A Multiwavelength Differential Imaging Experiment for the High Contrast Imaging Testbed

作者：Biller Beth^*; Trauger John; Moody Dwight; Close Laird; Kuhnert Andreas; Stapelfeldt Karl; Traub Wesley A; Kern Brian

来源：Publications of the Astronomical Society of the Pacific, 2009, 121(881): 716-727.

DOI：10.1086/603651

We discuss the results of a multiwavelength differential imaging lab experiment with the High Contrast Imaging Testbed (HCIT) at the Jet Propulsion Laboratory. The HCIT combines a Lyot coronagraph with a Xinetics deformable mirror in a vacuum environment to simulate a space telescope in order to test technologies and algorithms for a future exoplanet coronagraph mission. At present, ground-based telescopes have achieved significant attenuation of speckle noise using the technique of spectral differential imaging (SDI). We test whether ground-based SDI can be generalized to a nonsimultaneous spectral differential imaging technique (NSDI) for a space mission. In our lab experiment, a series of five filter images centered around the O(2)(A) absorption feature at 0.762 mu m were acquired at nominal contrast values of 10(-6), 10(-7), 10(-8), and 10(-9). Outside the dark hole, single differences of images improve contrast by a factor of similar to 6. Inside the dark hole, we found significant speckle chromatism as a function of wavelength offset from the nulling wavelength, leading to a contrast degradation by a factor of 7.2 across the entire similar to 80 nm bandwidth. This effect likely stems from the chromatic behavior of the current occulter. New, less chromatic occulters are currently in development; we expect that these new occulters will resolve the speckle chromatism issue.

• 出版日期2009-7