The Nancy Grace Roman Space Telescope (formally WFIRST) will be launched in the mid-2020’s with an onboard coronagraph instrument which will serve as a technology demonstrator for exoplanet direct imaging. The Roman Coronagraph will be capable of detecting and characterizing exoplanets and circumstellar disks in visible light at an unprecedented contrast level of ~10-8 or lower. Such a contrast level, which is several magnitudes better than state-of-the-art visible or near-infrared coronagraphs, raises entirely new challenges that will be overcome using a combination of hardware, calibration and data processing. In particular, the Roman Coronagraph will be the first space-based coronagraphic instrument with real-time active wavefront control through the use of large format deformable mirrors, and its EMCCD detector will enable faint signal detection in photon-counting mode. The Roman Coronagraph instrument passed its critical design review successfully in April 2021, and is now well on its path to demonstrate many core technologies at the levels required for future exo-Earth direct imaging missions.
Operating in an unprecedented contrast regime (10 − 7 to 10 − 9), the Roman Coronagraph Instrument (CGI) will serve as a pathfinder for key technologies needed for future Earth-finding missions such as HabEx and LUVOIR. The Roman Exoplanet Imaging Data Challenge (Roman EIDC) was a community engagement effort that tasked participants with extracting exoplanets and their orbits for a 47-UMa-like target star given: (1) 15 years of simulated precursor radial velocity (RV) data and (2) six epochs of simulated imaging taken over the course of the Roman mission. Led by the Turnbull CGI Science Investigation Team, the Roman EIDC was preceded by four tutorial “hack-a-thon” events in Baltimore, Pasadena, New York City, and Tokyo. The Roman EIDC officially launched in October 2019 and ran for 8 months, offering a unique opportunity for exoplanet scientists of all experience levels to get acquainted with realistic near-future imaging data. The Roman EIDC simulated images include four epochs with CGI’s Hybrid Lyot Coronagraph (HLC) plus two epochs with a starshade (SS) assumed to arrive as part of a Starshade Rendezvous later in the mission. We focus on our in-house analysis of the outermost planet “d,” for which the SS’s higher throughput and lower noise floor present a factor of ∼4 improvement in the signal-to-noise ratio over the narrow-field HLC. We find that, although the RV detection was marginal for planet d, the precursor RV data enabled the mass and orbit to be constrained with only two epochs of SS imaging. Including the HLC images in the analysis results in improved measurements over RV + SS alone, with the greatest gains resulting from images taken at epochs near maximum elongation. Combining the two epochs of SS imaging with the RV + HLC data resulted in a factor of ∼2 better orbit and mass determinations over RV + HLC alone. In summary, the Roman CGI, combined with precursor RV data and latermission SS imaging, forms a powerful trifecta in detecting exoplanets and determining their masses, albedos, and system configurations. While the Roman CGI will break new scientific and technological ground with direct imaging of giant exoplanets within ∼5 AU of V ˜ 5 and brighter stars, a Roman Starshade Rendezvous mission would additionally enable the detection of planets out to ∼8 AU in those systems.
Organized by the Turnbull Science Investigation Team (SIT), the 2019-2020 Roman Exoplanet Imaging Data Challenge (EIDC) launched in mid October 2019 and ran for eight months. This data challenge was a unique opportunity for exoplanet scientists of all backgrounds and experience levels to get acquainted with realistic Roman CGI (coronagraphic) simulated data with a new contrast regimes at 10-8 to 10-9 enabling to unveil planets down to the Neptune-mass in reflected light. Participating teams had to recover the astrometry of an exoplanetary system combining precursor radial velocity data (also simulated across 15 years) with two to six coronagraphic imaging epochs (HLC and Star Shade). They had to perform accurate orbital fitting and determine the mass of any planet hidden in the data. It involved PSF subtraction techniques, post-processing and other astrophysics hurdles to overcome such as contamination sources (stellar, extragalactic and exozodiacal light). We organized four tutorial "hack-a-thon" events to get as many people on-board. The EIDC proved to be an excellent way to engage with the intricacies of the first mission to perform wavefront control in space, as a pathfinder to future flagship missions. It also generated a lot of positive interactions between open source package owners and a whole new set of young exoplanet scientists running them. As a community we are a few steps closer to being ready to analyze real CGI data!
The Exoplanet Imaging Data Challenge is a community-wide effort meant to offer a platform for a fair and common comparison of image processing methods designed for exoplanet direct detection. For this purpose, it gathers on a dedicated repository (Zenodo), data from several high-contrast ground-based instruments worldwide in which we injected synthetic planetary signals. The data challenge is hosted on the CodaLab competition platform, where participants can upload their results. The specifications of the data challenge are published on our website https://exoplanet-imaging-challenge.github.io/. The first phase, launched on the 1st of September 2019 and closed on the 1st of October 2020, consisted in detecting point sources in two types of common data-set in the field of high-contrast imaging: data taken in pupil-tracking mode at one wavelength (subchallenge 1, also referred to as ADI) and multispectral data taken in pupil-tracking mode (subchallenge 2, also referred to as ADI+mSDI). In this paper, we describe the approach, organisational lessons-learnt and current limitations of the data challenge, as well as preliminary results of the participants’ submissions for this first phase. In the future, we plan to provide permanent access to the standard library of data sets and metrics, in order to guide the validation and support the publications of innovative image processing algorithms dedicated to high-contrast imaging of planetary systems.
The Coronagraph Instrument (CGI) for NASA's Wide Field Infrared Survey Telescope (WFIRST) will constitute a dramatic step forward for high-contrast imaging, integral field spectroscopy, and polarimetry of exoplanets and circumstellar disks, aiming to improve upon the sensitivity of current ground-based direct imaging facilities by 2-3 orders of magnitude. Furthermore, CGI will serve as a pathfinder for future exo-Earth imaging and characterization missions by demonstrating wavefront control, coronagraphy, and spectral retrieval in a new contrast regime, and by validating instrument and telescope models at unprecedented levels of precision. To achieve this jump in performance, it is critical to draw on the experience of ground-based high-contrast facilities. We discuss several areas of relevant commonalities, including: wavefront control, post-processing of integral field unit data, and calibration and observing strategies.
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