The Orbiting Configurable Artificial Star (ORCAS) mission in collaboration with the W. M. Keck Observatory (WMKO) is poised to deliver near diffraction limited observations in visible light. The ability to conduct such observations will enable significant scientific discoveries in fields related to Active Galactic Nuclei (AGN), Dark Energy, Flux Calibration, the High Redshift Universe, Exoplanets, and the Solar System. The ORCAS team has successfully completed three primary mission development goals to enable such observations. The performance demonstration with the ORCAS Keck Instrument Demonstrator (ORKID) captured arguably the highest resolution image at visible wavelengths from a large (10 meter) segmented telescope on the ground to date. High resolution AO imaging of the galaxy UGC 4729 in Natural Guide Star (NGS) mode was performed by locking onto a foreground asteroid passing nearby, which simulated an observation with a moving guide star validating post processing capabilities and demonstrating how regions unreachable by NGS and LGS could be explored. Additionally, the ORCAS team has successfully locked onto a laser source onboard the Laser Communications Relay Demonstration (LCRD) and closed the adaptive optics loop to perform near diffraction limited imaging at 1550 nm with the Keck 10 meter, the first demonstration of such capability with a large segmented telescope. All of these results validate the feasibility of the ORCAS mission. Following these accomplishments, ORCAS will be strongly positioned to propose a full-scale mission to upcoming opportunities.
We present the optical requirement-driven observational constraints of the Remote Occulter, an orbiting starshade designed to work with ground-based telescopes to produce visible-band images and spectra of temperate planets around Sun-like stars. We then utilize these constraints to develop and present numerical simulations of time-dependent observable sky regions along with each region’s nightly available exposure duration and show that nearly the entire sky could be observed for up to 8 h a night. We further examine how changes introduced to our established constraints will impact such observational windows and discuss their implications, setting the ground for upcoming studies aiming to further investigate the Remote Occulter mission capabilities and architecture.
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), was one of four candidate flagship missions studied in detail by NASA, which were submitted for consideration to the 2020 Decadal Survey in Astronomy and Astrophysics for possible launch in the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sun-like stars to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx was designed to be the Great Observatory of the 2030s and beyond, with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR.
The Remote Occulter (Orbiting Starshade) is a proposed 100-meter class starshade working with a ground-based telescope, designed for visible-band imaging and spectroscopy of temperate planets around sun-like stars. With advanced adaptive optics and the largest telescopes like the 39 m ELT, it would enable the study of planetary systems and a wide variety of exoplanets. In this paper, we describe the geometrical constraints and establish which parts of the sky are observable.
The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffractionlimited at 0.4 μm and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument.
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.
KEYWORDS: Exoplanets, Solar system, Astrophysics, UV optics, Galactic astronomy, Space telescopes, Near ultraviolet, Near infrared, Planets, Scientific research
The Habitable-Exoplanet Imaging Mission (HabEx) is a candidate flagship mission being studied by NASA and the astrophysics community in preparation of the 2020 Decadal Survey. The HabEx mission concept is a large (~4 to 6.5m) diffraction-limited optical space telescope, providing unprecedented resolution and contrast in the optical, with extensions into the near UV and near infrared domains.
The primary goal of HabEx is to answer fundamental questions in exoplanet science, searching for and characterizing potentially habitable worlds, providing the first complete “family portraits” of planets around our nearest Sun-like neighbors and placing the solar system in the context of a diverse set of exoplanets.
At the same time, HabEx will enable a broad range of Galactic, extragalactic, and solar system astrophysics, from resolved stellar population studies that inform the stellar formation history of nearby galaxies, to characterizing the life cycle of baryons as they flow in and out of galaxies, to detailed studies of bodies in our own solar system.
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. In particular, we present architectures trade study results, quantify technical requirements and predict scientific yield for a small number of design reference missions, all with broad capabilities in both exoplanet science and cosmic origins science.
