The high contrast and spatial resolution requirements for directly imaging exoplanets requires effective coordination of wavefront control, coronagraphy, observation techniques, and post-processing algorithms. However, even with this suite of tools, identifying and retrieving exoplanet signals embedded in resolved scattered light regions can be extremely challenging due to the increased noise from scattered light off the circumstellar disk and the potential misinterpretation of the true nature of the detected signal. This issue pertains not only to imaging terrestrial planets in habitable zones within zodiacal and exozodiacal emission but also to young planets embedded in circumstellar, transitional, and debris disks. This is particularly true for Hα detection of exoplanets in transitional disks. This work delves into recent Hα observations of three transitional disks systems with MagAO-X, an extreme adaptive optics system for the 6.5-meter Magellan Clay telescope. We employed angular differential imaging (ADI) and simultaneous spectral differential imaging (SSDI) in combination with KLIP, a PCA algorithm in post-processing, for optimal starlight suppression and quasi-static noise removal. We discuss the challenges in protoplanet identification with MagAO-X in environments rich with scattered and reflected light from disk structures and explore a potential solution for removing noise contributions from real astronomical objects with current observation and post-processing techniques.
MagAO-X is the coronagraphic extreme adaptive optics system for the 6.5m Magellan Clay Telescope. We report the results of commissioning the first phase of MagAO-X. Components now available for routine observations include: the >2kHz high-order control loop consisting of a 97 actuator woofer deformable mirror (DM), a 2040 actuator tweeter DM, and a modulated pyramid wavefront sensor (WFS); classical Lyot coronagraphs with integrated low-order (LO) WFS and control using a third 97-actuator non-common path correcting (NCPC) DM; broad band imaging in g, r, i, and z filters with two EMCCDs; simultaneous differential imaging in Hα; and integral field spectroscopy with the VIS-X module. Early science results include the discovery of an Hα jet, images of accreting protoplanets at Hα, images of young extrasolar giant planets in the optical, discovery of new white dwarf companions, resolved images of evolved stars, and high-contrast images of circumstellar disks in scattered light in g-band (500nm). We have commenced an upgrade program, called “Phase II”, to enable high-contrast observations at the smallest inner working angles possible. These upgrades include a new 952 actuator NCPC DM to enable coronagraphic wavefront control; phase induced amplitude apodization coronagraphs; new fast cameras for LOWFS and Lyot-LOWFS; and real-time computer upgrades. We will report the status of these upgrades and results of first on-sky testing in March-May 2024.
High-contrast imaging data analysis depends on removing residual starlight from the host star to reveal planets and disks. Most observers do this with principal components analysis (i.e. KLIP) using modes computed from the science images themselves. These modes may not be orthogonal to planet and disk signals, leading to over-subtraction. The wavefront sensor data recorded during the observation provide an independent signal with which to predict the instrument point-spread function (PSF). MagAO-X is an extreme adaptive optics (ExAO) system for the 6.5-meter Magellan Clay telescope and a technology pathfinder for ExAO with GMagAO-X on the upcoming Giant Magellan Telescope. MagAO-X is designed to save all sensor information, including kHz-speed wavefront measurements. Our software and compressed data formats were designed to record the millions of training samples required for machine learning with high throughput. The large volume of image and sensor data lets us learn a PSF model incorporating all the information available. This allows us to probe smaller star-planet separations at greater sensitivities, which will be needed for rocky planet imaging.
The next generation of extreme adaptive optics (AO) must be calibrated exceptionally well to achieve the desired contrast for ground-based direct imaging exoplanet targets. Current wavefront sensing and control system responses deviate from lab calibration throughout the night due to non linearities in the wavefront sensor (WFS) and signal loss. One cause of these changes is the optical gain (OG) effect, which shows that the difference between actual and reconstructed wavefronts is sensitive to residual wavefront errors from partially corrected turbulence. This work details on-sky measurement of optical gain on MagAO-X, an extreme AO system on the Magellan Clay 6.5m. We ultimately plan on using a method of high-temporal frequency probes on our deformable mirror to track optical gain on the Pyramid WFS. The high-temporal frequency probes, used to create PSF copies at 10-22 λ/D, are already routinely used by our system for coronagraph centering and post-observation calibration. This method is supported by the OG measurements from the modal response, measured simultaneously by sequenced pokes of each mode. When tracked with DIMM measurements, optical gain calibrations show a clear dependence on Strehl Ratio, and this relationship is discussed. This more accurate method of calibration is a crucial next step in enabling higher fidelity correction and post processing techniques for direct imaging ground based systems.
