The Orbiting Carbon Observatory-3 (OCO-3) was launched on 04 May 2019 and provides a new perspective to the important task of studying atmospheric carbon dioxide (CO2) as well as solar-induced chlorophyll fluorescence (SIF), a bonus product, from space. The flight spare three-channel grating spectrometer instrument built for OCO-2 has been adapted for use on the International Space Station (ISS) as OCO-3 by modifying the entrance optics, using a new calibrator assembly, incorporating a two-axis pointing mirror assembly (PMA), and adding two context cameras. The ISS’ recessing orbit allows measurements to be collected from dawn to dusk in the equatorial to northern & southern mid-latitude regions and the PMA enables a new snapshot area mapping mode where ~80 km x ~80 km areas can be examined in more detail. The OCO-3 payload underwent an extensive ground test and calibration program in a 3 m diameter thermal vacuum chamber. The chamber has a port/window that allowed optical ground support equipment, including a heliostat, to illuminate the instrument under operating environmental conditions. The payload’s performance in space during the in-orbit checkout (IOC) period compares favorably with ground test results. Initial and not-yet-fully-calibrated retrieved estimates of the column-averaged dry air mole fraction of CO2 (XCO2) are reasonable when compared to ground-based measurements. SIF estimates show clear contrast between areas of high and low vegetation. There is high confidence that the three-year prime mission will deliver the data needed for science/research, data applications, and informed decision-making.
This paper provides an overview of technology development for the Terrestrial Planet Finder Interferometer (TPF-I). TPF-I is a mid-infrared space interferometer being designed with the capability of detecting Earth-like planets in the habitable zones around nearby stars.
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.
In 2009 the Astrophysics Division at NASA Headquarters established the Strategic Astrophysics Technology (SAT) solicitation as a new technology maturation program to fill the needed gap for mid-Technology Readiness Level (TRL) levels (3≤ TRL <6). In three full proposal selection cycles since the inception of this program, more than 40 investigations have been selected, many meritorious milestones have been met and advances have been achieved. In this paper, we review the process of establishing technology priorities, the management of technology advancements and milestones, and the incipient success of some of these investigations in light of the need of future space missions.
We present and compare experimental results in high contrast imaging representing the state of the art in coronagraph and starshade technology. These experiments have been undertaken with the goal of demonstrating the capability of detecting Earth-like planets around nearby Sun-like stars. The contrast of an Earth seen in reflected light around a Sun-like star would be about 1.2 × 10−10. Several of the current candidate technologies now yield raw contrasts of 1.0 × 10−9 or better, and so should enable the detection of Earths, assuming a gain in sensitivity in post-processing of a factor of 10. We present results of coronagraph and starshade experiments conducted at visible and infrared wavelengths. Cross-sections of dark fields are directly compared as a function of field angle and bandwidth. The strength and differences of the techniques are compared.
Small-angle coronagraphy is technically and scientifically appealing because it enables the use of smaller telescopes,
allows covering wider wavelength ranges, and potentially increases the yield and completeness of circumstellar
environment – exoplanets and disks – detection and characterization campaigns. However, opening up
this new parameter space is challenging. Here we will review the four posts of high contrast imaging and their
intricate interactions at very small angles (within the first 4 resolution elements from the star). The four posts
are: choice of coronagraph, optimized wavefront control, observing strategy, and post-processing methods. After
detailing each of the four foundations, we will present the lessons learned from the 10+ years of operations of
zeroth and first-generation adaptive optics systems. We will then tentatively show how informative the current
integration of second-generation adaptive optics system is, and which lessons can already be drawn from this
fresh experience. Then, we will review the current state of the art, by presenting world record contrasts obtained
in the framework of technological demonstrations for space-based exoplanet imaging and characterization mission
concepts. Finally, we will conclude by emphasizing the importance of the cross-breeding between techniques
developed for both ground-based and space-based projects, which is relevant for future high contrast imaging
instruments and facilities in space or on the ground.
The direct imaging of planets around nearby stars is exceedingly difficult. Only about 14 exoplanets have been
imaged to date that have masses less than 13 times that of Jupiter. The next generation of planet-finding
coronagraphs, including VLT-SPHERE, the Gemini Planet Imager, Palomar P1640, and Subaru HiCIAO have
predicted contrast performance of roughly a thousand times less than would be needed to detect Earth-like
planets. In this paper we review the state of the art in exoplanet imaging, most notably the method of Locally
Optimized Combination of Images (LOCI), and we investigate the potential of improving the detectability of
faint exoplanets through the use of advanced statistical methods based on the concepts of the ideal observer
and the Hotelling observer. We propose a formal comparison of techniques using a blind data challenge with an
evaluation of performance using the Receiver Operating Characteristic (ROC) and Localization ROC (LROC)
curves. We place particular emphasis on the understanding and modeling of realistic sources of measurement
noise in ground-based AO-corrected coronagraphs. The work reported in this paper is the result of interactions
between the co-authors during a week-long workshop on exoplanet imaging that was held in Squaw Valley,
California, in March of 2012.
