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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Good imaging with very fast paraboloidal primaries - An optical solution and some applications

Attention is given to the imaging performance improvement obtainable in telescopes with fast parabolic primaries by means of two-mirror correctors of the Paul-Baker type. Images with 80 percent of the energy concentrated within 0.2 arcsec are projected for an f/1 primary relaying to an f/2 final focus, over a 1 deg-diameter field. It is noted that the mechanical structure and enclosure of a large telescope built with these fast optics should be significantly smaller and less expensive than those for conventional optics. The application of the Paul-Baker corrector system is explored for such diverse telescope types as those employing six off-axis primary mirrors, UV astronomy telescopes with no chromatic aberration, a low emissivity IR astronomy instrument with an off-axis f/1 parent primary mirror part, and thin rectangular aperture telescopes which are useful for spectroscopy and photometry.

Angel, J. R. P.↗
NASA NTRS1993

Acousto-optic infrared spectral imager for Pluto fast flyby

Acousto-optic tunable filters (AOTF's) enable the design of compact, two-dimensional imaging spectrometers with high spectral and spatial resolution and with no moving parts. Tellurium dioxide AOTF's operate from about 400 nm to nearly 5 microns, and a single device will tune continuously over one octave by changing the RF acoustic frequency applied to the device. An infrared (1.2-2.5 micron) Acousto-Optic Imaging Spectrometer (AImS) was designed that closely conforms to the surface composition mapping objectives of the Pluto Fast Flyby. It features a 75-cm focal length telescope, infrared AOTF, and 256 x 256 NICMOS-3 focal plane array for acquiring narrowband images with a spectral resolving power (lambda/delta(lambda)) exceeding 250. We summarize the instrument design features and its expected performance at the Pluto-Charon encounter.

Glenar, D. A.↗
NASA NTRS2011

A Compact, Fast, Wide-Field Imaging Spectrometer System

We present test results from a compact, fast (F/1.4) imaging spectrometer system with a 33 degree field of view, operating in the 450-1650 nm wavelength region with an extended response InGaAs detector array. The system incorporates a simple two-mirror telescope and a steeply concave bilinear groove diffraction grating made with gray scale x-ray lithography techniques. High degree of spectral and spatial uniformity (97%) is achieved.

diffraction grating↗
NASA NTRS1993

Visible Imaging on the Pluto Fast Flyby Mission

Objectives for visible imaging of the Pluto-Charon system, as prescribed by the Outer Planets Science Working Group, are to acquire (1) global observations (FOV of approximately 5000 IFOV's) at 1 km/line-pair for the purpose of characterizing surface morphology and geology, (2) global observations in 3-5 broadband colors at 5-10 km/line-pair for studies of surface properties and composition as it relates to morphology, and (3) selected observations at higher spatial resolution for study of surface processes. Several factors of the Pluto Fast Flyby mission make these difficult to achieve. These factors along with other aspects of the mission are discussed.

Malin, M. C.↗
NASA NTRS2015

A Fast Visible-Infrared Imaging Radiometer Suite Simulator for Cloudy Atmopheres

A fast instrument simulator is developed to simulate the observations made in cloudy atmospheres by the Visible Infrared Imaging Radiometer Suite (VIIRS). The correlated k-distribution (CKD) technique is used to compute the transmissivity of absorbing atmospheric gases. The bulk scattering properties of ice clouds used in this study are based on the ice model used for the MODIS Collection 6 ice cloud products. Two fast radiative transfer models based on pre-computed ice cloud look-up-tables are used for the VIIRS solar and infrared channels. The accuracy and efficiency of the fast simulator are quantify in comparison with a combination of the rigorous line-by-line (LBLRTM) and discrete ordinate radiative transfer (DISORT) models. Relative errors are less than 2 for simulated TOA reflectances for the solar channels and the brightness temperature differences for the infrared channels are less than 0.2 K. The simulator is over three orders of magnitude faster than the benchmark LBLRTM+DISORT model. Furthermore, the cloudy atmosphere reflectances and brightness temperatures from the fast VIIRS simulator compare favorably with those from VIIRS observations.

VIIRS Instrument Simulator↗
NASA NTRS1991

A fast algorithm for image-based ranging

Image-based ranging has emerged as a critical issue in the low altitude operation of flight vehicles such as rotorcraft and planetary landers. These flight regimes require ranging systems for recovering the geometry of the terrain and obstacles for use with guidance algorithms. The development of a ranging equation combining image irradiance together with various order spatial partial derivatives and the vehicle motion parameters is discussed. The ranging equation is in the form of a polynomial in scene depth. Two-dimensional linear filters are then used to compute the coefficients of this polynomial to result in a fast image-based ranging algorithm. Performance of the algorithm is demonstrated using laboratory images.

