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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

The James Webb Space Telescope: Mission Overview and Status

The James Webb Space Telescope (JWST) is the infrared successor to the Hubble Space Telescope. It is a cryogenic infrared space observatory with a 25 sq. m aperture (6 m telescope yielding diffraction limited angular resolution at a wavelength of 2 micron. The science instrument payload includes three passively cooled near-infrared instruments providing broad- and narrow-band imagery, coronagraphy, as well as multi object and integral-field spectroscopy over the 0.6 < 0 < 5.0 micron spectrum. An actively cooled mid-infrared instrument provides broad-band imagery, coronagraphy, and integral-field spectroscopy over the 5.0 < 0 < 29 micron spectrum. The JWST is being developed by NASA, in partnership with the European and Canadian Space Agencies, as a general user facility with science observations to be proposed by the international astronomical community in a manner similar to the Hubble Space Telescope. Technology development and mission design are complete, and construction is underway in all areas of the program. The JWST is on schedule to reach launch readiness during 2014.

Greenhouse, Matthew A.↗
NASA NTRS2011

The James Webb Space Telescope: Mission Overview and Status

The James Webb Space Telescope (JWST) is the Infrared successor to the Hubble Space Telescope. It is a cryogenic infrared space observatory with a 25 sq m aperture (6 m class) telescope yielding diffraction limited angular resolution at a wave1ength of 2 micron. The science instrument payload includes three passively cooled near-infrared instruments providing broad- and narrow-band imagery, coronagraphy, as well as multi-object and integral-field spectroscopy over the 0.6 <lambda < 5.0 micron spectrum. An actively cooled mid-infrared instrument provides broad-band imagery, coronagraphy, and integral-field spectroscopy over the 5.0 < lambda < 29 micron spectrum. The JWST is being developed by NASA, in partnership with the European and Canadian Space Agencies, as a general user facility with science observations to be proposed by the international astronomical community in a manner similar to the Hubble Space Telescope. Technology development and mission design are complete, and construction is underway in all areas of the program.

Greenhouse, Matthew A.↗
NASA NTRS2015

Studies of the Effects of Control Bandwidth and Dark-Hole Size on the HCIT Contrast Performance

We have carried out both theoretical and experimental studies of the sensitivity of dark hole contrast to the control bandwidth and dark-hole dimensions in high-contrast broadband stellar coronagraphy. We have evaluated the performance of DM actuator solutions in the presence of occulting mask defects using one to five 2% -wide bands spanning a 10% bandpass. We have also investigated the dependence of the HCIT contrast performance on the size of dark -hole area including large dark holes formed at the Nyquist limit of the DM.

exoplanets↗
DOE OSTI2021

Going Forward with the Nancy Grace Roman Space Telescope Transient Survey: Validation of Precision Forward-modeling Photometry for Undersampled Imaging

The Nancy Grace Roman Space Telescope (Roman) is an observatory for both wide-field observations and coronagraphy that is scheduled for launch in the mid-2020s. Part of the planned survey is a deep, cadenced field or fields that enable cosmological measurements with type Ia supernovae (SNe Ia). With a pixel scale of 0$_.^"$11, the Wide Field Instrument will be undersampled, presenting a difficulty for precisely subtracting the galaxy light underneath the SNe. We use simulated data to validate the ability of a forward-model code (such codes are frequently also called “scene-modeling” codes) to perform precision supernova photometry for the Roman SN survey. Our simulation includes over 760,000 image cutouts around SNe Ia or host galaxies (~10% of a full-scale survey). To have a realistic 2D distribution of underlying galaxy light, we use the VELA simulated high-resolution images of galaxies. We run each set of cutouts through our forward-modeling code which automatically measures time-dependent SN fluxes. Given our assumed inputs of a perfect model of the instrument point-spread functions and calibration, we find biases at the millimagnitude level from this method in four red filters (Y106, J129, H158, and F184), easily meeting the 0.5% Roman inter-filter calibration requirement for a cutting-edge measurement of cosmological parameters using SNe Ia. Simulated data in the bluer Z087 filter shows larger ~ 2–3 mmg biases, also meeting this requirement, but with more room for improvement. Our forward-model code has been released on Zenodo.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Spectroscopic Fourth-order Coronagraph for the Characterization of Terrestrial Planets at Small Angular Separations from Host Stars

