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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Fourier Domain Sensing

Methods and systems are disclosed of sensing an object. A first radiation is spatially modulated to generate a structured second radiation. The object is illuminated with the structured second radiation such that the object produces a third radiation in response. Apart from any spatially dependent delay, a time variation of the third radiation is spatially independent. With a single-element detector, a portion of the third radiation is detected from locations on the object simultaneously. At least one characteristic of a sinusoidal spatial Fourier-transform component of the object is estimated from a time-varying signal from the detected portion of the third radiation.

Feldkhun, Daniel↗
DOE OSTI2025

The System for Classification of Low-Pressure Systems (SyCLoPS): An All-In-One Objective Framework for Large-Scale Data Sets

We propose the first unified objective framework (SyCLoPS) for detecting and classifying all types of low-pressure systems (LPSs) in a given data set. We use the state-of-the-art automated feature tracking software TempestExtremes (TE) to detect and track LPS features globally in ERA5 and compute 16 parameters from commonly found atmospheric variables for classification. A Python classifier is implemented to classify all LPSs at once. The framework assigns 16 different labels (classes) to each LPS data point and designates four different types of high-impact LPS tracks, including tracks of tropical cyclone (TC), monsoonal system, subtropical storm and polar low. The classification process involves disentangling high-altitude and drier LPSs, differentiating tropical and non-tropical LPSs using novel criteria, and optimizing for the detection of the four types of high-impact LPS. A comparison of our labels with those in the International Best Track Archive for Climate Stewardship (IBTrACS) revealed an overall accuracy of 95% in distinguishing between tropical systems, extratropical cyclones, and disturbances. SyCLoPS produces a better TC detection skill compared to the previous algorithms, highlighted by an approximately 6% reduction in the false alarm rate compared to the previous TE algorithm. The vertical cross section composite of the four types of high-impact LPS we detect each shows distinct structural characteristics. Finally, we demonstrate that SyCLoPS is valuable for investigating various aspects of LPSs in climate data, such as the evolution of a single LPS track, patterns of LPS frequencies, and precipitation or wind influence associated with a particular LPS class.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Particle Acceleration and Pitch-angle Evolution in Relativistic Turbulence

Synchrotron radiation detected from relativistic astrophysical objects such as pulsar-wind nebulae and jets from active galactic nuclei depends on the magnetic fields and the distribution functions of energetic electrons in these systems. Relativistic magnetically dominated turbulence has been recognized as an efficient mechanism for structure formation and nonthermal particle acceleration in these environments. Recent numerical simulations of relativistic turbulence have provided insights into the energy distribution functions of accelerated electrons. Much less is currently understood about their pitch angle distributions, which are crucial for accurately interpreting the spectra of synchrotron radiation. We perform a detailed case study of the pitch angle distributions formed during the process of turbulent acceleration for B 0 /δB 0 = 10 and $\tilde{σ}$ 0 ~40, where B0 is the uniform component of the magnetic field, δB0 is the fluctuating component, and $\tilde{σ}$ 0 is the plasma magnetization based on the magnetic fluctuations. We find that even minimal numerical noise can cause substantial pitch angle scattering, but we demonstrate techniques for overcoming the numerical challenges associated with the evolution of very small pitch angles. Our numerical results are consistent with the phenomenological considerations found in C. Vega et al. (2024a, 2025).

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1973

Hard cosmic X-ray sources.

A review of the observational status of X-ray sources detected in the 20 to 500 keV range is presented. Of the approximately 115 sources listed in the March 1972 edition of the UHURU 2-6 keV sky survey catalog, about 15 sources have been studied in hard X rays. Most of the data have been obtained from balloons, although the OSO-3, and more recently the OSO-7, have contributed. With the exception of CEN A, the SMC, and possibly M-87, all the sources detected at higher energies are galactic and heavily concentrated in the galactic plane. The Crab Nebula has been measured to about 500 keV in continuous emission and a component at the 33-msec pulsar period comprising about 20% of the total emission has been detected to 10 MeV. Objects such as SCO-1 and CYG-2 are characterized by an exponential spectrum, which varies over a 10-min time scale about a factor of two, and a flatter spectrum extending to above 40 keV which exhibits independent variability.

Peterson, L. E.↗
NASA NTRS1978

Sharpening stellar images

A prototype telescope system with six movable elements has been used with sharpness detection procedures to observe objects as dim as fifth magnitude. The real-time image sharpening technique does not rely on the use of a reference star. By correcting for atmospherically induced phase perturbations, the sharpening system has permitted restoration of stellar images to the diffraction limit (in one dimension) for a 30-cm telescope. Application of the system to the separation of double stars is reported.

