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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Image Gradient Decomposition for Parallel and Memory-Efficient Ptychographic Reconstruction

Ptychography is a popular microscopic imaging modality for many scientific discoveries and sets the record for highest image resolution. Unfortunately, the high image resolution for ptychographic reconstruction requires significant amount of memory and computations, forcing many applications to compromise their image resolution in exchange for a smaller memory footprint and a shorter reconstruction time. In this paper, we propose a novel image gradient decomposition method that significantly reduces the memory footprint for ptychographic reconstruction by tessellating image gradients and diffraction measurements into tiles. In addition, we propose a parallel image gradient decomposition method that enables asynchronous point-to-point communications and parallel pipelining with minimal overhead on a large number of GPUs. Our experiments on a Titanate material dataset (PbTiO3) with 16632 probe locations show that our Gradient Decomposition algorithm reduces memory footprint by 51 times. In addition, it achieves time-to-solution within 2.2 minutes by scaling to 4158 GPUs with a super-linear strong scaling efficiency at 364% compared to runtimes at 6 GPUs. This performance is 2.7 times more memory efficient, 9 times more scalable and 86 times faster than the state-of-the-art algorithm.

Wang, Xiao↗
DOE OSTI2023

High-Resolution Image Products Acquired from Mid-Sized Uncrewed Aerial Systems for Land–Atmosphere Studies

We assess the viability of deploying commercially available multispectral and thermal imagers designed for integration on small uncrewed aerial systems (sUASs, <25 kg) on a mid-size Group-3-classification UAS (weight: 25–600 kg, maximum altitude: 5486 m MSL, maximum speed: 128 m/s) for the purpose of collecting a higher spatial resolution dataset that can be used for evaluating the surface energy budget and effects of surface heterogeneity on atmospheric processes than those datasets traditionally collected by instrumentation deployed on satellites and eddy covariance towers. A MicaSense Altum multispectral imager was deployed on two very similar mid-sized UASs operated by the Atmospheric Radiation Measurement (ARM) Aviation Facility. This paper evaluates the effects of flight on imaging systems mounted on UASs flying at higher altitudes and faster speeds for extended durations. We assess optimal calibration methods, acquisition rates, and flight plans for maximizing land surface area measurements. We developed, in-house, an automated workflow to correct the raw image frames and produce final data products, which we assess against known spectral ground targets and independent sources. We intend this manuscript to be used as a reference for collecting similar datasets in the future and for the datasets described within this manuscript to be used as launching points for future research.

47 OTHER INSTRUMENTATION↗
NASA NTRS1976

High-resolution imaging X-ray detector

The paper describes an X-ray detector using microchannel plates as a photocathode surface and imaging photoelectron multiplier, and a crossed wire grid as a two-dimensional position-sensitive detector. The position resolution is 10 microns. The crossed wire grid consists of 100-micron-diam wires on 200-micron centers. Position sensing is accomplished by electronic interpolation to 1/20 of the wire spacing. The quantum efficiency of the microchannel plates varies from 29% at 0.28 keV to 5% at 3 keV. This detector will provide second-of-arc X-ray imaging in the focal plane of the 342.9-cm focal length grazing-incidence telescope being prepared for the HEAO-B observatory. By addition of suitable photocathodes, it can be used for single-photon imaging light detection in the UV, visible, and near-IR-ranges. In all cases, it gives a very low dark counting rate, allows timing of individual events to 1 microsec or less, and can handle counting rates up to 10,000 per sec.

Kellogg, E.↗
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 NTRS1980

High resolution imaging at large telescopes

Image recovery at a resolution limited only by diffraction is now possible at large telescopes. The theory of speckle image reconstruction is explained and the current status of a video recording and digitization system for the reconstruction procedure is described. Potential applications of the process when used with very large telescopes are discussed. The constraints on telescope design imposed by these techniques are listed.

Nisenson, P.↗
NASA NTRS1985

The LAMAR telescope module for high throughput imaging and spectroscopy

Kirkpatrick-Baez mirror assemblies for the LAMAR experiment of the Space Shuttle are described. The aperture is 20 cm x 30 cm and the distance from the front of the mirror to the focal plane is 3.4 m. The reflectors are made from 1.8 mm gold coated float glass. A prototype brassboard mirror was constructed with only one-third of the plates. Its angular resolution is 35 arcsec (HPW) in visible light. X-ray tests over small areas indicate very little scattering. The fabrication technique is applicable to larger mirror systems such as those of XMM. The use of flatter material for the reflectors results in better angular resolution.

Gorenstein, P.↗
NASA NTRS1986

Optical astronomical interferometry - Requirements on stellar Michelson interferometry and heterodyne interferometry for high-resolution imaging

The requirements for optical path compensation on space-based (no atmospheric-induced disturbance) heterodyne interferometers and generalized Michelson stellar interferometers are developed. It is demonstrated that heterodyne interferometers require optical path compensation to well within the coherence length dictated by its bandwidth, while Michelson stellar interferometers require compensation to a fraction of their utilized wavelength.

Silverglate, P. R.↗
NASA NTRS1986

High resolution imaging

Diffraction-limited telescopic observations were obtained of solar system objects and a program of research into Uranus, Neptune, Pluto and the asteroids based upon the data obtained was persued. Two camera systems appropriate for this work were developed. Most importantly, the PAPA photon address camera was developed and proven. Algorithms were developed for both phase and amplitude recovery and were validated on theoretical and laboratory data and to a limited extent on telescopic data. A laboratory simulator was constructed that was used for development but is also available for controlled investigation of image reconstruction. During 1985 two successful expeditions were made to Hawaii and Cerro Tololo and a large body of data on Pluto, Uranus, Neptune and two asteroids are on tape.

