Diffractive Interfero Coronagraph Exoplanet Resolver (DICER) is a notional infrared space observatory that would detect all habitable exoplanets within 10 pc of the Sun and determine whether there is ozone in their atmospheres. We are aiming at an approximate $1B target cost for a several year mission, and an observatory that easily fits in a Falcon heavy launch vehicle. Light (near 10 microns) is collected with two flat diffraction gratings that are each 10 meters long. Each grating feeds light into smaller focusing secondary optics that are 1 meter across. An achromatic interferometer (Dispersion Leverage Coronagraph, DLC) reduces the light from the host star by a factor of at least 105. A second high resolution spectrograph separates exoplanet light from the background. The one-dimensional diffraction limit of this system (0.1") is sufficient to resolve an Earth-like planet orbiting a Sun-like star at a distance of 10 pc. The gratings can be tilted to scan through a small range of wavelengths around 10 microns so that the ozone absorption line can be detected.
The Contemporaneous LEnsing Parallax and Autonomous TRansient Assay (CLEoPATRA) space mission concept is designed to provide variable-baseline simultaneous microlensing parallax measurements for NASA’s flagship Roman Space Telescope mission and for terrestrial telescopes. We here describe the design of the mission, including discussion of our efforts to develop the means to greatly reduce the data downlink bandwidth using artificial intelligence and modern fanless GPUs, FPGAs and Tensor Processing Units. We demonstrate a reduction of data downlinked by a factor of up to 28,000 permitting communications between Earth and a small, power-limited craft in deep space. We describe radiation testing of inferencing hardware, functionality of our artificial intelligence code, compressive sensing applied to photometric lightcurves and the implementation of new, integrated optics to permit a 20cm baffled telescope to fit fully inside a small scientific spacecraft.
KEYWORDS: Stars, Compressed sensing, Signal to noise ratio, Monte Carlo methods, Point spread functions, Error analysis, Sensors, Reconstruction algorithms, Data acquisition, Binary data
Compressive sensing (CS) is a unique mathematical technique for simultaneous data acquisition and compression. This technique is particularly apt for time-series photometric measurements; we apply CS to time-series photometric measurements specifically obtained due to gravitational microlensing events. We show the error sensitivity in detecting microlensing event parameters through simulation modeling. Particularly, we show the relation of both the amount of error and its impact on the microlensing parameters of interest. We derive statistical error bounds to apply those as a baseline for analyzing the effectiveness of CS application. Our results of single and binary microlensing events conclude that we can obtain error less than 1% over a three-pixel radius of the center of the microlensing star by using 25% Nyquist rate measurements.
We propose an architecture for the control system of BETTII,1 a far-infrared, balloon-borne interferometer with a baseline of 8 meters. This system involves multiple synchronized control loops for real-time pointing control and precise attitude knowledge. This will enable accurate phase estimation and control, a necessity for successful interferometry. We present the overall control strategy and describe our flight hardware in detail. We also show our current test setup and the first results of our coarse pointing loop.
The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-meter baseline far-infrared interferometer designed to fly on a high altitude balloon. BETTII uses a double-Fourier Michelson interferometer to simultaneously obtain spatial and spectral information on science targets; the long baseline permits subarcsecond angular resolution, a capability unmatched by other far-infrared facilities. This program started in 2011, and is now in the process of building and testing components of the mission, aiming for first flight in fall of 2015. This paper will provide an overview of the BETTII experiment, with a discussion of current progress and of future plans.
The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-meter baseline far-infrared
interferometer to fly on a high altitude balloon. Operating at wavelengths of 30-90 microns, BETTII will obtain spatial
and spectral information on science targets at angular resolutions down to less than half an arcsecond, a capability
unmatched by other far-infrared facilities. This requires attitude control of the gondola at the several arcsecond level,
and phase correction of the gondola attitude at a level of less than a tenth of an arcsecond, great challenges for a
lightweight balloon-borne system. We have designed a precision attitude determination system to provide gondola
attitude knowledge at a level of 2 milliarcseconds at rates up to 100Hz, with accurate absolute attitude determination at the half arcsecond level at rates of up to 10Hz. A multi-stage control system involving rigid body motion and tip-tiltpiston correction provides precision pointing stability to the level required for the far-infrared instrument to perform its spatial/spectral interferometry in an open-loop control. We present key aspects of the design of the attitude determination and control and its development status.
The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-meter baseline far-infrared
interferometer designed to fly on a high altitude balloon. BETTII uses a double-Fourier Michelson interferometer to
simultaneously obtain spatial and spectral information on science targets; the long baseline permits subarcsecond angular
resolution, a capability unmatched by other far-infrared facilities. Here, we present key aspects of the overall design of
the mission and provide an overview of the current status of the project. We also discuss briefly the implications of this
experiment for future space-based far-infrared interferometers.
