25 August 2009 Visible nulling coronagraph testbed results
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Abstract
We report on our recent laboratory results with the NASA/Goddard Space Flight Center (GSFC) Visible Nulling Coronagraph (VNC) testbed. We have experimentally achieved focal plane contrasts of 1 x 108 and approaching 109 at inner working angles of 2 * wavelength/D and 4 * wavelength/D respectively where D is the aperture diameter. The result was obtained using a broadband source with a narrowband spectral filter of width 10 nm centered on 630 nm. To date this is the deepest nulling result with a visible nulling coronagraph yet obtained. Developed also is a Null Control Breadboard (NCB) to assess and quantify MEMS based segmented deformable mirror technology and develop and assess closed-loop null sensing and control algorithm performance from both the pupil and focal planes. We have demonstrated closed-loop control at 27 Hz in the laboratory environment. Efforts are underway to first bring the contrast to > 109 necessary for the direct detection and characterization of jovian (Jupiter-like) and then to > 1010 necessary for terrestrial (Earth-like) exosolar planets. Short term advancements are expected to both broaden the spectral passband from 10 nm to 100 nm and to increase both the long-term stability to > 2 hours and the extent of the null out to a ~ 10 * wavelength / D via the use of MEMS based segmented deformable mirror technology, a coherent fiber bundle, achromatic phase shifters, all in a vacuum chamber at the GSFC VNC facility. Additionally an extreme stability textbook sized compact VNC is under development.
© (2009) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Richard G. Lyon, Richard G. Lyon, Mark Clampin, Mark Clampin, Robert A. Woodruff, Robert A. Woodruff, Gopal Vasudevan, Gopal Vasudevan, Patrick Thompson, Patrick Thompson, Peter Petrone, Peter Petrone, Timothy Madison, Timothy Madison, Maxime Rizzo, Maxime Rizzo, Gary Melnick, Gary Melnick, Volker Tolls, Volker Tolls, } "Visible nulling coronagraph testbed results", Proc. SPIE 7440, Techniques and Instrumentation for Detection of Exoplanets IV, 744011 (25 August 2009); doi: 10.1117/12.827423; https://doi.org/10.1117/12.827423
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