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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Evaluation of digitally corrected ERTS images

The discussion is limited to processes by which a set of data samples collected on a geometrically distorted grid can be converted to samples on a different precisely specified grid. It is assumed that a mathematical expression for the desired transformation already exists. Concern will be the effects on image quality (specifically loss of resolution, photometric accuracy, and miscellaneous aberations) that result from various techniques used in accomplishing the resampling. The resampling techniques evaluated have included nearest neighbor, bilinear, cubic convolution, and various truncated versions of sinc (x). The conclusion is that cubic convolution yields substantially higher quality output data for scenes typically encountered and can, in some instances, substantially enhance one's ability to abstract information.

Taber, J. E.↗
NASA NTRS1975

Crop identification technology assessment for remote sensing (CITARS). Volume 10: Interpretation of results

The CITARS was an experiment designed to quantitatively evaluate crop identification performance for corn and soybeans in various environments using a well-defined set of automatic data processing (ADP) techniques. Each technique was applied to data acquired to recognize and estimate proportions of corn and soybeans. The CITARS documentation summarizes, interprets, and discusses the crop identification performances obtained using (1) different ADP procedures; (2) a linear versus a quadratic classifier; (3) prior probability information derived from historic data; (4) local versus nonlocal recognition training statistics and the associated use of preprocessing; (5) multitemporal data; (6) classification bias and mixed pixels in proportion estimation; and (7) data with differnt site characteristics, including crop, soil, atmospheric effects, and stages of crop maturity.

Bizzell, R. M.↗
NASA NTRS1976

OAST Space Theme Workshop. Volume 3: Working group summary. 2: Data handling, communications (E-2). A. Statement. B. Technology needs (form 1). C. Priority assessment (form 2)

Technologies required to support the stated OAST thrust to increase information return by X1000, while reducing costs by a factor of 10 are identified. The most significant driver is the need for an overall end-to-end data system management technology. Maximum use of LSI component technology and trade-offs between hardware and software are manifest in most all considerations of technology needs. By far, the greatest need for data handling technology was identified for the space Exploration and Global Services themes. Major advances are needed in NASA's ability to provide cost effective mass reduction of space data, and automated assessment of earth looking imagery, with a concomitant reduction in cost per useful bit. A combined approach embodying end-to-end system analysis, with onboard data set selection, onboard data processing, highly parallel image processing (both ground and space), low cost, high capacity memories, and low cost user data distribution systems would be necessary.

Source record↗
NASA NTRS1978

Thematic mapper design parameter investigation

Simulated multispectral data sets used in the Thematic Mapper design parameter investigation are analyzed. The sets were produced by processing high-resolution digital multispectral data through models of the various Thematic Mapper configurations and then through three resampling techniques as a simulation of ground processing. Emphasis is placed on classification processing and analysis of results.

Colby, C. P., Jr.↗
NASA NTRS1981

Baseline mathematics and geodetics for tracking operations

Various geodetic and mapping algorithms are analyzed as they apply to radar tracking systems and tested in extended BASIC computer language for real time computer applications. Closed-form approaches to the solution of converting Earth centered coordinates to latitude, longitude, and altitude are compared with classical approximations. A simplified approach to atmospheric refractivity called gradient refraction is compared with conventional ray tracing processes. An extremely detailed set of documentation which provides the theory, derivations, and application of algorithms used in the programs is included. Validation methods are also presented for testing the accuracy of the algorithms.

James, R.↗
NASA NTRS1981

Report of MAGSAT project by Survey of India

Magsat data fo quiet days for the period 4.11.79, 17.11.79 to 24.11.79, which pertains to 44 passes, was screened to exclude the the period of exclude the period of maximum diurnal variation. The results of this screening process is a data set that has the effect, (or at least the major part of the effect), of the external field removed from it. Such a data set is the basis for further analysis which is in hand. The data set is now being reduced to horizontal plane. The mathematical techniques uses a finite harmonic series representation of the three dimensional data, combined with least squares approach for the solution of coefficients. A computer programme was developed to reduce satellite data to a common elevation.

