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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Waveguide Photonic Choke Joint with Wide Out-of-Band Rejection

A photonic choke joint structure with a wide-stop-band is proposed for use as a waveguide flange interface. The structure consists of arrays of square metal pillars arranged in a periodic pattern to suppress the dominant-mode wave propagation in parallel-plate waveguide over a wide frequency bandwidth. The measurement results at microwave frequencies confirm that the structure can provide broadband suppression of more than 56dB over 6.25 times its operating frequency. Applications at millimeter wavelength are discussed.

U-yen, Kongpop↗
NASA NTRS2015

Waveguide Photonic Choke Joint with Wide Out-of-Band Rejection

A photonic choke joint structure with a wide- stop-band is proposed for use as a waveguide flange interface. The structure consists of arrays of square metal pillars arranged in a periodic pattern to suppress the dominant-mode wave propagation in parallel-plate waveguide over a wide frequency bandwidth. The measurement results at microwave frequencies confirm the structure can provide broadband suppression, more than 56 dB over 6.25 times its operating frequency. Applications at millimeter wavelength are discussed.

U-yen, Kongpop↗
NASA NTRS2016

Wide-Field InfraRed Survey Telescope (WFIRST) Slitless Spectrometer: Design, Prototype, and Results

The slitless spectrometer plays an important role in the Wide-Field InfraRed Survey Telescope (WFIRST) mission for the survey of emission-line galaxies. This will be an unprecedented very wide field, HST quality 3D survey of emission line galaxies. The concept of the compound grism as a slitless spectrometer has been presented previously. The presentation briefly discusses the challenges and solutions of the optical design, and recent specification updates, as well as a brief comparison between the prototype and the latest design. However, the emphasis of this paper is the progress of the grism prototype: the fabrication and test of the complicated diffractive optical elements and powered prism, as well as grism assembly alignment and testing. Especially how to use different tools and methods, such as IR phase shift and wavelength shift interferometry, to complete the element and assembly tests. The paper also presents very encouraging results from recent element tests to assembly tests. Finally we briefly touch the path forward plan to test the spectral characteristic, such as spectral resolution and response.

Grism↗
NASA NTRS2017

Precision Pointing for the Wide-Field Infrared Survey Telescope (WFIRST)

The Wide-Field Infrared Survey Telescope (WFIRST) mission, scheduled for a mid-2020's launch, is currently in its definition phase. The mission is designed to investigate essential questions in the areas of dark energy, exoplanets, and infrared astrophysics. WFIRST will use a 2.4-meter primary telescope (same size as the Hubble Space Telescope's primary mirror) and two instruments: the Wide Field Instrument (WFI) and the Coronagraph Instrument (CGI). In order to ad-dress the critical science requirements, the WFIRST mission will conduct large-scale surveys of the infrared sky, requiring both agility and precision pointing (11.6 milli-arcsec stability, 14 milli-arcsec jitter). This paper describes some of the challenges this mission profile presents to the GNC subsystem, and some of the design elements chosen to accommodate those challenges. The high-galactic-latitude survey is characterized by 3-minute observations separated by slews ranging from 0.025 deg to 0.8 deg. The need for observation efficiency drives the slew and settle process to be as rapid as possible. A description of the shaped slew profile chosen to minimize excitation of structural oscillation, and the handoff from star tracker-gyro control to fine guidance sensor control is detailed. Also presented is the fine guidance sensor (FGS), which is integral with the primary instrument (WFI). The FGS is capable of tracking up to 18 guide stars, enabling robust FGS acquisition and precision pointing. To avoid excitation of observatory structural jitter, reaction wheel speeds are operationally maintained within set limits. In addition, the wheel balance law is designed to maintain 1-Hz separation between the wheel speeds to avoid reinforcing jitter excitation at any particular frequency. The wheel balance law and operational implications are described. Finally, the candidate GNC hardware suite needed to meet the requirements of the mission is presented.

Stoneking, Eric↗
NASA NTRS2017

Precision Pointing for the Wide-Field Infrared Survey Telescope(WFIRST)

