Effect of periodic surface-potential variation on high-field tunneling in field-ionization processes
Field-ion microscope image formation, determining periodic surface potential variation effects on high field tunneling
Schrenk, G. L.↗
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The improvement of star positions by photographic methods
A brief description is given of the new astrometric camera and of the program on which it is being employed. This is the photography of the southern sky so that each star appears on at least four overlapping plates. Sets of star coordinates measured on each plate are combined with a limited set of provisional meridian places to give an accurate set of relative star positions which are independent of the meridian system together with a set of residuals for each plate-star. The technique is based on a simple geometrical model of image formation on photographic plates. Current investigations are concerned with the elimination of sources of systematic deviation from this model.
Clube, S. V. M.↗
ERTS two-inch RBV cameras performance characteristics.
A very-high resolution multispectral television camera system is being developed for NASA for use on the ERTS program. There are three cameras in the system, each viewing the same area but operating in the blue-green, red, and near-infrared spectral bands. In the laboratory, the cameras' limiting resolution is 4500 TV lines over the 25x25-mm image format of the return beam vidicon (RBV). Analysis of typical ERTS scenes shows that actual contrast ratios will be much lower than those of laboratory test targets. A model was developed to predict the resolving power performance of the RBV camera under realistic conditions.
Miller, B. P.↗
Electronographic cameras for space astronomy.
Magnetically-focused electronographic cameras have been under development at the Naval Research Laboratory for use in far-ultraviolet imagery and spectrography, primarily in astronomical and optical-geophysical observations from sounding rockets and space vehicles. Most of this work has been with cameras incorporating internal optics of the Schmidt or wide-field all-reflecting types. More recently, we have begun development of electronographic spectrographs incorporating an internal concave grating, operating at normal or grazing incidence. We also are developing electronographic image tubes of the conventional end-window-photo-cathode type, for far-ultraviolet imagery at the focus of a large space telescope, with image formats up to 120 mm in diameter.
Carruthers, G. R.↗
Lunar laser ranging data deposited in the National Space Science Data Center: Filtered Observations for July through December 1972 and unfiltered photon dections for January through July 1973
The data acquired by the lunar laser ranging experiment are described for the six months period ending 31 December, 1972. The data are contained on two files of a binary tape written in card image format, using a CDC 6400/6600 computer. Photon detections, and unfiltered photon stops are included.
Mulholland, J. D.↗
Kitt Peak speckle camera
The speckle camera in regular use at Kitt Peak National Observatory since 1974 is described in detail. The design of the atmospheric dispersion compensation prisms, the use of film as a recording medium, the accuracy of double star measurements, and the next generation speckle camera are discussed. Photographs of double star speckle patterns with separations from 1.4 sec of arc to 4.7 sec of arc are shown to illustrate the quality of image formation with this camera, the effects of seeing on the patterns, and to illustrate the isoplanatic patch of the atmosphere.
Breckinridge, J. B.↗
The detection of urban expansion from Landsat imagery
Two methodologies for detecting and mapping land cover changes in and around growing urban regions are being studied at Jet Propulsion Laboratory. Both approaches, primarily based on digital image processing techniques, have been developed to supplement data stored in an Image Based Information System (IBIS). The structure of this information system enables the depiction of land cover changes in image format concurrently with statistical reports in tabular form. To date the expansion of two urban areas, Houston, Texas and Orlando, Florida, has been monitored.
Friedman, S. Z.↗
An investigation of the modulation of capillary and short gravity waves in the open ocean
A preliminary investigation of the modulation of capillary and gravity waves by long ocean waves is described. A pressure transducer is used to obtain water surface displacements, and a high-response laser-optical system is used to detect short-wave slopes. Analytical techniques are developed to account for the orbital motion of long waves. The local mean squared wave slope is found to be maximum leeward of the long-wave crests. For the long waves studied here and for short waves from 1 cm to 1 m, the longer a short-wave component is, the more leeward its maximum tends to occur. Also, the shortest waves tend to modulate least. The modulation of short waves is found to be strong enough to be an important component of the synthetic aperture radar image formation mechanism for long ocean waves.
