N. Kasdin/Princeton University

In support of NASA's Exoplanet Exploration Program and the Technology Development for Exoplanet Missions (TDEM), this proposal describes continuing work to verify the design and performance of an external occulter for starlight suppression. Our current TDEM effort is focused on petal design and manufacturing; we will demonstrate that a full-scale petal can be built using flight like processes and materials and to near-flight tolerances. Static metrology will be used to measure the petal shape and show that it corresponds to a contrast performance of better than 10^-9.

For this second TDEM we propose to focus our efforts on post-deployment metrology and thermal modeling. We plan to perform repeated stow-and-deploys, around the existing hub, of the composite petal built in phase 1. We will then repeat the shape measurements to verify the petal maintained accuracy even after deployment.

The main emphasis of the study will be thermal. While we will have demonstrated in phase 1 that a static petal can be built to the needed accuracy, we will not yet have verified that the shape can be maintained throughout the varying thermal loading of a real mission. In this TDEM we propose to perform thermal vacuum testing of critical structural components of the petal, namely, segments of the battens and spine, to characterize the thermal properties, and then to build more accurate models of the starshade for thermal analysis. We will also continue to perform material studies and coupon tests to refine our selection of the lowest CTE materials.

The combined results of our experiences in phase 1, our deployment tests, and our thermal tests and modeling will result in a second-generation petal design and material selection.