We present the preliminary design of GMagAO-X, the first-light high-contrast imager planned for the Giant Magellan Telescope. GMagAO-X will realize the revolutionary increase in spatial resolution and sensitivity provided by the 25 m GMT. It will enable, for the first time, the spectroscopic characterization of nearby potentially habitable terrestrial exoplanets orbiting late-type stars. Additional science cases include: reflected light characterization of mature giant planets; measurement of young extrasolar giant planet variability; characterization of circumstellar disks at unprecedented spatial resolution; characterization of benchmark stellar atmospheres at high spectral resolution; and mapping of resolved objects such as giant stars and asteroids. These, and many more, science cases will be enabled by a 21,000 actuator extreme adaptive optics system, a coronagraphic wavefront control system, and a suite of imagers and spectrographs. We will review the science-driven performance requirements for GMagAO-X, which include achieving a Strehl ratio of 70% at 800 nm on 8th mag and brighter stars, and post-processed characterization at astrophysical flux-ratios of 1e-7 at 4 lambda/D (26 mas at 800 nm) separation. We will provide an overview of the resulting mechanical, optical, and software designs optimized to deliver this performance. We will also discuss the interfaces to the GMT itself, and the concept of operations. We will present an overview of our end-to-end performance modeling and simulations, including the control of segment phasing, as well as an overview of prototype lab demonstrations. Finally, we will review the results of Preliminary Design Review held in February, 2024.
We introduce an optical system design of the calibration system for Giant Magellan Telescope Near-Infrared Spectrograph (GMTNIRS), capable of operating across a wavelength range of 1.08 - 5.4 μm. The calibration system fulfills several critical functions, including flat-fielding, wavelength calibration, dark current measurements, and focusing of the spectrograph. The system consists of flat lamp collimator, illuminator, relay optics, and three targets – the USAF 1951 resolution target, a pinhole, and a dark mirror. The focal ratio of the output beam in image space is designed to be 8, replicating the Giant Magellan Telescope. The flatness of the light from the calibration system is evaluated using a non-sequential ray tracing method, confirming over 99% flatness across the slit area.
We present a status update for MagAO-X, a 2000 actuator, 3.6 kHz adaptive optics and coronagraph system for the Magellan Clay 6.5 m telescope. MagAO-X is optimized for high contrast imaging at visible wavelengths. Our primary science goals are detection and characterization of Solar System-like exoplanets, ranging from very young, still-accreting planets detected at H-alpha, to older temperate planets which will be characterized using reflected starlight. First light was in Dec, 2019, but subsequent commissioning runs were canceled due to COVID19. In the interim, MagAO-X has served as a lab testbed. Highlights include implementation of several focal plane and low-order wavefront sensing algorithms, development of a new predictive control algorithm, and the addition of an IFU module. MagAO-X also serves as the AO system for the Giant Magellan Telescope High Contrast Adaptive Optics Testbed. We will provide an overview of these projects, and report the results of our commissioning and science run in April, 2022. Finally, we will present the status of a comprehensive upgrade to MagAO-X to enable extreme-contrast characterization of exoplanets in reflected light. These upgrades include a new post-AO 1000-actuator deformable mirror inside the coronagraph, latest generation sCMOS detectors for wavefront sensing, optimized PIAACMC coronagraphs, and computing system upgrades. When these Phase II upgrades are complete we plan to conduct a survey of nearby exoplanets in reflected light.
