28 August 2014 ADDEDPT: apparatus for direct detection of exoplanets by diffractive pupil telescopy
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Direct observations of habitable zone exoplanets within 10 pc require very high contrast attenuation of the parent star. While "pale blue dot" earth twins have strong signals in the near-UV and blue portion of the spectrum, and a G-class star like our sun has the most energy in the same region, the contrast ratio of star to exoplanet is 1010. However the ratio is 108 when the exoplanet albedo is reflecting an emission band inside of the spectrum of the star's absorption band. These interlaced emission and absorption bands are numerous and sharply defined in the blue region when the system is viewed through circular diffractive pupil optics. We show how to use a circular diffraction grating pupil to create asymmetrical circular diffraction images of exoplanetary systems that can be extracted from the central star's perfectly circular diffraction pattern by a series of iterative data reduction steps. We present a model of the apparatus that forms the diffraction images and a demonstration of the process in a laboratory experiment. The process may prove useful if large circular diffractive optic telescopes are successfully fabricated in on-going projects for earth reconnaissance from GEO where 10 meter diffractive optic telescopes are now contemplated.
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Thomas D. Ditto, Thomas D. Ditto, } "ADDEDPT: apparatus for direct detection of exoplanets by diffractive pupil telescopy", Proc. SPIE 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, 914339 (28 August 2014); doi: 10.1117/12.2055493; https://doi.org/10.1117/12.2055493

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