* Astronomy

Title: The AMiBA Hexapod Telescope Mount
Authors: Patrick M. Koch (1), Michael Kesteven (2), Hiroaki Nishioka (1), Homin Jiang (1), Kai-Yang Lin (1,3), Keiichi Umetsu (1,4), Yau-De Huang (1), Philippe Raffin (1), Ke-Jung Chen (1), Fabiola Ibanez-Romano (1), Guillaume Chereau (1), Chih-Wei Locutus Huang (3,4), Ming-Tang Chen (1), Paul T. P. Ho (1,5), Konrad Pausch (6), Klaus Willmeroth (6), Pablo Altamirano (1), Chia-Hao Chang (1), Shu-Hao Chang (1), Su-Wei Chang (1), Chih-Chiang Han (1), Derek Kubo (1), Chao-Te Li (1), Yu-Wei Liao (3,4), Guo-Chin Liu (1,7), Pierre Martin-Cocher (1), Peter Oshiro (1), Fu-Cheng Wang (3,4), Ta-Shun Wei (1), Jiun-Huei Proty Wu (3,4), Mark Birkinshaw (8), Tzihong Chiueh (3), Katy Lancaster (8), Kwok Yung Lo (9), Robert N.Martin (10), Sandor M. Molnar (1), Ferdinand Patt (11), Bob Romeo (10) ((1) Academia Sinica, Institute of Astronomy and Astrophysics, (2) Australia Telescope National Facility, (3) Department of Physics, Institute of Astrophysics and Center for Theoretical Sciences, National Taiwan University, (4) Leung center for Cosmology and Particle Astrophysics, (5) Harvard-Smithsonian Center for Astrophysics, (6) Vertex Antennentechnik GmbH, (7) Department of Physics, Tamkang University, (8) Department of Physics, University of Bristol, (9) National Radio Astronomy Observatory, (10) CMA, (11) ESO Headquarters Garching)

AMiBA is the largest hexapod astronomical telescope in current operation. We present a description of this novel hexapod mount with its main mechanical components -- the support cone, universal joints, jack screws, and platform -- and outline the control system with the pointing model and the operating modes that are supported. The AMiBA hexapod mount performance is verified based on optical pointing tests and platform photogrammetry measurements. The photogrammetry results show that the deformations in the inner part of the platform are less than 120 micron rms. This is negligible for optical pointing corrections, radio alignment and radio phase errors for the currently operational 7-element compact configuration. The optical pointing error in azimuth and elevation is successively reduced by a series of corrections to about 0.4 arcmin rms which meets our goal for the 7-element target specifications.

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