Measurement of the alignment error of the telescope mirrors is an essential and demanding task in the telescope assembly phase. One method is to examine the aberration over the whole telescope field of view from sky images with stars, but there are complicated issues in the case of large telescopes. The focal plane of the University of Tokyo Atacama Observatory (TAO) 6.5-m telescope has a large diameter of 546mm and a field curvature. Therefore, many imaging sensors must be arrayed on the curved focal plane. We propose a concept of a screen camera for the TAO 6.5-m telescope. To lower the cost, we accept the degradation of the spatial resolution up to ∼2 arcseconds and the decrease in optical throughput. This system consists of a transparent screen, a camera lens, and a CMOS sensor, and it obtains sky images through the telescope on the screen. The transparent spherical screen with one side sanded is placed at the telescope focal plane. A CMOS sensor with a commercially available camera lens and filters is placed at about 1.5 meters from the screen and captures the starry sky on the screen. The pixel scale on the CMOS sensor is calculated to be 0.31 arcseconds, and the estimated limiting magnitude is about 13 in a 10-second exposure at a 10σ level. After the telescope mirror alignment, the screen camera will provide focused sky images in the whole field of view, 25 arcminutes diameter.
The University of Tokyo Atacama Observatory (TAO) is a project to build and operate a 6.5m telescope at the summit of Co. Chajnantor (5640 m.a.s.l). This is promoted by the Institute of Astronomy, School of Science, the University of Tokyo in collaboration with many institutes and universities in Japan and Chile. The site construction started in 2018 and was successfully completed by April 2024. An operation support building and an enclosure have already been constructed and are operational at the summit. Electricity is supplied by two generators installed in the operations building. The telescope mount and mirrors have already completed their tests in Japan and the U.S., respectively. They were transported to Chile and wait for the assembly. The first light instruments, NICE and MIMIZUKU, are undergoing final adjustment in Japan and will be transported to Chile as the telescope assembly progresses. The near-infrared instrument SWIMS has completed its open use on the Subaru telescope and returned back to Japan in Aug. 2023 for upgrading for TAO. The near-infrared spectrograph TARdYS, which is being developed in collaboration with Pontificia Universidad Católica de Chile, is also making progress in the development of its optics and detectors. In addition to these, the development of a new optical instrument has been started this year. Allocation of the observing time was also determined. TAO will use approximately 45% of its scientific observation time as project time, 35% as Japan open time for the Japanese community, and 10% as Chilean time for the Chilean community. 5-15% will be provided as paid observing time.
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