This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Thousands of exoplanets are known to orbit nearby stars and small rocky planets are established to be common. The ambitious goal of identifying a habitable or inhabited world is within reach. The race to find habitable exoplanets has accelerated with the realization that “big Earths” transiting small stars can be both discovered and characterized with current technology, such that the James Webb Space Telescope has a chance to be the first to provide evidence of biosignature gases. Transiting exoplanets require a fortuitous alignment and the fast-track approach is therefore only the first step in a long journey. The next step is sophisticated starlight suppression techniques for large ground-based telescopes now under construction and hopeful future space-based based telescopes to observe small exoplanets directly. These ideas will lead us down a path to where future generations will implement very large space-based telescopes to search thousands of all types of stars for hundreds of Earths to find signs of life amidst a yet unknown range of planetary environments. What will it take to identify habitable worlds with the telescopes available to us?
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.
G. Ricker, R. Vanderspek, J. Winn, S. Seager, Z. Berta-Thompson, A. Levine, J. Villasenor, D. Latham, D. Charbonneau, M. Holman, J. Johnson, D. Sasselov, A. Szentgyorgyi, G. Torres, G. Bakos, T. Brown, J. Christensen-Dalsgaard, H. Kjeldsen, M. Clampin, S. Rinehart, D. Deming, J. Doty, E. Dunham, S. Ida, N. Kawai, B. Sato, J. Jenkins, J. Lissauer, G. Jernigan, L. Kaltenegger, G. Laughlin, D. Lin, P. McCullough, N. Narita, J. Pepper, K. Stassun, S. Udry
KEYWORDS: Exoplanets, Stars, Satellites, Planets, Cameras, Space telescopes, James Webb Space Telescope, Space operations, Charge-coupled devices, Observatories
The Transiting Exoplanet Survey Satellite (TESS) will discover thousands of exoplanets in orbit around the brightest stars in the sky. This first-ever spaceborne all-sky transit survey will identify planets ranging from Earth-sized to gas giants. TESS stars will be far brighter than those surveyed by previous missions; thus, TESS planets will be easier to characterize in follow-up observations. For the first time it will be possible to study the masses, sizes, densities, orbits, and atmospheres of a large cohort of small planets, including a sample of rocky worlds in the habitable zones of their host stars.
Very precise on-ground characterization and calibration of TESS CCD detectors will significantly assist in the analysis of the science data from the mission. An accurate optical test bench with very high photometric stability has been developed to perform precise measurements of the absolute quantum efficiency. The setup consists of a vacuum dewar with a single MIT Lincoln Lab CCID-80 device mounted on a cold plate with the calibrated reference photodiode mounted next to the CCD. A very stable laser-driven light source is integrated with a closed-loop intensity stabilization unit to control variations of the light source down to a few parts-per-million when averaged over 60 s. Light from the stabilization unit enters a 20 inch integrating sphere. The output light from the sphere produces near-uniform illumination on the cold CCD and on the calibrated reference photodiode inside the dewar. The ratio of the CCD and photodiode signals provides the absolute quantum efficiency measurement. The design, key features, error analysis, and results from the test campaign are presented.
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.
KEYWORDS: Stars, Planets, Exoplanets, Space operations, Satellites, Cameras, Charge-coupled devices, Space telescopes, James Webb Space Telescope, Observatories
The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its 2-year mission, TESS will employ four wide-field optical charge-coupled device cameras to monitor at least 200,000 main-sequence dwarf stars with IC≈4−13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from 1 month to 1 year, depending mainly on the star’s ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10 to 100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every 4 months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.
KEYWORDS: Stars, Planets, Space operations, Cameras, Charge-coupled devices, Space telescopes, Exoplanets, Observatories, James Webb Space Telescope, Sensors
The Transiting Exoplanet Survey Satellite (TESS ) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its two-year mission, TESS will employ four wide-field optical CCD cameras to monitor at least 200,000 main-sequence dwarf stars with IC (approximately less than) 13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from one month to one year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10-100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every four months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.