Buffington, A.↗
NASA NTRS1979

The Spacelab Wide Angle Telescope (SWAT)

A fast wide angle telescope that will be capable of imaging to the darker sky limit and in the ultraviolet wavelength region available above the atmosphere is described. The telescope (SWAT) has a resolution comparable to that of the large ground-based Schmidt telescope and a field of at least five degrees. A number of astrophysically important investigations can only be accomplished with such a telescope, e.g., detection of hidden, hot objects like hot white dwarfs and subwarfs in stellar binary systems, and energetic regions in globular clusters and galaxy nuclei. It permits unique studies of the UV-morphology of extended objects and allows discovery of very faint extensions, halos, jets, and filaments in galaxies. It can contribute to the investigation of dust in the Milky Way and in other galaxies and, with an objective prism, spectra of very faint objects can be obtained. The SWAT will localize objects for further study with the narrow-field Space Telescope.

West, R. M.↗
NASA NTRS1982

Observations of NGC 604 over six decades in frequency

Maps in the near-infrared, H-alpha and radio continuum have been obtained of NGC 604, the brightest H II region complex in M33, as well as a measurement of the UV spectrum of the ionizing star cluster. The data show that NGC 604 consists of about ten components of typical size 10 pc, embedded in a much larger envelope with dimensions of 225 pc. At least one component is optically almost completely obscured; it is located close to another object that is only detected in the near-infrared and whose nature is uncertain.

Israel, F. P.↗
NASA NTRS1982

Diameters of Triton and Pluto

The Neptune satellite Triton and the planet Pluto, whose diameter and albedo must be estimated by indirect methods, invite comparative study because of their similar brightness and current distance of 30 AU from the sun. IR spectroscopy has detected methane on both objects. Upper limits are given for the thermal IR emission from these objects which allow the determination of significant upper diameter limits. It is also demonstrated that both are high albedo objects, excluding the possibility that Triton is the largest planetary satellite and consistent with the small Pluto dimensions deduced from other data

Morrison, D.↗
NASA NTRS1984

Power transfer from natural emitters to collection apertures at microwave wavelengths

The power transfer criteria necessary and sufficient to produce a detection of the emitting object by the collecting aperture and its receiver are shown. Range equations show the transfer of microwave energy from a passive, diffuse, emitting object that is located on a planetary surface, to a collecting aperture that is carried on an aerial platform or spacecraft. The mathematical relationships show in closed form the expressions for signal to noise ratio as a function of certain key parameters. The practical case of an emitting object on the Earth and a collecting aperture in orbit is presented.

Stacey, J. M.↗
NASA NTRS1986

Future directions for H sub x O sub y detection

The activities and recommendations of the NASA workshop on the Future Directions for H sub x O sub y detection are given. The objective of this workshop was to access future directions for the measurement of the OH radical as well as other H sub x O sub y species. The workshop discussions were focused by two broad questions: (1) What are the capabilities of potential measurement methods? and (2) Will the results from the most promising method be useful in furthering understanding of tropospheric chemistry?

Crosley, David R.↗
NASA NTRS1988

Direct imaging of extra-solar planetary systems with the Circumstellar Imaging Telescope (CIT)

In a joint study conducted by the Jet Propulsion Laboratory and the Perkin-Elmer Corporation it was found that an earth orbital, 1.5 meter diameter low scattered light coronagraphic telescope can achieve a broad range of scientific objectives including the direct detection of Jupiter-sized planets around the nearby stars. Recent major advances in the understanding of coronagraphic performance and in the field of super smooth mirror fabrication allow such an instrument to be designed and built within current technology. Such a project, called the Circumstellar Imaging Telescope (CIT), is currently being proposed.

Terrile, Richard J.↗
NASA NTRS1989

Bayesian learning

In 1983 and 1984, the Infrared Astronomical Satellite (IRAS) detected 5,425 stellar objects and measured their infrared spectra. In 1987 a program called AUTOCLASS used Bayesian inference methods to discover the classes present in these data and determine the most probable class of each object, revealing unknown phenomena in astronomy. AUTOCLASS has rekindled the old debate on the suitability of Bayesian methods, which are computationally intensive, interpret probabilities as plausibility measures rather than frequencies, and appear to depend on a subjective assessment of the probability of a hypothesis before the data were collected. Modern statistical methods have, however, recently been shown to also depend on subjective elements. These debates bring into question the whole tradition of scientific objectivity and offer scientists a new way to take responsibility for their findings and conclusions.