Sawhney, J. L.↗
NASA NTRS1981

Simulation and studies of spaceborne synthetic aperture radar image quality with reduced bit rate

A computer simulation program that is used to study the effects of digitization in spaceborne synthetic aperture radar systems is described. An analytical study of the distortion noise introduced by the digitization process at various gain settings, sampling rates and bit error rates is presented and the results agree well with those obtained from the simulation program. The simulation program is also used to study the spatial frequency response of hard-limiting (quantizing to 1-bit) synthetic aperture radar systems. The implications of these results on synthetic aperture radar system design are discussed.

Li, F.↗
NASA NTRS1980

Preliminary design of a future integrated design system

IPAD is a system of computer programs and data supporting the aerospace-vehicle design process by providing a set of services to aid in the management of a design project, project technical work, and project support work. Its purpose is to integrate people, programs, and data into a unified aerospace-vehicle design system. All project-management and technical data, together with certain standard data, are stored in a data base. The IPAD functions allow project personnel to query the data base and to perform operations on the data. This permits the orderly sequencing of the task elements of a complex operation and provides common access to a single data base by various participating groups who otherwise would require many separate files. These capabilities will be provided on a single host computer or across multiple heterogeneous computers on a distributed progress basis.

Diggins, R. M.↗
NASA NTRS1982

Content-addressable read/write memories for image analysis

The commonly encountered image analysis problems of region labeling and clustering are found to be cases of search-and-rename problem which can be solved in parallel by a system architecture that is inherently suitable for VLSI implementation. This architecture is a novel form of content-addressable memory (CAM) which provides parallel search and update functions, allowing speed reductions down to constant time per operation. It has been proposed in related investigations by Hall (1981) that, with VLSI, CAM-based structures with enhanced instruction sets for general purpose processing will be feasible.

Snyder, W. E.↗
NASA NTRS1985

Development and application of a unified balancing approach with multiple constraints

The development of a general analytic approach to constrained balancing that is consistent with past influence coefficient methods is described. The approach uses Lagrange multipliers to impose orbit and/or weight constraints; these constraints are combined with the least squares minimization process to provide a set of coupled equations that result in a single solution form for determining correction weights. Proper selection of constraints results in the capability to: (1) balance higher speeds without disturbing previously balanced modes, thru the use of modal trial weight sets; (2) balance off-critical speeds; and (3) balance decoupled modes by use of a single balance plane. If no constraints are imposed, this solution form reduces to the general weighted least squares influence coefficient method. A test facility used to examine the use of the general constrained balancing procedure and application of modal trial weight ratios is also described.

Zorzi, E. S.↗
NASA NTRS1985

A new description of combined trellis coding with asymmetric modulation

The combination of rate k/(k+t) trellis codes with digital modulations described by an asymmetric 2 sup k+1-point signal constellation has been recently shown to yield performance improvement over the traditional symmetric constellation combined with the same trellis code. The approach taken is to specify an underlying trellis code and then map the output code symbols into the fixed signal constellation based on a rule called mapping by set partitioning. The latter process is tantamount to assigning signals from the constellation to the trellis code transitions so as to maximize the free Euclidean distance of the code. Recently, a new description of trellis codes has been given that combines the above two steps into one. The ideas introduced are further explored, placing particular emphasis on the optimization of the signal constellation asymmetry. It can be concluded that the trellis-coded amplitude modulation (AM) designs given are very close to being optimum.

Simon, M. K.↗
NASA NTRS1985

Heating of thermal helium in the equatorial magnetosphere - A simulation study

The heating of He(+) ions observed by the GEOS satellite at L of about seven starting from an initial anisotropic proton distribution is studied. A simulation of electromagnetic ion cyclotron waves in a plasma consisting of hot anisotropic protons, a dominant thermal hydrogen plasma, and a minority species of helium ions is utilized. It is shown that the thermal ions are heated to 100 times their initial temperature due to the growth of large-amplitude ion cyclotron waves. He(+) ions are heated mainly in the perpendicular direction, and they are heated more than cold H(+) ions. The He(+) ions are heated in a two-step process. First, they are set into oscillations by the growing wave until some of the ions reach a parallel velocity on the order of the resonant velocity; then, strong heating occurs.

