The expected yield of potentially Earth-like planets is a useful metric for designing future exoplanet-imaging missions. Recent yield studies of direct-imaging missions have focused primarily on yield methods and trade studies using "toy" models of missions. Here we increase the fidelity of these calculations substantially, adopting more realistic exoplanet demographics as input, an improved target list, and a realistic distribution of exozodi levels. Most importantly, we define standardized inputs for instrument simulations, use these standards to directly compare the performance of realistic instrument designs, include the sensitivity of coronagraph contrast to stellar diameter, and adopt engineering-based throughputs and detector parameters. We apply these new high-fidelity yield models to study several critical design trades: monolithic vs segmented primary mirrors, on-axis vs off-axis secondary mirrors, and coronagraphs vs starshades. We show that as long as the gap size between segments is sufficiently small (ă 0.1% of telescope diameter), there is no difference in yield for coronagraph-based missions with monolithic off-axis telescopes and segmented off-axis telescopes, assuming that the requisite engineering constraints imposed by the coronagraph can be met in both scenarios. We show that there is currently a factor of "2 yield penalty for coronagraph-based missions with on-axis telescopes compared to off-axis telescopes, and note that there is room for improvement in coronagraph designs for on-axis telescopes. We also reproduce previous results in higher fidelity showing that the yields of coronagraph-based missions continue to increase with aperture size while the yields of starshade-based missions turnover at large apertures if refueling is not possible. Finally, we provide absolute yield numbers with uncertainties that include all major sources of astrophysical noise to guide future mission design.

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We present an analysis of the Occulting Ozone Observatory (O 3 ) -a $1 billion class mission dedicated to finding extra-solar planets down to Earth size, performing photometric characterizations of planets and disks, detecting the presence of ozone, and general astrophysics. We present trade studies for the observatory, composed of a 1 to 2 m telescope based on heritage imaging systems and a complementary sized, free-flying occulter spacecraft, to maximize the expected science yield for this mission class. Using a camera with four filters each in the 250-550 nm and 500-1100 nm bands, this modest-size telescope can detect atmospheric ozone in Earth-like planets, methane in gas giants, determine planetary spin rotation periods, characterize the surface composition of rocky planets and determine or constrain the values of basic orbital elements. We present multiple different mission designs along with the expected number of planetary detections and photometric characterizations.

An occulter is an instrument designed to suppress starlight by diffraction from its edges; most are designed to be circular, with a set of identical "petals" running around the outside. Proposed space-based occulters are lightweight, deployed screens tens of meters in diameter with challenging accuracy requirements. In this paper we describe the design of an occulter for the THEIA mission concept. THEIA consists of a 4-meter telescope diffraction limited to 300 nm, and a 40-meter external occulter to provide high-contrast imaging. Operating from 250 to 1000 nm, it will provide a rich family of science projects, including exoplanet characterization, ultraviolet spectroscopy, and very wide-field imaging. Originally conceived of as a hybrid system employing both an occulter and internal coronagraph, THEIA now uses a single occulter to achieve all of the starlight suppression but at two different distances from the telescope in order to minimize size and distance. We describe the basic design principles of the THEIA occulter, its final configuration, performance, and sensitivity.