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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Mapping Impervious Surface Expansion using Medium-resolution Satellite Image Time Series: A Case Study in the Yangtze River Delta, China

Cities have been expanding rapidly worldwide, especially over the past few decades. Mapping the dynamic expansion of impervious surface in both space and time is essential for an improved understanding of the urbanization process, land-cover and land-use change, and their impacts on the environment. Landsat and other medium-resolution satellites provide the necessary spatial details and temporal frequency for mapping impervious surface expansion over the past four decades. Since the US Geological Survey opened the historical record of the Landsat image archive for free access in 2008, the decades-old bottleneck of data limitation has gone. Remote-sensing scientists are now rich with data, and the challenge is how to make best use of this precious resource. In this article, we develop an efficient algorithm to map the continuous expansion of impervious surface using a time series of four decades of medium-resolution satellite images. The algorithm is based on a supervised classification of the time-series image stack using a decision tree. Each imerpervious class represents urbanization starting in a different image. The algorithm also allows us to remove inconsistent training samples because impervious expansion is not reversible during the study period. The objective is to extract a time series of complete and consistent impervious surface maps from a corresponding times series of images collected from multiple sensors, and with a minimal amount of image preprocessing effort. The approach was tested in the lower Yangtze River Delta region, one of the fastest urban growth areas in China. Results from nearly four decades of medium-resolution satellite data from the Landsat Multispectral Scanner (MSS), Thematic Mapper (TM), Enhanced Thematic Mapper plus (ETM+) and China-Brazil Earth Resources Satellite (CBERS) show a consistent urbanization process that is consistent with economic development plans and policies. The time-series impervious spatial extent maps derived from this study agree well with an existing urban extent polygon data set that was previously developed independently. The overall mapping accuracy was estimated at about 92.5% with 3% commission error and 12% omission error for the impervious type from all images regardless of image quality and initial spatial resolution.

Gao, Feng↗
NASA NTRS2014

Design, Fabrication and Test of WFIRST-AFTA GRISM Assembly

The Wide-Field Infra-Red Survey Telescope (WFIRST) is designed to perform wide-field imaging and slitless spectroscopic survey of the sky. A compound Grism assembly is selected as its slitless dispersing element. Compared to the grisms in several instruments installed on the Hubble space telescope, the challenge of this grism is the much wider Field Of View (FOV), larger dispersion, and smaller f. The image quality of the slitless spectrometer is directly related to how deep of the sky the spectrometer is able to see. This paper discusses how to use a diffractive lens surface to compensate the wavelength dependent aberration created by the grating in non-collimated space to make the spectrometer diffraction limited, as well as how to intelligently combine the two diffractive surfaces (lens and grating) to reduce the unwanted diffraction orders from the grating. The paper also discusses how to improve the diffraction efficiency of the diffractive surfaces, as well as how to align and assemble the optics.

Diffractive Optics↗
NASA NTRS2011

Measuring Total and Germinable Spore Populations

It has been shown that bacterial endospores can be enumerated using a microscopy based assay that images the luminescent halos from terbium ions bound to dipicolinic acid, a spore specific chemical marker released upon spore germination. Further development of the instrument has simplified it towards automation while at the same time improving image quality. Enumeration of total spore populations has also been developed allowing measurement of the percentage of viable spores in any population by comparing the germinable/culturable spores to the total. Percentage viability will allow a more quantitative comparison of the ability of spores to survive across a wide range of extreme environments.

microbial life↗
NASA NTRS2015

Differential Deposition for Surface Figure Corrections in Grazing Incidence X-Ray Optics

Differential deposition corrects the low- and mid- spatial-frequency deviations in the axial figure of Wolter-type grazing incidence X-ray optics. Figure deviations is one of the major contributors to the achievable angular resolution. Minimizing figure errors can significantly improve the imaging quality of X-ray optics. Material of varying thickness is selectively deposited, using DC magnetron sputtering, along the length of optic to minimize figure deviations. Custom vacuum chambers are built that can incorporate full-shell and segmented Xray optics. Metrology data of preliminary corrections on a single meridian of full-shell x-ray optics show an improvement of mid-spatial frequencies from 6.7 to 1.8 arc secs HPD. Efforts are in progress to correct a full-shell and segmented optics and to verify angular-resolution improvement with X-ray testing.

