Ground and Space-Based Telescopes

Dynamic analysis of the Green Bank Telescope structure and servo system

[+] Author Affiliations
Trupti Ranka, Mario Garcia-Sanz

Case Western Reserve University, Department of EECS, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States

Arthur Symmes

National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22903, United States

John M. Ford, Timothy Weadon

National Radio Astronomy Observatory, Routes 28/92, Green Bank, West Virginia 24944, United States

J. Astron. Telesc. Instrum. Syst. 2(1), 014001 (Jan 07, 2016). doi:10.1117/1.JATIS.2.1.014001
History: Received June 5, 2015; Accepted December 4, 2015
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Abstract.  The Green Bank Telescope is a 100-m aperture single-dish radio telescope. For high-frequency observations (above 100 GHz), it needs a tracking error below 1.5 arc sec rms. The present system has a tracking error of 1 arc sec rms for very low wind speeds of 1  m/s, which increases well above 1.5 arc sec for wind speeds above 4 m/s. Hence, improvements in the servo control system are needed to achieve pointing accuracy goals for high-frequency observations. As a first step toward this goal, it is necessary to evaluate the dynamic response of the present servo system and the telescope, which forms a large flexible structure. We derive the model of the telescope dynamics using finite element analysis data. This model is further tuned and validated using system identification experiments performed on the telescope. A reduced model is developed for controller design by using modes with the highest Hankel singular value for frequencies up to 2 Hz. We quantify the uncertainty in azimuth axis dynamics with a change in elevation angle by varying the zeros of the model. We discuss the effects of transient response, wind disturbances, and azimuth track joint disturbances on telescope tracking performance.

© 2016 Society of Photo-Optical Instrumentation Engineers

Citation

Trupti Ranka ; Mario Garcia-Sanz ; Arthur Symmes ; John M. Ford and Timothy Weadon
"Dynamic analysis of the Green Bank Telescope structure and servo system", J. Astron. Telesc. Instrum. Syst. 2(1), 014001 (Jan 07, 2016). ; http://dx.doi.org/10.1117/1.JATIS.2.1.014001


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