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Visible Nulling Coronagraphy for Exo-Planetary Detection and Characterization

Published online by Cambridge University Press:  02 May 2006

Richard G. Lyon
Affiliation:
NASA/Goddard Space Flight Center, Greenbelt, MD email:Richard.G.Lyon@nasa.gov, 301-286-4302
Mark Clampin
Affiliation:
NASA/Goddard Space Flight Center, Greenbelt, MD email:Richard.G.Lyon@nasa.gov, 301-286-4302
Robert Woodruff
Affiliation:
Lockheed-Martin, Civil Space, Denver, CO
Gopal Vasudevan
Affiliation:
Lockheed-Martin, Advanced Technology Center, Palo Alto, CA
Mike Shao
Affiliation:
NASA/Goddard Space Flight Center, Greenbelt, MD email:Richard.G.Lyon@nasa.gov, 301-286-4302
Martin Levine
Affiliation:
NASA/Jet Propulsion Laboratory, Pasadena, CA
Gary Melnick
Affiliation:
NASA/Goddard Space Flight Center, Greenbelt, MD email:Richard.G.Lyon@nasa.gov, 301-286-4302
Volker Tolls
Affiliation:
Harvard/SAO Center for Astrophysics, Cambridge, MA
Peter Petrone
Affiliation:
NASA/Goddard Space Flight Center, Greenbelt, MD email:Richard.G.Lyon@nasa.gov, 301-286-4302
Peter Dogoda
Affiliation:
Sigma Space, Lanham, MD
Julia Duval
Affiliation:
CNES, France
Jian Ge
Affiliation:
University of Florida
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Abstract

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Visible Nulling Coronagraphy (VNC) is the proposed method of detecting and characterizing exo-solar Jovian planets (null depth $10^{-9}$) for the proposed NASA's Extrasolar Planetary Imaging Coronagraph (EPIC) Clampin & Lyon 2004 and is an approach under evaluation for NASA's Terrestrial Planet Finder (TPF) mission. The VNC approach uses a single unobscured filled-aperture telescope and splits, via a 50:50 beamsplitter, its re-imaged pupil into two paths within a Mach-Zender interferometer. An achromatic PI phase shift is imposed onto one beam path and the two paths are laterally sheared with respect to each other. The two beams are recombined at a second 50:50 beamsplitter. The net effect is that the on axis (stellar) light is transmitted out of the bright interferometer arm while the off-axis (planetary) light is transmitted out of the nulled interferometer arm. The bright output is used for fine pointing control and coarse wavefront control. The nulled output is relayed to the science camera for science imagery and fine wavefront control. The actual transmission pattern, projected on the sky, follows a $\theta^2$ pattern for a single shear, $\theta^4$ for a double shear, with the spacing of the successive maxima proportional to the inverse of the relative lateral shear. Combinations of shears and spacecraft rolls build up the spatial frequency content of the sky transmission pattern in the same manner as imaging interferometer builds up the spatial frequency content of the image.

Type
Contributed Papers
Copyright
© 2006 International Astronomical Union