GMTNIRS, the Giant Magellan Telescope Near-Infrared Spectrograph, is a high resolution (R=65,000~80,000) near-infrared spectrograph selected as a first-generation instrument for the Giant Magellan Telescope. The instrument covers J, H, K, L, and M spectral bands in a single shot through 6-channel spectrographs. The L band is shared by two channels. Thanks to the use of silicon immersion gratings, the design is compact for its capability. GMTNIRS will be located on the GMT instrument rotator upper disk and operating in adaptive optics mode. We detail the optical system design, imaging performance, spectral formats, and fabrication/alignment budget.
GMTNIRS, the Giant Magellan Telescope Near-Infrared Spectrograph, is a high resolution (R = 65,000 - 80,000) near infrared spectrograph selected as a first-generation instrument for the Giant Magellan Telescope (GMT). It simultaneously observes the J, H, K, L, and M bands using five immersion gratings. GMTNIRS will be located on the GMT instrument rotator upper disk and operating in adaptive optics mode. The cryostat and optical bench design is based on the heritage of the highly successful immersion grating spectrograph, IGRINS. The cryostat is octagonal with a width of 1.7 m and a height of 1 m. It consists of top piece, bottom plate, passive radiation shields, and warm window assembly. Cryocoolers, electronics, and vacuum components are installed on the bottom plate. The optical bench system is comprised of two optical benches, bench interface structure, and active radiation shield. It is thermally isolated from the cryostat by eight sets of G10 supports. The sub-bench accommodates the fore-optics, a pupil mask, and an on instrument wave front sensor, while the spectrographs, slit-mask imager, and slit viewing camera are located on the main bench. Structure and thermal analysis have been performed to verify bench flexure by gravity vector change, integrity of the cryostat by vacuum pressure, and temperature distribution at the operating temperature of 70 K. We also present some design strategies to prevent light leakage.
GMTNIRS, the first-generation instrument of the Giant Magellan Telescope, is a high-resolution (R = 65,000 – 80,000) near-infrared spectrograph. We introduce the preliminary design of optical mounts for slit, beam splitters, mirrors, and gratings installed in the cryogenic spectrograph. Optical components are mounted on aluminum structures and fixed by titanium springs and spring plungers. Static analysis of optical mounts with 1g-force at various directions has been performed to verify the stability of the optical system. In addition, stability in the seismic environment is evaluated with modal analysis and non-linear dynamic analysis. Design and simulation results are compared to the tolerance limits of the system.
GMTNIRS (Giant Magellan Telescope Near-Infrared Spectrograph) is a high resolution (R = 65,000 – 80,000) wide-band near-infrared spectrograph, one of the first-generation instruments of the Giant Magellan Telescope. We present the preliminary design of the electronics system including temperature control, power distribution, vacuum pressure monitoring, moving mechanism, and packaging. Design for infrared detector subsystems for science bands (J, H, K, L, and M) and a slit-view camera is planned. The electronics system makes use of EtherCAT as fieldbus standard according to the requirement of the GMT.
Our past GAPplanetS survey over the last 5 years with the MagAO visible AO system discovered the first examples of accreting protoplanets (by direct observation of H-alpha emission). Examples include LkCa15 b (Sallum et al. 2015) and PDS70 b (Wagner et al. 2018). In this paper we review the science performance of the newly (Dec. 2019) commissioned MagAO-X extreme AO system. In particular, we use the vAPP coronagraphic contrasts measured during MagAO-X first light. We use the Massive Accreting Gap (MAG) protoplanet model of Close 2020 to predict the H-alpha contrasts of 19 of the best transitional disk systems (ages 1-5 Myr) for the direct detection of H-alpha from accretion of hydrogen onto these protoplanets. The MAG protoplanet model applied to the observed first light MagAO-X contrasts predict a maximum yield of 46±7 planets from 19 stars (42 of these planets would be new discoveries). This suggests that there is a large, yet, unexplored reservoir of protoplanets that can be discovered with an extreme AO coronagraphic survey of 19 of the best transitional disk systems. Based on our first light contrasts we predict a healthy yield of protoplanets from our MaxProtoPlanetS survey of 19 transitional disks with MagAO-X.