We present the results of the fifth Interferometric Imaging Beauty Contest. The contest consists in blind imaging of test data sets derived from model sources and distributed in the OIFITS format. Two scenarios of imaging with CHARA/MIRC-6T were offered for reconstruction: imaging a T Tauri disc and imaging a spotted red supergiant. There were eight different teams competing this time: Monnier with the software package MACIM; Hofmann, Schertl and Weigelt with IRS; Thiebaut and Soulez with MiRA ; Young with BSMEM; Mary and Vannier with MIROIRS; Millour and Vannier with independent BSMEM and MiRA entries; Rengaswamy with an original method; and Elias with the radio-astronomy package CASA. The contest model images, the data delivered to the contestants and the rules are described as well as the results of the image reconstruction obtained by each method. These results are discussed as well as the strengths and limitations of each algorithm.
A flower-like starshade positioned between a star and a space telescope is an attractive option for blocking the starlight
to reveal the faint reflected light of an orbiting Earth-like planet. Planet light passes around the petals and directly enters
the telescope where it is seen along with a background of scattered light due to starshade imperfections. We list the
major perturbations that are expected to impact the performance of a starshade system and show that independent models
at NGAS and JPL yield nearly identical optical sensitivities. We give the major sensitivities in the image plane for a
design consisting of a 34-m diameter starshade, and a 2-m diameter telescope separated by 39,000 km, operating
between 0.25 and 0.55 um. These sensitivities include individual petal and global shape terms evaluated at the inner
working angle. Following a discussion of the combination of individual perturbation terms, we then present an error
budget that is consistent with detection of an Earth-like planet 26 magnitudes fainter than its host star.
Optical long baseline interferometry is a technique that has generated almost 850 refereed papers to date.
The targets span a large variety of objects from planetary systems to extragalactic studies and all branches of
stellar physics. We have created a database hosted by the JMMC and connected to the Optical Long Baseline
Interferometry Newsletter (OLBIN) web site using MySQL and a collection of XML or PHP scripts in order to
store and classify these publications. Each entry is defined by its ADS bibcode, includes basic ADS informations
and metadata. The metadata are specified by tags sorted in categories: interferometric facilities, instrumentation,
wavelength of operation, spectral resolution, type of measurement, target type, and paper category, for example.
The whole OLBIN publication list has been processed and we present how the database is organized and can
be accessed. We use this tool to generate statistical plots of interest for the community in optical long baseline
interferometry.
We present the results of the fourth Optical/IR Interferometry Imaging Beauty Contest. The contest consists
of blind imaging of test data sets derived from model sources and distributed in the OI-FITS format. The test
data consists of spectral data sets on an object "observed" in the infrared with spectral resolution. There were 4
different algorithms competing this time: BSMEM the Bispectrum Maximum Entropy Method by Young, Baron
& Buscher; RPR the Recursive Phase Reconstruction by Rengaswamy; SQUEEZE a Markov Chain Monte Carlo
algorithm by Baron, Monnier & Kloppenborg; and, WISARD theWeak-phase Interferometric Sample Alternating
Reconstruction Device by Vannier & Mugnier. The contest model image, the data delivered to the contestants
and the rules are described as well as the results of the image reconstruction obtained by each method. These
results are discussed as well as the strengths and limitations of each algorithm.
The Optical Long Baseline Interferometry News (OLBIN) is a website and forum for scientists, engineers, and
students who share a common interest in long-baseline stellar interferometry. Through OLBIN you will find
links to projects devoted to stellar interferometry, as well as news items, recent papers and preprints, notices of
upcoming meetings, and resources for further research. This paper describes the history of the website, how it
has evolved to serve the community, and the current plans for its future development. The website can be found
at http://olbin.jpl.nasa.gov/.
The Terrestrial Planet Finder (TPF) was proposed as a mission concept to the 2000 Decadal Survey, and received
a very high ranking amongst the major initiatives that were then reviewed. As proposed, it was a formationflying
array of four 3.5-m class mid-infrared telescopes, linked together as an interferometer. Its science goal
was to survey approximately 150 nearby stars for the presence of Earth-like planets, to detect signs of life or
habitability, and to enable revolutionary advances in high angular resolution astrophysics. The Decadal Survey
Committee recommended that $200M be invested to advance TPF technology development in the Decade of
2000-2010. This paper presents the results of NASA's investment.