The Wide-Field Infrared Survey Telescope (WFIRST) mission, scheduled for a mid-2020's launch, is currently in its definition phase. The mission is designed to investigate essential questions in the areas of dark energy, exoplanets, and infrared astrophysics. WFIRST will use a 2.4-meter primary telescope (same size as the Hubble Space Telescope's primary mirror) and two instruments: the Wide Field Instrument (WFI) and the Coronagraph Instrument (CGI). In order to address the critical science requirements, the WFIRST mission will conduct large-scale surveys of the infrared sky, requiring both agility and precision pointing (11.6 milli-arcsec stability, 14 milli-arcsec jitter). This paper describes some of the challenges this mission profile presents to the Guidance, Navigation, and Control (GNC) subsystem, and some of the design elements chosen to accommodate those challenges. The high-galactic-latitude survey is characterized by 3-minute observations separated by slews ranging from 0.025 deg to 0.8 deg. The need for observation efficiency drives the slew and settle process to be as rapid as possible. A description of the shaped slew profile chosen to minimize excitation of structural oscillation, and the handoff from star tracker-gyro control to fine guidance sensor control is detailed. Also presented is the fine guidance sensor (FGS), which is integral with the primary instrument (WFI). The FGS is capable of tracking up to 18 guide stars, enabling robust FGS acquisition and precision pointing. To avoid excitation of observatory structural jitter, reaction wheel speeds are operationally maintained within set limits. In addition, the wheel balance law is designed to maintain 1-Hz separation between the wheel speeds to avoid reinforcing jitter excitation at any particular frequency. The wheel balance law and operational implications are described. Finally, the candidate GNC hardware suite needed to meet the requirements of the mission is presented.

Stoneking, Eric T.↗
NASA NTRS2016

Wide Field-of-View Soft X-Ray Imaging for Solar Wind-Magnetosphere Interactions

Soft X-ray imagers can be used to study the mesoscale and macroscale density structures that occur whenever and wherever the solar wind encounters neutral atoms at comets, the Moon, and both magnetized and unmagnetized planets. Charge exchange between high charge state solar wind ions and exospheric neutrals results in the isotropic emission of soft X-ray photons with energies from 0.1 to 2.0 keV. At Earth, this process occurs primarily within the magnetosheath and cusps. Through providing a global view, wide field-of-view imaging can determine the significance of the various proposed solar wind-magnetosphere interaction mechanisms by evaluating their global extent and occurrence patterns. A summary of wide field-of-view (several to tens of degrees) soft X-ray imaging is provided including slumped micropore microchannel reflectors, simulated images, and recent flight results.

xray↗
NASA NTRS2017

Optical Design of the WFIRST Phase-A Wide Field Instrument

The WFIRST Wide-Field Infrared Survey Telescope TMA optical design provides 0.28-sq degrees FOV at 0.11” pixel scale to the Wide Field Instrument, operating between 0.48-2.0 micrometers, including a spectrograph mode (1.0-2.0 micrometers). An Integral Field Channel provides 2-D discrete spectroscopy at 0.15” & 0.3” sampling.

Pasquale, Bert A.↗
NASA NTRS2016

Recent Experiments Conducted with the Wide-Field Imaging Interferometry Testbed (WIIT)

The Wide-field Imaging Interferometry Testbed (WIIT) was developed at NASA's Goddard Space Flight Center to demonstrate and explore the practical limitations inherent in wide field-of-view double Fourier (spatio-spectral) interferometry. The testbed delivers high-quality interferometric data and is capable of observing spatially and spectrally complex hyperspectral test scenes. Although WIIT operates at visible wavelengths, by design the data are representative of those from a space-based far-infrared observatory. We used WIIT to observe a calibrated, independently characterized test scene of modest spatial and spectral complexity, and an astronomically realistic test scene of much greater spatial and spectral complexity. This paper describes the experimental setup, summarizes the performance of the testbed, and presents representative data.

Leisawitz, David T.↗
NASA NTRS2018

Optical Design and Predicted Performance of the WFIRST Phase-B Imaging Optics Assembly and Wide Field Instrument

Now in Phase-B, the architecture of the Wide-Field Infra-Red Survey Telescope (WFIRST) payload has matured since 2013 to accommodate various opto-mechanical constraints. Based on a 2.4-meter aperture Forward Optical Assembly (FOA), the Imaging Optics Assembly (IOA) provides corrected optical fields to each on-board instrument. Using a Three Mirror Anastigmat (TMA) optical design, the Wide-Field Channel (WFC) provides ~1/3-square degree of instantaneous field coverage at 0.11 arcsecond pixel scale. The WFC as-built predictive analysis anticipates near diffraction-limited imaging over a focal plane of 300.8 million pixels, operating in seven panchromatic bands between 0.48 - 2.0μm, or a 1-octive multi-spectral imaging mode from ~0.95-1.93μm. The IOA provides the Coronagraph Instrument (CGI) a collimated beam with very specific wavefront constraints. We present configuration changes since 2013 that improved interfaces, improved testability, and reduced technical risk. We provide an overview of our Integrated Modeling results, performed at an unprecedented level for a phase-A study, to illustrate performance margins with respect to static wavefront error, jitter, and thermal drift.

