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6 July 2006 The cold focal plane chopper of HERSCHEL's PACS instrument
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HERSCHEL's 3.5 m primary mirror will be passively cooled to T ~ 80 K in the L2 orbit. In order to reduce the effects of the remaining high thermal background on the sensitive far infrared detectors (60..210 μm), a focal plane chopper is a vital element in the entrance optics of the imaging and spectroscopic instrument PACS. A gold coated 32 × 26 mm2 plane mirror, suspended by two flexural pivots and driven by a linear motor, allows for precise square wave chopping with up to 9° throw at a frequency 10 Hz with a position accuracy of 1 arcmin. The power required at T ~ 4 K is about 1 mW. The chopper has undergone an extensive qualification programme, including 650 million cold chop throws, 15 cold-warm-cold thermal cycles, 3-axis 26 G-vibration at T ~ 4 K etc. Five models were built and thoroughly tested; the flight model of the chopper is now integrated into the flight model of PACS, ready for the HERSCHEL/PLANCK launch in 2008 by an ARIANE5 rocket and the following 5-year mission.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Oliver Krause, Dietrich Lemke, Ralph Hofferbert, Armin Böhm, Ulrich Klaas, Josef Katzer, Frank Höller, and Manfred Salvasohn "The cold focal plane chopper of HERSCHEL's PACS instrument", Proc. SPIE 6273, Optomechanical Technologies for Astronomy, 627325 (6 July 2006); doi: 10.1117/12.671271;


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