| After the James Webb Space Telescope and the Space Interferometry Mission, NASA's next large telescope will be the Terrestrial Planet Finder Coronagraph (TPF-C). The goal of TPF is to survey the habitable zone of the nearest 150 F, G, and K stars for terrestrial planets. Earth-like planets detection from space must overcome diffracted star light and scattered light front optical components defects. The very high contrast required (up to 10-10 for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront.; Currently, all proposed solutions to the space-based high contrast imaging problem address the contrast issue in its ideal form with no aberrations in the system. However, the correction algorithms lag behind. The goal of my research was to develop a correction method for the Shaped Pupil Coronagraph (SPC) with the contrast specifications of TPF.; I start by describing the "speckle nulling'' algorithm. I present simulations of this algorithm with three different high contrast imaging systems and analyze its feasibility for the SPC for TPF.; Next, I describe the "frequency folding" phenomenon, explaining why conventional phase conjugation is not able to achieve the contrast needed for Earth-like planet detection. Then, I present an optimized solution for the shape of the deformable mirror based on the Fourier decomposition of the effective phase and amplitude aberrations.; In the last part of this thesis I present the "Peak-a-boo" correction algorithm, a closed loop correction system that I designed for the SPC. This algorithm iteratively finds the commands for the deformable mirror's (DM) actuators that minimize the total intensity of light in a predetermined region on one side of the image plane where a planet could be found. The algorithm's name comes from its reconstruction stage which uses a pinhole addition to the shaped pupil. At comparable abberations cases, this algorithm yields a better contrast than the "speckle nulling" algorithm with significantly fewer iterations. Moreover, this algorithm is shown to be effective in the presence of photon noise, deformable mirror modeling errors and overcoming defective actuators in the deformable mirror. |
