Thermal imaging of the Large Millimeter Telescope structure

A dominant problem for large, high precision telescopes is the deformation due to temperature changes in the structure. Even for active surface designs such as the Large Millimeter Telescope/Gran Telescopio Milimetrico (LMT), accurate knowledge of the temperature distribution in the structure is necessary in order to adjust the primary reflector panels and make pointing corrections. The design of thermal management system of the LMT consists of a fully-cladded structure, a forced ventilation system, and a collection of temperature sensors distributed throughout the telescope. During the design, both steady-state and dynamic thermal models were developed to predict the thermal behavior. Additionally, some thermal measurements were taken during construction, before the cladding was installed. Since the structure is now completely enclosed with insulating cladding, it is an excellent candidate for thermal imaging at this stage of the commissioning. Thermal images of the structure are presented, showing the actual temperature distribution of the LMT alidade structure and reflector. The images are taken from a consistent set of positions to show the how the structural temperature distribution evolves over day and night conditions.