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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

High-resolution imaging of QSO 2305 + 187 (= 4C 18.68)

Optical imaging of QSO 2305 + 187 with resolution ranging from 0.1 to 1.0 arcsec in continuum and line emission is presented. The data are from FOCAM and the HR Cam of the Canada-France-Hawaii Telescope, and the Wide Field Camera of the Hubble Space Telescope. These are compared with previously published optical and radio images. The QSO host galaxy has the basic properties of an elliptical, but has significant irregularities, and tidal tails which indicate an ongoing gravitational interaction with a close companion.

Hutchings, J. B.↗
NASA NTRS1986

Preliminary system concepts for MODIS - A moderate resolution imaging spectrometer for EOS

Plans are underway at NASA Goddard to develop a moderate-resolution (0.5-1.0-km) imaging spectrometer with 104 spectral bands in the range from 0.4 to 14.2 microns for use as a NASA facility aboard the Space Station Earth Observation System. Science requirements call for the system to image the earth's surface every 2 d for a period of 10 yr, using two electrooptic sensors. MODIS-T (tilt) has 64 10-nm-wide channels in the 400-1000-nm range. The system has 5-cm-diameter optics, scans + or - 45 deg, and can be pointed + or - 60 deg along track. Calculated S/N is in excess of 800:1 near 400 nm. MODIS-N (nadir) scans + or - 45 deg about nadir with 12 500-m- and 28 1000-m-resolution channels, including two polarization channels and 14 thermal-IR channels. With 20-cm-diameter optics the calculated S/N of the majority of the reflected solar bands is over 1000:1. NETD values for the thermal bands are on the order of 0.1-0.2 K at 300 K. Combined MODIS-T and MODIS-N data rates are 8.3 Mb/s in daylight and 1.5 Mb/s at night, resulting in a total of 360 Gb/d.

Barnes, W. L.↗
NASA NTRS1986

Interpreting forest and grassland biome productivity utilizing nested scales of image resolution and biogeographical analysis

Data acquisition, initial site characterization, image and geographic information methods available, and brief evaluations of first-year for NASA's Thematic Mapper (TM) working group are presented. The TM and other spectral data are examined in order to relate local, intensive ecosystem research findings to estimates of carbon cycling rates over wide geographic regions. The effort is to span environments ranging from dry to moist climates and from good to poor site quality using the TM capability, with and without the inclusion of geographic information system (GIS) data, and thus to interpret the local spatial pattern of factors conditioning biomass or productivity. Twenty-eight TM data sets were acquired, archived, and evaluated. The ERDAS image processing and GIS system were installed on the microcomputer (PC-AT) and its capabilities are being investigated. The TM coverage of seven study areas were exported via ELAS software on the Prime to the ERDAS system. Statistical analysis procedures to be used on the spectral data are being identified.

Iverson, L. R.↗
NASA NTRS1993

High-resolution imaging gamma-ray spectroscopy with externally segmented germanium detectors

Externally segmented germanium detectors promise a breakthrough in gamma-ray imaging capabilities while retaining the superb energy resolution of germanium spectrometers. An angular resolution of 0.2 deg becomes practical by combining position-sensitive germanium detectors having a segment thickness of a few millimeters with a one-dimensional coded aperture located about a meter from the detectors. Correspondingly higher angular resolutions are possible with larger separations between the detectors and the coded aperture. Two-dimensional images can be obtained by rotating the instrument. Although the basic concept is similar to optical or X-ray coded-aperture imaging techniques, several complicating effects arise because of the penetrating nature of gamma rays. The complications include partial transmission through the coded aperture elements, Compton scattering in the germanium detectors, and high background count rates. Extensive electron-photon Monte Carlo modeling of a realistic detector/coded-aperture/collimator system has been performed. Results show that these complicating effects can be characterized and accounted for with no significant loss in instrument sensitivity.