We propose a new approach for high-contrast imaging at the diffraction limit using segmented telescopes in a modest observation bandwidth. This concept, named “spectroscopic fourth-order coronagraphy,” is based on a fourth-order coronagraph with a focal-plane mask that modulates the complex amplitude of the Airy disk along one direction. While coronagraphs applying the complex amplitude mask can achieve the theoretical limit performance for any arbitrary pupils, the focal-plane mask severely limits the bandwidth. Here, focusing on the fact that the focal-plane mask modulates the complex amplitude along one direction, we noticed that the mask can be optimized for each spectral element generated by a spectrograph. We combine the fourth-order coronagraph with two spectrographs to produce a stellar spectrum on the focal plane and reconstruct a white pupil on the Lyot stop. Based on the wave-front analysis of an optical design applying an Offner-type imaging spectrograph, we found that the achievable contrast of this concept is 10{sup −10} at 1.2–1.5 times the diffraction limit over the wavelength range of 650–750 nm for the entrance pupil of the LUVOIR telescope. Thus, this coronagraph concept could bring new habitable planet candidates not only around G- and K-type stars beyond 20–30 pc but also around very nearby M-type stars. This approach potentially promotes the characterization of the atmospheres of nearby terrestrial planets with future on- and off-axis segmented large telescopes.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Autodifferentiable Spectrum Model for High-dispersion Characterization of Exoplanets and Brown Dwarfs

We present an autodifferentiable spectral modeling of exoplanets and brown dwarfs. This model enables a fully Bayesian inference of the high-dispersion data to fit the ab initio line-by-line spectral computation to the observed spectrum by combining it with the Hamiltonian Monte Carlo in recent probabilistic programming languages. An open-source code, ExoJAX, developed in this study, was written in Python using the GPU/TPU compatible package for automatic differentiation and accelerated linear algebra, JAX. We validated the model by comparing it with existing opacity calculators and a radiative transfer code and found reasonable agreements for the output. As a demonstration, we analyzed the high-dispersion spectrum of a nearby brown dwarf, Luhman 16 A, and found that a model including water, carbon monoxide, and H 2 /He collision-induced absorption was well fitted to the observed spectrum (R = 10 5 and 2.28-2.30 μm). As a result, we found that T0 = 1295$^{-32}_{+35}$ K at 1 bar and C/O = 0.62 ± 0.03, which is slightly higher than the solar value. This work demonstrates the potential of a full Bayesian analysis of brown dwarfs and exoplanets as observed by high-dispersion spectrographs and also directly imaged exoplanets as observed by high-dispersion coronagraphy.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1995

Detection of a very low mass companion to the astrometric binary Gliese 105A

Optical coronagraph images of the high proper motion astrometric binary Gl 105A reveal a very red companion, Gl 105C, located 3.27 arcsecs from Gl 105A at P.A. 287 deg. At this location, it is not clear whether Gl 105C can fully account for the astrometric perturbation of Gl 105A. Aperture photometry gives I(sub C) = 12.6 and R(sub C) - I(sub C) = 3.7 for Gl 105C, indicating that it is a very low mass M dwarf. Using the observed I(sub C), an empirical M(sub I) versus I-K relation, and an assumed distance of 8.2 pc to Gl 105A, M(sub K) = 9.7 is derived for Gl 105C. An empirical mass-M(sub K) relation for low-mass stars suggest a mass of 0.084 solar mass for Gl 105C, which is just above the minimum mass for stable hydrogen burning. Gl 105C was not detected in previous K-band searches; its detection demonstrates the usefulness of optical coronagraphy for identifying very low mass objects.

Golimowski, D. A.↗
NASA NTRS1998

Mid-Infrared Astronomy with the NGST

We present an overview of the science capabilities enabled by a mid-infrared camera/spectrometer on board the NGST. Even without full mid-IR optimization, a mid-infrared (5-30 microns) instrument on the NGST will be orders of magnitude more sensitive than any equivalent ground-based instrument/telescope combination. In the extragalactic arena, the mid-IR region is critical for a complete understanding of the or high-redshift universe, dusty star-formation regions at low and high redshifts, and starburst vs. AGN discrimination. In the local universe, great strides forward can be made using mid-IR imaging, spectroscopy, and coronagraphy of dusty and rocky disks of all ages, from protostellar to remnant debris disks. Near-neighbor detection and characterization can also be greatly advanced by mid-infrared observations.

