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26 September 2007 GREAT: the German first light heterodyne instrument for SOFIA
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GREAT, the German REceiver for Astronomy at Terahertz frequencies, is a first generation SOFIA dual channel heterodyne PI−instrument for high resolution spectroscopy. The system is developed by a consortium of German research institutes. The receiver will allow simultaneous observations in two out of the following three far−infrared frequency bands: * a low−frequency (1.4−1.9 THz) channel for e.g. the fine-structure lines of ionized nitrogen [NII] at 205μm and ionized carbon [CII] at 158μm; * a mid−frequency (2.4−2.7 THz) channel for e.g. the 112μm transition of HD; and * a high−frequency (4.7 THz channel) for the 63 μm fine−structure line of neutral atomic oxygen. Hot electron bolometers (HEB) mixers provide state of the art sensitivity. A spectral resolving power of up to 108 is achieved with chirp transform spectrometers, and a total bandwidth of 4 GHz at 1 MHz resolution is reached with wide band acousto-optical spectrometers. The modular concept of GREAT allows to observe with any combination of two out of the three channels aboard SOFIA. A more complete frequency coverage of the THz regime by adding additional GREAT channels is possible in the future. The adaptation of new LO−, mixer− or backend−techniques is easily possible. We describe details of the receiver and the results of first performance tests of the system at 1.9 THz. As an outlook to future developments we show first results obtained with phase locking a quantum cascade laser, the most promising option for future high power local oscillators in the Terahertz regime.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Urs U. Graf, Stefan Heyminck, Rolf Güsten, Paul Hartogh, Heinz-Wilhelm Hübers, Jürgen Stutzki, Jérôme Faist, Milan Fischer, Karl Jacobs, Martin Philipp, David Rabanus, Alexej Semenov, Peter van der Wal, Armin Wagner-Gentner, Christoph Walther, and Martina Wiedner "GREAT: the German first light heterodyne instrument for SOFIA", Proc. SPIE 6678, Infrared Spaceborne Remote Sensing and Instrumentation XV, 66780K (26 September 2007);

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