This paper provides a survey of the state-of-the-art in coronagraph and starshade technologies and highlights areas where advances are needed to enable future NASA exoplanet missions. An analysis is provided of the remaining technology gaps and the relative priorities of technology investments leading to a mission that could follow JWST. This work is being conducted in support of NASAs Astrophysics Division and the NASA Exoplanet Exploration Program (ExEP), who are in the process of assessing options for future missions. ExEP has funded Science and Technology Definition Teams to study coronagraphs and starshade mission concepts having a lifecycle cost cap of less than $1B. This paper provides a technology gap analysis for these concepts.
CubeSats are a class of nanosatellites that conform to a standardized 10 cm x 10 cm x 10 cm, 1 kg form factor.
This miniaturization, along with a standardized deployment device for launch vehicles, allows CubeSats to be
launched at low cost by sharing the trip to orbit with other spacecraft. Part of the original motivation for the
CubeSat platform was also to allow university students to participate more easily in space technology development
and to gain hands-on experience with flight hardware. The Department of Aeronautics and Astronautics along
with the Department of Earth, Atmospheric, and Planetary Studies (EAPS) at the Massachusetts Institute of
Technology (MIT) recently completed a three semester-long course that uses the development of a CubeSat-based
science mission as its core teaching method. Serving as the capstone academic experience for undergraduates,
the goal of this class is to design and build a CubeSat spacecraft that serves a relevant science function, such
as the detection of exoplanets transiting nearby stars. This project-based approach gives students essential
first hand insights into the challenges of balancing science requirements and engineering design. Students are
organized into subsystem-specific teams that refine and negotiate requirements, explore the design trade space,
perform modeling and simulation, manage interfaces, test subsystems, and finally integrate prototypes and flight
hardware. In this work we outline the heritage of capstone design/build classes at MIT, describe the class format
in greater detail, and give results on the ability to meet learning objectives using this pedagogical approach.
KEYWORDS: Stars, Space operations, Charge-coupled devices, Exoplanets, Interference (communication), Sensors, Planets, Signal to noise ratio, Space telescopes, CCD image sensors
Nanosatellites, i.e. spacecraft that weigh between 1 and 10 kg, are drawing increasing interest as platforms
for conducting on-orbit science. This trend is primarily driven by the ability to piggyback nanosatellites on
the launch of large spacecraft and hence achieve orbit at greatly reduced cost. The CubeSat platform is a
standardized nanosatellite configuration, consisting of one, two, or three 10 cm x 10 cm x 10 cm units (1, 2,
or 3 "U"s) arranged in a row. We present a CubeSat-based concept for the discovery of transiting exoplanets
around the nearest and brightest Sun-like stars. The spacecraft prototype - termed ExoplanetSat - is a 3U space
telescope capable of monitoring a single target star from low Earth orbit. Given the volume limitations of
the CubeSat form factor, designing a capable spacecraft requires overcoming significant challenges. This work
presents the initial satellite configuration along with several subsystem-specific solutions to the aforementioned
constraints. An optical design based on a modified commercial off-the-shelf camera lens is given. We also
describe a novel two-stage attitude control architecture that combines 3-axis reaction wheels for coarse pointing
with a piezoelectric translation stage at the focal plane for fine pointing. Modeling and simulation results are
used to demonstrate feasibility by quantifying ExoplanetSat pointing precision, signal-to-noise ratio, guide star
magnitude, and additional design parameters which determine system performance.
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.
ExoplanetSat is a proposed three-unit CubeSat designed to detect down to Earth-sized exoplanets in an orbit
out to the habitable zone of Sun-like stars via the transit method. To achieve the required photometric precision
to make these measurements, the target star must remain within the same fraction of a pixel, which is equivalent
to controlling the pointing of the satellite to the arcsecond level. The satellite will use a two-stage control
system: coarse control will be performed by a set of reaction wheels, desaturated by magnetic torque coils, and
fine control will be performed by a piezoelectric translation stage. Since no satellite of this size has previously
demonstrated this high level of pointing precision, a simulation has been developed to prove the feasibility of
realizing such a system.