We present the results of the third Optical/IR Interferometry Imaging Beauty Contest. A formal comparison is
presented of the performance of algorithms used for imaging data from optical/infrared long-baseline interferometers.
The contest consists of blind imaging of test data sets derived from model sources and distributed in the
OI-FITS format. The test data consisted of datasets on two objects each "observed" in J, H, and K bands. The
majority of the entries produced accurate reconstructions of the initial models. Each of the methods presented
is discussed.
The Fourier-Kelvin Stellar Interferometer (FKSI) mission is a two-telescope infrared space interferometer with a 12.5
meter baseline on a boom, operating in the spectral range 3 to 8 (or 10) microns, and passively cooled to about 60 K.
The main goals for the mission are the measurement and characterization of the exozodiacal emission around nearby
stars, debris disks, and the atmospheres of known exoplanets, and the search for Super Earths around nearby stars. We
discuss progress on this mission in the context of the upcoming Decadal Survey, in particular how FKSI is ideally suited
to be an Exoplanet Probe mission in terms of crucial observations which should be done before a flagship mission can be
undertaken, as well as technical readiness, cost, and risk.
Modal filters are necessary to the proposed high-performance mid-infrared nulling interferometers, because they can
help achieve deeper interferometric nulls. Silver halide fibers of composition AgClxBr1-x(0
This paper provides an overview of technology development for the Terrestrial Planet Finder Interferometer
(TPF-I). TPF-I is a mid-infrared space interferometer being designed with the capability of detecting Earth-like
planets in the habitable zones around nearby stars. The overall technology roadmap is presented and progress
with each of the testbeds is summarized.
Infrared interferometric nulling is a promising technology for exoplanet detection. Nulling
research for the Terrestrial Planet Finder Interferometer has explored several interferometer architectures at
the Jet Propulsion Laboratory (JPL). The most recent efforts have focused on an architecture which
employs a geometric field flip to achieve the necessary π phase delay in the interferometer. The periscope
design currently in use allows for a completely achromatic phase flip. Deep interferometric nulling
requires optical path stability, precision optical alignment, intensity balancing, and dispersion correction.
This paper will discuss recent efforts to implement a precision optical alignment, stabilize the
interferometer environment, implement optical path metrology, control intensity balance, and compensate
for dispersion introduced by beamsplitter mismatch.
This paper provides an overview of technology development for the Terrestrial Planet Finder Interferometer
(TPF-I). TPF-I is a mid-infrared space interferometer being designed with the capability of detecting Earth-like
planets in the habitable zones around nearby stars. The overall technology roadmap is presented and progress
with each of the testbeds is summarized. The current interferometer architecture, design trades, and the viability
of possible reduced-scope mission concepts are also presented.
Initial high-fidelity, flight-like ground demonstrations of precision formation flying spacecraft are presented. In
these demonstrations, maneuvers required for distributed spacecraft interferometry, such as for the Terrestrial
Planet Finder Interferometer, were performed to near-flight precision. Synchronized formation rotations for
"on-the-fly" observations require the highest precision. For this maneuver, ground demonstration performance
requirements are 5 cm in relative position and 6 arc minutes in attitude. These requirements have been met for
initial demonstrations of formation-keeping and synchronized formation rotations.
The maneuvers were demonstrated in the Formation Control Testbed (FCT). The FCT currently consists
of two, five degree-of-freedom, air bearing-levitated robots. The final sixth degree-of-freedom is being added in
August 2007. Each robot has a suite of flight-like avionics and actuators, including a star tracker, fiber-optic
gyroscopes, reaction wheels, cold-gas thrusters, inter-robot communication, and on-board computers that run
the Formation and Attitude Control System (FACS) software.
The FCT robots and testbed environment are described in detail. Then several initial demonstrations results
are presented, including (i) a sub-millimeter formation sensor, (ii) an algorithm for synchronizing control cycles
across multiple vehicles, (iii) formation keeping, (iv) reactive collision avoidance, and (iv) synchronized formation
rotations.
This paper reviews recent progress with technology being developed for the Terrestrial Planet Finder Interferometer (TPF-I). TPF-I is a mid-infrared space interferometer being designed with the capability of detecting Earth-like planets in the habitable zones around nearby stars. TPF-I is in the early phase of its development. The science requirements of the mission are described along with the current design of the interferometer. The goals of the nulling and formation-flying testbeds are reviewed. Progress with TPF-I technology milestones are highlighted.
