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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Multi-Star Wavefront Control at the Occulting Mask Coronagraph Testbed: Monochromatic Laboratory Demonstration for the Roman Coronagraph Instrument

The Astro2020 decadal survey recommended a direct imaging flagship mission with a goal for mission yield of 25 or more potentially habitable exoplanets. A majority of Sun-like stars have a stellar companion that can introduce additional noise into the field of view of any high-contrast imaging instrument and enabling exoplanet discovery around binary stars represents a path to increased coronagraphic instrument efficiency. This includes both of the Alpha Centauri A and B stars which would represent the top science target for direct imaging if companion leakage can be suppressed. Multi-Star Wavefront Control (MSWC) is a technique that removes stellar leakage from both stellar components, enabling direct imaging of exoplanets in many binary star systems. We present the latest testbed results obtained with MSWC as part of the technology development effort focusing on demonstrations conducted on the Occulting Mask Coronagraph (OMC) testbed at JPL. OMC has a layout similar to the Roman Space Telescope coronagraph instrument (CGI) and is outfitted with a MSWC mask with the same design as the contributed mask for the Roman CGI. Our testbed results represent the first demonstrations of this technique using the recently installed full binary source for a geometry matching potential Alpha Centauri observations. Technical Review Abstract: The Astro2020 decadal survey recommended a direct imaging flagship mission with a goal for mission yield of 25 or more potentially habitable exoplanets. A majority of Sun-like stars have a stellar companion that can introduce additional noise into the field of view of any high-contrast imaging instrument and enabling exoplanet discovery around binary stars represents a path to increased coronagraphic instrument efficiency by increasing the available science target pool of bright nearby stars. This includes both of the Alpha Centauri A and B stars which would represent the top science target for direct imaging if companion leakage can be suppressed. Multi-Star Wavefront Control (MSWC) is a technique that removes stellar leakage from both stellar components, enabling direct imaging of exoplanets in many binary star systems . We present the latest testbed results obtained with MSWC as part of the technology development effort focusing on demonstrations conducted on the Occulting Mask Coronagraph (OMC) testbed at JPL during the completed first vacuum window and recent results from the ongoing second vacuum window. The MSWC mask consists of a shaped pupil mask similar to the one used for the Wide-Field of View mode but also includes a set of superimposed, regularly-spaced dots that serve as a diffraction grating. OMC has a layout similar to the Roman Space Telescope coronagraph instrument (CGI) and is configured with a binary imaging mode with a MSWC mask using same design as the contributed mask for the Roman CGI. Our testbed results represent the first demonstrations of this technique using the recently installed full binary source. We present results obtained in Super-Nyquist regime demonstrating suppression in the Super-Nyquist regime for the 3rd diffraction order reaching 8.7e-9 contrast with the Roman pupil. In addition, we present results obtained with the binary-star regime demonstrating 9.6e-8 contrast for a geometry matching potential Alpha Centauri observations in a monochromatic wavelength similar to Band 1. Planned demonstrations in the 2nd vacuum window will focus on Band 3d and Band 4 using the full MSWC mode for an Alpha Centauri geometry.

High-contrast imaging↗
NASA NTRS2018

Climate Modeling of a Potential ExoVenus

The planetary mass and radius sensitivity of exoplanet discovery capabilities has reached into the terrestrial regime. The focus of such investigations is to search within the Habitable Zone where a modern Earth-like atmosphere maybe a viable comparison. However, the detection bias of the transit and radial velocity methods lies close to the host star where the received flux at the planet may push the atmosphere into a runaway greenhouse state. One such exoplanet discovery, Kepler-1649b, receives a similar flux from its star as modern Venus does from the Sun, and so was categorized as a possible exoVenus. Here we discuss the planetary parameters of Kepler-1649b in relation to Venus to establish its potential as a Venus analog. We utilize the general circulation model ROCKE-3D (Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics) to simulate the evolution of the surface temperature of Kepler-1649b under various assumptions, including relative atmospheric abundances. We show that in all our simulations the atmospheric model rapidly diverges from temperate surface conditions toward a runaway greenhouse with rapidly escalating surface temperatures. We calculate transmission spectra for the evolved atmosphere and discuss these spectra within the context of the James Webb Space Telescope Near-Infrared Spectrograph capabilities. We thus demonstrate the detectability of the key atmospheric signatures of possible runaway greenhouse transition states and outline the future prospects of characterizing potential Venus analogs.

