Launching a starshade to rendezvous with the Nancy Grace Roman Space Telescope (Roman) would provide the first opportunity to directly image the habitable zones (HZs) of nearby sunlike stars in the coming decade. A report on the science and feasibility of such a mission was recently submitted to NASA as a probe study concept. The driving objective of the concept is to determine whether Earth-like exoplanets exist in the HZs of the nearest sunlike stars and have biosignature gases in their atmospheres. With the sensitivity provided by this telescope, it is possible to measure the brightness of zodiacal dust disks around the nearest sunlike stars and establish how their population compares with our own. In addition, known gas-giant exoplanets can be targeted to measure their atmospheric metallicity and thereby determine if the correlation with planet mass follows the trend observed in the Solar System and hinted at by exoplanet transit spectroscopy data. We provide the details of the calculations used to estimate the sensitivity of Roman with a starshade and describe the publicly available Python-based source code used to make these calculations. Given the fixed capability of Roman and the constrained observing windows inherent for the starshade, we calculate the sensitivity of the combined observatory to detect these three types of targets, and we present an overall observing strategy that enables us to achieve these objectives.
The Habitable-Exoplanet Observatory (HabEx) is a candidate flagship mission being studied by NASA and the astrophysics community in preparation of the 2020 Decadal Survey. The first HabEx mission concept that has been studied is a large (~4m) diffraction-limited optical space telescope, providing unprecedented resolution and contrast in the optical, with extensions into the near ulttraviolet and near infrared domains. We report here on our team’s efforts in defining a scientifically compelling HabEx mission that is technologically executable, affordable within NASA’s expected budgetary envelope, and timely for the next decade. We also briefly discuss our plans to explore less ambitious, descoped missions relative to the primary mission architecture discussed here.
HabEx is one of four candidate flagship missions being studied in detail by NASA, to be submitted for consideration to
the 2020 Decadal Survey in Astronomy and Astrophysics for possible launch in the 2030s. It will be optimized for direct
imaging and spectroscopy of potentially habitable exoplanets, and will also enable a wide range of general astrophysics
science. HabEx aims to fully characterize planetary systems around nearby solar-type stars for the first time, including
rocky planets, possible water worlds, gas giants, ice giants, and faint circumstellar debris disks. In particular, it will
explore our nearest neighbors and search for signs of habitability and biosignatures in the atmospheres of rocky planets
in the habitable zones of their parent stars. Such high spatial resolution, high contrast observations require a large
(roughly greater than 3.5m), stable, and diffraction-limited optical space telescope. Such a telescope also opens up
unique capabilities for studying the formation and evolution of stars and galaxies. We present some preliminary science
objectives identified for HabEx by our Science and Technology Definition Team (STDT), together with a first look at
the key challenges and design trades ahead.
Exoplanets are revolutionizing planetary science by enabling statistical studies of a large number of planets. Empirical measurements of planet occurrence rates inform our understanding of the ubiquity and efficiency of planet formation, while the identification of sub-populations and trends in the distribution of observed exoplanet properties provides insights into the formation and evolution processes that are sculpting distant Solar Systems. In this paper, we review the current best estimates of planet populations. We focus in particular on η⊕, the occurrence rate of habitable zone rocky planets, since this factor strongly influences the design of future space based exoplanet direct detection missions.
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