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The characterization of exozodiacal light emission is both important for the understanding of planetary systems evolution and for the preparation of future space missions aiming to characterize low mass planets in the habitable zone of nearby main sequence stars. The Large Binocular Telescope Interferometer (LBTI) exozodi survey aims at providing a ten-fold improvement over current state of the art, measuring dust emission levels down to a typical accuracy of ~12 zodis per star, for a representative ensemble of ~30+ high priority targets. Such measurements promise to yield a final accuracy of about 2 zodis on the median exozodi level of the targets sample. Reaching a 1 σ measurement uncertainty of 12 zodis per star corresponds to measuring interferometric cancellation (“null”) levels, i.e visibilities at the few 100 ppm uncertainty level. We discuss here the challenges posed by making such high accuracy mid-infrared visibility measurements from the ground and present the methodology we developed for achieving current best levels of 500 ppm or so. We also discuss current limitations and plans for enhanced exozodi observations over the next few years at LBTI.

The Space High Angular Resolution Probe for the Infrared (SHARP-IR) is a new mission currently under study. As part of the preparation for the Decadal Survey, NASA is currently undertaking studies of four major missions, but interest has also been shown in determining if there are feasible sub-$1B missions that could provide significant scientific return. SHARP-IR is being designed as one such potential probe. In this talk, we will discuss some of the potential scientific questions that could be addressed with the mission, the current design, and the path forward to concept maturation.

In preparation of the 2020 Astrophysics Decadal Survey, National Aeronautics and Space Administration (NASA) has commenced a process for the astronomical community to study several large mission concepts leveraging the lessons learned from past Decadal Surveys. This will enable the Decadal Survey committee to make more informed recommendations to NASA on its astrophysics science and mission priorities with respect to cost and risk. Four astrophysics large mission concepts were identified. Each of them had a Science and Technology Definition Teem (STDT) chartered to produce scientifically compelling, feasible, and executable design reference mission (DRM) concepts to present to the 2020 Decadal Survey. In addition, The Aerospace Corporation will perform an independent cost and technical evaluation (CATE) of each of these mission concept studies in advance of the 2020 Decadal Survey, by interacting with the STDTs to provide detailed technical details on certain areas for which “deep dives” are appropriate. This paper presents the status and path forward for one of the four large mission concepts, namely, the Large UltraViolet, Optical, InfraRed surveyor (LUVOIR).

The scale and design of a future mission capable of directly imaging extrasolar planets will be influenced by the detectable number (yield) of potentially Earth-like planets. Currently, coronagraphs and starshades are being considered as instruments for such a mission. We will use a novel code to estimate and compare the yields for starshade- and coronagraph-based missions. We will show yield scaling relationships for each instrument and discuss the impact of astrophysical and instrumental noise on yields. Although the absolute yields are dependent on several yet-unknown parameters, we will present several limiting cases allowing us to bound the yield comparison.

Exo-S is a direct imaging space-based mission to discover and characterize exoplanets. The mission is comprised of two formation-flying spacecraft – a starlight suppressing starshade and a telescope separated by ~30,000 km. To align the starshade between the target star and telescope, one of the two spacecraft must perform a retargeting slew. This drives the need for a sophisticated program to help optimize this path to maximize target yield within mission constraints such as solar and earth avoidance angles, thrust and fuel limitations, and target scheduling for previously-discovered known giant planets. The Design Reference Mission (DRM) describes the sequence of observations to be performed and estimates the number of planets that will be detected and characterized. It is executed with a Matlab-based tool developed for the Exo-S Study. Here we analyze four case studies: • Case 1: Starshade with a 1.1m dedicated telescope prioritizing the search for earths in the Habitable Zone (HZ). • Case 2: Starshade with a 1.1m dedicated telescope focused on maximizing planet harvest return and characterization. • Case 3: Starshade that rendezvous with a 2.4 m shared telescope prioritizing the search for earths in the HZ. • Case 4: A Rendezvous Earth Finder mission based on a 40-m diameter starshade with a 2.4 m telescope, operating for 4 years, and focused exclusively on detecting Earths in the HZ Previous starshade DRM tools have been reported in the literature, all of them focused on detection and/or characterization of Earth-twins in the habitable zone. This study has taken then next step and focused on total planet harvest including known Gas Giants, Earths in the Habitable Zone and elsewhere, super-earths, sub-Neptunes, and Jupiters. The DRM employs a hierarchical approach: an observation schedule of known radial velocity gas giants, whose availabilities for observation are known form their orbital parameters, forms a "framework" of observation that have a high probability of success. Between these observations, the next highest priority stars are scheduled and these in turn form the framework for the next observational tier. We report the expected observational completeness, planet yields, and planet characterizations for the three case studies.