Menon, P. K. A.↗
NASA NTRS1994

Fast computational scheme of image compression for 32-bit microprocessors

This paper presents a new computational scheme of image compression based on the discrete cosine transform (DCT), underlying JPEG and MPEG International Standards. The algorithm for the 2-d DCT computation uses integer operations (register shifts and additions / subtractions only); its computational complexity is about 8 additions per image pixel. As a meaningful example of an on-board image compression application we consider the software implementation of the algorithm for the Mars Rover (Marsokhod, in Russian) imaging system being developed as a part of Mars-96 International Space Project. It's shown that fast software solution for 32-bit microprocessors may compete with the DCT-based image compression hardware.

Kasperovich, Leonid↗
NASA NTRS2006

Fast Lossless Compression of Multispectral-Image Data

An algorithm that effects fast lossless compression of multispectral-image data is based on low-complexity, proven adaptive-filtering algorithms. This algorithm is intended for use in compressing multispectral-image data aboard spacecraft for transmission to Earth stations. Variants of this algorithm could be useful for lossless compression of three-dimensional medical imagery and, perhaps, for compressing image data in general.

Klimesh, Matthew↗
NASA NTRS1972

Image Display and Manipulation System (IDAMS) program documentation, Appendixes A-D

The IDAMS Processor is a package of task routines and support software that performs convolution filtering, image expansion, fast Fourier transformation, and other operations on a digital image tape. A unique task control card for that program, together with any necessary parameter cards, selects each processing technique to be applied to the input image. A variable number of tasks can be selected for execution by including the proper task and parameter cards in the input deck. An executive maintains control of the run; it initiates execution of each task in turn and handles any necessary error processing.

Cecil, R. W.↗
NASA NTRS1999

Weighted MinMax Algorithm for Color Image Quantization

The maximum intercluster distance and the maximum quantization error that are minimized by the MinMax algorithm are shown to be inappropriate error measures for color image quantization. A fast and effective (improves image quality) method for generalizing activity weighting to any histogram-based color quantization algorithm is presented. A new non-hierarchical color quantization technique called weighted MinMax that is a hybrid between the MinMax and Linde-Buzo-Gray (LBG) algorithms is also described. The weighted MinMax algorithm incorporates activity weighting and seeks to minimize WRMSE, whereby obtaining high quality quantized images with significantly less visual distortion than the MinMax algorithm.

Reitan, Paula J.↗
NASA NTRS1988

Adaptive Bandwidth Compression For Moving Images

Data compressed in images with fast motion and expanded when motion slows. Proposed data-compression scheme adapts transmission rate for moving image to speed of motion of image. Laser rangefinder measures speed of target. Adaptive sampler determines required resolution of target image on basis of measured speed and provides decommutator at control station with more or fewer partial image fields per unit time. When monitor displays maximum number of fields simultaneously, resolution is highest.

Graham, Olin L.↗
NASA NTRS1997

Thermal Characterization of Defects in Aircraft Structures Via Spatially Controlled Heat Application

Recent advances in thermal imaging technology have spawned a number of new thermal NDE techniques that provide quantitative information about flaws in aircraft structures. Thermography has a number of advantages as an inspection technique. It is a totally noncontacting, nondestructive, imaging technology capable of inspecting a large area in a matter of a few seconds. The development of fast, inexpensive image processors have aided in the attractiveness of thermography as an NDE technique. These image processors have increased the signal to noise ratio of thermography and facilitated significant advances in post-processing. The resulting digital images enable archival records for comparison with later inspections thus providing a means of monitoring the evolution of damage in a particular structure. The National Aeronautics and Space Administration's Langley Research Center has developed a thermal NDE technique designed to image a number of potential flaws in aircraft structures. The technique involves injecting a small, spatially controlled heat flux into the outer surface of an aircraft. Images of fatigue cracking, bond integrity and material loss due to corrosion are generated from measurements of the induced surface temperature variations. This paper will present a discussion of the development of the thermal imaging system as well as the techniques used to analyze the resulting thermal images. Spatial tailoring of the heat coupled with the analysis techniques represent a significant improvement in the delectability of flaws over conventional thermal imaging. Results of laboratory experiments on fabricated crack, disbond and material loss samples will be presented to demonstrate the capabilities of the technique. An integral part of the development of this technology is the use of analytic and computational modeling. The experimental results will be compared with these models to demonstrate the utility of such an approach.