Callas, J. L.↗
NASA NTRS1973

Electron-optic limitations on image resolution

Various approaches are considered to the solution of the electron-optical problem of designing an image tube configuration. Emphasis is placed on the method of computer design, and an illustration is given in which the technique is used in the design of an 80-mm image tube with a zoom capability of 3:1. The solutions are discussed to such problems as image distortion, magnification, and electron bundles striking the zoom electrode. Three types of an electron-optical configuration are examined for the electron-optic limitations to resolution: (1) the proximity image tube, (2) the magnetic-type image tube having uniform electric and magnetic fields, and (3) the electrostatic-type image tube such as the 80-mm zoom tube.

Engstrom, R. W.↗
NASA NTRS1990

High-resolution imaging of globular cluster cores

An approach based on the maximum entropy method aimed at increasing angular resolution to study globular cluster cores is presented. To perform the image restoration the Gull-Skilling (1989) MEMSYS-3 code for maximum entropy reconstruction of arbitrary data sets was used. This software was recently applied to restoration of ESO images of the R136 object in the core of the 30 Doradus nebula. It was demonstrated that the software made it possible to restore an image at subpixel spatial scales which facilitates the detection of very high-resolution structure in the restored image.

Weir, N.↗
NASA NTRS1992

High resolution images of P/Tempel 1 and P/Tempel 2 constructed from IRAS survey data

Infrared images of P/Tempel 1 and P/Tempel 2 were constructed from IRAS survey data using a computer algorithm based on the Maximum Correlation Method for Image Construction (Aumann et al, 1990). The resulting images are of sufficiently high quality and resolution to delineate coma and tail morphology, and permit accurate photometry of the total dust complex. Comparisons of the infrared colors and photometric profiles of Tempel 1 and Tempel 2 at similar heliocentric distances show that the grains produced by the two comets are quite similar in radiometric and dynamic properties. Tempel 1 is found to produce about 30 percent more dust in its coma and tail than Tempel 2. The comae of Tempel 1 and Tempel 2 are expanding with mean velocities of 5.8 plus or minus 0.07 and 6.1 plus or minus 0.17 m/sec respectively, indicative of the ejection of large grains. The IRAS cataloged infrared fluxes (Walker, 1986) are found to be underestimated by as much as a factor of three for the comets. Therefore, it is essential to create images of the comets to obtain meaningful IRAS photometry.

Walker, Russell G.↗
NASA NTRS2003

MRO High Resolution Imaging Science Experiment (HiRISE): Instrument Development

The primary functional requirement of the HiRISE imager is to allow identification of both predicted and unknown features on the surface of Mars to a much finer resolution and contrast than previously possible. This results in a camera with a very wide swath width, 6km at 300km altitude, and a high signal to noise ratio, >100:1. Generation of terrain maps, 30 cm vertical resolution, from stereo images requires very accurate geometric calibration. The project limitations of mass, cost and schedule make the development challenging. In addition, the spacecraft stability must not be a major limitation to image quality. The nominal orbit for the science phase of the mission is a 3pm orbit of 255 by 320 km with periapsis locked to the south pole. The track velocity is approximately 3,400 m/s.

Alan Delamere↗
NASA NTRS2015

Near-IR High-Resolution Imaging Polarimetry of the SU Aur Disk: Clues for Tidal Tails?

We present new high-resolution (approximately 0.09) H-band imaging observations of the circumstellar disk around the T Tauri star SU Aur. Our observations with Subaru-HiCIAO have revealed the presence of scattered light as close as 0.15 (approximately 20 AU) to the star. Within our image, we identify bright emission associated with a disk with a minimum radius of approximately 90 AU, an inclination of approximately 35 deg from the plane of the sky, and an approximate PA of 15 deg for the major axis. We find a brightness asymmetry between the northern and southern sides of the disk due to a non-axisymmetric disk structure. We also identify a pair of asymmetric tail structures extending east and west from the disk. The western tail extends at least 2. 5 (350 AU) from the star, and is probably associated with a reflection nebula previously observed at optical and near-IR wavelengths. The eastern tail extends at least 1 (140 AU) at the present signal-to-noise. These tails are likely due to an encounter with an unseen brown dwarf, but our results do not exclude the explanation that these tails are outflow cavities or jets.

