GTCdigital
News
Refrigerated cupboards?
22/08/2003
Every home has at least one cupboard. We use them to keep all kinds of possessions out of the way and in a place where they can be easily found. They can hold clothes, shoes, games, tools, food, all the souvenirs we have accumulated and junk from all over the place.
The GTC will have lots of cupboards, all of them very similar, but these ones will house something very different: information and commands in the shape of advanced technology. They will be no ordinary cupboards, being designed to solve two of the problems that all large telescopes face: protecting the telescope from the heat emitted by the electronic equipment, and protecting the equipment from the conditions the telescope needs if it is to observe correctly. The result is a clash between hot and cold that needs to be properly managed.
So how will we control this clash between the two conditions? We will use specially designed refrigerated cupboards to house almost all of the telescope’s electronic equipment. There are two problems posed by this equipment: it creates thermal disturbances and it is operated by mechanisms, both of which can affect the telescope’s optical systems. The temperature and humidity levels inside the telescope can also affect the smooth running of the equipment, and there lies the challenge: the GTC’s refrigerated cupboards will have to minimise and manage both of these risks.
What are they like?
The cupboards are based on a standard design, that has been customised to incorporate thermal insulation material, a heat containment system, isolation for the mechanisms and a humidity control system.
To provide thermal insulation, the back of the cupboards’ external panels has been covered with 50mm of special foams, which will insulate them and prevent heat from escaping into the telescope environment. Sensors will monitor the temperature inside the cupboard and activate the water-operated refrigeration system as and when needed.
A 1500 w fire could be turned on inside these cupboards without affecting either the electronic equipment or the telescope's optical systems.
To isolate the mechanisms and deaden sound, rubber will be attached to various points on the inside and outside to filter out the vibrations caused by the equipment.
For relative humidity control, a mixture of substances will be used for "passsive" (unpowered) control of the water vapor pressure inside the cupboard. It is a highly sensitive system, consisting of small packets of a mixture of absorbent materials that have been treated at high temperatures so that they become carbonised. The result is a product that can retain water by both absorption and adsorption. In other words, it will either absorb or release water to maintain a stable environment inside the cupboard.
They will not be affected by temperature fluctuations, vibrations or humidity levels...as you can see, they are no ordinary cupboards!
Natalia R. Zelman