X-Ray Optics↗
NASA NTRS2009

Beam Width Robustness of a 670 GHz Imaging Radar

Detection of a replica bomb belt concealed on a mannequin at 4 m standoff range is achieved using a 670 GHz imaging radar. At a somewhat larger standoff range of 4.6 m, the radar's beam width increases substantially, but the through-shirt image quality remains good. This suggests that a relatively modest increase in aperture size over the current design will be sufficient to detect person-borne concealed weapons at ranges exceeding 25 meters.

Cooper, K. B.↗
NASA NTRS2010

Wavefront Controls for a Large Submillimeter-Wave Observatory

The 25-m aperture Cornell Caltech Atacama Telescope (CCAT) will have a primary mirror that is divided into 162 individual segments, each of which is equipped with 3 positioning actuators. This paper presents a mathematical description of the telescope, its actuators and sensors, and uses it to derive control laws for figure maintenance. A Kalman Filter-based Optical State Estimator is used to continuously estimate the aberrations of the telescope; these are used in a state-feedback controller to maintain image quality. This approach provides the means to correct for the optical effects of errors that occur in unactuated degrees of freedom, such as lateral translations of the segments. The control laws are exercised in Monte Carlo and covariance analysis, to bound the closed-loop performance of the telescope and to conduct control design trades.

edge sensors↗
NASA NTRS2010

Modeling a Large Submillimeter-Wave Observatory

The 25 meter aperture Cornell Caltech Atacama Telescope (CCAT) will provide an enormous increase in sensitivity in the submillimeter bands compared to existing observatories, provided it can establish and maintain excellent image quality. To accomplish this at a very low cost, it is necessary to conduct accurate engineering trades, including the most effective segment and wavefront sensing and control approach, to determine the best method for continuously maintaining wavefront quality in the operational environment. We describe an integrated structural/optical/controls model that provides accurate performance prediction. We also detail the analysis methods used to quantify critical design trades.

Segment Sensing↗
NASA NTRS2015

NASA NDE Program

The current activities in the National Aeronautics and Space Administration Nondestructive Evaluation (NDE) Program are presented. The topics covered include organizational communications, orbital weld inspection, electric field imaging, fracture critical probability of detection validation, monitoring of thermal protection systems, physical and document standards, image quality indicators, integrity of composite pressure vessels, and NDE for additively manufactured components.

Generazio, Ed↗
NASA NTRS2014

Recent Progress with the JWST Observatory

The James Webb Space Telescope (JWST) is a large aperture (6.5 meter), cryogenic space telescope with a suite of near and mid-infrared instruments covering the wavelength range of 0.6 micrometers - 28 micrometers. JWST's primary science goal is to detect and characterize the first galaxies. It will also study the assembly of galaxies, star formation, and the formation of evolution of planetary systems. JWST is a segmented mirror telescope operating at (is) approximately 40K, a temperature achieved by passive cooling of the observatory, via a large, 5-layer membrane-based sunshield. We present an overview of the observatory systems design, the science instruments and the mission science objectives. With the completion of the Spacecraft Critical Design Review, the spacecraft has also fully transitioned to fabrication. We will discuss recent highlights associated with the Observatory, including completion and delivery of the primary mirror segments, delivery of the primary mirror backplane and its wings, and the delivery of five template membrane layers. We will also summarize the current predicted performance of the telescope, including stray light, pointing and image quality following the completion of the final design review. Finally, the current schedule through to launch will be presented with a summary of integration and test activities planned when the science payload is delivered to Northrop Grumman following cryo-optical testing at the Johns Space Flight Center.

James Webb Space Telescope (JWST)↗
NASA NTRS2014

Hubble Space Telescope Observations of the Afterglow, Supernova and Host Galaxy Associated with the Extremely Bright GRB 130427A

We present Hubble Space Telescope (HST) observations of the exceptionally bright and luminous Swift gamma-ray burst, GRB 130427A. At z=0.34 this burst affords an excellent opportunity to study the supernova and host galaxy associated with an intrinsically extremely luminous burst (E(sub iso) greater than 10(exp 54) erg): more luminous than any previous GRB with a spectroscopically associated supernova. We use the combination of the image quality, UV capability and and invariant PSF of HST to provide the best possible separation of the afterglow, host and supernova contributions to the observed light approximately 17 rest-frame days after the burst utilising a host subtraction spectrum obtained 1 year later. Advanced Camera for Surveys (ACS) grism observations show that the associated supernova, SN 2013cq, has an overall spectral shape and luminosity similar to SN 1998bw (with a photospheric velocity, vph approximately 15,000 kilometers per second). The positions of the bluer features are better matched by the higher velocity SN 2010bh (vph approximately 30,000 kilometers per second), but SN 2010bh (vph approximately 30,000 kilometers per second but this SN is significantly fainter, and fails to reproduce the overall spectral shape, perhaps indicative of velocity structure in the ejecta. We find that the burst originated approximately 4 kpc from the nucleus of a moderately star forming (1 Solar Mass yr(exp-1)), possibly interacting disc galaxy. The absolute magnitude, physical size and morphology of this galaxy, as well as the location of the GRB within it are also strikingly similar to those of GRB980425SN 1998bw. The similarity of supernovae and environment from both the most luminous and least luminous GRBs suggests broadly similar progenitor stars can create GRBs across six orders of magnitude in isotropic energy.

