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At least 685 records · Page 38

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NASA NTRS1985

The Use of Thematic Mapper Data for Land Cover Discrimination: Preliminary Results from the UK Satmap Programme

The principal objectives of the UK SATMaP program are to determine thematic mapper (TM) performance with particular reference to spatial resolution properties and geometric characteristics of the data. So far, analysis is restricted to images from the U.S. and concentrates on spectra and radiometric properties. The results indicate that the data are inherently three dimensional compared with the two dimensional character of MSS data. Preliminary classification results indicate the importance of the near infrared band (TM 4), at least one middle infrared band (TM 5 or TM 6) and at least one of the visible bands (preferably either TM 3 or TM 1). The thermal infrared also appears to have discriminatory ability despite its coarser spatial resolution. For band 4 the forward and reverse scans show somewhat different spectral responses in one scene but this effect is absent in the other analyzed. From examination of the histograms it would appear that the full 8 bit quantization is not being effectively utilized for all the bands.

Jackson, M. J.↗

NASA NTRS1985

A Software Simulation Study of a Sequential Decoder Using the Fano Algorithm

A set of subroutines was developed to simulate the performance of a sequential decoder based on the Fano algorithm. This simulation can be used to verify the coding performance of the International Cometary Explorer (ICE) communication link. The probability of frame deletion can be measured as a function of the number of computations allowed per frame and of E(b)/N(o). Both hard and soft quantized inputs are considered.

Pollara, F.↗

NASA NTRS1985

Study of spectral/radiometric characteristics of the Thematic Mapper for land use applications

Progress during ERIM's tenth quarter of effort under the LANDSAT-4 and 5 Image Data Quality Assessment program for the Thematic Mapper is described. Coincident LANDSAT-4 and 5 fully corrected (CCT-PT) TM data are analyzed in more detail and revised band-by-band relationships between the two sensors derived. An analysis technique employing the matching of cumulative distributions is developed and used and is believed to offer advantages over the histogram matching procedure currently used to produce LANDSAT data. Multiplicative factors ranging from 0.987 to 1.145 and offsets ranging from -2.7 to -6.2 video quantum levels are required to cause LANDSAT-5 data to match LANDSAT-4 data values. Evidence of low level clipping is found in TM Bands 5 and 7 of LANDSAT-5 but not LANDSAT-4. Analysis of the information content of LANDSAT TM and MSS data is continued. Components of information loss are identified and quantified and the effects of coarsened quantization are explored.

Malila, W. A.↗

NASA NTRS1984

A variational method for the calculation of dynamic polarizabilities and two-photon transition moments - The dressed molecule approach

The solution of the time-dependent Schroedinger equation of the molecule + radiation field system is analyzed. A quantized radiation field is used. The relationship between the oscillatory wave function and the dressed state wave function is established, the oscillatory wave function being the solution if the radiation field is turned on at t = 0 and the dressed state being the stationary solution satisfying the boundary condition only if the field is present at t = negative infinity. In general, the oscillatory wave function can be expressed using a complete set of dressed states. However, in the presence of a nonresonant radiation field, the system is well represented by a single dressed state. Molecular properties such as dynamic polarizabilities and two-photon transition moments can be deduced from the dressed state wave function instead of the oscillatory wave function as in previous methods. Because of its stationary character, the dressed state is more amenable to approximate calculations. A CI method is developed for this purpose. The CI matrix is simple in form and can be readily constructed using existing computer codes. The present method can also be adapted to calculate other optical properties.

Huo, W. M.↗

NASA NTRS1983

Impact of thematic mapper sensor characteristics on classification accuracy

A three factor (spectral, spatial, and radiometric resolution), two level (TM and MSS) analysis of variance (ANOVA) approach allowed evaluation of the effects of each factor individually and in all possible combinations. Digital classification accuracy was used as the figure of merit. Nine study sites in Washington, DC, each of approximately 256 x 256 TM pixels, were randomly selected from the full scene for analysis. These results strongly suggest that the quantization level improvements and the addition of new spectral bands in the visible and middle IR regions (both afforded by the TM sensor design) can result in improved capabilities to accurately delineate land cover categories using a per point Gaussian maximum likelihood classifier. On the other hand, results indicate that the increase in spatial resolution to 30 m does not significantly enhance classification accuracy. The spatial result points to an inherent limitation of a per point classifier and to the need to improve data analysis techniques to handle high spatial resolution data.

Williams, D. L.↗

NASA NTRS1985

Survey of multispectral imaging systems for earth observations

Fifty-six multispectral imaging systems are described in terms of their instantaneous fields of view, spectral bands, fields of view, and number of quantization levels. These systems have been used during the past decade for earth resources studies from aircraft or spacecraft, or are currently in the proposal or design and development stage.