Serabyn, E.↗
NASA NTRS2002

Coronagraphic Imaging with HST and STIS

Revealing faint circumstellar nebulosity and faint stellar or substellar companions to bright stars typically requires use of techniques for rejecting the direct, scattered, and diffracted light of the star. One such technique is Lyot coronagraphy. We summarize the performance of the white-light coronagraphic capability of the Space Telescope Imaging spectrograph, on board the Hubble Space Telescope.

Grady, C. A.↗
NASA NTRS2003

Coronagraphic Amplitude and Phase Correction for Detecting Planets

Detection of earth-like planets around other stars using coronagraphy requires the optical beam into the coronagraph to be extremely uniform in both phase and amplitude. Errors in phase can be corrected using a deformable mirror, and error in amplitude can be corrected using a spatial light modulator, both in the pupil plan,a. These corrections can be combined using a Michelson interferometer. If amplitude corrections of only a few percent range are needed, the required accuracy of 10 (circumflex) -4 can be obtained with spatial light modulators with the modest dynamic range of 8 bits.

Woodgate, Bruce E.↗
NASA NTRS2003

Pupil configurations for an interferometric TPF mission

The primary goal of the proposed Terrestrial Planet Finder mission is the direct detection of radiation from potential terrestrial planets orbiting around nearby stars. However, the faintness of the expected signals leads to very stringent technical requirements on the optical performance. As a result, both of the candidate approaches currently under active development by the TPF project, infrared nulling interferometry with separated aperture telescopes, and optical coronagraphy with a large singl aperture telescope, require complex optical systems which push the state of the art.

TPF interferometry Terrestrial Planet Finder↗
NASA NTRS2005

Terrestrial Planet Finder Coronagraph 2005: Overview of Technology Development and System Design Studies

Technology research, design trades, and modeling and analysis guide the definition of a Terrestrial Planet Finder Coronagraph Mission that will search for and characterize earth-like planets around near-by stars. Operating in visible wavebands, this mission will use coronagraphy techniques to suppress starlight to enable capturing and imaging the reflected light from a planet orbiting in the habitable zone of its parent star. The light will be spectrally characterized to determine the presence of life-indicating chemistry in the planet atmosphere.

coronagraph↗
NASA NTRS2011

Vacuum Nuller Testbed (VNT) Performance, Characterization and Null Control: Progress Report

Herein we report on the development. sensing and control and our first results with the Vacuum Nuller Testbed to realize a Visible Nulling Coronagraph (VNC) for exoplanet coronagraphy. The VNC is one of the few approaches that works with filled. segmented and sparse or diluted-aperture telescope systems. It thus spans a range of potential future NASA telescopes and could be Hown as a separate instrument on such a future mission. NASA/Goddard Space Flight Center (GSFC) has a well-established effort to develop VNC technologies. and has developed an incremental sequence of VNC testbeds to advance this approach and the enabling technologies associated with it. We discuss the continued development of the vacuum Visible Nulling Coronagraph testbed (VNT). Tbe VNT is an ultra-stable vibration isolated testbed that operates under closed-loop control within a vacuum chamber. It will be used to achieve an incremental sequence of three visible-light nulling milestones with sequentially higher contrasts of 10(sup 8), 10(sup 9) and ideally 10(sup 10) at an inner working angle of 2*lambda/D. The VNT is based on a modified Mach-Zehnder nulling interferometer, with a "W" configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters. We discuss the initial laboratory results, the optical configuration, critical technologies and the null sensing and control approach.

Lyon, Richard G.↗
NASA NTRS2012

High Contrast Vacuum Nuller Testbed (VNT) Contrast, Performance and Null Control

Herein we report on our contrast assessment and the development, sensing and control of the Vacuum Nuller Testbed to realize a Visible Nulling Coronagraphy (VNC) for exoplanet detection and characterization. Tbe VNC is one of the few approaches that works with filled, segmented and sparse or diluted-aperture telescope systems. It thus spans a range of potential future NASA telescopes and could be flown as a separate instrument on such a future mission. NASA/Goddard Space Flight Center has an established effort to develop VNC technologies, and an incremental sequence of testbeds to advance this approach and its critical technologies. We discuss the development of the vacuum Visible Nulling Coronagraph testbed (VNT). The VNT is an ultra-stable vibration isolated testbed that operates under closed-loop control within a vacuum chamber. It will be used to achieve an incremental sequence of three visible-light nulling milestones with sequentially higher contrasts of 10(exp 8), 10(exp 9) and ideally 10(exp 10) at an inner working angle of 2*lambda/D. The VNT is based on a modified Mach-Zehnder nulling interferometer, with a "W" configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters. We discuss the laboratory results, optical configuration, critical technologies and the null sensing and control approach.