The current baseline simulation has demonstrated the ability to hold the target star to within 0.05 pixels
or 1.8 arcseconds (with an 85 mm lens and 15 μm pixels), in the presence of large reaction wheel disturbances
as well as external environmental disturbances. This meets the current requirement of holding the target star
to 0.14 pixels or 5.0 arcseconds. Other high-risk aspects of the design have been analyzed such as the effect of
changing the guide star centroiding error, changing the CMOS sampling frequency, and reaction wheel selection
on the slew performance of the satellite. While these results are promising as an initial feasibility analysis,
further model improvements and hardware-in-the-loop tests are currently underway.
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.
The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for a spacecraft-borne nulling
interferometer for high-resolution astronomy and the direct detection of exoplanets and assay of their
environments and atmospheres. FKSI is a high angular resolution system operating in the near to mid-infrared
spectral region and is a scientific and technological pathfinder to the Darwin and Terrestrial Planet
Finder (TPF) missions. The instrument is configured with an optical system consisting, depending on
configuration, of two 0.5 - 1.0 m telescopes on a 12.5 - 20 m boom feeding a symmetric, dual Mach-
Zehnder beam combiner. We report on progress on our nulling testbed including the design of an optical
pathlength null-tracking control system and development of a testing regime for hollow-core fiber
waveguides proposed for use in wavefront cleanup. We also report results of integrated simulation studies
of the planet detection performance of FKSI and results from an in-depth control system and residual
optical pathlength jitter analysis.
The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Discovery mission to image
and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will
provide insights into the physical nature of a variety of planets in other solar systems complimenting radial
velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets
identified by radial velocity surveys, determine orbital inclinations and masses, characterize the
atmospheres around A and F type stars which cannot be found with RV techniques, and observe the inner
spatial structure and colors of debris disks. EPIC has a proposed launch date of 2012 to heliocentric Earth
trailing drift-away orbit, with a 3 year mission lifetime (5 year goal), and will revisit planets at least three
times at intervals of 9 months. The robust mission design is simple and flexible ensuring mission success
while minimizing cost and risk. The science payload consists of a heritage optical telescope assembly
(OTA), and visible nulling coronagraph (VNC) instrument. The instrument achieves a contrast ratio of 109
over a 4.84 arcsecond field-of-view with an unprecedented inner working angle of 0.14 arcseconds over the
spectral range of 440-880 nm, with spectral resolutions from 10 - 150. The telescope is a 1.5 meter offaxis
Cassegrain with an OTA wavefront error of λ/9, which when coupled to the VNC greatly reduces the
requirements on the large scale optics, compressing them to stability requirements within the relatively
compact VNC optical chain. The VNC features two integrated modular nullers, a spatial filter array (SFA),
and an E2V-L3 photon counting CCD. Direct null control is accomplished from the science focal
mitigating against complex wavefront and amplitude sensing and control strategies.
During the last few years, considerable effort has been directed towards large-scale (> $1 Billion) missions to detect and
characterize earth-like planets around nearby stars, such as the Terrestrial Planet Finder Interferometer and Darwin
missions. However, technological issues such as formation flying, cryocooling, obtaining sufficient null depth for
broadband signals, and control of systematic noise sources will likely prevent these missions from entering Phase A
until at least the end of the present decade. Futhermore, a large mission like TPF-I will also need the endorsement of
the next Astronomical Decadal Survey to obtain a Phase A start in the next decade. Thus, given the present
circumstances, we can expect TPF-I to launch no earlier than about 2020 or even as late as 2025.
Presently more than 168 planets have been discovered by precision radial velocity survey techniques, and little is known
about the majority of them. A simplified nulling interferometer operating in the near- to mid-infrared (e.g. ~ 3-8
microns), like the Fourier Kelvin Stellar Interferometer (FKSI), can characterize the atmospheres of a large sample of
the known planets. Many other scientific problems can be addressed with a system like FKSI, including the imaging of
debris disks, active galactic nuclei, and low mass companions around nearby stars. We discuss the rationale, both
scientific and technological, for a competed mission in the $450-600 Million range, of which FKSI is an example. Such
a mission is essential to develop our community and keep the larger community, including young scientists, engaged in
the long-term effort towards the detection of Earth-like planets.