Slater, P. N.↗

NASA NTRS1985

The exact eigenfunctions and eigenvalues of a two-dimensional rigid rotor obtained using Gaussian wave packet dynamics

Exact eigenfunctions for a two-dimensional rigid rotor are obtained using Gaussian wave packet dynamics. The wave functions are obtained by propagating, without approximation, an infinite set of Gaussian wave packets that collectively have the correct periodicity, being coherent states appropriate to this rotational problem. This result leads to a numerical method for the semiclassical calculation of rovibrational, molecular eigenstates. Also, a simple, almost classical, approximation to full wave packet dynamics is shown to give exact results: this leads to an a posteriori justification of the De Leon-Heller spectral quantization method.

Reimers, J. R.↗

NASA NTRS1985

Comparison of the information contents of Landsat TM and MSS data

A communications-theory approach is taken to analyze the dispersion and concentration of signal values in various data spaces, irrespective of specific class membership. Entropy is used to quantify information, and mutual information is used to measure the information represented by subsets of spectral variables. Several different comparisons of information content are made. These include comparisons of system design capacities, of data volumes occupied by agricultural data in the spaces defined by original bands and by transformed spectral (Tasseled Cap) variables, of the information contents of original bands and Tasseled Cap variables, and of the information contents of TM and MSS for the given agricultural data sets. Also, the effects of sample size, scene content, and quantization level are examined.

Malila, W. A.↗

NASA NTRS1985

Meteor Wind Results at Durham (43 Deg N, 71 Deg W) During the ATMAP November 1981 and May 1982 Campaigns

Winds modeled from data measured with the University of New Hampshire Meteor Wind Radar System at Durham, New Hampshire, over the two 4-day periods November 20 to 23, 1981 and May 8 to 11, 1982 are presented. The raw meteor wind data was fit in a least square sense to a three dimensional model containing mean, 12-, 24-, and 48-h periods. The means winds for both periods are very close to the three year average values at Durham during May and November, respectively. The semidiurnal component for the November period had a normal amplitude and phase, and an estimated veritcal wavelength of 60 km. The May period results were essentially typical except that the Northward amplitude was 3 to 4 times smaller than normal. The diurnal amplitudes measured for both periods are typical for Durham and the diurnal phase is normally not very consistent. The 48-hour component amplitude is typical for these months. The intrinsic errors fo the radar are approximately + or - 2 km in position and + or - 4 m/s in radial velocity including quantization errors. These errors are random with zero mean and should not bias the wind results.

Clark, R. R.↗

NASA NTRS1985

Comparison of the information contents of LANDSAT TM and MSS data

Malila, W. A.↗

NASA NTRS1985

The non-Newtonian heat and mass transport of He 2 in porous media used for vapor-liquid phase separation

This investigation of vapor-liquid phase separation (VLPS) of He 2 is related to long-term storage of cryogenic liquid. The VLPS system utilizes porous plugs in order to generate thermomechanical (thermo-osmotic) force which in turn prevents liquid from flowing out of the cryo-vessel (e.g., Infrared Astronomical Satellite). An apparatus was built and VLPS data were collected for a 2 and a 10 micrometer sintered stainless steel plug and a 5 to 15 micrometer sintered bronze plug. The VLPS data obtained at high temperature were in the nonlinear turbulent regime. At low temperature, the Stokes regime was approached. A turbulent flow model was developed, which provides a phenomenological description of the VLPS data. According to the model, most of the phase separation data are in the turbulent regime. The model is based on concepts of the Gorter-Mellink transport involving the mutual friction known from the zero net mass flow (ZNMF) studies. The latter had to be modified to obtain agreement with the present experimental VLPS evidence. In contrast to the well-known ZNMF mode, the VLPS results require a geometry dependent constant (Gorter-Mellink constant). A theoretical interpretation of the phenomenological equation for the VLPS data obtained, is based on modelling of the dynamics of quantized vortices proposed by Vinen. In extending Vinen's model to the VLPS transport of He 2 in porous media, a correlation between the K*(GM) and K(p) was obtained which permits an interpretation of the present findings. As K(p) is crucial, various methods were introduced to measure the permeability of the porous media at low temperatures. Good agreement was found between the room temperature and the low temperature K(p)-value of the plugs.

Yuan, S. W. K.↗

NASA NTRS1986

Theoretical and material studies on thin-film electroluminescent devices

A theoretical study of resonant tunneling in multilayered heterostructures is presented based on an exact solution of the Schroedinger equation under the application of a constant electric field. By use of the transfer matrix approach, the transmissivity of the structure is determined as a function of the incident electron energy. The approach presented is easily extended to many layer structures where it is more accurate than other existing transfer matrix or WKB models. The transmission resonances are compared to the bound state energies calculated for a finite square well under bias using either an asymmetric square well model or the exact solution of an infinite square well under the application of an electric field. The results show good agreement with other existing models as well as with the bound state energies. The calculations were then applied to a new superlattice structure, the variablly spaced superlattice energy filter, (VSSEP) which is designed such that under bias the spatial quantization levels fully align. Based on these calculations, a new class of resonant tunneling superlattice devices can be designed.

