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Proceedings Paper

Pointing and control system performance and improvement strategies for the SOFIA Airborne Telescope
Author(s): Friederike Graf; Andreas Reinacher; Holger Jakob; Ulrich Lampater; Enrico Pfueller; Manuel Wiedemann; Jürgen Wolf; Stefanos Fasoulas
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Paper Abstract

The Stratospheric Observatory for Infrared Astronomy (SOFIA) has already successfully conducted over 300 flights. In its early science phase, SOFIA's pointing requirements and especially the image jitter requirements of less than 1 arcsec rms have driven the design of the control system. Since the first observation flights, the image jitter has been gradually reduced by various control mechanisms. During smooth flight conditions, the current pointing and control system allows us to achieve the standards set for early science on SOFIA. However, the increasing demands on the image size require an image jitter of less than 0.4 arcsec rms during light turbulence to reach SOFIA's scientific goals. The major portion of the remaining image motion is caused by deformation and excitation of the telescope structure in a wide range of frequencies due to aircraft motion and aerodynamic and aeroacoustic effects. Therefore the so-called Flexible Body Compensation system (FBC) is used, a set of fixed-gain filters to counteract the structural bending and deformation. Thorough testing of the current system under various flight conditions has revealed a variety of opportunities for further improvements. The currently applied filters have solely been developed based on a FEM analysis. By implementing the inflight measurements in a simulation and optimization, an improved fixed-gain compensation method was identified. This paper will discuss promising results from various jitter measurements recorded with sampling frequencies of up to 400 Hz using the fast imaging tracking camera.

Paper Details

Date Published: 27 July 2016
PDF: 16 pages
Proc. SPIE 9906, Ground-based and Airborne Telescopes VI, 99061T (27 July 2016); doi: 10.1117/12.2231803
Show Author Affiliations
Friederike Graf, Univ. Stuttgart (Germany)
SOFIA Science Ctr., NASA Ames Research Ctr. (United States)
Andreas Reinacher, Univ. Stuttgart (Germany)
SOFIA Airborne Systems Operations Ctr., NASA Armstrong Flight Research Ctr. (United States)
Holger Jakob, Univ. Stuttgart (Germany)
SOFIA Airborne Systems Operations Ctr., NASA Armstrong Flight Research Ctr. (United States)
Ulrich Lampater, Univ. Stuttgart (Germany)
Enrico Pfueller, Univ. Stuttgart (Germany)
SOFIA Science Ctr., NASA Ames Research Ctr. (United States)
Manuel Wiedemann, Univ. Stuttgart (Germany)
SOFIA Science Ctr., NASA Ames Research Ctr. (United States)
Jürgen Wolf, Univ. Stuttgart (Germany)
SOFIA Science Ctr., NASA Ames Research Ctr. (United States)
Stefanos Fasoulas, Univ. Stuttgart (Germany)


Published in SPIE Proceedings Vol. 9906:
Ground-based and Airborne Telescopes VI
Helen J. Hall; Roberto Gilmozzi; Heather K. Marshall, Editor(s)

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