Second-Earth Imager For Tmt (Seit): Concept And Its Numerical Simulation

Thirty Meter Telescope (TMT) will see the first light in 2019. We propose Second-Earth Imager for TMT (SEIT) as a future instrument of TMT. The central science case of SEIT is direct imaging and characterization of habitable planets around nearby late-type stars. Focusing on simultaneous spectroscopy of the central star and the planet, SEIT allows us to remove an impact from the telluric absorption and then reveal the presence of oxygen molecules on the Earth-like planets.In order to achieve such a science goal, an extreme AO, a coronagraph, and a post-process technique for achieving high contrast at the small inner working angle are key components. The combination of a shearing nulling interferometer and a pupil remapping interferometer is applied to the first SEIT concept. The shearing nulling interferometer suppresses the diffracted starlight after the extreme AO wavefront correction, and then the pupil remapping interferometer tackles the speckle noise from starlight. Focusing on a fact that the pupil remapping interferometer has difficulty reconstructing the wavefront from only the speckle noise, we found an unbalnced nulling technique enhances the performance of the pupil remapping interferometer. We performed a numerical simulation to validate this concept and found this concept achieves the 5-sigma detection contrast down to 8x10(-8) at 10 mas for 5 hours. Thus, the SEIT concept detects habitable planets with a radius two times that of the Earth around ten nearby M stars.