External occulters for direct observation of exoplanets: an overview

Formation Design of Distributed Telescopes in Earth Orbit for Astrophysics Applications

“…where R is the starshade radius, z is the separation between the starshade and telescope, and λ is the wavelength. From previous studies [3,42], the required F to achieve sufficient contrast to image Earth-like planets is approximately 10. It follows that it is necessary to minimize R and z as much as possible while minimizing the impact on F to enable deployment of a small-scale starshade formation in Earth orbit.…”

Optics technology for large-aperture space telescopes: from fabrication to final acceptance tests

“…While this level of suppression may be sufficient for future extremely large ground-based telescopes with significant post-processing of the data [53], the most likely, and efficient, means of characterizing exoplanets is with space telescopes. The extreme level of starlight suppression will be achieved using an optical occulter, either in the form of an external starshade [54][55][56] or an internal coronagraph [57][58][59]. The direct light from a star is blocked by the starshade by minimizing the diffraction pattern in the region of the telescope's aperture.…”

Phase-induced amplitude apodization (PIAA) coronagraph testing at the High Contrast Imaging Testbed

“…In addition to interferometric techniques [2] and external occulters [3], a number of coronagraph technologies have been proposed to enable these missions [4]. Of the coronagraph technologies proposed for space missions, a few techniques stand out as being the most efficient at the smallest angular separations.…”