host↗
NASA NTRS1975

Interim Report of the Astronomy Spacelab Payloads Study: Ultraviolet and Optical Astronomy - Volume 2

The Space Shuttle will comprise NASA's primary transportation system into near-earth orbit during the 1980s. The Shuttle will provide the astronomical community with a major new capability to send a wide variety of instrumentation into orbit, to utilize it there under manned or automatic control for periods from seven to thirty days, and to return it to the ground. To this end the European Space Research Organization (ESRO) is developing Spacelab, an array of interchangeable components -pressurized manned modules, unpressurized pallets and related support systems - to be mounted in the Shuttle payload bay. Spacelab will offer important opportunities to carry out astronomical research with instruments optimized for specific objectives. With a high flight frequency and with the ability to modify or interchange telescopes and instruments between flights, one will not need to make rigid long-term commitments to specific and compromised telescope/instrument/ detector combinations as is the case for automated satellites. Observational techniques demanding the physical return of data and equipment - in particular the use of photographic film, instruments requiring tight calibration controls, cryogens, high-risk detectors and degradeable optical coatings -will open research areas not readily addressed by automated satellites. Although Shuttle flight duration will be limited to periods from seven to thirty days, substantial data can be obtained with a single instrument on short missions, if targets are carefully selected and prioritized, and a large number of instruments can be accommodated on a single flight. Important astronomical data are regularly obtained on sounding rocket flights of five minutes duration. Spacelab will provide far longer observing periods for large and small telescopes, with resources greatly exceeding those of sounding rockets, while retaining much of the sounding rocket philosophy in terms of instrument flexibility, simplicity, reliability assurance and development costs. The Ultraviolet and Optical Astronomy Program on Spacelab is being planned to provide optical astronomers with relatively simple and regular access to the extended wavelength coverage, the superior image quality and the darkness of the night sky available above the earth's atmosphere. In a rapidly evolving science one cannot predict what problems will be timely in the 1980s. Extrapolating from the current epoch, however, one can envision a continuing interest in such areas as the structure, composition and phenomenology of planetary surfaces and atmospheres; the composition and physical nature of the interstellar medium; the composition, structure and life history of stars, especially those in advanced stages of evolution; the stellar population of other galaxies; such enigmatic phenomena as X-ray binary black holes, pulsars, active galactic nuclei and quasars; large scale interactions between galaxies and the nature of the intergalactic medium; precise calibration of the Hubble law for the expansion of the universe; the average density of the universe; and the existence of extraterrestrial life.

Source record↗
NASA NTRS2017

Optical Design of the WFIRST Phase-A Integral Field Channel

WFIRST is one of NASA's Decadal Survey Missions and is currently in Phase-A development. The optical design of the WFIRST Integral Field Channel (IFC), one of three main optical channels of WFIRST, is presented, and the evolution of the IFC channel since Mission Concept Review (MCR, end of Pre-Phase A) is discussed. The IFC has two sub-channels: Supernova (IFC-S) and Galaxy (IFC-G) channels, with Fields of View of 3"x4.5" and 4.2"x9" respectively, and approximately R 75 spectral analysis over waveband 0.42 approximately 2.0 micrometers. The Phase-A IFC optical design meets image quality requirements over the FOV areas while balancing cost and volume constraints.

Gao, Guangjun↗
NASA NTRS2017

Improving X-Ray Optics via Differential Deposition

Differential deposition, a post-fabrication figure correction technique, has the potential to significantly improve the imaging quality of grazing-incidence X-ray optics. DC magnetron sputtering is used to selectively coat the mirror in order to minimize the figure deviations. Custom vacuum chambers have been developed at NASA MSFC that will enable the implementation of the deposition on X-ray optics. A factor of two improvement has been achieved in the angular resolution of the full-shell X-ray optics with first stage correction of differential deposition. Current efforts are focused on achieving higher improvements through efficient implementation of differential deposition.

differential deposition grazing↗
NASA NTRS2017

Applications for Freeforms Optics at NASA

Review freeform optic applications as NASA. Describe design study results showing benefits of freeform optics to the instrument size, image quality, and field of view. Review areas of study and improvements needed to freeform manufacturing for future applications.

