SISTERS: a space interferometer for the search for terrestrial exo-planets by rotation shearing

A concept for a space-based interferometer dedicated to the detection of extrasolar earth-like planets is presented. Detection is done in the near infrared (10 micrometers ) where the expected star to planet flux ratio is down to 106 compared to 1010 in the visible. The longer wavelength also makes is easier to avoid light scatter due to optics micro-roughness. Parent star cancellation is obtained with a rotation shearing interferometer working at its null on axis. The interferometer is of the Fizeau configuration with an aperture composed of twelve 1.2 meter mirrors on a 20 meter ring. This size, which corresponds to a resolving power of 0.05 arcsecond, allows for the investigation of about 30 candidate stars. The interferometer is supported by a chemically rigidized structure deployed by inflation. All optical elements are passively cooled to about 70 degrees Kelvin to reduce the instrumental infrared background. The spacecraft is located at the second Lagrangian point of the earth-sun system in order to minimize attitude control and baffling requirements.