Summers, C. J.↗

NASA NTRS1985

On-line data processing techniques for MST radars

The various techniques which are or could be used in the processing of mesosphere-stratosphere-troposphere radar scattering data are outlined. The principles of pulse compression, frequency stepping, and coherent integration are reviewed in some detail. Coarse quantization and the calculation of spectral moments are treated very briefly.

Farley, D. T.↗

NASA NTRS1985

A heterodyne receiver for the submillimeter wavelength region based on cyclotron resonance in InSb at low temperatures

A heterodyne receiver has been developed for observation of interstellar atomic and molecular lines in the submillimeter wavelength region. The main detection mechanism of the device is cyclotron resonance in bulk n-InSb due to a quantized magnetic field. Measurements were carried out between 492 and 812 GHz in order to determine the sensitivity of the device for astrophysical applications. Double sideband receiver noise temperatures of 250 K at 492 GHz; 350 K at 625 GHz; and 510 K at 812 GHz were obtained. The magnetic induction for the laboratory tests was about 2.5 KG and the mixer operating temperature was about 1.6 K. It is shown that the receiver is sensitive enough to identify the narrow rotation lines of diatomic hydrides in dark-cloud regions of the interstellar medium.

Brown, E. R.↗

NASA NTRS1985

The effects of sensor advancements on Thematic Mapper data classification

Analyses of Landsat Thematic Mapper (TM) data were conducted to assess the effects of sensor advancements on the thematic classification of remote sensing data. The effects of altering three sensor characteristics (spatial resolution, data quantization, and spectral band configuration) from Landsat Multispectral Scanner (MSS) specifications were investigated using analysis-of-variance (ANOVA). Analyses were conducted on data from two TM scenes: Washington, D.C. (late autumn) and western Pennsylvania (late summer). Results indicate that the contribution of sensor advancements to thematic classification are highly dependent of spectral and spatial scene attributes.

Irons, J. R.↗

NASA NTRS1986

Thermal equilibrium of a cryogenic magnetized pure electron plasma

The thermal equilibrium correlation properties of a magnetically confined pure electron plasma (McPEP) are related to those of a one-component plasma (OCP). The N-particle spatial distribution rho sub s and the Helmholtz free energy F are evaluated for the McPEP to O(lambda sub d-squared/a-squared), where lambda sub d is the thermal de Broglie wavelength and is an interparticle spacing. The electron gyromotion is allowed to be fully quantized while the guiding center motion is quasi-classical. The distribution rho sub s is shown to be identical to that of a classical OCP with a slightly modified potential. To O(lambda sub d-squared/a-squared) this modification does not affect that part of F that is caused by correlations, as long as certain requirements concerning the size of the plasma are met. This theory is motivated by a current series of experiments that involve the cooling of a magnetically confined pure electron plasma to the cryogenic temperature range.

Dubin, D. H. E.↗

NASA NTRS1986

Noise in remote-sensing systems - The effect on classification error

Several types of noise in remote-sensing systems are treated. The purpose is to provide enhanced understanding of the relationship of noise sources to both analysis results and sensor design. The context of optical sensors and spectral pattern recognition analysis methods is used to enable tractability for quantitative results. First, the concept of multispectral classification is reviewed. Next, stochastic models are discussed for both signals and noise, including thermal, shot and quantization noise along with atmospheric effects. A model enabling the study of the combined effect of these sources is presented, and a system performance index is defined. Theoretical results showing the interrelated effects of the noise sources on system performance are given. Results of simulations using the system model are presented for several values of system parameters, using some noise parameters of the Thematic Mapper scanner as an illustration. Results show the relative importance of each of the noise sources on system performance, including how sensor noise interacts with atmospheric effects to degrade accuracy.

Landgrebe, D. A.↗

NASA NTRS1985

Noncoherent sampling technique for communications parameter estimations

This paper presents a method of noncoherent demodulation of the PSK signal for signal distortion analysis at the RF interface. The received RF signal is downconverted and noncoherently sampled for further off-line processing. Any mismatch in phase and frequency is then compensated for by the software using the estimation techniques to extract the baseband waveform, which is needed in measuring various signal parameters. In this way, various kinds of modulated signals can be treated uniformly, independent of modulation format, and additional distortions introduced by the receiver or the hardware measurement instruments can thus be eliminated. Quantization errors incurred by digital sampling and ensuing software manipulations are analyzed and related numerical results are presented also.

Su, Y. T.↗