Evans, D. D.↗
Crop identification studies using Landsat data Separation of barley from other spring small grains and corn and soybean decision logic
Two labeling procedures were developed which identify various agricultural crops through the use of Landsat data. One procedure separates barley from other spring small grains, and the other identifies corn and soybeans. For both procedures, a minimum data set (critical acquisition time) has been designated. Landsat data in both image format and various graphic displays were used along with ancillary data to obtain information which aided in labeling the spectral signatures. The corn and soybean procedure also employed a structured decision logic. Test results for the barley separation procedure emphasized the importance of obtaining a critical acquisition and showed some success especially in areas where spring crops followed the expected growth patterns. Two tests of the corn and soybean procedure produced good labeling accuracies. Problems with the procedure were easy to identify, and some solutions were implemented for the second test. Automation of various parts of the procedure and extension to other crops and regions were recommended.
Dailey, C. L.↗
Velocity and attenuation of sound in arterial tissues
The velocity of sound in excised human and canine arterial tissues is measured in order to serve as a basis for the development and application of ultrasonic techniques for the diagnosis of atherosclerotic lesions. Measurements of sound velocity at different regions of 11 human and six canine aortas were made by a time delay spectrometer technique at frequencies from 2 to 10 MHz, and compared with ultrasonic attenuation parameters and the results of biochemical assays. Sound velocity is found to increase with increasing attenuation at all frequencies, and with increasing collagen content. A strong dependence of sound velocity on cholesterol content or low calcium contents is not observed, although velocities of up to 2000 m/sec are observed in highly organized calcified lesions. A decrease in velocity with decreasing temperature is also noted. It is thus concluded that it is principally the differences in tissue collagen levels that contribute to image formation according to sound velocity.
Rooney, J. A.↗
Interface control document between the NASA Goddard Space Flight Center (GSFC) and Department of Interior EROS Data Center (EDC) for LANDSAT-D. Thematic mapper high resolution 241 mm film
The 241 mm photographic product produced by the Goddard Space Flight Center Data Management System for LANDSAT-D is described. Film type and format, image dimensions, frame ID, gray scale, resolution patterns, registration marks, etc. are addressed.
Source record↗
Low-level water vapor fields from the VAS split-window channels at 11 and 12 microns
Originally, the VAS split window channels were designed to use the differential water vapor absorption between 11 and 12 microns to estimate sea surface temperature by correcting for the radiometric losses caused by atmospheric moisture. It is shown that it is possible to reverse the procedure in order to estimate the vertically integrated low level moisture content with the background surface (skin) temperature removed, even over the bright, complex background of the land. Because the lower troposphere's water vapor content is an important factor in convective instability, the derived fields are of considerable value to mesoscale meteorology. Moisture patterns are available as quantitative fields (centimeters of precipitable water) at full VAS resolution (as fine as 7 kilometers horizontal resolution every 15 minutes), and are readily converted to image format for false color movies. The technique, demonstrated with GOES-5, uses a sequence of split window radiances taken once every 3 hours from dawn to dusk over the Eastern and Central United States. The algorithm is calibrated with the morning radiosonde sites embedded within the first VAS radiance field; then, entire moisture fields are calculated at all five observation times. Cloud contamination is removed by rejecting any pixel having a radiance less than the atmospheric brightness determined at the radiosonde sites.
Chesters, D.↗
Design trade-offs for a multispectral linear array (MLA) instrument
The NASA Landsat program with imagery produced by the Multispectral Scanner has been thoroughly successful. The second generation of Landsat is represented by the Thematic Mapper, while the MLA sensor belongs to a third generation. It is pointed out that the strength of the MLA concept emanates from the pushbroom image-formation approach, which offers some fundamental improvements over opto-mechanically scanned instruments. The increased dwell time of the MLA sensor can be employed to improve signal-to-noise, spectral resolution, and spatial resolution simultaneously. Problems regarding design tradeoffs are considered, taking into account instrument sizing, configuration tradeoffs, optical design tradeoffs, aspects of spectral separation and registration, and radiometric accuracy and calibration tradeoffs. A description is provided of the instrument concept to which the design tradeoffs have led.