We report the development of the first high resolution cross-dispersed silicon immersion grating spectrometer. This instrument is called the Florida IR Silicon immersion grating specTrometer (FIRST). FIRST can produce R = 50,000 under a 0.6 arcsec seeing and
simultaneously cover 1.3-1.8 μm with a 1kx1k HgCdTe array at the Apache Point Observatory 3.5 meter telescope. FIRST has a 50 mm diameter collimated beam and the overall instrument is within a volume of 0.8x0.5x0.5 m3. The high dispersion, large wavelength coverage and small instrument volume become possible due to the use of a silicon immersion grating (54.7 deg blaze angle and 50 mm diameter entrance pupil) with extremely high dispersion power (3.4 times dispersion power of a conventional echelle) and coarse grooves (16.1 l/mm, coarser than the commercially available echelles). The silicon immersion grating used in a lab bench mounted Czeney-Turner spectrograph with an only 25 mm diameter collimated beam and a 100 um core fiber has produced R = 55,000 cross-dispersed solar spectra. This instrument is designed to precisely measure radial velocities of low mass stars, M dwarfs for detecting 5-10 Earth mass planets. The estimated Doppler precision is ~ 3 m/s for a J = 9 M5V dwarf in 15 min at the APO 3.5m telescope.
The Terrestrial Planet Finder Coronagraph (TPF-C) is a deep space mission designed to detect and characterize Earth-like planets around nearby stars. TPF-C will be able to search for signs of life on these planets. TPF-C will use spectroscopy to measure basic properties including the presence of water or oxygen in the atmosphere, powerful signatures in the search for habitable worlds. This capability to characterize planets is what allows TPF-C to transcend other astronomy projects and become an historical endeavor on a par with the discovery voyages of the great navigators.
The CorECam Instrument Concept Study (ICS) addressed the requirements and science program for the
Terrestrial Planet Finder Coronagraph's (TPF-C) primary camera. CorECam provides a simple interface to
TPF-C's Starlight Suppression System (SSS) which would be provided by the TPF-C Program, and
comprises camera modules providing visible, and near-infrared (NIR) camera focal plane imaging. In its
primary operating mode, CorECam will conduct the core science program of TPF-C, detecting terrestrial
planets at visible wavelengths. CorECam additionally provides the imaging capabilities to characterize
terrestrial planets, and conduct an extended science program focused on investigating the nature of the
exosolar systems in which terrestrial planets are detected. In order to evaluate the performance of CorECam
we developed a comprehensive, end-to-end model using OSCAR which has provided a number of key
conclusions on the robustness of the TPF-C baseline design, and allows investigation of alternative
techniques for wavefront sensing and control. CorECam recommends photon counting detectors be
baselined for imaging with TPF-C since they provide mitigations against the background radiation
environment, improved sensitivity and facilitate alternative WFSC approaches.
The nulling coronagraph is one of 5 instrument concepts selected by NASA for study for potential use in the TPF-C
mission. This concept for extreme starlight suppression has two major components, a nulling interferometer to suppress
the starlight to ~10-10 per airy spot within 2 λ/D of the star, and a calibration interferometer to measure the residual
scattered starlight. The ability to work at 2 λ/D dramatically improves the science throughput of a space based
coronagraph like TPF-C. The calibration interferometer is an equally important part of the starlight suppression system.
It measures the measures the wavefront of the scattered starlight with very high SNR, to 0.05nm in less than 5 minutes
on a 5mag star. In addition, the post coronagraph wavefront sensor will be used to measure the residual scattered light
after the coronagraph and subtract it in post processing to 1~2x10-11 to enable detection of an Earthlike planet with a
SNR of 5~10.
