DARWIN fringe sensor: experimental results on the BRISE bench

Interferometer performances are linked to the measurement and the correction of telescope aberrations. For cophasing the large number of beams required by the DARWIN mission with the specified requirements (realtime piston/tip/tilt correction and measurement of higher orders up to spherical aberration), focal-plane approach has been selected due to its simple opto-mechanical device. Several focal-plane algorithms, developed at ONERA and gathered in the stand-alone MASTIC tool, were validated by experiment with a dedicated breadboard on the laboratory test bench BRISE. Our study shows the correct behaviour of the algorithms for linearity and repeatability; specific requirements are reached for piston/tip/tilt and higher order aberrations. These results confirm the validity of focal-plane sensors for the cophasing of multiple-aperture telescopes.