Cramer, K. Elliott↗
NASA NTRS2007

OMCat: Catalogue of Serendipitous Sources Detected with the XMM-Newton Optical Monitor

The Optical Monitor Catalogue of serendipitous sources (OMCat) contains entries for every source detected in the publically available XMM-Newton Optical Monitor (OM) images taken in either the imaging or "fast" modes. Since the OM records data simultaneously with the X-ray telescopes on XMM-Newton, it typically produces images in one or more near-UV/optical bands for every pointing of the observatory. As of the beginning of 2006, the public archive had covered roughly 0.5% of the sky in 2950 fields. The OMCat is not dominated by sources previously undetected at other wavelengths; the bulk of objects have optical counterparts. However, the OMCat can be used to extend optical or X-ray spectral energy distributions for known objects into the ultraviolet, to study at higher angular resolution objects detected with GALEX, or to find high-Galactic-latitude objects of interest for UV spectroscopy.

Kuntz, K. D.↗
NASA NTRS2010

Fast, High-Resolution Terahertz Radar Imaging at 25 Meters

We report improvements in the scanning speed and standoff range of an ultra-wide bandwidth terahertz (THz) imaging radar for person-borne concealed object detection. Fast beam scanning of the single-transceiver radar is accomplished by rapidly deflecting a flat, light-weight subreflector in a confocal Gregorian optical geometry. With RF back-end improvements also implemented, the radar imaging rate has increased by a factor of about 30 compared to that achieved previously in a 4 m standoff prototype instrument. In addition, a new 100 cm diameter ellipsoidal aluminum reflector yields beam spot diameters of approximately 1 cm over a 50x50 cm field of view at a range of 25 m, although some aberrations are observed that probably arise from misaligned optics. Through-clothes images of a concealed threat at 25 m range, acquired in 5 seconds, are presented, and the impact of reduced signal-to-noise from an even faster frame rate is analyzed. These results inform the system requirements for eventually achieving sub-second or video-rate THz radar imaging.

standoff concealed weapons detection↗
NASA NTRS2007

Hybrid-dual-fourier tomographic algorithm for a fast three-dimensionial optical image reconstruction in turbid media

A reconstruction technique for reducing computation burden in the 3D image processes, wherein the reconstruction procedure comprises an inverse and a forward model. The inverse model uses a hybrid dual Fourier algorithm that combines a 2D Fourier inversion with a 1D matrix inversion to thereby provide high-speed inverse computations. The inverse algorithm uses a hybrid transfer to provide fast Fourier inversion for data of multiple sources and multiple detectors. The forward model is based on an analytical cumulant solution of a radiative transfer equation. The accurate analytical form of the solution to the radiative transfer equation provides an efficient formalism for fast computation of the forward model.

Alfano, Robert R.↗
NASA NTRS2021

Recent Improvements in the Dart Model for Atmosphere, Topography, Large Landscape, Chlorophyll Fluorescence, Satellite Image Inversion

Physical models simulating the radiative budget (RB) and remote sensing (RS) observation of three-dimensional (3D) landscapes are critical to better understand human and natural components of the Earth system and further develop RS technology. DART is one of the most comprehensive 3D models of Earth-atmosphere optical radiative transfer (RT), from ultraviolet (UV) to thermal infrared (TIR). It simulates the optical signal of proximal, aerial and satellite imaging spectrometers and laser scanners, the 3D RB and solar induced chlorophyll fluorescence (SIF) signal, for any urban or natural landscape and any experimental or instrument configuration. It is freely available for research and teaching activities (https://dart.omp.eu). Here, five recent advances are presented. 1) Atmosphere RT. 2) RT in non repetitive topography. 3) Monte Carlo modelling for fast RS image simulation of large landscapes. 4) SIF modelling for vegetation simulated as facets and turbid cells. 5) RS image inversion for mapping the optical properties of urban material and the urban radiative budget.

DART↗
NASA NTRS2019

The Solar Neutron TRACking (SONTRAC) Instrument for the Detection of Fast Neutrons

The detection of fast neutrons has important applications in several fields including solar, Geospace and planetary physics. Neutrons are challenging to detect and measurements of them typically suffer from high background rates. High-energy neutrons (>50 MeV) pose even more challenges, because the traditional double-scatter technique based on a time-of-flight (ToF) measurement is limited by short flight paths and small detector sizes characteristic of small satellite platforms. It is now possible to perform high-energy neutron measurements inside a large monolithic detector by imaging the recoil proton tracks, thus eliminating the need for a measure of the time-of-flight. The concept is based on a spectrometer assembled from numerous thin hydrogenous scintillating fibers that allow ionization track imaging. Fine grained readout is now possible with arrays of1-mm pitch silicon photomultipliers (SiPMs). The Solar Neutron TRACking (SONTRAC) instrument, equipped with scintillating fibers readout with SiPMs sensors, provides high-resolution, fine grained, imaging of fast (between 20-200 MeV) neutron scatters in a compact, low-power design ideal for small satellite(and aircraft) platforms. We discuss below applications of this technology and performance characteristics of the prototype SONTRAC instrument.

de Nolfo, Georgia A.↗