Laboratory Studies of Petal-Shaped Occulters

摘要

We present laboratory studies of scaled occulting starshades for the New Worlds Observer (NOW). A deep reactive ion etched silicon starshade has been fabricated by NIST, designed to cover the same number of Fresnel zones as in the proposed mission. The broadband shadow is mapped with a photometer in a dark vacuum tunnel fed by a heliostat at HAO. CCD images provide direct contrast measurements of different features around the starshade. Preliminary measurements reach 5×10~(-6)suppression in the center of the shadow at the focal plane. The two-dimensional structure of the starshade diffraction pattern is compared to that produced by the Fresnel integral.