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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 NTRS1984

High-resolution color images of Io

Color versions of the highest resolution Voyager images of Io were produced by combining the low resolution color images with the high resolution, clear filter images. High resolution versions of the orange, blue, and violet filter images are produced by: orange = high-res clear * low-res orange / low-res clear blue = high-res clear * low-res blue / low-res clear violet = high-res clear * low-res violet / low-res clear. The spectral responses of the high and low resolution clear filter images cancel, leaving the color, while the spatial frequencies of the two low resolution images cancel, leaving the high resolution.

Mcewen, A. S.↗
NASA NTRS2016

Alignment and Distortion-Free Integration of Lightweight Mirrors into Meta-Shells for High-Resolution Astronomical X-Ray Optics

High-resolution, high throughput optics for x-ray astronomy requires fabrication of well-formed mirror segments and their integration with arc-second level precision. Recently, advances of fabrication of silicon mirrors developed at NASA/Goddard prompted us to develop a new method of mirror integration. The new integration scheme takes advantage of the stiffer, more thermally conductive, and lower-CTE silicon, compared to glass, to build a telescope of much lighter weight. In this paper, we address issues of aligning and bonding mirrors with this method. In this preliminary work, we demonstrated the basic viability of such scheme. Using glass mirrors, we demonstrated that alignment error of 1" and bonding error 2" can be achieved for mirrors in a single shell. We will address the immediate plan to demonstrate the bonding reliability and to develop technology to build up a mirror stack and a whole "meta-shell".

X-ray optics↗
NASA NTRS2010

An Overview of High-Resolution, Non-Dispersive, Imaging Spectrometers for High-Energy Photons

High-resolution x-ray spectroscopy has become a powerful tool for studying the evolving universe. The grating spectrometers on the XMM and Chandra satellites initiated a new era in x-ray astronomy. Despite their successes, there is still need for instrumentation that can provide higher spectral resolution with high throughput in the Fe-K band and for extended sources. What is needed is a non-dispersive imaging spectrometer - essentially a 14-bit x-ray color camera. And a requirement for a nondispersive spectrometer designed to provide eV-scale spectral resolution is a temperature below 0.1 K. The required spectral resolution and the constraints of thermodynamics and engineering dictate the temperature regime nearly independently of the details of the sensor or the read-out technology. Low-temperature spectrometers can be divided into two classes - - equilibrium and non-equilibrium. In the equilibrium devices, or calorimeters, the energy is deposited in an isolated thermal mass and the resulting increase in temperature is measured. In the non-equilibrium devices, the absorbed energy produces quantized excitations that are counted to determine the energy. The two approaches have different strong points, and within each class a variety of optimizations have been pursued. I will present the basic fundamentals of operation and the details of the most successful device designs to date. I will also discuss how the measurement priorities (resolution, energy band, count rate) influence the optimal choice of detector technology.

Kilbourne, Caroline↗
NASA NTRS1986

High-resolution mapping of mass loss from highly evolved carbon stars

The molecular component of the mass outflow at high resolution was mapped with the Owens Valley Millimeter-Wave Interferometer in two well-known objects, CRL 2688 and CIT 6. Interferometric observations of a pair of carbon stars which are evolving toward the planetary nebula stage have revealed evidence of episodic, nonspherically symmetric mass loss, and may lead to a fuller understanding of shielding properties of the dust grains involved in these flows.

Ball, R.↗
NASA NTRS1979

AVHRR/1-FM Advanced Very High Resolution Radiometer

The advanced very high resolution radiometer is discussed. The program covers design, construction, and test of a breadboard model, engineering model, protoflight model, mechanical/structural model, and a life test model. Special bench test and calibration equipment was developed for use on the program. The flight model program objectives were to fabricate, assemble and test four of the advanced very high resolution radiometers along with a bench cooler and collimator.

Source record↗
NASA NTRS2016

High Resolution Image Reconstruction from Projection of Low Resolution Images DIffering in Subpixel Shifts

In this paper, we demonstrate a simple algorithm that projects low resolution (LR) images differing in subpixel shifts on a high resolution (HR) also called super resolution (SR) grid. The algorithm is very effective in accuracy as well as time efficiency. A number of spatial interpolation techniques using nearest neighbor, inverse-distance weighted averages, Radial Basis Functions (RBF) etc. used in projection yield comparable results. For best accuracy of reconstructing SR image by a factor of two requires four LR images differing in four independent subpixel shifts. The algorithm has two steps: i) registration of low resolution images and (ii) shifting the low resolution images to align with reference image and projecting them on high resolution grid based on the shifts of each low resolution image using different interpolation techniques. Experiments are conducted by simulating low resolution images by subpixel shifts and subsampling of original high resolution image and the reconstructing the high resolution images from the simulated low resolution images. The results of accuracy of reconstruction are compared by using mean squared error measure between original high resolution image and reconstructed image. The algorithm was tested on remote sensing images and found to outperform previously proposed techniques such as Iterative Back Projection algorithm (IBP), Maximum Likelihood (ML), and Maximum a posterior (MAP) algorithms. The algorithm is robust and is not overly sensitive to the registration inaccuracies.

0↗
NASA NTRS1992

Resolution and noise properties of the Goddard High-Resolution Spectrograph

The Goddard High-Resolution Spectrograph (GHRS) observation characteristics and data analysis procedures, including deconvolution, are discussed. Particular attention is given to the detection of weak absorption lines in low-signal-to-noise observations. It is found that observations with the GHRS large aperture provide greater sensitivity for the detection of weak, isolated spectral features than does the small aperture for equal observing times. The noise characteristics are well represented by a Poisson distribution at low signal-to-noise characteristics. It is proposed that GHRS observations should be routinely structured with the use of comb-addition, quarter-substepping, FP-SPLITS, and multiple repeats to enable the proper discrimination against noise events capable of mimicking spectral features.

