CABLE MECHANIMS FOR A RADIO-TELESCOPE

Radioastronomers have launched an international initiative whose objective is the construction of a radiotelescope with a collective surface collectrice equivalent to one square kilometre. This instrument, named SKA (Square Kilometer Array), would allow astronomers to reach several objectives, such as determine the age of the universe (the period when the first stars were formed) and to understand the origin and evolution of cosmic magnetism. In addition to a collective surface of 1 km2, some of the other main constraints imposed upon the project by radioastronomers include the cost of development (fixed at 1 billion US$) and the coverage of the largest possible part of the sky (up to 60 degrees from zenith).

Given that a unique surface of 1 km2 is practically impossible to achieve, the instrument will be composed of several individual stations linked by fiber optics to obtain an equivalent collective surface. Several countries (Australia, Canada, China, Europe and the United States) have developed concepts and Canada's contribution was proposed by a group of university and industry researchers, supervised by the Federal Radioastrophysics Observatory (A CNRC institute located in Penticton, B. C.).

The concept, named LAR (Large Adaptative Reflector) is illustrated in the figures below and is composed of three elements:

1. A low-curvature deformable parabolic reflector located near the ground. This reflector enables wabes to be reflected towards a focal point. It is actuated in such a way as to direct the curvature towards the part of the sky which one wishes to observe.
2. A radio receptor which must be positioned at the focal point to capture the signal coming from the reflected sky via a primary collector.
3. A positioning mechanism capable of moving and orienting the radio receptor in accordance with the position of the focal point determined by the shape of the reflector.