The mechanical performances and the metrology system of the European ALMA antenna

F. Rampini; G. Marchiori; R. Biasi; S. Stanghellini; L. Ghedin

doi:10.1117/12.859265

6 August 2010 The mechanical performances and the metrology system of the European ALMA antenna

F. Rampini, G. Marchiori, R. Biasi, S. Stanghellini, L. Ghedin

Proceedings Volume 7733, Ground-based and Airborne Telescopes III; 773314 (2010) https://doi.org/10.1117/12.859265
Event: SPIE Astronomical Telescopes + Instrumentation, 2010, San Diego, California, United States

Abstract

The Atacama Large Millimeter Array (ALMA) consists of a large number of 12 m diameter antennas that will operate up to 950GHz. The mechanical performances in terms of surface accuracy, pointing stability and residual delay are very tight. The antennas must work at full performances in free air during night and day with also the request to observe the sun. The mechanical performances are affected by all the not repeatable error sources and in particular by the temperature variations and wind component blowing from different directions. The design of the antenna has been done in order to have a very light and stiff structure, in particular all the elevation structure is in carbon fibre with also a very low thermal expansion coefficient, but to achieve the ALMA specification, two different systems able to predict the above error sources have been implemented in the control of the antenna. The first system is composed by a determined number of thermal sensors distributed in the alidade of the antenna (is the only part in steel ) and compensates the elevation axis deformation due to the temperature variation by means of a deformation matrix. The second system is based on two high accuracy inclinometers with a very short recovery time opportunely placed on the antenna and correct the wind induced errors. These innovative systems and instruments have been design and tested in the prototype antenna to the production phase.

Citation Download Citation

F. Rampini, G. Marchiori, R. Biasi, S. Stanghellini, and L. Ghedin "The mechanical performances and the metrology system of the European ALMA antenna", Proc. SPIE 7733, Ground-based and Airborne Telescopes III, 773314 (6 August 2010); https://doi.org/10.1117/12.859265

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