protoplanetary disks↗
NASA NTRS1987

X-ray optics - A technique for high resolution imaging

Both scattering and figure errors in grazing incidence optics are larger in the plane of incidence than out-of-plane by a factor equal to 1/sin theta, where theta is the graze angle. When the full annular aperture of a grazing incidence telescope is stopped down, the point spread function becomes highly elliptical with a width as much as sin theta times narrower than the full image. In practice, this means that improvements in resolution of up to 100 times can be achieved, and effective resolution can approach the diffraction limit. Laboratory data demonstrating the effect are presented.

Cash, Webster↗
NASA NTRS1988

Optical system design alternatives for the Moderate-Resolution Imaging Spectrometer-Tilt (MODIS-T) for the Earth Observing System (EOS)

The MODIS consists of two synergistic sensors with a total of 104 spectral bands in the 0.4-14.2-micron range. MODIS-T (Tilt) is one of these sensors. It is a 64-channel imaging spectrometer with a required 10 nm spectral resolution (FWHM) in the 400 to 1040 nm spectral range. The system will have a 1 km IFOV, a wide scan for global coverage in three days, and be capable of being pointed fore and aft of nadir by + or - 50 degrees.

Maymon, Peter W.↗
NASA NTRS2001

Two-photon interferometry for high-resolution imaging

We discuss advantages of using non-classical states of light for two aspects of optical imaging: creating of miniature images on photosensitive substrates, which constitutes the foundation for optical lithography, and conversely, imaging of micro objects. In both cases, the classical resolution limit given by the Rayleigh criterion is approximately a half of the optical wavelength. It has been shown, however, that by using multi-photon quantum states of the light field, and multi-photon sensitive material or detector, this limit can be surpassed. In the present work, we give a rigorous quantum mechanical treatment of this problem, address some particularly widespread misconceptions and discuss the requirements arising on the way of turning the research on quantum imaging into a practical technology.

quantum technology↗
NASA NTRS1981

Wide area, coarse resolution imaging with satellite-borne synthetic aperture radars in low-earth and geosynchronous orbits

The LEOSAR (low-earth-orbit synthetic aperture radar) can map around the earth, while the GEOSAR (geosynchronous synthetic aperture radar) can map a large global area bounded in both longitudinal and latitudinal ranges. This paper presents the mapping capabilities and power requirements of both LEOSAR and GEOSAR. For a low-earth-orbit SAR, images of swath widths of the order of 700 km are possible with 100-m resolution and 300 watts of average transmitter power at 9375 MHz. From a SAR in a 50-deg inclined geosynchronous circular orbit, the contiguous United States can be imaged in about 6.4 hours with 100-m resolution, 345 watts of average transmitter power, and a data rate of 6 megabits/sec at 2450 MHz.

Tomiyasu, K.↗
NASA NTRS1982

High-resolution imaging with a two-dimensional resistive anode photon counter

A method to achieve high spatial resolution readout of individual photoelectron events using microchannel plates and a resistive anode is presented. A clamped pair of microchannel plates is used, followed by a gap and a clamped triplet of microchannel plates in cascade to achieve a high stable electron gain of 3 x 10 to the 7th. The gain allows the position determination of each photoelectron event with a very high signal-to-noise ratio. A model consisting of a windowless vacuum-ultraviolet image sensor is presented to demonstrate 500 x 500 pixel images of 50 micron FWHM over a 25-mm circular field of view. The detector offers sufficient speed, sensitivity and resolution for a variety of applications, and the mount design is compatible with planar, remotely-processed, proximity-focused photocathodes.