Mika, A. M.↗
Radiometric calibration of the Shuttle Imaging Radar (SIR-C) system
The radiometric calibration accuracy of the Shuttle Imaging Radar (SIR-C) sensor is discussed. The analysis includes the antenna, RF electronics, the digital data handling system, the platform attitude control, attitude determination accuracy, and orbit effects. The radiometric distortion of the image products by the ground processing system used for the image formation is also considered. Since the SIR-C system is a dual-frequency quad-polarized system (i.e., 8 channels), the amplitude and phase error is considered over all possible operating modes and environments for absolute and relative (long-term and short-term) calibration within a channel and across channels.
Curlander, John C.↗
Relative dating of Hawaiian lava flows using multispectral thermal infrared images - A new tool for geologic mapping of young volcanic terranes
The weathering of Hawaiian basalts in arid and semiarid environments is accompanied by changes in their thermal infrared emittance spectra. The spectral differences can be measured and mapped with multispectral imaging systems. The differences appear to be related to the degree of development, preservation, and alteration of glassy crusts; the oxidation of iron; and the accretion of silica-rich surface veneers. Because the measurements are quantitative and in image format, they are useful for estimating relative ages in geologic mapping of lava flows. In Hawaii this technique is most diagnostic for distinguishing among sparsely vegetated flows less than 1.5 ka in age.
Kahle, Anne B.↗
Mosaic wedge-and-strip arrays for large format microchannel plate detectors
The authors present a novel method for joining wedge-and-strip patterns on single anodes in a mosaic array. With only a modest increase in complexity over three-conductor anodes currently in use, the ultimate detector position resolution can be significantly improved, and large-format microchannel plate detectors with pore-size-limited resolution are made possible. The problem of the transition from one anode to the next has been solved with a novel linear encoding scheme, which exhibits essentially distortionless behavior at boundaries parallel to the conducting elements and only slight distortion at the orthogonal boundaries. The ultimate resolution for two anode designs, one designed for large-format imaging and the other for high-resolution spectroscopy, is also predicted.
Martin, Christopher↗
On the signal-to-noise ratio in IUE high-dispersion spectra
An observational and data reduction technique for fixed pattern noise (FPN) and random noise (RN) in fully extracted IUE high-dispersion spectra is described in detail, along with actual empirical values of signal-to-noise ratio (S/N) achieved. A co-addition procedure, involving SWP and LWR cameras observations of the same spectrum at different positions in the image format, provides a basis to disentangle FPN from RN, allowing each average amplitude, within a given wavelength interval, to be estimated as a function of average flux number. Empirical curves, derived with the noise algorithm, make it possible to estimate the S/N in individual spectra at the wavelengths investigated. The average S/N at the continuum level in well-exposed stellar spectra varies from 10 to 20, for the orders analyzed, depending on position in the spectral format. The co-addition procedure yields an improvement in S/N by factors ranging from 2.3 to 2.9. Direct measurements of S/N in narrow, line-free wavelength intervals of individual and co-added spectra for weak-lined stars yield comparable, or in some cases somewhat higher, S/N values and improvement factors.
Leckrone, David S.↗
Surface characterization and testing II; Proceedings of the Meeting, San Diego, CA, Aug. 10, 11, 1989
Various papers on surface characterization and testing are presented. Individual topics addressed include: simple Hartmann test data interpretation, optimum configuration of the Offner null corrector, system for phase-shifting interferometry in the presence of vibration, fringe variation and visibility in speckle-shearing interferometry, functional integral representation of rough surfaces, calibration of surface heights in an interferometric optical profiler, image formation in common path differential profilometers, SEM of optical surfaces, measuring surface profiles with scanning tunneling microscopes, surface profile measurements of curved parts, high-resolution optical profiler, scanning heterodyne interferometer with immunity from microphonics, real-time crystal axis measurements of semiconductor materials, radial metrology with a panoramic annular lens, surface analysis for the characterization of defects in thin-film processes, Spacelab Optical Viewport glass assembly optical test program for the Starlab mission, scanning differential intensity and phase system for optical metrology.
Greivenkamp, John E.↗