][8][9]. A schematic image of the optical system and a photograph of the 800-mm-diameter primary mirror used in the experiment are shown in Fig.…”