Design↗
NASA NTRS2017

Vascular Patterning Analysis by VESGEN 2D/3D with Bioinformatics: Updates for Rodent Tissues

Fractally branching vascular systems are a complex physiological requirement shared by humans with all higher terrestrial life forms, including other vertebrates, insects, and higher land plants. Vascular trees, networks, and tree-network composites are therefore mapped and quantified by the VESsel GENeration Analysis (VESGEN) software according to weighted physiological vascular rules that include vessel connectivity, tapering and bifurcational branching. According to fluid dynamics, successful vascular transport depends upon a complex distributed system of highly regulated laminar flow. VESGEN has elucidated changes in vascular patterning resulting from inflammatory, developmental and other signaling pathways within numerous tissues of major model organisms important for Space Biology, especially for rodents. Important early stage regenerative opportunities have been identified by VESGEN vascular analysis for visual impairments in the human retina, and is currently being used for research into astronaut visual and ocular disorders associated with long duration missions. The VESGEN 2D software is a mature, automated, widely published capability for which beta testing and public release by NASA is planned for the upcoming year. Early-stage capabilities for VESGEN 3D analysis are under development for the rodent retina and intestine as prototype tissues. A prototype VESGEN 2D Bioinformatics software capability has also been developed to associate phenotypic changes in molecular expression with vascular structure and function. By new VESGEN bioinformatic innovations, expression patterns of the genetic, transcriptional, protein and other markers for regulatory molecules such as vascular endothelial growth factor (VEGF) and their receptors, often indicators of tissue oxygenation status, are co-localized with alterations in vascular pattern. Biomarkers are therefore mapped and quantified as information dimensions directly correlated with the spatial dimensions of a vascular pattern. Further important technology innovations by NASA include substantial image segmentation advances for more automated binary extraction of the grayscale vascular patterns, together with informative associated image quality assessments. Vascular mapping and quantification capabilities for the rodent retina and intestine are illustrated for VESGEN 2D, along with technology status reports on VESGEN 3D and Bioinformatic capabilities. Research partially supported by Ames Center Innovation Awards.

Parsons-Wingerter, P.↗
NASA NTRS2018

Ground-Based X-Ray Calibration of the Astro-H/Hitomi Soft X-Ray Telescopes

We present the summary of the on-ground calibration of two soft x-ray telescopes (SXT-I and SXT-S), developed by NASA's Goddard Space Flight Center (GSFC), onboard Astro-H/Hitomi. After the initial x-ray measurements with a diverging beam at the GSFC 100-meter beamline, we performed the full calibration of the x-ray performance, using the 30-meter x-ray beamline facility at the Institute of Space and Astronautical Science of Japan Aerospace Exploration Agency in Japan. We adopted a raster scan method with a narrow x-ray pencil beam with a divergence of approximately 15 arc secs. The on-axis effective area (EA), half-power diameter, and vignetting function were measured at several energies between 1.5 and 17.5 kiloelectronvolts. The detailed results appear in tables and figures in this paper. We measured and evaluated the performance of the SXT-S and the SXT-I with regard to the detector-limited field-of-view and the pixel size of the paired flight detector, i.e., SXS and the SXI, respectively. The primary items measured are the EA, image quality, and stray light for on-axis and off-axis sources. The accurate measurement of these parameters is vital to make the precise response function of the ASTRO-H SXTs. This paper presents the definitive results of the ground-based calibration of the ASTRO-H SXTs.

Iizuka, Ryo↗
NASA NTRS2018

The James Webb Space Telescope: Observatory Status and Preparations for Launch

The James Webb Space Telescope (JWST) is a large (6.5 meter) segmented aperture telescope equipped with near- and mid-infrared instruments (0.6-28 microns), all of which are passively cooled to approximately 40 degrees Kelvin by a 5-layer sunshield while the mid-infrared instrument is actively cooled to 7 degrees Kelvin. The JWST telescope recently completed its cryogenic test program and the sunshield has been fully integrated and deployed. JWST is currently in the final stages of the test program at the Observatory level. The current estimated JWST performance metrics will be presented, such as the image quality, pointing stability, sensitivity, and stray light backgrounds. The JWST development status and future plans will be described for the final testing, launch, and commissioning.

McElwain, Michael↗