We present a formal comparison of the performance of algorithms used for synthesis imaging with optical/infrared long-baseline interferometers. Five different algorithms are evaluated based on their performance with simulated test data. Each set of test data is formatted in the OI-FITS format. The data are calibrated power spectra and bispectra measured with an array intended to be typical of existing imaging interferometers. The strengths and limitations of each algorithm are discussed.
KEYWORDS: Planets, Stars, Space operations, Interferometers, Nulling interferometry, Computer simulations, Interferometry, Robots, Telescopes, Control systems
The interferometric version of the Terrestrial Planet Finder (TPF-I) has the potential to find and characterize earth-sized
planets in the habitable zones of over 250 nearby stars and to search for life using biomarkers in the atmospheres of any
planets found. The scientific case for such a mission continues to be strengthened by on-going progress in the detection
of planets via indirect means. This paper summarizes the status of TPF-I, illustrative scientific requirements for the
mission, and its enabling technologies.
This paper presents an overview of contributions in astrophysics made since 2004 through the use of long-baseline
optical/infrared interferometers. Emphasis is placed on new results at near- and mid-infrared wavelengths. These
results include new insights into our understanding of Cepheid and Mira variables, Young Stellar Objects, dust
shells, spectroscopic binaries, and the limb-darkening of rapidly rotating stars. Plans for future work are also
described.
The Antarctic Planet Interferometer is a concept for an instrument designed to detect and characterize extrasolar planets by exploiting the unique potential of the best accessible site on earth for thermal infrared interferometry. High-precision interferometric techniques under development for extrasolar planet detection and characterization (differential phase, nulling and astrometry) all benefit substantially from the slow, low-altitude turbulence, low water vapor content, and low temperature found on the Antarctic plateau. At the best of these locations, such as the Concordia base being developed at Dome C, an interferometer with two-meter diameter class apertures has the potential to deliver unique science for a variety of topics, including extrasolar planets, active galactic nuclei, young stellar objects, and protoplanetary disks.
We present a formal comparison of the performance of algorithms used for synthesis imaging with optical/infrared long-baseline interferometers. Five different algorithms are evaluated based on their performance with simulated test data. Each set of test data is formatted in the OI-FITS format. The data are calibrated power spectra and bispectra measured with an array intended to be typical of existing imaging interferometers. The strengths and limitations of each algorithm are discussed.
We report on the progress in developing cryogenic delay lines and
integrated optics components. These are some of the critical components needed to enable far-IR direct-detection interferometers. To achieve background-limited performance in the 40 to 400 μm region, th einterferometer optics and delay lines must be cooeld to near liquid Helium temperatures. Our cryogenic delay line designs incorporate a number of novel features and has been operated at liquid nitrogen temperatures. Our integrated optics effort has focued on producing single-mode spatial filters and beam combiners.
Laser induced, micro-chemical etching is a promising new technology that can be used to fabricate three dimensional structures many millimeters across with micrometer accuracy. Laser micromachining possesses a significant edge over more conventional techniques. It does not require the use of masks and is not confined to crystal planes. A non-contact process, it eliminates tool wear and vibration problems associated with classical milling machines. At the University of Arizona we have constructed the first such laser micromaching system optimized for the fabrication of THz and far IR waveguide and quasi-optical components. Our system can machine many millimeters across down to a few microns accuracy in a short time, with a remarkable surface finish. This paper presents the design, operation and performance of our system, and its applications to waveguide devices for sub millimeter and far IR interferometry.
A simple desktop optical interferometer is described and demonstrated as a teaching tool for concepts of long-baseline stellar interferometry. The interferometer is compact, portable, and easily aligned. It sits on a base 8" x 10" and uses an aperture mask which is mounted to rotate within a precision ball-bearing. Fringes produced from an artificial star are observed through a microscope by means of a video camera and are displayed on an overhead television monitor. When the aperture mask is rotated rapidly, the rotating fringe patterns seen on the monitor are observed to synthesize sources that are unresolved by individual holes in the mask. Fringes from an artificial double star are used to illustrate
the relationship between fringe visibility and source structure and to demonstrate image synthesis.
Four teams incorporating scientists and engineers from more than 50 universities and 20 engineering firms have assessed techniques for detecting and characterizing terrestrial planets orbiting nearby stars. The primary conclusion from the effort of the past two years is that with suitable technology investment starting now, a mission to detect terrestrial planets around 150 nearby stars could be launched within a decade. Missions of smaller scale could carry out more modest programs capable of detecting and characterizing gas giant planets around tens of stars and of detecting terrestrial planets around the nearest stars.