Astrobiology↗
NASA NTRS2018

Climate Modeling of a Potential Exovenus

The planetary mass and radius sensitivity of exoplanet discovery capabilities has reached into the terrestrial regime. The focus of such investigations is to search within the Habitable Zone where a modern Earth-like atmosphere may be a viable comparison. However, the detection bias of the transit and radial velocity methods lies close to the host star where the received flux at the planet may push the atmosphere into a runaway greenhouse state. One such exoplanet discovery, Kepler-1649b, receives a similar flux from its star as modern Venus does from the Sun, and so was categorized as a possible exoVenus. Here we discuss the planetary parameters of Kepler-1649b in relation to Venus to establish its potential as a Venus analog. We utilize the general circulation model ROCKE-3D to simulate the evolution of the surface temperature of Kepler-1649b under various assumptions, including relative atmospheric abundances. We show that in all our simulations the atmospheric model rapidly diverges from temperate surface conditions toward a runaway greenhouse with rapidly escalating surface temperatures. We calculate transmission spectra for the evolved atmosphere and discuss these spectra within the context of the James Webb Space Telescope Near-Infrared Spectrograph capabilities. We thus demonstrate the detectability of the key atmospheric signatures of possible runaway greenhouse transition states and outline the future prospects of characterizing potential Venus analogs.

Astrobiology↗
NASA NTRS2010

Feasibility of Exoplanet Coronagraphy with the Hubble Space Telescope

Herein we report on a preliminary study to assess the use of the Hubble Space Telescope (HST) for the direct detection and spectroscopic characterization of exoplanets and debris disks - an application for which HST was not originally designed. Coronagraphic advances may enable the design of a science instrument that could achieve limiting contrasts approx.10deg beyond 275 milli-arcseconds (4 lambda/D at 800 nm) inner working angle, thereby enabling detection and characterization of several known jovian planets and imaging of debris disks. Advantages of using HST are that it already exists in orbit, it's primary mirror is thermally stable and it is the most characterized space telescope yet flown. However there is drift of the HST telescope, likely due to thermal effects crossing the terminator. The drift, however, is well characterized and consists of a larger deterministic components and a smaller stochastic component. It is the effect of this drift versus the sensing and control bandwidth of the instrument that would likely limit HST coronagraphic performance. Herein we discuss the science case, quantifY the limiting factors and assess the feasibility of using HST for exoplanet discovery using a hypothetical new instrument. Keywords: Hubble Space Telescope, coronagraphy, exoplanets, telescopes

Lyon, Richard G.↗
NASA NTRS2016

Technology needs to discover Earth 2.0

Dr. Nick Siegler of the NASA Jet Propulsion Laboratory (JPL) began his talk by stating that the main goal of the Exoplanet Exploration Program technology effort is to enable future space missions to observe a planetary spectrum of a rocky planet in the habitable zone of its star and understand it in the context of potential life. He went on to say that the main exoplanet discovery tools, the radial velocity and transit techniques, which have discovered more than 95% of the more than 3,400 exoplanets, will not be the techniques to directly image exoplanets, which is needed to get a reflected light spectrum. Spectroscopy will be hard though because there simply aren’t many photons available to use, but it will not be the biggest problem. The biggest problem will be suppressing the light from the stars which can be 10 billion times brighter than a rocky planet in the habitable zone of a Sun analog. Starlight suppression could be done in one of three ways: internal occulters (i.e., coronagraphs), external occulters (i.e., starshades), and nulling interferometers. The latter option is the least technologically mature of the options and one that NASA is not currently pursuing.

Schmitt, Joseph↗
NASA NTRS2019

Habitable Exoplanet Observatory (HabEx) starshade-only architectures

The HabEx mission concept is intended to directly image planetary systems around nearby stars, and to perform a wide range of general astrophysics and solar system observations. The baseline HabEx design would use both a coronagraph and a starshade for exoplanet discovery and characterization. We describe a lower-cost alternative HabEx mission design, which would only use a starshade for exoplanet science. The starshade would provide excellent exoplanet science performance, but for a smaller number of detected exoplanets of all types, including exoEarth candidates, and a smaller fraction of exoplanets with measured orbits. The full suite of HabEx general astrophysics and solar-system science would be supported.

