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Study of High Performance Coronagraphic TechniquesThe goal of the Study of High Performance Coronagraphic Techniques project (called CoronaTech) is: 1) to verify the Labeyrie multi-step speckle reduction method and 2) to develop new techniques to manufacture soft-edge occulter masks preferably with Gaussian absorption profile. In a coronagraph, the light from a bright host star which is centered on the optical axis in the image plane is blocked by an occulter centered on the optical axis while the light from a planet passes the occulter (the planet has a certain minimal distance from the optical axis). Unfortunately, stray light originating in the telescope and subsequent optical elements is not completely blocked causing a so-called speckle pattern in the image plane of the coronagraph limiting the sensitivity of the system. The sensitivity can be increased significantly by reducing the amount of speckle light. The Labeyrie multi-step speckle reduction method implements one (or more) phase correction steps to suppress the unwanted speckle light. In each step, the stray light is rephased and then blocked with an additional occulter which affects the planet light (or other companion) only slightly. Since the suppression is still not complete, a series of steps is required in order to achieve significant suppression. The second part of the project is the development of soft-edge occulters. Simulations have shown that soft-edge occulters show better performance in coronagraphs than hard-edge occulters. In order to utilize the performance gain of soft-edge occulters. fabrication methods have to be developed to manufacture these occulters according to the specification set forth by the sensitivity requirements of the coronagraph.
Document ID
20050019586
Acquisition Source
Headquarters
Document Type
Contractor or Grantee Report
Authors
Crane, Phil (NASA Headquarters Washington, DC United States)
Tolls, Volker (Smithsonian Astrophysical Observatory Cambridge, MA, United States)
Date Acquired
September 7, 2013
Publication Date
December 1, 2004
Subject Category
Instrumentation And Photography
Funding Number(s)
CONTRACT_GRANT: NNG04GC57G
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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