The New Worlds Observer, currently studied under a NASA Institute for Advanced Concepts grant, will be a pinhole camera in space designed to directly detect and study extrasolar terrestrial planets. An apodized occultor or pinhole creates an image of the planetary system in the focal plane far away, where a second telescope craft orbits to detect the light. In this study we simulate the expected signal of NWO to find the optimal configuration and specifications of the two craft. The efficiency of direct detection through photometric imaging depends strongly on occulter and telescope size, while preliminary studies on absorption biomarker detection and photometric variability measurements are summarized.
The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for an imaging and nulling interferometer for the near infrared to mid-infrared spectral region (3-8 microns). FKSI is a scientific and technological pathfinder to TPF/DARWIN as well as SPIRIT, SPECS, and SAFIR. It will also be a high angular resolution system complementary to JWST. There are four key scientific issues the FKSI mission is designed to address. First, we plan to characterize the atmospheres of the known extra-solar giant planets. Second, we will explore the morphology of debris disks to look for resonant structures to find and characterize extrasolar planets. Third, we will observe young stellar systems to understand their evolution and planet forming potential, and study circumstellar material around a variety of stellar types to better understand their evolutionary state. Finally, we plan to measure detailed structures inside active galactic nuclei. We report results of simulation studies of the imaging capabilities of the FKSI with various configurations of two to five telescopes including the effects of thermal noise and local and exozodiacal dust emission. We also report preliminary results from our symmetric Mach-Zehnder nulling testbed.
The New World Observer has the potential to discover and study planets around other stars without expensive and risky technical heroics. We describe the starshade, a large, deployable sheet on a separate spacecraft that is flown into position along the line of sight to a nearby star. We show how a starshade can be designed and built in a practical and affordable manner to fully remove starlight and leave only planet light entering a telescope. The simulations demonstrate That NWI can detect planetary system features as faint as comets, perform spectroscopy to look for water and life signs, and perform photometry to search for oceans, continents, clouds and polar caps.
The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for a nulling interferometer for the near-to-mid-infrared spectral region (3-8µm). FKSI is conceived as a scientific and technological precursor to TPF. The scientific emphasis of the mission is on the evolution of protostellar systems, from just after the collapse of the precursor molecular cloud core, through the formation of the disk surrounding the protostar, the formation of planets in the disk, and eventual dispersal of the disk material. FKSI will answer key questions about extrasolar planets:
Σ What are the characteristics of the known extrasolar giant planets?
Σ What are the characteristics of the extrasolar zodiacal clouds around nearby stars?
Σ Are there giant planets around classes of stars other than those already studied?
We present preliminary results of a detailed design study of the FKSI. Using a nulling interferometer configuration, the optical system consists of two 0.5m telescopes on a 12.5m boom feeding a Mach-Zender beam combiner with a fiber wavefront error reducer to produce a 0.01% null of the central starlight. With this system, planets around nearby stars can be detected and characterized using a combination of spectral and spatial resolution.
The New Worlds Observer (NWO) is a proposed space mission to provide high resolution spectroscopy from the far UV to the near IR of extra-solar terrestrial sized planets. The design of NWO is based on the concept of a large, space-based, pinhole camera made up of two spacecraft flying in formation. The first spacecraft is a large, thin occulting shield (perhaps hundreds of meters in diameter) with a shaped "pinhole" aperture about 10m in diameter. The second spacecraft is a conventional-quality space telescope (possibly with a 10m primary mirror) which "flies" through the pinhole image of the planetary system to observe the extra-solar planets free from stellar background. In this paper we describe the design of the two spacecraft system. In particular, the shaped-pinhole design utilizes the shaped-pupil coronagraph pioneered for the Terrestrial Planet Finder. In this paper we describe some of the NWO's technology challenges and science opportunities. Additionally, we describe an extension of the design to provide 100km resolution images of extra-solar planets.
The Extrasolar Planetary Imaging Coronagraph (EPIC) will provide the first direct measurements of a broad range of fundamental physical characteristics of giant planets in other solar systems. These characteristics include orbital inclination, mass, brightness, color, the presence (or absence) of CH4 and H2O, and orbital or rotational-driven variability. EPIC utilizes a 1.5 meter telescope coupled to a Visible Nulling Coronagraph to achieve these science goals. EPIC has been proposed as a Discovery Mission.