Dark Energy↗
NASA NTRS2018

Multi-Star Wavefront Control for the Wide-Field Infrared Survey Telescope

The Wide-Field Infrared Survey Telescope (WFIRST) is planned to have a coronagraphic instrument (CGI) to enable high-contrast direct imaging of exoplanets around nearby stars. The majority of nearby FGK stars are located in multi-star systems, including the Alpha Centauri stars which may represent the best quality targets for the CGI on account of their proximity and brightness potentially allowing the direct imaging of rocky planets. However, a binary system exhibits additional leakage from the off-axis companion star that may be brighter than the target exoplanet. Multi-Star Wavefront Control (MSWC) is a wavefront-control technique that allows suppression of starlight of both stars in a binary system thus enabling direct imaging of circumstellar planets in binary star systems such as Alpha Centauri. We explore the capabilities of the WFIRST CGI instrument to directly image multi-star systems using MSWC. We consider several simulated scenarios using the WFIRST CGI's Shaped Pupil Coronagraph Disk Mask. First, we consider close binaries such as Mu Cassiopeia that require no modifications to the WFIRST CGI instrument and can be implemented as a purely algorithmic solution. Second, we consider wide binaries such as Alpha Centauri that require a diffraction grating to enable suppression of the off-axis starlight leakage at Super-Nyquist separations. We demonstrate via simulation dark holes in 10 percent broadband compatible with the WFIRST CGI.

Sirbu, Dan↗
NASA NTRS2018

Solar System Science with the Wide-Field Infrared Survey Telescope

We present a community-led assessment of the solar system investigations achievable with NASA's next-generation space telescope, the Wide Field Infrared Survey Telescope (WFIRST). WFIRST will provide imaging, spectroscopic, and coronagraphic capabilities from 0.43 to 2.0 m and will be a potential contemporary and eventual successor to the James Webb Space Telescope (JWST). Surveys of irregular satellites and minor bodies are where WFIRST will excel with its 0.28 deg2 field-of-view Wide Field Instrument. Potential ground- breaking discoveries from WFIRST could include detection of the first minor bodies orbiting in the inner Oort Cloud, identification of additional Earth Trojan asteroids, and the discovery and characterization of asteroid binary systems similar to Ida/Dactyl. Additional investigations into asteroids, giant planet satellites, Trojan asteroids, Centaurs, Kuiper belt objects, and comets are presented. Previous use of astrophysics assets for solar system science and synergies between WFIRST, Large Synoptic Survey Telescope, JWST, and the proposed Near-Earth Object Camera mission is discussed. We also present the case for implementation of moving target tracking, a feature that will benefit from the heritage of JWST and enable a broader range of solar system observations.

Holler, Bryan J.↗
NASA NTRS2018

Wide-bandgap Semiconductors in Space: Appreciating the Benefits but Understanding the Risks

Dr. Jean-Marie Lauenstein, NASA Goddard Space Flight Center, will present the radiation challenges of adopting wide-bandgap semiconductors for space applications. Wide-bandgap devices are attractive for space applications due to improved performance such as faster switching speeds, lower power losses, and their ability to operate at higher temperature as compared with their silicon counterparts. Their tolerance to total ionizing dose levels (> 100 krad(Si)) further enhances the desirability of these technologies. This short course will focus on silicon carbide and gallium nitride power rectifying, switching, and RF devices as these technologies are now readily available commercially. The radiation hardness assurance issues presented by the heavy-ion radiation environment will be discussed.

Lauenstein, Jean-Marie↗
NASA NTRS2019

Astrometry with the Wide-Field Infrared Space Telescope

The Wide-Field Infrared Space Telescope (WFIRST) will be capable of delivering precise astrometry for faint sources over the enormous field of view of its main camera, the Wide-Field Imager (WFI). This unprecedented combination will be transformative for the many scientific questions that require precise positions, distances, and velocities of stars. We describe the expectations for the astrometric precision of the WFIRST WFI in different scenarios, illustrate how a broad range of science cases will see significant advances with such data, and identify aspects of WFIRST’s design where small adjustments could greatly improve its power as an astrometric instrument.

Robyn E. Sanderson↗
NASA NTRS2017

DSN Wide Area Network Architecture, Capacity and Performance

This paper discusses the architecture of the wide area network that connects key communications facilities within the National Aeronautic and Space Administration (NASA) Deep Space Network (DSN). Several considerations are given to the design of this wide area network to ensure a timely, reliable, and secure data delivery between the mission users and their spacecraft. The network star configuration simplifies data delivery to users and minimizes operational cost. The dual-path connections maximize the system reliability, with geographical diversity in data routing to avoid single point of failure. Data encryption enhances the protection of mission users’ data. The system bandwidth is determined by balancing the needs to minimize the operating bandwidth cost and to have sufficient bandwidth to be able to deliver data to all users within the required. The DSN uses a class base weighted fair queuing (CBWFQ) method in its data delivery. This scheme guarantees a minimum bandwidth to each class of users and allows users to also access any unused bandwidth by other groups. The paper will also show performance of system reliability and bandwidth margin.