The Palomar Testbed Interferometer is a long-baseline near- infrared interferometer operating at Palomar Observatory, CA. The interferometer has a maximum baseline of 110 m, 40- cm collecting apertures, and active fringe tracking. It also incorporates a dual-star architecture to enable cophasing and narrow-angle astrometry. We will discuss recent system improvements and engineering results. These include upgrades to allow for longer coherent integration times, H band operation, and cophasing using delay line feedforward. Recent engineering tests of astrometry in dual-star mode have shown a night-to-night repeatability of 100 (mu) as on a bright test target. Several new observation planning tools have been developed, and data reduction tools have been automated to allow fully pipelined nightly reductions and archiving.
The Palomar Testbed Interferometer is a long-baseline interferometer that uses both phase and group-delay measurements for narrow-angle astrometry. The group-delay measurements are performed using 5 spectral channels across the band from 2.0 to 2.4 micrometers . Group delay is estimated from phasors (sine and cosine of fringe phase) calculated for each spectral channel using pathlength modulation of one wavelength. Normally the group delay is estimated to be the delay corresponding to the peak of the power spectrum of these complex phasors. The Fourier transform does not however yield a least-squares estimate of the delay. Nevertheless, the precision of phase estimation can be achieved in a group-delay estimate using a least-squares approach. We describe the least-squares group-delay estimator that has been implemented at PTI and illustrate its performance as applied to narrow-angle astrometry.
We discuss concepts for deploying direct-detection interferometers in space which are optimized for the wavelength range 40 micrometers to 500 micrometers . In particular, we introduce two missions in NASA's current strategic plan: SPIRIT (SPace InfraRed Interferometric Telescope) and SPECS (Submillimeter Probe of the Evolution of Cosmic Structure).
There are difficult problems involved in building a near-infrared interferometer which uses more than two elements simultaneously. These problems have been overcome at the Cambridge Optical Aperture Synthesis Telescope(COAST). This has allowed us to make the first closure phase measurements on an astronomical source in the infrared.
We describe a scheme for fast, low noise readout of an infrared focal-plane array detector, capable of adequately sampling pupil plane fringes on three simultaneous baselines, as well as a procedure for aligning a many-component beam-combiner in the infrared. Finally, the performance of the working COAST infrared system is discussed.
A low-resolution CCD spectrometer has been installed at COAST to provide multi-wavelength fringe measurements across the band 650-950 nm. The measurements are based on the analysis of time-series of channeled spectra. Laboratory tests and stellar observations are presented. The advantages and limitations of the system are discussed.
Visibility measurements obtained with optical astronomical interferometers are corrupted by random wavefront distortions of atmospheric origin. In this paper we discus how spatial filtering using pinholes can lead to increased measured visibility, improved signal-to-noise ratio and reduced dependence on seeing fluctuations. The potential for calibrating visibility measurements without resorting to a separate calibrator target is also discussed. Results of preliminary pinhole experiments carried out with the Cambridge Optical Aperture Synthesis Telescope are presented.
This paper reviews the current performance of the Cambridge Optical Aperture Synthesis Telescope as an imaging array. Tests of the hardware and methods of measuring fringe visibility and closure phase are described in the context of prospects for a Large Optical Array.
The Cambridge optical aperture synthesis telescope (COAST) is a four element interferometer which measures visibility amplitudes and closure-phases. It produced its first images in 1995 and is now in a complete form, very similar to the original conception. In this paper we discuss the design and current status of the interferometer.
The Cambridge optical aperture synthesis telescope (COAST) has now been developed to the point where stellar images with a resolution of 20 mas can be produced in a routine manner. Based upon our experiences in the design and commissioning of COAST this paper discusses the possible design of a next generation interferometer.
In September 1995 the Cambridge optical aperture synthesis telescope (COAST) became the first optical interferometer to produce an image of a stellar source from phase-closure and visibility amplitude measurements. These observations demonstrated for the first time the feasibility of operating long-baseline optical/near-infrared interferometers for high dynamic range high-resolution imaging. Here we present these and subsequent observations made with COAST and describe the methods used to analyze such data.
This paper describes the present status of the Grand Interferometre a 2 Telescopes (GI2T). We review the general features of this instrument and present the scientific programs pursued by our group. Attention is given here to procedures of instrumental and visibility calibration, including the response of both the detector and spectrometer. We discuss the method of data analysis and the attainable accuracy of astrophysical parameters. The current limitations of the GI2T and development of our new optical table are presented.
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