Denning, Peter J.↗
NASA NTRS1990

Smaller solar system bodies and orbits; Proceedings of Symposium 3, Workshops II, III, and XXVI, and Topical Meetings of the 27th COSPAR Plenary Meeting, Espoo, Finland, July 18-29, 1988

Topics discussed in this volume include the reappraisal of the moon and Mars/Phobos/Deimos; the origin and evolution of planetary and satellite systems; asteroids, comets, and dust (a post-IRAS perspective); satellite dynamics; future planetary missions; and orbital debris. Papers are presented on a comparison of the chemistry of moon and Mars, the use of a mobile surface radar to study the atmosphere and ionosphere, and laser-ionization studies with the technical models of the LIMA-D/Phobos. Attention is given to planetogonic scenarios and the evolution of relatively mass-rich preplanetary disks, the kinetic behavior of planetesimals revolving around the sun, the planetary evolution of Mars, and pre- and post-IRAS asteroid taxonomies. Consideration is also given to ocean tides and tectonic plate motions in high-precision orbit determination, the satellite altimeter calibration techniques, a theory of the motion of an artificial satellite in the earth atmosphere, ESA plans for planetary exploration, and the detection of earth orbiting objects by IRAS.

Runcorn, S. K.↗
NASA NTRS1989

Comparison of thermal (FLIR) and television images

The human eye is sensitive to electromagnetic radiation in the 0.4 to 0.7 micron band (light). Thermal imaging (TI) systems are sensitive to heat radiation in the infrared band (3-5 or 8-14 microns) and are capable of transforming the distribution of relative temperatures in a scene into a visible TV image. The present experiment was designed to investigate the impact of the difference between TIs and regular TV images on the detection and identification of natural and man-made targets. Parallel TV and TI videotapes were recorded during helicopter flights. Fifteen subjects who viewed both the TV and the TI images (separately), were asked to detect predefined targets and to identify features pointed out to them by the experimenter. In general, performance with TVs was superior to performance with TIs in terms of response times and errors. However, subjects required significantly less time to detect man-made objects with TIs than with TVs. The correlation between the performance of the same task with the two kinds of images was very low. The results are discussed in terms of image quality and in terms of humans' internal representations of natural categories.

Brickner, Michael S.↗
NASA NTRS1990

Motion detection, novelty filtering, and target tracking using an interferometric technique with a GaAs phase conjugate mirror

A method and apparatus is disclosed for detecting and tracking moving objects in a noise environment cluttered with fast-and slow-moving objects and other time-varying background. A pair of phase conjugate light beams carrying the same spatial information commonly cancel each other out through an image subtraction process in a phase conjugate interferometer, wherein gratings are formed in a fast photo-refractive phase conjugate mirror material. In the steady state, there is no output. When the optical path of one of the two phase conjugate beams is suddenly changed, the return beam loses its phase conjugate nature and the inter-ferometer is out of balance, resulting in an observable output. The observable output lasts until the phase conjugate nature of the beam has recovered. The observable time of the output signal is roughly equal to the formation time of the grating. If the optical path changing time is slower than the formation time, the change of optical path becomes unobservable, because the index grating can follow the change. Thus, objects traveling at speeds which result in a path changing time which is slower than the formation time are not observable and do not clutter the output image view.

Cheng, Li-Jen↗
NASA NTRS1991

Development of an optical fiber interferometer for detection of surface flaws in aluminum

The main objective was to demonstrate the potential of using an optical fiber interferometer (OFI) to detect surface flaws in aluminum samples. Standard ultrasonic excitation was used to generate Rayleigh surface waves. After the waves interacted with a defect, the modified responses were detected using the OFI and the results were analyzed for time-of-flight and frequency content to predict the size and location of the flaws.

Gilbert, John A.↗
NASA NTRS1991

Fuzzy geometry, entropy, and image information

Presented here are various uncertainty measures arising from grayness ambiguity and spatial ambiguity in an image, and their possible applications as image information measures. Definitions are given of an image in the light of fuzzy set theory, and of information measures and tools relevant for processing/analysis e.g., fuzzy geometrical properties, correlation, bound functions and entropy measures. Also given is a formulation of algorithms along with management of uncertainties for segmentation and object extraction, and edge detection. The output obtained here is both fuzzy and nonfuzzy. Ambiguity in evaluation and assessment of membership function are also described.

Pal, Sankar K.↗
NASA NTRS1992

Radio properties of optically selected high-redshift quasars. I - VLA observations of 22 quasars at 6 cm

A total of 22 optically selected high-redshift QSOs were obseved at 5 GHz with the VLA. The measured radio properties of low-redshift optically selected quasars indicate that radio emission should have been detected from 5-10 objects in this sample of high-redshift QSOs, but only one QSO was found to have a radio flux above the 5 sigma limit of roughly 0.2 mJy. Possible explanations of this finding are considered.

Schneider, Donald P.↗