Benson, Jonathan↗
NASA NTRS2015

Supercomputing in the Age of Discovering Superearths, Earths and Exoplanet Systems

With the Kepler Mission, exoplanet science has entered the era of Big Data and has benefited tremendously from the availability of the NAS (NASA Advanced Supercomputing Division) Pleiades supercomputer. This presentation provides an overview of the history of exoplanet discoveries and highlights the key enabling technologies for Kepler. I provide an overview of the Kepler science pipeline and the algorithms used to analyze the data and detect transiting planets, all of which run routinely on the NAS Pleiades system. The presentation also provides a description of the Blender analysis program used to validate Kepler planet discoveries statistically, and the effort to discover exomoons lurking in Kepler data, both of which also run on Pleiades. Finally, I describe NASA's TESS (Transiting Exoplanet Survey Satellite) Mission, which leverages Kepler heritage to provide a science pipeline similar to that for Kepler and that will also run routinely on the NAS Pleiades supercomputer.

big data↗
NASA NTRS2022

EarthShine: Observing Our World as an Exoplanet from the Surface of the Moon

NASA’s return to the Moon coincides with explosive growth in exoplanet discovery. Missions are being formulated to search for habitable planets orbiting other stars, making this the ideal time to deploy an instrument suite to the lunar surface to help us recognize a habitable exoplanet when we see it. We present EarthShine, a technically mature, three-instrument suite to observe the whole Earth from the Moon as an exoplanet proxy. Earth Shine data will validate and improve models critical for designing missions to image and characterize exoplanets, thus informing observing strategies for flagship missions to directly image exoplanets. EarthShine will answer interconnected questions in Earth and lunar science, exoplanets, and astrobiology, related to the credo“ follow the water.” Earth Shine can take advantage of current NASA programs to conduct science from the Moon with low-cost, mature space hardware to reduce risk and assure success. Like the 1968 Apollo Earthrise image of our home planet, lonely in the black sky, the appeal of Earth Shine to a multidisciplinary array of researchers in Earth Science, Planetary Science, and astrophysics will maximize both its scientific impact and its impact on the general public.

EarthShine↗
NASA NTRS2017

Synergies Between the Kepler, K2 and TESS Missions with the PLATO Mission (Revised)

Two transit survey missions will have been flown by NASA prior to the launch of ESA's PLATO Mission in 2026, laying the groundwork for exoplanet discovery via the transit method. The Kepler Mission, which launched in 2009, collected data on its 100+ square degree field of view for four years before failure of a reaction wheel ended its primary mission. The results from Kepler include 2300+ confirmed or validated exoplanets, 2200+ planetary candidates, 2100+ eclipsing binaries. Kepler also revolutionized the field of asteroseismology by measuring the pressure mode oscillations of over 15000 solar-like stars spanning the lifecycle of such stars from hydrogen-burning dwarfs to helium-burning red giants. The re-purposed Kepler Mission, dubbed K2, continues to observe fields of view in and near the ecliptic plane for 80 days each, significantly broadening the scope of the astrophysical investigations as well as discovering an additional 156 exoplanets to date. The TESS mission will launch in 2017 to conduct an all-sky survey for small exoplanets orbiting stars 10X closer and 100X brighter than Kepler exoplanet host stars, allowing for far greater follow-up and characterization of their masses as well as their sizes for at least 50 small planets. Future assets such as James Webb Space Telescope, and ground-based assets such as ESOs Very Large Telescope (VLT) array, the Exremely Large Telescope (ELT), and the Thirty Meter Telescope (TMT) will be able to characterize the atmospheric composition and properties of these small planets. TESS will observe each 24 X 96 field of view for 30 days and thereby cover first the southern and then the northern hemisphere over 13 pointings during each year of the primary mission. The pole-most camera will observe the James Webb continuous viewing zone for one year in each hemisphere, permitting much longer period planets to be detected in this region. The PLATO mission will seek to detect habitable Earth-like planets with an instrument composed of 26 small telescopes in several 2232 square deg FOVs with a range of observation durations over a mission lifetime of up to eight years. This paper summarizes the findings of the KeplerK2 missions, previews the likely results from the TESS mission, and explores the lessons learned and to be learned from these prior missions that can be incorporated into the observation and data reduction strategy for the PLATO Mission so as to maximize the science return.

exoplanet detection↗
NASA NTRS2018

Life Beyond the Solar System: Remotely Detectable Biosignatures

For the first time in human history, we will soon be able to apply to the scientific method to the question "Are We Alone?" The rapid advance of exoplanet discovery, planetary systems science, and telescope technology will soon allow scientists to search for life beyond our Solar System through direct observation of extrasolar planets. This endeavor will occur alongside searches for habitable environments and signs of life within our Solar System. While these searches are thematically related and will inform each other, they will require separate observational techniques. The search for life on exoplanets holds potential through the great diversity of worlds to be explored beyond our Solar System. However, there are also unique challenges related to the relatively limited data this search will obtain on any individual world.

