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Proceedings Paper

SOFIA telescope modal survey test and test-model correlation
Author(s): Paul Keas; Rick Brewster; Jorge Guerra; Ulrich Lampater; Hans Kärcher; Stefan Teufel; Jörg Wagner
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Paper Abstract

The NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA) employs a 2.5-meter reflector telescope in a Boeing 747SP. The telescope is housed in an open cavity and will be subjected to aeroacoustic and inertial disturbances. The image stability goal for SOFIA is 0.2 arc-seconds (RMS). Throughout the development phase of the project, analytical models were employed to predict the image stability performance of the telescope, and to evaluate pointing performance improvement measures. These analyses clearly demonstrated that key aspects which determined performance were: 1) Disturbance environment and relevant load-paths 2) Telescope modal behavior 3) Sensor and actuator placement 4) Control algorithm design The SOFIA program is now entering an exciting phase in which the characteristics of the telescope and the cavity environment are being verified through ground and airborne testing. A modal survey test (MST) was conducted in early 2008 to quantify the telescope modal behavior. We will give a brief overview of analytical methods which have been employed to assess/improve the pointing stability performance of the SOFIA telescope. In this context, we will describe the motivation for the MST, and the pre-test analysis which determined the modes of interest and the required MST sensor/shaker placement. A summary will then be given of the FEM-test correlation effort, updated end-to-end simulation results, and actual data coming from telescope activation test flights.

Paper Details

Date Published: 4 August 2010
PDF: 26 pages
Proc. SPIE 7738, Modeling, Systems Engineering, and Project Management for Astronomy IV, 77380K (4 August 2010); doi: 10.1117/12.856507
Show Author Affiliations
Paul Keas, CSA Engineering, Inc. (United States)
Rick Brewster, Orbital Sciences Corp. (United States)
NASA Ames Research Ctr. (United States)
Jorge Guerra, CSA Engineering, Inc. (United States)
Ulrich Lampater, Deutsches SOFIA Institut (Germany)
Hans Kärcher, MT Aerospace AG (Germany)
Stefan Teufel, Deutsches SOFIA Institut (Germany)
Jörg Wagner, Deutsches SOFIA Institut (Germany)

Published in SPIE Proceedings Vol. 7738:
Modeling, Systems Engineering, and Project Management for Astronomy IV
George Z. Angeli; Philippe Dierickx, Editor(s)

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