Residual speckle removal by aperture modification

Imaging extra-solar planets requires exceptional dynamic range detection. Extreme adaptive optics and coronagraphy improve the planet-to-star intensity ratio, but residual atmospheric speckles still dominate the field of view. Optics images are reduced by removing redundancies. Some speckles are always left, pinned mostly to the Airy rings of the stellar image, and these obscure the planets. Adding corrective phase to the deformable mirror can modulate the speckles, but only further off the central star. Breaking the symmetry of the telescope aperture, namely by applying a non-centrosymmetric mask to its image the shape of the diffraction rings is modified. Thus we rotated this mask to wobble the rings and the speckles pinned to them enough to reveal planets hidden below them. Having a set of star-planet images at different mask rotations, there are different ways to data analysis. In essence, the intensity in each pixel of the image is modulated by the mask rotation. However, the time trace is strongly affected by pixel location, atmospheric residual errors, Poisson noise from star and planet, and detector read-out noise. The temporal approach to identify the harmonic signal and the planet´s constant bias was not very successful for faint objects. Model has been developed for this case of statistics of minima with added noisy periodic signals for testing on simulated data. Finally it should be noted that this simple method can also improve the contrast ratio and the resolution of other imaging systems, such as in microscopy.