Experimental evaluation of the stability and mechanical behavior of contacts in Silicon Carbide for the design of the basic angle monitoring system of GAIA

The satellite GAIA will be launched in ca. 2010 to make a 3-D map of our Galaxy. The payload module of the satellite will carry two astrometric telescopes amongst other instrumentation. The optical bench and astrometric telescopes will be constructed for a large part in Silicon Carbide (SiC). A truss structure concept design was developed, which could serve as optical bench for the scientific instrumentation of GAIA. It is lightweight and has a first eigenfrequency of 80 Hz. Also a concept design has been developed for the Basic Angle Monitoring (BAM) system of GAIA, which will measure 1 micro-arcsecond (ƒÝas) variations of the angle between the lines-of-sight of the two telescopes. For the design of these systems, contact mechanics is an important issue and therefore experiments have been conducted to obtain practical experience of the contact behaviour of SiC. This knowledge will be used in our project for a design of the BAM system. These experiments consist of friction experiments and experiments in which SiC tubes are bonded with several techniques like bolting, brazing and gluing