Improving the alignment of a large telescope structure using thermographic measurements

Rogerio Enriquez; David R. Smith

doi:10.1117/12.552490

29 September 2004 Improving the alignment of a large telescope structure using thermographic measurements

Rogerio Enriquez, David R. Smith

Proceedings Volume 5495, Astronomical Structures and Mechanisms Technology; (2004) https://doi.org/10.1117/12.552490
Event: SPIE Astronomical Telescopes + Instrumentation, 2004, Glasgow, United Kingdom

Abstract

While many telescopes employ some form of thermal monitoring and control to reach their surface accuracy and pointing specifications, such thermal systems are generally not available during field erection of the telescope structure. This presents a problem for large structures, because their size results in structural members with long time constants and substantial total deformations. These characteristics can potentially result in the development of significant thermal gradients across the structure or even across the width of a member. The resulting temperature variations complicate the alignment of critical features, including the main axes. As a result, it would be advantageous to monitor the thermal behavior of a large telescope structure during its construction. In the past, such monitoring was made difficult because of the size of the structure, continuing construction work, or rugged field conditions. However, with the advent of affordable field-ready thermal imaging systems, it is now possible to perform such monitoring. In this paper, we present thermal images of the alidade structure of the Large Millimeter-wave Telescope (LMT/GTM) at its site at 4600m on the top of Volcan Sierra Negra in central Mexico. We present images of typical thermal distributions for different times of day, and compare them with basic analytical models. Finally, we use the thermal imaging results to predict the effects of the temperature distribution on the location of the azimuth bogie connections and the elevation axis.

Citation Download Citation

Rogerio Enriquez and David R. Smith "Improving the alignment of a large telescope structure using thermographic measurements", Proc. SPIE 5495, Astronomical Structures and Mechanisms Technology, (29 September 2004); https://doi.org/10.1117/12.552490

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KEYWORDS

Thermal modeling

Telescopes

Temperature metrology

Thermography

Solar radiation models

Reflection

Cameras

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