Goody, R.↗
NASA NTRS1986

Conceptual design of the High-Resolution Imaging Spectrometer (HIRIS) for EOS

The design concept and practical realization of HIRIS, the imaging spectrometer being developed for the Space Station Earth Observation System (EOS) on the basis of the Shuttle Imaging Spectrometer Experiment (SISEX), are discussed. Nominal operating parameters for HIRIS include altitude 705 km, GIFOV 30 m, swath 48.4 km, spectral sampling interval 10 nm, spectral coverage 400-2450 nm, cross-track pointing +20/-20 deg, down-track pointing +60/-30 deg, and raw data rate (at 8 bits/pixel) 621 Mb/s. The f/1.9 optical configuration for HIRIS is shown in a drawing, and consideration is given to technological challenges being encountered in modifying the SISEX focal-plane detectors, data-reduction procedures, and cooling system to meet the HIRIS requirements.

Herring, Mark↗
NASA NTRS1987

Color enhancement of highly correlated images. II - Channel ratio and 'chromaticity' transformation techniques

Two techniques for enhancing the color of multispectral images are described; both involve ratioing of data from different image channels. In the first technique, the ratioed data are assigned the primary color for display as color ratio pictures, and in the second method, image data are transformed to RGB chromaticity coordinates by ratioing the data acquired in three channels to the sum of their intensities. The two techniques are applied to a NASA Thermal-IR Multispectral Scanner (TIMS) image of Death Valley and to a Landsat MSS image of the Mojave Desert. The basic principles of ratioing are discussed, and the effects of atmospheric path radiances on the interpretation of ratioed images are investigated. It is observed that the color pictures produced using these two enhancement techniques are similar to the pictures enhanced by decorrelation and hue-saturation-intensity methods.

Gillespie, Alan R.↗
NASA NTRS1987

Large format, high resolution images sensors

The performance requirements for scientific-quality CCDs are discussed, focusing on the design of two devices, and the progress toward achieving the desired performance is discussed. These devices are intended for rear-illuminated applications and have 512 x 512 and 2048 x 2048 pixel formats. The thinned 10 to 20 micron thick Si membrane is fully supported by a unique glass ceramic substrate. Quantum efficiencies of greater than 70 percent at 700 nm and greater than 40 percent at wavelengths less than 400 nm have been measured on a test device. Dark currents as low as 6 pA/sq cm also have been measured recently.

Blouke, Morley M.↗
NASA NTRS1988

HIRIS: NASA's high-resolution imaging spectrometer for the Earth Observing System (EOS)

The HIRIS design includes 10 nm spectral bands from 0.4 to 2.5 micron at 30 m spatial resolution over a 24 or 30 km swath. This resolution allows identification of many minerals in rocks and soils, important algal pigments in oceans and inland water and spectral changes in land canopy. In the 824 km orbit altitude proposed, the cross track pointing capability allows 4 to 5 views during a 16 day revisit cycle.

Dozier, J.↗
NASA NTRS1990

Summary of results and conclusions based on analysis of volume imaging and high spectral resolution lidar data acquired during FIRE phase 1, part 2

Since the fall of 1986, cirrus clouds were observed with backscatter cross sections ranging from less than 1 x 10(exp -7) to 4.2 x 10(exp -5)m/sr, optical thicknesses ranging from less than .003 to greater than 2.7, and bulk average backscatter phase functions from .02 to .065/sr. Cirrus cloud structures were recorded ranging in vertical extent from 0.1 to 8 km, having horizontal scales from 10's of meters to 266 km, and exhibiting aspect ratios of from 1:5 to 1:100. The altitude relationship between cloud top and bottom boundaries and the optical center of the cloud is influenced by the type of formation observed. Cirrus morphology and generation processes appear to be related to the wind field. The high spectral resolution lidar (HSRL) was adapted to the task of cirrus cloud optical property measurement. The HSRL data reported were collected with the CuCl2 transmitter producing 50 mW of output power, achieving eye safe, direct optical depth and backscatter cross section measurements with 10 minute averaging times.

Grund, Christian J.↗
NASA NTRS1991

High accuracy image centroiding with a moving Ronchi ruling

A moving Ronchi ruling at the focal plane of a telescope has been employed to measure the relative motions of stars with great accuracy. The method has long-term stability and exceptional linearity over a relatively large field-of-view. This measurement technique may prove useful in other applications where such capabilities are required. This paper employs Fourier optics to describe the operation of the device, explore performance at very long and very short periods, and consider ruling profiles and other means of optimizing performance.

Lawrence, George N.↗
NASA NTRS1990

High Resolution Imaging Spectrometer (HIRIS) - A major advance in imaging spectrometry

HIRIS, a facility instrument on the Earth Observing System Platform, will enable scientists to both identify and interpret changes, in the global environment, at a level of detail unavailable with previous instrumentation. This instrument will make localized measurements of biological, ecological, climatological, hydrological, and geological properties, and, with its finer wavelength sampling and full spectral coverage over the wavelength region of interest, will allow these properties to be identified and studied quantitatively from space. The data obtained will be downlinked from space, processed, catalogued, stored in active archives for easy access, and distributed to users.

Rockey, Donald E.↗