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Experimental study of starshade at flight Fresnel numbers in the laboratory

A starshade or external occulter is a spacecraft flown along the line-of-sight of a space telescope to suppress starlight and enable high-contrast direct imaging of exoplanets. Because of its large size and scale it is impossible to fully test a starshade system on the ground before launch. Therefore, laboratory verification of starshade designs is necessary to validate the optical models used to design and predict starshade performance. At Princeton, we have designed and built a testbed that allows verification of scaled starshade designs whose suppressed shadow is mathematically identical to that of a comparable space starshade. The starshade testbed uses 77.2 m optical propagation distance to realize the flight-appropriate Fresnel numbers of 14.5. Here we present the integration status of the testbed and simulations predicting the ultimate contrast performance. We will also present our results of wavefront error measurement and its implementation of suppression and contrast.