KEYWORDS: Fourier transforms, Detection and tracking algorithms, Visibility, Actuators, Interferometry, Stars, Mirrors, Interferometers, Sensors, Signal to noise ratio
We present the design of a fringe tracking system for the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII). BETTII is a balloon- borne, far-infrared, 8 m-baseline interferometer with two 50 cm siderostats. Beams from the two arms are combined in the pupil plane to enable double-Fourier, spatio-spectral interferometry. To maintain the phase stability of the system, we need to actively correct of the optical path difference (OPD) between the two arms. The fringe-tracking system will work in the near-infrared and will use a reference star within the field of view to achieve two goals: overlap the beams coming from the two siderostats, and track the location of the central fringe packet, which is a measure of the OPD. The fringe tracker will share most of the optical train with the science instrument. This system is part of the overall control architecture that feeds fast steering tip/ tilt mirrors and a warm delay line to ensure proper beam combination and OPD control for the science instrument. This paper investigates the different sources of perturbations that are expected at float altitude, and derives the sensitivity of the fringe-tracking system. We show progress on validating our design using a visible light, broadband Mach-Zehnder interferometer that was developed at NASA/GSFC. This system demonstrates the viability of our OPD determination approach and provides a means of testing and characterizing several OPD determination and control algorithms.
We report here on some of the major astronomical observations obtained by the Keck Interferometer Nuller (KIN), the
high dynamic range instrument recombining the Keck Telescopes at wavelengths of 8 to 13 microns. A few science
targets were observed during the commissioning phase (2004-2007). These early observations aimed at demonstrating
the KIN’s ability to spatially resolve and characterize circumstellar dust emission around a variety of targets, ranging
from evolved stars to young debris disks. Science operations started then in 2008 with the more demanding KIN exozodi key science programs, augmented by observations of YSOs and hot debris disks between 2009 and 2011. The last
KIN observations were gathered in 2011B, and the interpretation of some of the results depicted here is still preliminary
(exo-zodi survey) or pending (complicated behavior observed in YSOs). We discuss in particular the initial results of the
KIN’s exo-zodi observations, which targeted a total of 40 nearby main sequence single stars. We look for trends in this
sample, searching for possible correlations between the measured KIN excesses and basic stellar properties such as
spectral type or the presence of dust inferred from separate observations.
The New Worlds, New Horizons report released by the Astronomy and Astrophysics Decadal Survey Board in 2010
listed the Wide Field Infrared Survey Telescope (WFIRST) as the highest-priority large space mission for the coming
decade. This observatory will provide wide-field imaging and slitless spectroscopy at near infrared wavelengths. The
scientific goals are to obtain a statistical census of exoplanets using gravitational microlensing, measure the expansion
history of and the growth of structure in the Universe by multiple methods, and perform other astronomical surveys to be
selected through a guest observer program. A Science Definition Team has been established to assist NASA in the
development of a Design Reference Mission that accomplishes this diverse array of science programs with a single
observatory. In this paper we present the current WFIRST payload concept and the expected capabilities for planet
detection. The observatory, with science goals that are complimentary to the Kepler exoplanet transit mission, is
designed to complete the statistical census of planetary systems in the Galaxy, from habitable Earth-mass planets to free
floating planets, including analogs to all of the planets in our Solar System except Mercury. The exoplanet microlensing
survey will observe for 500 days spanning 5 years. This long temporal baseline will enable the determination of the
masses for most detected exoplanets down to 0.1 Earth masses.
The Extrasolar Planet Observation Characterization and the Deep Impact Extended Investigation missions (EPOXI) are
currently observing the transits of exoplanets, a comet nucleus at short range, and Earth using the High Resolution
Instrument (HRI) - a 0.3 m f/35 telescope - on the Deep Impact flyby spacecraft. The HRI is in a permanently
defocused state with the instrument point of focus about 0.6 cm before the focal plane due to the use of a reference flat
mirror that became a powered optic due to thermal warping during ground thermal-vacuum testing. Consequently, the
point spread function (PSF) covers approximately nine pixels FWHM and is characterized by a patch with three-fold
symmetry due to the three-point support structures of the primary and secondary mirrors. The PSF is also strongly color
dependent varying in shape and size with change in filtration and target color. While defocus is highly desirable for
exoplanet transit observations to limit sensitivity to intra-pixel variation, it is suboptimal for observations of spatially
resolved targets. Consequently, all images used in our analysis of such objects were deconvolved with an instrument
PSF. The instrument PSF is also being used to optimize transit analysis. We discuss development and usage of an
instrument PSF for these observations.