Domagal-Goldman, Shawn↗
NASA NTRS2023

Multi-Star Wavefront Control at the Occulting Mask Coronagraph Testbed: Monochromatic Laboratory Demonstration for the Roman Coronagraph Instrument

The Astro2020 decadal survey recommended the Habitable Worlds Observatory (HWO), NASA’s direct imaging flagship mission, with a goal to achieve a statistically robust mission yield of 25 or more potentially habitable exoplanets. One way to achieve is to increase the instrument effectiveness by introducing additional bright, nearby targets. A majority of Sun-like stars have a stellar companion that can introduce additional noise into the field of view of any high-contrast imaging instrument and enabling exoplanet discovery around binary stars represents a path to increased corona graphic instrument efficiency by increasing the available science target pool of bright nearby stars. This includes both of the Alpha Centauri A and B stars which would represent the top science target for direct imaging if companion leakage could be suppressed. Multi-Star Wavefront Control(MSWC) is a technique that removes stellar leakage from both stellar components, enabling direct imaging of exoplanets in many binary star systems which can potentially increase corona graphic instrument effectivenessWe present the latest testbed results obtained with MSWC as part of the technology development effort focusing on demonstrations conducted on the Occulting Mask Coronagraph (OMC) testbed at JPL during thevacuum test window last winter, with an additional vacuum test planned for this fall. The MSWC mask consists of a shaped pupil mask similar to the one used for the Wide-Field of View mode, but also includes a set of superimposed, regularly-spaced dots that serve as a diffraction grating. OMC has a layout similar to the RomanSpace Telescope coronagraph instrument and configured with a binary imaging mode with a MSWC mask using same design as the contributed mask for the Roman coronagraph. Our testbed results represent the first demonstrations of this technique using the recently installed full binary source. We present results demonstrating suppression in the Super-Nyquist regime for the 3rd diffraction order reaching 8.7e-9 contrast with the Roman pupil. In addition, we present results obtained with a physical binary source and running MSWC in a binary star regime demonstrating 9.6e-8 contrast for a geometry matching potential Alpha Centauri observations in a515 nm monochromatic wavelength (similar but bluer than for Band 1) using the 5th diffraction order. Planned demonstrations in the upcoming vacuum window this fall will focus on Band 3d and Band 4 using the full MSWC mode for an Alpha Centauri geometry.

Roman Coronagraph Instrument↗
NASA NTRS2019

TESS Discoveries

TESS discoveries have already become fruitful targets for HST follow up, and this will undoubtedly continue through the JWST era. In addition to providing targets for atmospheric characterization, TESS' Level One Science Requirement is to measure masses for 50 transiting planets smaller than 4 Earth radii. A full suite of ground based facilities will be working together to optimize the TESS science yield. Somewhat surprisingly though, no study has quantified the accuracy of mass constraints required to yield robust atmospheric properties of small planets. Previous work showed that the mass of a transiting exoplanet could be inferred from its transmission spectrum alone. The method leverages the effect of the planet's surface gravity on the atmospheric scale height, which in turn influences the transmission spectrum. However, significant degeneracies exist between transmission spectra of planets with different masses and compositions, making difficult to unambiguously determine the planet's mass and composition in many cases. I will present the first quantitative answer to this pressing question. Our analysis places definitive limits on how accurate mass constraints need to be in order to unambiguously determine atmospheric composition for a diverse array of planets ranging from terrestrial-size (TRAPPIST-1-like) to mini-Neptunes and hot Jupiters. These results broadly impact the community of scientists working on exoplanets -- from the full breadth of ground based observers conducting TESS follow-up, to those studying planet populations, and finally to those planning atmospheric investigations. This is particularly timely as the STScI Director charged the HST-TESS Advisory committee to report to the Space Telescope Users Committee on how HST can best support follow-up observations of TESS exoplanet discoveries. The community needs to determine optimal strategies for maximizing the rapid scientific return from TESS targets.

Batalha, Natasha E.↗
NASA NTRS2010

The Kepler Full Frame Images

NASA's exoplanet discovery mission Kepler provides uninterrupted 1-min and 30-min optical photometry of a 100 square degree field over a 3.5 yr nominal mission. Downlink bandwidth is filled at these short cadences by selecting only detector pixels specific to 105 preselected stellar targets. The majority of the Kepler field, comprising 4 x 10(exp 6) m_v < 20 sources, is sampled at much lower 1-month cadence in the form of a full-frame image. The Full Frame Images (FFIs) are calibrated by the Science Operations Center at NASA Ames Research Center. The Kepler Team employ these images for astrometric and photometric reference but make the images available to the astrophysics community through the Multimission Archive at STScI (MAST). The full-frame images provide a resource for potential Kepler Guest Observers to select targets and plan observing proposals, while also providing a freely-available long-cadence legacy of photometric variation across a swathe of the Galactic disk.