Omura, Y.↗
NASA NTRS1984

An attempt to extend the ATI technique to estimate convective rain volumes using satellite data

Digital satellite and radar data of a thunderstorm event that occurred on June 12, 1981 are examined. The processing of both data sets is described. Cumulative area versus count values, and threshold count values for IR and visible satellite data for 13 consecutive time steps are analyzed. The IR and visible satellite images are compared. The relation between radar reflectivity, temperature, and echo height is studied.

Doneaud, A. A.↗
NASA NTRS1986

Status of NTD Ge bolometer material and devices

The first IR Detector Technology Workshop took place at NASA Ames Research Center on July 12 and 13, 1983. The conclusions presented at that meeting are still valid. More was learned about the physics of hopping conduction at very low temperatures which will be important for bolometer design and operation at ever decreasing temperatures. Resistivity measurements were extended down to 50 mK. At such low temperatures, precise knowledge of the neutron capture cross sections sigma (sub n) of the various Ge isotopes is critical if one is to make an accurate prediction of the dopant concentrations and compensation, and therefore resistivity, that will result from a given irradiation. An empirical approach for obtaining the desired resistivity material is described and the process of conducting a set of experiments which will improve the knowledge of the effective sigma (sub n) values for a given location in a particular reactor is discussed. A wider range of NTD Ge samples is now available. Noise measurements on bolometers with ion implanted contacts show the no 1/f noise component appears down to 1 Hz and probably lower.

Haller, E. E.↗
NASA NTRS1987

The Land Analysis System (LAS) - A general purpose system for multispectral image processing

The present, general-purpose Land Analysis System (LAS) for image processing furnishes a comprehensive set of functions for the manipulation of MSS data; the initial version has more than 240 functions and utilities ranging from pixel manipulation to complex classification. A LAS user's guide describes each such function in terms of purpose, input parameters, illustrative examples, algorithms, error messages, and user codes. The LAS source code is so distributed as to simplify system maintenance; the Transportable Application Executive is employed as the user interface, thereby accommodating both expert and novice users by means of menus and tutored prompting.

Wharton, Stephen W.↗
NASA NTRS1988

A mathematical theory of learning control for linear discrete multivariable systems

When tracking control systems are used in repetitive operations such as robots in various manufacturing processes, the controller will make the same errors repeatedly. Here consideration is given to learning controllers that look at the tracking errors in each repetition of the process and adjust the control to decrease these errors in the next repetition. A general formalism is developed for learning control of discrete-time (time-varying or time-invariant) linear multivariable systems. Methods of specifying a desired trajectory (such that the trajectory can actually be performed by the discrete system) are discussed, and learning controllers are developed. Stability criteria are obtained which are relatively easy to use to insure convergence of the learning process, and proper gain settings are discussed in light of measurement noise and system uncertainties.

Phan, Minh↗
NASA NTRS1986

NASA PC software evaluation project

The USL NASA PC software evaluation project is intended to provide a structured framework for facilitating the development of quality NASA PC software products. The project will assist NASA PC development staff to understand the characteristics and functions of NASA PC software products. Based on the results of the project teams' evaluations and recommendations, users can judge the reliability, usability, acceptability, maintainability and customizability of all the PC software products. The objective here is to provide initial, high-level specifications and guidelines for NASA PC software evaluation. The primary tasks to be addressed in this project are as follows: to gain a strong understanding of what software evaluation entails and how to organize a structured software evaluation process; to define a structured methodology for conducting the software evaluation process; to develop a set of PC software evaluation criteria and evaluation rating scales; and to conduct PC software evaluations in accordance with the identified methodology. Communication Packages, Network System Software, Graphics Support Software, Environment Management Software, General Utilities. This report represents one of the 72 attachment reports to the University of Southwestern Louisiana's Final Report on NASA Grant NGT-19-010-900. Accordingly, appropriate care should be taken in using this report out of context of the full Final Report.

Dominick, Wayne D.↗