Air turbulence can be created in the telescope chamber by temperature differences between the various levels and components. Air turbulence affects optical quality and so must be avoided, making it vital to control the temperature of the area around the telescope. The GTC has been designed with a range of systems for this purpose.
The dome will be thermally insulated to reduce heat absorption from the sun during the day, and the telescope chamber will be air-conditioned to keep it at the air temperature expected at nightfall.
Two rows of ventilation apertures will be built into the dome, with sliding doors for night time use to control natural ventilation in the telescope chamber. A total of 16 large moving ventilation doors, each approximately 4 m x 4 m will be sited on the same level as the primary mirror - they will be an integral part of the temperature control process. The system gives optimum ambient conditions on the interior. There will also be a forced air system as a back up.
The design of the enclosure is so tall that there is room for another row of ventilation apertures and doors in its base. This will improve ventilation to the mirror cell and the floor where the telescope chamber is housed. An air chamber between the base of the enclosure and the telescope chamber will reduce the amount of heat transferred from one to the other.