Gilliland, Ronald L.↗
NASA NTRS1988

High resolution X-ray spectroscopy using microcalorimeters

The use of microcalorimeters for high-resolution, high quantum efficiency, nondispersive X-ray spectroscopy has been demonstrated over the past few years. In this paper, the principles of X-ray calorimetry are reviewed, and the results of ongoing X-ray tests using microcalorimetry are summarized. An approach to building an X-ray calorimeter spectrometer is discussed.

Kelley, R. L.↗
NASA NTRS2017

Kinematic Alignment and Bonding of Silicon Mirrors for High-Resolution Astronomical X-Ray Optics

Optics for the next generation's high-resolution, high throughput x-ray telescope requires fabrication of well-formed lightweight mirror segments and their integration at arc-second precision. Recent advances in the fabrication of silicon mirrors developed at NASA/Goddard prompted us to develop a new method of mirror alignment and integration. In this method, stiff silicon mirrors are aligned quasi-kinematically and are bonded in an interlocking fashion to produce a "meta-shell" with large collective area. We address issues of aligning and bonding mirrors with this method and show a recent result of 4 seconds-of-arc for a single pair of mirrors tested at soft x-rays.

X-ray optics↗
NASA NTRS1973

Very high resolution radiometer

A very high resolution radiometer is reported that produces visible and infrared images onboard meteorological satellites. The device has a visible and an infrared channel, a resolution in both spectral bands of 0.9260 kilometers from a 1460 kilometer polar orbit, and scans from horizon to horizon. A two stage radiant cooler with cooled outer housing permits operation in the 100 degrees kelvin range.

Schulman, J. R.↗
NASA NTRS1973

High resolution planetary observation

High-resolution ground-based planetary observations, visual and photographic, have, for several decades, seemed to have reached a rather firm limit. The causes for this restriction are briefly reviewed. At the time when space probes make major advances possible, at incomparably higher levels of expenditure, the need arises to re-examine the limiting factors of earth-based planetary resolution. In addition to familiar refinements (of which seven are listed) carried somewhat further, a specific approach, yet insufficiently developed, is the study of the atmospheric boundary layer over the observatory site and the use of an appropriately elevated station.

Kuiper, G. P.↗
NASA NTRS1986

High resolutions spectroscopy of P/Halley

High resolution spectra of the coma of P/Halley were obtained on 25 April, 2 May, and 3 May 1986. The self-scanned Digicon detector of the 2.7 m telescope coude spectrograph was used to obtain spectra at a resolution of 0.6A. Results of the observation of the NH (A 3 Pi i yields X 3 Sigma (-)) band near 3360 A are presented. The summed NH spectrum represents the results of 190 min of integration centered on the nucleus of the comet. Eight rotational lines from the P and R branches of the band are detected. The lines from the Q branch are especially weak, and are not obviously resolved in the spectrum. The data are compared with the theoretical emission spectrum of Litvak and Kuiper (1982) and substantial discrepancies are found. These discrepancies are explained through a consideration of the relative timescales for collisions, resonance fluorescence, and radiative decays of the NH molecules in the coma.

Cochran, W. D.↗
NASA NTRS1989

High resolution Doppler lidar

A high resolution lidar system was implemented to measure winds in the lower atmosphere. The wind speed along the line of sight was determined by measuring the Doppler shift of the aerosol backscattered laser signal. The system in its present configuration is stable, and behaves as indicated by theoretical simulations. This system was built to demonstrate the capabilities of the detector system as a prototype for a spaceborne lidar. The detector system investigated consisted of a plane Fabry-Perot etalon, and a 12-ring anode detector. This system is generically similar to the Fabry-Perot interferometer developed for passive wind measurements on board the Dynamics Explorer satellite. That this detector system performs well in a lidar configuration was demonstrated.

Abreu, Vincent J.↗
NASA NTRS1989

Spectral characteristics of chlorites and Mg-serpentines using high-resolution reflectance spectroscopy

High-resolution reflectance spectroscopy is used to determine the spectral characteristics of serpentines and chlorites. The structure and chemistry of hydrous layered silicates are reviewed. The possibility of distinguishing between isochemical end-members of the Mg-rich serpentine group and the capability of recognizing spectral variations in chlorites as a function of Fe/Mg ratio are demonstrated. Consideration is given to the application of the findings to terrestrial, asteroid, and meteorite studies.

King, Trude V. V.↗
NASA NTRS1991

Design of spherical varied line-space gratings for a high-resolution EUV spectrometer

A highly efficient EUV spectrograph is designed for high-resolution spectroscopic observation. The spectrograph is designed for point source astronomy in a 40-120 nm bandpass and is to be ORFEUS (Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer), scheduled for launch as the first payload of a German space platform Astro-SPAS (Astronomy Shuttle Pallet Satellite). The design uses spherical varied line-space (SVLS) grating to minimize astigmatism, coma, and spherical aberration. The effectiveness and practical feasibility of the design is proved by an SVLS grating for visible use. The image focusing properties of the SVLS grating for ORFEUS are compared to those with toroidal uniform line-space (TULS) design. The SVLS design is superior to the TULS, theoretically in resolution and image concentration, but also practically with not only fabrication ease. Four SVLS gratings with nominal groove densities of 6000, 4550, 3450, and 2616 gr./mm, and a 200 mm x 200 mm ruled area have been ruled using a numerically controlled ruling engine for use in ORFEUS.

Harada, Tatsuo↗