A Proposal to use FBG sensors for thermo-vacuum tests of space structures

Fiber Bragg Grating (FBG) sensors are used in various engineering fields, due to their physical properties. Multiple FBG sensors (up to 30) can be multiplexed on the same fiber, and their measurements can be read at the same time by the interrogation system, thus drastically reducing the number and dimension of cables on the structure to be monitored. A Fiber Bragg grating is made by inducing a periodic change in the refraction index in the glass core of the fiber; FBG sensors work as optical strain gages, since they provide strain by measuring a wavelength shift. Strain can be due to mechanical stress or to thermal deformation. While the use of FBG as strain gages is fairly common, there are few experiments about their use as thermal sensors. Some arrays of FBG sensors are planned to be used during the ground test of the Galileo Giove-B satellite in Thales Alenia Space facilities in Rome. The thermal test will be performed in a thermo-vacuum chamber in which the pressure of 10-4 Pa, and temperatures from -120°C to +120°C will be used. The experimental work is aimed to: · compare the measurement of FBG sensors with the ones acquired using traditional sensors; · test the technological problem given by the use of optical fibers (fragility of the fiber, connectors technology, handling), and testing possible solutions.