Dotson, Jessie L.↗
NASA NTRS2018

Wide Field Infrared Survey Telescope (WFIRST) Observatory Overview

NASA's Wide Field Infrared Survey Telescope (WFIRST) is being designed to deliver unprecedented capability in dark energy and exoplanet science, and to host a technology demonstration coronagraph for exoplanet imaging and spectroscopy. The observatory design has matured since 2013; we present a comprehensive description of the observatory configuration as refined during the WFIRST Phase-A study. The observatory is based on an existing, repurposed 2.4 meter space telescope coupled with a 288 megapixel near-infrared (0.6 to 2 microns) HgCdTe focal plane array with multiple imaging and spectrographic modes. Together they deliver a 0.28 square degree field of view, which is approximately 100 times larger than the Hubble Space Telescope, and a sensitivity that enables rapid science surveys. In addition, the coronagraph technology demonstration will prove the feasibility of new techniques for exoplanet discovery, imaging, and spectral analysis. A composite truss structure meters both instruments to the telescope assembly, and the instruments and the spacecraft are flight serviceable. We present configuration changes since 2013 that improved interfaces, improved testability, and reduced technical risk. We provide an overview of our Integrated Modeling results, performed at an unprecedented level for a phase-A study, to illustrate performance margins with respect to static wavefront error, jitter, and thermal drift.

Casey, T.↗
NASA NTRS2020

Prospects for Interstellar Propulsion

In recognition of the increasing prospects for Earth-like exoplanet discoveries and its significance for spurring future interstellar voyages of discovery, the United States Congress recently directed NASA to undertake an interstellar mission technology assessment report. In response to this legislative charge to action, NASA has undertaken a series of extramural interstellar workshops aimed at identifying and evaluating technology concepts for enabling an interstellar scientific probe mission, associated technical challenges, technology readiness level assessments, risks, potential near-term milestones, and funding requirements. This paper summarizes these activities and discusses the scientific and technical rationale for a long-term program consisting of incremental, staged technical developments that are extensible for interstellar travel to a nearby star system over many decades.

Litchford, Ronald J.↗
NASA NTRSDate not supplied

Assessment of Control Schemes for Aerocapture at the Ice Giants

The Ice Giants, Uranus and Neptune, are two relatively unexplored worlds in the solar system, with exploration only cosisting of flybys from the Voyager 2 mission several decades ago. Recent exoplanet discoveries have indicated that Neptune- or Uranus-like worlds are very common elsewhere in the galaxy. Further study of Neptune and/or Uranus therefore may help unlock the keys to under- standing the formation of both our own solar system and those of other stars. Further exploration of the Ice Giants is so important among the planetary science community that they were considered high priority destinations in the current and previous Planetary Science Decadal Surveys. In partic- ular, the current survey lists a flagship mission to Uranus as the prime candidate.

Daniel L. Engel↗
NASA NTRS2019

Discovery and Vetting of Exoplanets. I. Benchmarking K2 Vetting Tools

We have adapted the algorithmic tools developed during the Kepler mission to vet the quality of transit-like signals for use on the K2 mission data. Using the four sets of publicly available light curves at MAST, we produced a uniformly vetted catalog of 772 transiting planet candidates from K2 as listed at the NASA Exoplanet Archive in the K2 Table of Candidates. Our analysis marks 676 of these as planet candidates and 96 as false positives. All confirmed planets pass our vetting tests. Sixty of our false positives are new identifications, effectively doubling the overall number of astrophysical signals mimicking planetary transits in K2 data. Most of the targets listed as false positives in our catalog show either prominent secondary eclipses, transit depths suggesting a stellar companion instead of a planet, or significant photocenter shifts during transit. We packaged our tools into the open-source, automated vetting pipeline Discovery and Vetting of Exoplanets (DAVE), designed to streamline follow-up efforts by reducing the time and resources wasted observing targets that are likely false positives. DAVE will also be a valuable tool for analyzing planet candidates from NASA's TESS mission, where several guest-investigator programs will provide independent light-curve sets—and likely many more from the community. We are currently testing DAVE on recently released TESS planet candidates and will present our results in a follow-up paper.

Kostov, Veselin B.↗