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Estimate on SOT light level in flight with throughput measurements in SOT sun tests

Estimate on SOT light level in flight with throughput measurements in SOT sun tests. T. Shimizu 1 , T. Tarbell 2 , T. Berger 2 , Y. Suematsu 3 , M. Kubo 1 , K. Ichimoto 3 , Y. Katsukawa 3 , M. Miyashita 3 , M. Noguchi 3 , M. Nakagiri 3 , S. Tsuneta 3 , D. Elmore 4 , B. Lites 4 and SOT team

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Estimate on SOT light level in flight with throughput measurements in SOT sun tests

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  1. Estimate on SOT light level in flight with throughput measurements in SOT sun tests T. Shimizu1, T. Tarbell2, T. Berger2, Y. Suematsu3, M. Kubo1, K. Ichimoto3, Y. Katsukawa3, M. Miyashita3, M. Noguchi3, M. Nakagiri3, S. Tsuneta3, D. Elmore4, B. Lites4 and SOT team 1. ISAS/JAXA, 2. LMSAL, 3. NAOJ, 4. HAO/NCAR

  2. Light throughput measurement before the flight is very important to confirm that CCD will not be over-saturated in flight as well as signal-to-noise performance. • Natural solar light was fed to the integrated SOT flight model in two sun-test opportunities. • CCD exposures provide the number of photons accumulated in an exposure-duration in clean room test condition. • A pinhole-PSD (position sensitive detector) sensor (525 nm band) was used to monitor the light level simultaneously, giving the “absolute” light level. • Transmissivity of heliostat two flat mirrors plus clean-room entrance window glass was also measured as a function of wavelength. • This throughput measurement with solar light has confirmed adequate light level in flight experimentally.

  3. Sun Tests Sun light illuminated OTA full aperture NAOJ Heliostat on the roof of clean room Test configuration

  4. Pre-calibrated standard Sensor • A pinhole-PSD (position sensitive detector) sensor (525 nm band) was used to monitor the light level simultaneously, giving the “absolute” light level. • The PSD sensor was pre-calibrated with continuous monitoring the solar light level in a day long under a clear constant sky condition, giving what is the voltage for one solar light level. Pinhole-PSD sensor

  5. Summary of photon level in flight for all the wavelengths

  6. Spectro-Polarimeter (SP) • SP data will have suitable number of photons in flight. • The continuum photon level accumulated in each exposure (0.1sec) is 34-40% of the CCD full well. • The signal-to-noise achieved with 4.8 sec (48 frame) accumulation is 1500 (0.07%). S/N with 3.2sec (32 frame) accumulation is 1235 (0.08%). Broadband Filter Imagers (BFI) • All the wavelengths are not saturated. • G-band has the shortest exposure time (~30 msec for half of full well). • Ca IIH has the longest exposure time (300-500msec for half of full well). Narrowband Filter Imagers (NFI) • Shuttered observables have exposure time of 100-400msec for 1x1 and 60-250msec for 2x2 (all the wavelengths). • Shutterless observables with 100msec works properly. • Since a few 200msec shutterless observables may be saturated, alternate observables (100msec exposures at two field of view) are prepared. Correlation Tracker (CT) • CT data will have suitable number of photons in flight. • The expected photon level in flight is 42% of the CCD full well.

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