Liao, Jason↗
NASA NTRS2017

Comparative View of Antenna/RF Subsystems between SIR-C and NISAR L-band SAR Systems for Wide-Swath Imaging

In 1994, SIR-C demonstrated ScanSAR, a mode of operating the SAR system that has become the “standard” implementation for wide-swath spaceborne imaging SAR systems. The NISAR SAR instruments introducing a new SAR architecture for wide-swath imaging call SweepSAR which is expected to have similar success. This paper compares the Antenna and RF subsystem design and the technology utilization considerations between the SIR-C planar phased array SAR system using the ScanSAR technique and NISAR off-set reflector with phased array feed using the SweepSAR technique.

Shaffer, Scott↗
NASA NTRS2020

WISE 2150-7520AB: A Very Low-mass, Wide Comoving Brown Dwarf System Discovered through the Citizen Science Project Backyard Worlds: Planet 9

We report the discovery of WISE 2150-7520AB (W2150AB): a widely separated (∼341 au) very low-mass L1 + T8 co-moving system. The system consists of the previously known L1 primary 2MASS J21501592-7520367 and a newly discovered T8 secondary found at position 21:50:18.99–75:20:54.6 (MJD = 57947) using Wide-field Infrared Survey Explorer data via the Backyard Worlds: Planet 9 citizen science project. We present Spitzer ch1 and ch2 photometry (ch1–ch2 = 1.41 ± 0.04 mag) of the secondary and Folded-port InfraRed Echellette prism spectra of both components. The sources show no peculiar spectral or photometric signatures, indicating that each component is likely field age. Using all observed data and the Gaia DR2 parallax of 41.3593 ± 0.2799 mas for W2150A we deduce fundamental parameters of log(L(bol)/L(☉)) = −3.69 ± 0.01, T(eff) = 2118 ± 62 K, and an estimated mass = 72 ± 12 M(Jup) for the L1 and log(L(bol)/L(☉)) = −5.64 ± 0.02, T(eff) = 719 ± 61 K, and an estimated mass = 34 ± 22 M(Jup) for the T8. At a physical separation of ∼341 au this system has E(bin) = 1041 erg, making it the lowest binding energy system of any pair with M(tot) < 0.1 M(Sun) not associated with a young cluster. It is equivalent in estimated mass ratio, E(bin), and physical separation to the ∼2 Myr M7.25 + M8.25 binary brown dwarf 2MASS J11011926-7732383AB (2M1101AB) found in the Chameleon star-forming region. W2150AB is the widest companion system yet observed in the field where the primary is an L dwarf or later.

Jacqueline Faherty↗
NASA NTRS2020

2MASS J15491331-3539118: a new low-mass wide companionof the GQ Lup system

Substellar companions at wide separation around stars hosting planets or brown dwarfs (BDs) yet close enough for their formation in the circumstellar disc are of special interest. In this Letter we report the discovery of a wide (projected separation ~16".0, or 2400AU, and position angle 114.61°) companion of the GQLup A-B system, most likely gravitationally bound to it. A VLT/X-shooter spectrum shows that this star, 2MASS J15491331-3539118, is a bonafide low-mass (~0.15 M(ʘ) ) young stellar object (YSO) with stellar and accretion/ejection properties typical of Lupus YSOs of similar mass, and with kinematics consistent with that of the GQLup A-B system. A possible scenario for the formation of the triple system is that GQ Lup A and 2MASS J15491331-3539118 formed by fragmentation of a turbulent core in the Lup I filament, while GQ Lup B, the BD companion of GQ Lup A at 0".7, formed in situ by the fragmentation of the circumprimary disc. The recent discoveries that stars form along cloud filaments would favour the scenario of turbulent fragmentation for the formation of GQ Lup A and 2MASS J15491331-3539118.

J. M. Alcalá↗
NASA NTRSDate not supplied

Li-ion Battery Aging with Hybrid Physics-Informed Neural Networks and Fleet-wide Data

In this work, we propose a hybrid model for Li-ion battery discharge and aging prediction that leverages fleet-wide data to predict future capacity drops.The model is built upon an hybrid approach merging physics-based and empirical equations, as well as neural network models in a recurrent neural network cell. The hybrid physics-informed neural network can predict voltage discharge cycles given the loading profile, and estimate the used capacity of the battery under random-loading conditions by tracking aging parameters connected to the residual capacity of the battery. By merging information on the battery aging parameters with existing fleet-wide aging data, the model can predict the future residual capacity of the battery that is being monitored, and therefore enable predictions of voltage discharge curves far ahead in the battery life cycle. We validated the approach using the NASA Prognostics Data Repository Battery data-set, which contains experimental data on Li-ion batteries discharged at random loading conditions in a controlled environment. The approach also allows the identification of discrepancies between the battery aging trend and the trend observed at the fleet level, so that batteries behaving differently from the rest of the fleet can be subject to closer monitoring and further testing to refine predictions.

PINN↗