The Fourier-Kelvin Stellar Interferometer (FKSI) is a structurally connected infrared space interferometer with 0.5 m
diameter telescopes on a 12.5 m baseline, and is passively cooled to ~ 60K. The FKSI operates in the thermal infrared
from 3-8 μm in a nulling (starlight suppressing) mode for the detection and characterization of exoplanets, debris disks,
and extrasolar zodiacal dust levels. The FKSI will have the highest angular resolution of any infrared space instrument
ever made with its nominal resolution of 40 mas at a 5 μm center wavelength. This resolution exceeds that of Spitzer by
a factor of 38 and JWST by a factor of 5. The FKSI mission is conceived as a "probe class" or "mid-sized" strategic
mission that utilizes technology advances from flagship projects like JWST, SIM, Spitzer, and the technology programs
of TPF-I/Darwin. During the past year we began investigating an enhanced version of FKSI with 1-2 m diameter
telescopes, passively cooled to 40K, on a 20-m baseline, with a sunshade giving a ± 45 degree Field-of-Regard. This
enhanced design is capable of detecting and characterizing the atmospheres of many 2 Earth-radius super-Earths and a
few Earth-twins. We will report progress on the design of the enhanced mission concept and current status of the
technologies needed for this mission.
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.
We report observations of the nova RS Ophiuchi using the Keck Interferometer Nuller (KIN) taken approximately
3.8 days following the most recent outburst that occurred on 2006 February 12. The KIN operates in N-band
from 8 to 12.5 μm in a nulling mode. In this mode the stellar light is suppressed by a destructive fringe, effectively
enhancing the contrast of the circumstellar material located near the star. In a second, constructive-fringe mode,
the instrument detects primarily the light from the central, bright source. These are the outer and inner spatial
regimes, respectively. We will describe the capabilities of the KIN, including these unique modes, and outline
how they were key in our discovery that dust was created between nova events. We also show how these first
results from the KIN are consistent with Spitzer data. The KIN data show evidence of enhanced neutral atomic
hydrogen emission and atomic metals including silicon located in the inner spatial regime (< 4 AU from theWD)
relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer
spatial region, centered at approximately ~ 17 AU from the WD, that are not found in the inner regime. The
KIN and Spitzer data suggest that these emissions were excited in the outer spatial regime before the blast wave
reached these regions. We describe the present results in terms of a new model for dust creation in recurrent
novae that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock
wave caused by the motion of the stars through the cool wind of the red giant star. These data show the power
and potential of the nulling technique which has been developed for the detection of Earth-like planets around
nearby stars for the Terrestrial Planet Finder Mission and Darwin missions.
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.
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.
The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for an imaging and nulling interferometer in the
near to mid-infrared spectral region (3-8 microns), and will be a scientific and technological pathfinder for upcoming
missions including TPF-I/DARWIN, SPECS, and SPIRIT. At NASA's Goddard Space Flight Center, we have
constructed a symmetric Mach-Zehnder nulling testbed to demonstrate techniques and algorithms that can be used to
establish and maintain the 104 null depth that will be required for such a mission. Among the challenges inherent in such
a system is the ability to acquire and track the null fringe to the desired depth for timescales on the order of hours in a
laboratory environment. In addition, it is desirable to achieve this stability without using conventional dithering
techniques. We describe recent testbed metrology and control system developments necessary to achieve these goals
and present our preliminary results.
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.
We present a comparative study of aperture-masking on the Keck-I telescope and adaptive optics with the Keck-II telescope. Recent results from an aperture-masking program at the Keck Observatory in the near-infrared amply demonstrate that this method occupies an important niche in achieving diffraction-limited images despite the many advances in adaptive optics technology. Examples of the efficacy of aperture-masking are the images of the persistent dust-producing Wolf-Rayet star WR 104 and the massive young star with IR excess, MWC 349A. Both these objects were resolved, providing fundamental new insights into their nature. Here we present images of these objects made using adaptive optics in the same wavelength band. These provide a unique opportunity for a direct comparison of two important and competing techniques for ground-based high-resolution imaging. From the AO images, we are unable to recover the gross morphology or detail seen in the aperture-masking results. We note that the AO program might have been hindered by less than ideal observing conditions.
We discuss work in progress on a near-infrared tunable bandpass filter for the Goddard baseline wide field camera concept of the Next Generation Space Telescope Integrated Science Instrument Module. This filter, the Demonstration Unit for Low Order Cryogenic Etalon (DULCE), is designed to demonstrate a high efficiency scanning Fabry-Perot etalon operating in interference orders 1 - 4 at 30 K with a high stability DSP based servo control system. DULCE is currently the only available tunable filter for lower order cryogenic operation in the near infrared. In this application, scanning etalons will illuminate the focal plane arrays with a single order of interference to enable wide field lower resolution hyperspectral imaging over a wide range of redshifts. We discuss why tunable filters are an important instrument component in future space-based observatories.
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