The presence of large amounts of dust in the habitable zones of nearby stars is a significant obstacle for future exo-Earth imaging missions. We executed the HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey to determine the typical amount of such exozodiacal dust around a sample of nearby main sequence stars. The majority of the data have been analyzed and we present here an update of our ongoing work. Nulling interferometry in N band was used to suppress the bright stellar light and to detect faint, extended circumstellar dust emission. We present an overview of the latest results from our ongoing work. We find seven new N band excesses in addition to the high confidence confirmation of three that were previously known. We find the first detections around Sun-like stars and around stars without previously known circumstellar dust. Our overall detection rate is 23%. The inferred occurrence rate is comparable for early type and Sun-like stars, but decreases from 71+11 -20% for stars with previously detected mid- to far-infrared excess to 11+9 -4% for stars without such excess, confirming earlier results at high confidence. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal luminosity function of the dust, we find upper limits on the median dust level around all stars without previously known mid to far infrared excess of 11.5 zodis at 95% confidence level. The corresponding upper limit for Sun-like stars is 16 zodis. An LBTI vetted target list of Sun-like stars for exo-Earth imaging would have a corresponding limit of 7.5 zodis. We provide important new insights into the occurrence rate and typical levels of habitable zone dust around main sequence stars. Exploiting the full range of capabilities of the LBTI provides a critical opportunity for the detailed characterization of a sample of exozodiacal dust disks to understand the origin, distribution, and properties of the dust.
Despite promising astrometric signals, to date there has been no success in direct imaging of a hypothesized third member of the Sirius system. Using the Clio instrument and MagAO adaptive optics system on the Magellan Clay 6.5 m telescope, we have obtained extensive imagery of Sirius through a vector apodizing phase plate (vAPP) coronagraph in a narrowband filter at 3.9 microns. The vAPP coronagraph and MagAO allow us to be sensitive to planets much less massive than the limits set by previous non-detections. However, analysis of these data presents challenges due to the target’s brightness and unique characteristics of the instrument. We present a comparison of dimensionality reduction techniques to construct background illumination maps for the whole detector using the areas of the detector that are not dominated by starlight. Additionally, we describe a procedure for sub-pixel alignment of vAPP data using a physical-optics-based model of the coronagraphic PSF.
MagAO-X is an entirely new extreme adaptive optics system for the Magellan Clay 6.5 m telescope, funded by the NSF MRI program starting in Sep 2016. The key science goal of MagAO-X is high-contrast imaging of accreting protoplanets at Hα. With 2040 actuators operating at up to 3630 Hz, MagAO-X will deliver high Strehls (> 70%), high resolution (19 mas), and high contrast (< 1 × 10-4 ) at Hα (656 nm). We present an overview of the MagAO-X system, review the system design, and discuss the current project status.
The Immersion GRating INfrared Spectrometer (IGRINS) was designed for high-throughput with the expectation of being a visitor instrument at progressively larger observing facilities. IGRINS achieves R∼45000 and > 20,000 resolution elements spanning the H and K bands (1.45-2.5μm) by employing a silicon immersion grating as the primary disperser and volume-phase holographic gratings as cross-dispersers. After commissioning on the 2.7 meter Harlan J. Smith Telescope at McDonald Observatory, the instrument had more than 350 scheduled nights in the first two years. With a fixed format echellogram and no cryogenic mechanisms, spectra produced by IGRINS at different facilities have nearly identical formats. The first host facility for IGRINS was Lowell Observatory’s 4.3-meter Discovery Channel Telescope (DCT). For the DCT a three-element fore-optic assembly was designed to be mounted in front of the cryostat window and convert the f/6.1 telescope beam to the f/8.8 beam required by the default IGRINS input optics. The larger collecting area and more reliable pointing and tracking of the DCT improved the faint limit of IGRINS, relative to the McDonald 2.7-meter, by ∼1 magnitude. The Gemini South 8.1-meter telescope was the second facility for IGRINS to visit. The focal ratio for Gemini is f/16, which required a swap of the four-element input optics assembly inside the IGRINS cryostat. At Gemini, observers have access to many southern-sky targets and an additional gain of ∼1.5 magnitudes compared to IGRINS at the DCT. Additional adjustments to IGRINS include instrument mounts for each facility, a glycol cooled electronics rack, and software modifications. Here we present instrument modifications, report on the success and challenges of being a visitor instrument, and highlight the science output of the instrument after four years and 699 nights on sky. The successful design and adaptation of IGRINS for various facilities make it a reliable forerunner for GMTNIRS, which we now anticipate commissioning on one of the 6.5 meter Magellan telescopes prior to the completion of the Giant Magellan Telescope.