KEYWORDS: Planets, Stars, Signal to noise ratio, Space telescopes, Hubble Space Telescope, Coronagraphy, Wavefronts, Exoplanets, Telescopes, Point spread functions
Recent advances in deformable mirror technology for correcting wavefront errors and in pupil shapes and masks for coronagraphic suppression of diffracted starlight enable a powerful approach to detecting extrasolar planets in reflected (scattered) starlight at visible wavelengths. We discuss the planet-finding performance of Hubble-like telescopes using these technical advances. A telescope of aperture of at least 4 meters could accomplish the goals of the Terrestrial Planet Finder (TPF) mission. The '4mTPF' detects an Earth around a Sun at five parsecs in about one hour of integration time. It finds molecular oxygen, ozone, water vapor, the 'red edge' of chlorophyll-containing land-plant leaves, and the total atmospheric column density -- all in forty hours or less. The 4mTPF has a strong science program of discovery and characterization of extrasolar planets and planetary systems, including other worlds like Earth. With other astronomical instruments sharing the focal plane, the 4mTPF could also continue and expand the general program of astronomical research of the Hubble Space Telescope.
Searching for transits provides a very promising technique for finding close-in extra-solar planets. Transiting planets present the advantage of allowing one to determine physical properties such as mass and radius unambiguously. The EXPLORE (EXtra-solar PLanet Occultation REsearch) project is a transit search project carried out using wide-field CCD imaging cameras on 4-m class telescopes, and 8--10m class telescopes for velocity verifications of the photometric candidates. We describe some of the considerations that go into the design of the EXPLORE transit search to maximize the discovery rate and minimize contaminating objects that mimic transiting planets. We show that high precision photometry (2 to 10 millimag) and high time sampling (few minutes) are crucial for sifting out contaminating signatures, such as grazing binaries. We have an efficient data reduction pipeline which allows us to completely reduce the data in less than one month after the imaging observations, allowing us to conduct same-semester velocity follow-up observations, reducing the phase uncertainty.
We have completed two searches using the 8k MOSAIC camera at the CTIO4m and the CFH12k camera at CFHT, with runs covering 11 and 16 nights, respectively. Using the 4400 images from the two fields, we obtained light curves for approximately 47,000 stars with better than $\sim1$\% photometric precision. A number of light curves with flat-bottomed eclipses consistent with being produced by transiting planets has been discovered. Preliminary results from follow-up spectroscopic observations using the VLT UVES spectrograph and the Keck HIRES spectrograph obtained for a number of the candidates are presented. Data from four of these can be interpreted consistently as possible planet candidates, although further data are still required for definitive confirmations.
For the first time in human history the possibility of detecting and studying Earth-like planets is on the horizon. Terrestrial Planet Finder (TPF), with a launch date in the 2015 timeframe, is being planned by NASA to find and characterize planets in the habitable zones of nearby stars. The mission Darwin from ESA has similar goals. The motivation for both of these space missions is the detection and spectroscopic characterization of extrasolar terrestrial planet atmospheres. Of special interest are atmospheric biomarkers-such as O2, O3, H2O, CO and CH4-which are either indicative of life as we know it, essential to life, or can provide clues to a planet's habitability. A mission capable of measuring these spectral features would also obtain sufficient signal-to-noise to characterize other terrestrial planet properties. For example, physical characteristics such as temperature and planetary radius can be constrained from low-resolution spectra. In addition, planet characteristics such as weather, rotation rate, presence of large oceans or surface ice, and existence of seasons could be derived from photometric measurements of the planet's variability. We will review the potential to characterize terrestrial planets beyond their spectral signatures. We will also discuss the possibility to detect strong surface biomarkers-such as Earth's vegetation red edge near 700 nm-that are different from any known atomic or molecular signature.
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