Achieving high-contrast ratios with a 60-cm starshade

Abstract

The external starshade is a prospective method for the direct detection and spectral characterization of terrestrial planets around other stars, a key goal identified in ASTRO2010. Validation of the numerical simulations that are critical to this approach has been challenging at very small scales (~4 cm) in the lab. We have successfully fabricated 60 cm starshades and begun a series of ground test experiments with them. We measured contrast better than 1×10 -8 under challenging environmental conditions at outdoor test sites. Our experimental setup is designed to provide starshade to telescope separation and telescope aperture size that are scaled as closely as possible from the flight system. In this paper, we describe the test setup, the data acquisition, the reduction techniques, and a preliminary comparison of measured to modeled results.

Special Section on Starshades: Overview and a Dialogue

“…This revelation, with subsequent explanation, 2 opened the door to experiments at larger separations to test at flight-like Fresnel numbers. Starshades have been tested over kilometers of separation on dry lakebeds [34][35][36] and with a heliostat on Kitt Peak. 37,38 Similarly, the optical experiments of Harness et al were conducted in air.…”

“…8. These tests have been done in a lab setting over tens of meters, 32,33,[60][61][62][63][64] on a dry lake bed over hundreds of meters, [34][35][36] and using a heliostat over kilometers. 37,38 The recent Fig.…”

“…37,38 (b) A starshade is tested over kilometers of separation on a dry lake bed. [34][35][36] Photo credit: Robert Brown (Northrop Grumman).…”