Exo-S is a direct imaging space-based mission to discover and characterize exoplanets. With its modest size, Exo-S bridges the gap between census missions like Kepler and a future space-based flagship direct imaging exoplanet mission. With the ability to reach down to Earth-size planets in the habitable zones of nearly two dozen nearby stars, Exo-S is a powerful first step in the search for and identification of Earth-like planets. Compelling science can be returned at the same time as the technological and scientific framework is developed for a larger flagship mission. The Exo-S Science and Technology Definition Team studied two viable starshade-telescope missions for exoplanet direct imaging, targeted to the $1B cost guideline. The first Exo-S mission concept is a starshade and telescope system dedicated to each other for the sole purpose of direct imaging for exoplanets (The "Starshade Dedicated Mission"). The starshade and commercial, 1.1-m diameter telescope co-launch, sharing the same low-cost launch vehicle, conserving cost. The Dedicated mission orbits in a heliocentric, Earth leading, Earth-drift away orbit. The telescope has a conventional instrument package that includes the planet camera, a basic spectrometer, and a guide camera. The second Exo-S mission concept is a starshade that launches separately to rendezvous with an existing on-orbit space telescope (the "Starshade Rendezvous Mission"). The existing telescope adopted for the study is the WFIRST-AFTA (Wide-Field Infrared Survey Telescope Astrophysics Focused Telescope Asset). The WFIRST-AFTA 2.4-m telescope is assumed to have previously launched to a Halo orbit about the Earth-Sun L2 point, away from the gravity gradient of Earth orbit which is unsuitable for formation flying of the starshade and telescope. The impact on WFIRST-AFTA for starshade readiness is minimized; the existing coronagraph instrument performs as the starshade science instrument, while formation guidance is handled by the existing coronagraph focal planes with minimal modification and an added transceiver.

A starshade with the James Webb Space Telescope (JWST) is the only possible path forward in the next decade to obtain images and spectra of a planet similar to the Earth, to study its habitability, and search for signs of alien life. While JWST was not specifically designed to observe using a starshade, its near-infrared instrumentation is in principle capable of doing so and could achieve major results in the study of terrestrialmass exoplanets. However, because of technical reasons associated with broadband starlight suppression and filter red-leak, NIRSpec would need a slight modification to one of its target acquisition filters to enable feasible observations of Earth-like planets. This upgrade would 1) retire the high risk associated with the effects of the current filter red leak which are difficult to model given the current state of knowledge on instrument stray light and line spread function at large separation angles, 2) enable access to the oxygen band at 0.76 μm in addition to the 1.26 μm band, 3) enable a smaller starshade by relaxing requirements on bandwidth and suppression 4) reduce detector saturation and associated long recovery times. The new filter would not affect neither NIRSpecs scientific performance nor its operations, but it would dramatically reduce the risk of adding a starshade to JWST in the future and enhance the performance of any starshade that is built. In combination with a starshade, JWST could be the most capable and cost effective of all the exoplanet hunting missions proposed for the next decade, including purpose built observatories for medium-size missions.

The presence of large amounts of exozodiacal dust around nearby main sequence stars is considered as a potential threat for the direct detection of Earth-like exoplanets (exoEarths) with future space-based coronagraphic and interferometric missions. In this paper, we estimate the amount of exozodiacal light that can be tolerated around various stellar types without jeopardizing the detection of exoEarths with a space-based visible coronagraph or a free-flying mid-infrared interferometer. We also address the possible effects of resonant structures in exozodiacal disks. We then review the sensitivity of current ground-based interferometric instruments to exozodiacal disks, based on classical visibility measurements and on the nulling technique. We show that the current instrumental performances are not sufficient to help prepare future exoEarth imaging missions, and discuss how new groundor space-based instruments could improve the current sensitivity to exozodiacal disks down to a suitable level.

The James Webb Space Telescope will be an extraordinary observatory, providing a huge range of exciting new astrophysical results. However, by itself it will not be capable of directly imaging planets in the habitable zone of nearby stars, one of the most fascinating goals of astronomy for the coming decade. In this paper we discuss the New Worlds Probe (NWP) concept whereby we use an external occulter (or starshade) to cast a shadow from the star onto the telescope, therefore canceling the direct star light while the light from a planet is not affected. This concept enables JWST to take images and spectra of extrasolar planets with sufficient contrast and inner working angle to be able to discover planets down to the size of the Earth in the habitable zone around nearby stars. JWST’s instruments are appropriate to achieve low resolution spectroscopy (R � 40) of these planets, and address a series of fundamental questions: are there planets in the habitable zone around nearby stars? What is the composition of their atmosphere? What are the brightness and structures of exozodiacal disks around nearby stars? What is the mass and composition of currently known giant planets? In this paper we study the starshade optimization for JWST given the instrumental constraints, and show that the modest optical quality of the telescope at short wavelength does not impact the possibility of using a starshade. We propose a solution to enable imaging and spectroscopy using target acquisition filters. We discuss possible time allocation among science goals based on exposure time estimates and total available observing time. The starshade can be launched up to 3 years after JWST and rendezvous with the telescope in orbit around L2.

We present the results of the Astrophysics Strategic Mission Concept Study for the New Worlds Observer (NWO). We show that the use of starshades is the most effective and affordable path to mapping and understanding our neighboring planetary systems, to opening the search for life outside our solar system, while serving the needs of the greater astronomy community. A starshade-based mission can be implemented immediately with a near term program of technology demonstration.