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Paper: Estimate on SOT Light Level in Flight with Throughput Measurements in SOT Sun Tests
Volume: 369, New Solar Physics with Solar-B Mission
Page: 51
Authors: Shimizu, T.; Kubo, M.; Tarbell, T.D.; Berger, T.E.; Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Miyashita, M.; Noguchi, M.; Nakagiri, M.; Tsuneta, S.; Elmore, D.F.; Lites, B.W.
Abstract: The SOT (Solar Optical Telescope, e.g., Shimizu 2004) optical system consists of 50cm-aperture optical telescope (OTA) and focal plane instrument (FPP). The solar light into the telescope penetrates through many optical elements located in OTA and FPP before illuminating CCDs. Natural solar light was fed to the integrated SOT in sun tests for verifying various optical aspects including the confirmation of photon throughput. CCD exposures provide the number of photons accumulated in an exposure duration with a clean-room test condition. To estimate the absolute intensity of the solar light at the telescope entrance in the clean-room test condition, we developed a pinhole-PSD sensor for simultaneous monitoring the solar light outside the clean room and measured the transmission of light through two flat mirrors of the heliostat and clean-room entrance window glass as a function of wavelength. The PSD sensor was pre-calibrated with continuous monitoring the solar light in a day long under a clear constant sky condition, determining the earth atmospheric attenuation and the PSD output for the solar light on orbit. These throughput measurements have provided an estimate on photon throughput for the SOT flight model. The results confirm suitable number of photons without saturation for proper CCD exposures in flight.
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