Firmani, C.↗
NASA NTRS1998

High Resolution Imaging of the Sun with CORONAS-1

We applied several image restoration and enhancement techniques, to CORONAS-I images. We carried out the characterization of the Point Spread Function (PSF) using the unique capability of the Blind Iterative Deconvolution (BID) technique, which recovers the real PSF at a given location and time of observation, when limited a priori information is available on its characteristics. We also applied image enhancement technique to extract the small scale structure imbeded in bright large scale structures on the disk and on the limb. The results demonstrate the capability of the image post-processing to substantially increase the yield from the space observations by improving the resolution and reducing noise in the images.

Karovska, Margarita↗
NASA NTRS1977

High resolution imaging X-ray detector for astronomical measurements

The article describes the X-ray detector which will provide second-of-arc images for the HEAO-B X-ray observatory. The instrument uses microchannel plates as a photocathode surface and imaging photoelectron multiplier, and a crossed wire grid as a two-dimensional position-sensitive detector. Position determination is accomplished by electronic interpolation between the coarse grid wires. The detector provides the arrival time and position of each event which occurs within its field of view. Measurements of the spatial resolution (15 microns), temporal resolution (7.8 microsec), image distortion (less than 10 microns), uniformity of efficiency (less than plus or minus 10%), dark counting rate (0.2 cts/sq cm/s), and quantum efficiency (10% at 1.54 keV) of this detector are described. A summary of the procedure which was found useful during the initial turn-on of microchannel plates is given.

Henry, J. P.↗
NASA NTRS2010

Super Resolution Image Enhancement for a Flash Lidar: Back Projection Method

In this paper a new image processing technique for flash LIDAR data is presented as a potential tool to enable safe and precise spacecraft landings in future robotic or crewed lunar and planetary missions. Flash LIDARs can generate, in real-time, range data that can be interpreted as a 3-dimensional (3-D) image and transformed into a corresponding digital elevation map (DEM). The NASA Autonomous Landing and Hazard Avoidance (ALHAT) project is capitalizing on this new technology by developing, testing and analyzing flash LIDARs to detect hazardous terrain features such as craters, rocks, and slopes during the descent phase of spacecraft landings. Using a flash LIDAR for this application looks very promising, however through theoretical and simulation analysis the ALHAT team has determined that a single frame, or mosaic, of flash LIDAR data may not be sufficient to build a landing site DEM with acceptable spatial resolution, precision, size, or for a mosaic, in time, to meet current system requirements. One way to overcome this potential limitation is by enhancing the flash LIDAR output images. We propose a new super-resolution algorithm applicable to flash LIDAR range data that will create a DEM with sufficient accuracy, precision and size to meet current ALHAT requirements. The performance of our super-resolution algorithm is analyzed by processing data generated during a series of simulation runs by a high fidelity model of a flash LIDAR imaging a high resolution synthetic lunar elevation map. The flash LIDAR model is attached to a simulated spacecraft by a gimbal that points the LIDAR to a target landing site. For each simulation run, a sequence of flash LIDAR frames is recorded and processed as the spacecraft descends toward the landing site. Each run has a different trajectory profile with varying LIDAR look angles of the terrain. We process the output LIDAR frames using our SR algorithm and the results show that the achieved level of accuracy and precision of the SR generated landing site DEM is more than adequate for detecting hazardous terrain features and identifying safe areas.

Bulyshev, Alexander↗
NASA NTRS1994

High-resolution imaging of the Pluto-Charon system with the Faint Object Camera of the Hubble Space Telescope

Images of the Pluto-Charon system were obtained with the Faint Object Camera (FOC) of the Hubble Space Telescope (HST) after the refurbishment of the telescope. The images are of superb quality, allowing the determination of radii, fluxes, and albedos. Attempts were made to improve the resolution of the already diffraction limited images by image restoration. These yielded indications of surface albedo distributions qualitatively consistent with models derived from observations of Pluto-Charon mutual eclipses.

Albrecht, R.↗