Lyon, Richard G.↗
NASA NTRS2012

Building the James Webb Space Telescope

The James Webb Space Telescope is the scientific successor to the Hubble and Spitzer Space Telescopes. It will be a large (6.6m) cold (50K) telescope launched into orbit around the second Earth-Sun Lagrange point. It is a partnership of NASA with the European and Canadian Space Agencies. JWST will make progress In almost every area of astronomy, from the first galaxies to form in the early universe to exoplanets and Solar System objects. Webb will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Near-Infrared Imager and Slitless Spectrograph will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. The observatory Is confirmed for launch in 2018; the design is complete and it is in its construction phase. Innovations that make JWST possible include large-area low-noise infrared detectors, cryogenic ASICs, a MEMS micro-shutter array providing multi-object spectroscopy, a non-redundant mask for interferometric coronagraphy and diffraction-limited segmented beryllium mirrors with active wavefront sensing and control. Recent progress includes the completion of the mirrors, the delivery of the first flight instruments and the start of the integration and test phase.

Gardner, Jonathan P.↗
NASA NTRS2012

Status of the Visible Nulling Coronagraph Technology Demonstration Program

We report on the development, sensing and control of the Vacuum Nuller Testbed to realize a Visible Nulling Coronagraphy (VNC) for exoplanet detection and characterization. The VNC is one of the few approaches that works with filled, segmented and sparse or diluted-aperture telescope systems. It thus spans a range of potential future NASA telescopes and could be flown as a separate instrument on such a future mission. NASA/Goddard Space Flight Center has an established effort to develop VNC technologies, and an incremental sequence of testbeds to advance this approach and its critical technologies. We will highlight results demonstrating the achievement of our TDEM contrast milestones, and highlight the performance of our wavefront sensing and control concept.

Clampin, M.↗
NASA NTRS2012

Studies of Supernovae, SNR, and Dust with the James Webb Space Telescope

The james Webb Space Telescope (JWST) will provide breakthrough capabilities for the study of supernovae and supernova remnants, as well as many other science objectives. JWST is a large aperture, cryogenic, infrared-optimized general purpose space observatory under construction by NASA, ESA, and CSA for launch in 2018. The JWST instrumentation will provide imaging, coronagraphy, and spectroscopy between 6000A to 29 microns. This spectral region contains many atomic, molecular, and particulate diagnostics that are especially relevant for the study of dust formation. The spectroscopic capabilities include velocity resolution down to approx. 100 km/sec, a near-IR multi-object spectrograph with a approx. 3x3 arcmin field of view array of approx. 250,000 addressable shutters, and near-IR and mid-IR approx. 3x3 arcsec integral field units. The JWST telescope will have a 6.5m-diameter segmented primary mirror and will be diffraction-limited at 2 microns (PSF FWHM - 0.07 arcsec). The imaging and spectroscopic sensitivities will be about 100x lower than previous capabilities in the near- and mid-IR. The JWST observatory will be placed in a L2 orbit by an Ariane 5 launch vehicle provided by ESA. The JWST telescope and instruments will be passively cooled to approx. 40K by a sunshield that will be unfolded after launch. The sunshield geometry limits the JWST pointing on the sky to be between 85 deg and 135 deg from the Sun. The observatory is designed for a 5-year prime science mission, with consumables for 10 years of science operations, and a Target of Opportunity response time of 48 hours.

Sonneborn, George↗
NASA NTRS2012

Operations Concept for Moving Target Observations with the James Webb Space Telescope

The James Webb Space Telescope (JWST) will provide breakthrough capabilities for the study of Solar System objects. JWST is a large aperture, cryogenic, infrared-optimized, general purpose space observatory under construction by NASA, ESA, and CSA for launch in 2018. The JWST instrumentation will provide imaging. coronagraphy, and spectroscopy between 6000A to 29 microns. This spectral region contains many atomic, molecular, and particulate diagnostics that are especially relevant for the study of gaseous, rocky and icy bodies in the Solar System. This talk describes the concept for observations of moving targets, including the system design for acquiring and tracking guide stars to hold the science target fIxed in the instrument field of view.

Sonneborne, George↗