NASA has funded a project called the Hunt for Observable Signatures of Terrestrial Systems (HOSTS) to survey nearby solar type stars to determine the amount of warm zodiacal dust in their habitable zones. The goal is not only to determine the luminosity distribution function but also to know which individual stars have the least amount of zodiacal dust. It is important to have this information for future missions that directly image exoplanets as this dust is the main source of astrophysical noise for them. The HOSTS project utilizes the Large Binocular Telescope Interferometer (LBTI), which consists of two 8.4-m apertures separated by a 14.4-m baseline on Mt. Graham, Arizona. The LBTI operates in a nulling mode in the mid-infrared spectral window (8-13 μm), in which light from the two telescopes is coherently combined with a 180 degree phase shift between them, producing a dark fringe at the location of the target star. In doing so the starlight is greatly reduced, increasing the contrast, analogous to a coronagraph operating at shorter wavelengths. The LBTI is a unique instrument, having only three warm reflections before the starlight reaches cold mirrors, giving it the best photometric sensitivity of any interferometer operating in the mid-infrared. It also has a superb Adaptive Optics (AO) system giving it Strehl ratios greater than 98% at 10 μm. In 2014 into early 2015 LBTI was undergoing commissioning. The HOSTS project team passed its Operational Readiness Review (ORR) in April 2015. The team recently published papers on the target sample, modeling of the nulled disk images, and initial results such as the detection of warm dust around η Corvi. Recently a paper was published on the data pipeline and on-sky performance. An additional paper is in preparation on β Leo. We will discuss the scientific and programmatic context for the LBTI project, and we will report recent progress, new results, and plans for the science verification phase that started in February 2016, and for the survey.
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.
Transition disks, protoplanetary disks with inner clearings, are promising objects in which to directly image forming planets. The high contrast imaging technique of non-redundant masking is well posed to detect planetary mass companions at several to tens of AU in nearby transition disks. We present non-redundant masking observations of the T Cha and LkCa 15 transition disks, both of which host posited sub-stellar mass companions. However, due to a loss of information intrinsic to the technique, observations of extended sources (e.g. scattered light from disks) can be misinterpreted as moving companions. We discuss tests to distinguish between these two scenarios, with applications to the T Cha and LkCa 15 observations. We argue that a static, forward-scattering disk can explain the T Cha data, while LkCa 15 is best explained by multiple orbiting companions.
The next generation of extremely large telescopes (ELTs) have the potential to image habitable rocky planets, if suitably optimized. This will require the development of fast high order "extreme" adaptive optics systems for the ELTs. Located near the excellent site of the future GMT, the Magellan AO system (MagAO) is an ideal on-sky testbed for high contrast imaging development. Here we discuss planned upgrades to MagAO. These include improvements in WFS sampling (enabling correction of more modes) and an increase in speed to 2000 Hz, as well as an H2RG detector upgrade for the Clio infrared camera. This NSF funded project, MagAO-2K, is planned to be on-sky in November 2016 and will significantly improve the performance of MagAO at short wavelengths. Finally, we describe MagAO-X, a visible-wavelength extreme-AO "afterburner" system under development. MagAO-X will deliver Strehl ratios of over 80% in the optical and is optimized for visible light coronagraphy.
The Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS) program on the Large Binocular Telescope Interferometer (LBTI) will survey nearby stars for faint exozodiacal dust (exozodi). This warm circumstellar dust, analogous to the interplanetary dust found in the vicinity of the Earth in our own system, is produced in comet breakups and asteroid collisions. Emission and/or scattered light from the exozodi will be the major source of astrophysical noise for a future space telescope aimed at direct imaging and spectroscopy of terrestrial planets (exo- Earths) around nearby stars. About 20% of nearby field stars have cold dust coming from planetesimals at large distances from the stars (Eiroa et al. 2013, A&A, 555, A11; Siercho et al. 2014, ApJ, 785, 33). Much less is known about exozodi; current detection limits for individual stars are at best ~ 500 times our solar system's level (aka. 500 zodi). LBTI-HOSTS will be the first survey capable of measuring exozodi at the 10 zodi level (3σ). Detections of warm dust will also reveal new information about planetary system architectures and evolution. We will describe the motivation for the survey and progress on target selection, not only the actual stars likely to be observed by such a mission but also those whose observation will enable sensible extrapolations for stars that will not be observed with LBTI. We briefly describe the detection of the debris disk around η Crv, which is the first scientific result from the LBTI coming from the commissioning of the instrument in December 2013, shortly after the first time the fringes were stabilized.
One of the primary goals of exoplanet science is to find and characterize habitable planets, and direct imaging will play a key role in this effort. Though imaging a true Earth analog is likely out of reach from the ground, the coming generation of giant telescopes will find and characterize many planets in and near the habitable zones (HZs) of nearby stars. Radial velocity and transit searches indicate that such planets are common, but imaging them will require achieving extreme contrasts at very small angular separations, posing many challenges for adaptive optics (AO) system design. Giant planets in the HZ may even be within reach with the latest generation of high-contrast imagers for a handful of very nearby stars. Here we will review the definition of the HZ, and the characteristics of detectable planets there. We then review some of the ways that direct imaging in the HZ will be different from the typical exoplanet imaging survey today. Finally, we present preliminary results from our observations of the HZ of α Centauri A with the Magellan AO system’s VisAO and Clio2 cameras.
MagAO is the new adaptive optics system with visible-light and infrared science cameras, located on the 6.5-m Magellan “Clay” telescope at Las Campanas Observatory, Chile. The instrument locks on natural guide stars (NGS) from 0th to 16th R-band magnitude, measures turbulence with a modulating pyramid wavefront sensor binnable from 28×28 to 7×7 subapertures, and uses a 585-actuator adaptive secondary mirror (ASM) to provide at wavefronts to the two science cameras. MagAO is a mutated clone of the similar AO systems at the Large Binocular Telescope (LBT) at Mt. Graham, Arizona. The high-level AO loop controls up to 378 modes and operates at frame rates up to 1000 Hz. The instrument has two science cameras: VisAO operating from 0.5-1μm and Clio2 operating from 1-5 μm. MagAO was installed in 2012 and successfully completed two commissioning runs in 2012-2013. In April 2014 we had our first science run that was open to the general Magellan community. Observers from Arizona, Carnegie, Australia, Harvard, MIT, Michigan, and Chile took observations in collaboration with the MagAO instrument team. Here we describe the MagAO instrument, describe our on-sky performance, and report our status as of summer 2014.
The Thermal Infrared imager for the GMT which provides Extreme contrast and Resolution (TIGER) is intended as a
small-scale, targeted instrument capable of detecting and characterizing exoplanets and circumstellar disks, around both
young systems in formation, and more mature systems in the solar neighborhood. TIGER can also provide general
purpose infrared imaging at wavelengths from 1.5-14 μm. The instrument will utilize the facility adaptive optics (AO)
system. With its operation at NIR to MIR wavelengths (where good image quality is easier to achieve), and much of the
high-impact science using modestly bright guide stars, the instrument can be used early in the operation of the GMT.
The TIGER concept is a dual channel imager and low resolution spectrometer, with high contrast modes of observations
to fulfill the above science goals. A long wavelength channel (LWC) will cover 7-14 μm wavelength, while a short
wavelength channel (SWC) will cover the 1.5-5 μm wavelength region. Both channels will have a 30° FOV. In addition
to imaging, low-resolution spectroscopy (R=300) is possible with TIGER for both the SWC and LWC, using insertable
grisms.
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.
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 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.
The STIS coronagraph performance is measured as a function of angle from the star, reaching 1×10-8 per resolution element compared to the total stellar flux at 2 arcsec with optimal PSF subtraction. Highly structured envelopes, disks, jets and
planetary clearings have been detected. Estimates of planet detectability with NGST show that Jupiter mass objects around the nearest stars should be detectable.
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