6 August 2014 Boresight calibration of FIFI-LS: in theory, in the lab and on sky
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Abstract
The Field-Imaging Far-Infrared Line-Spectrometer (FIFI-LS) entered service on the Stratospheric Observatory for Infrared Astronomy (SOFIA) on March 2014. Exact pointing of the instrument is important. The SOFIA telescope provides an absolute pointing stability of 1” rms, which is sufficient for FIFI-LS. The instrument boresight relative to the telescope reference system is established with accuracy better than 1”. FIFI-LS has a built-in rotating K-Mirror to derotate the instrument field of view. Perfect alignment of the optical axis of the K-Mirror and the optical axis of the optical systems in both instrument channels is practically impossible. The remaining offsets result in a dependence of the instrument boresight on the K-Mirror position. Therefore a boresight calibration model is established for each channel. With these models the instrument boresight is calculated and transferred to the telescope control software. Achieving precise calibration of the boresight has been an ongoing process including the first optical models of the instrument, measurements in different laboratories and finally measurements during the commissioning flight series. In this paper, the approach used to calibrate FIFI-LS’s boresight is explained. This includes the model used and an overview of the laboratory, as well as the in-flight measurements leading to the calibrated boresight model.
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Sebastian Colditz, Sebastian Colditz, Randolf Klein, Randolf Klein, Simon Beckmann, Simon Beckmann, Aaron Bryant, Aaron Bryant, Christian Fischer, Christian Fischer, Fabio Fumi, Fabio Fumi, Norbert Geis, Norbert Geis, Rainer Hönle, Rainer Hönle, Alfred Krabbe, Alfred Krabbe, Leslie W. Looney, Leslie W. Looney, Albrecht Poglitsch, Albrecht Poglitsch, Walfried Raab, Walfried Raab, Sarah E. Ragan, Sarah E. Ragan, Felix Rebell, Felix Rebell, Maureen L. Savage, Maureen L. Savage, } "Boresight calibration of FIFI-LS: in theory, in the lab and on sky", Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 91474S (6 August 2014); doi: 10.1117/12.2055335; https://doi.org/10.1117/12.2055335
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