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At least 1,189 records · Page 66
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Geometric accuracy assessment of Landsat-4 Thematic Mapper p-tapes

An analysis was performed on the P-format computer compatible tapes for the Landsat-4 Thematic Mapper (TM) scene 40109-15140 acquired November 2, 1982 over Washington, D.C. and environs. Three tests of sensor geometry were undertaken: (1) band-to-band registration, (2) line-to-line registration between swaths, and (3) geometric correction of sensor and spacecraft/ephemeris characteristics. The band-to-band and line-to-line registration was measured at one hundred pixel spacings along a line using the phase correlation image alignment method developed by Kuglin and Hines and adapted to a one-dimensional FFT correlation technique. The sensor and spacecraft geometric calibration analysis was checked by identifying 75 ground control points in the TM scene and on 1:24,000 topographic maps. A least squares fit of the gaps was computed and the vector offsets of the residuals was tabulated and plotted.

Bryant, N. A.↗
NASA NTRS1985

An algorithm for computing the number of distinct spectral vectors in thematic mapper data

A computationally efficient method was developed to compute the number of distinct spectral vectors and their frequency of occurrence in Landsat-4 Thematic Mapper (TM) data. The algorithm first partitions the image into spectrally disjoint subsets and then computes the frequency distribution of distinct spectral vectors within each subset from a multidimensional histogram. The overall frequency distribution is tabulated by accumulating the results from each subset. The number of distinct spectral vectors could be used as a measure of potential storage compaction of alternate data representations for data compression, or as a measure of information content in the comparison of spectral band combinations and/or spatial resolutions for an image. Results from processing three 512 x 512 pixel Landsat-4 TM images and one Landsat-4 Multispectral Scanner (MSS) image are presented as examples. An algorithm for computing the frequency distribution of distinct spectral vectors in MSS data is given in the Appendix.

Wharton, S. W.↗
NASA NTRS1984

Radiation effects response data for synthetic organic insulation and dielectrics

Existing radiation response data for 130 materials of the synthetic organic insulation and dielectric class are analyzed, and thresholds and 25-percent change dose levels for these materials are presented. Both the lowest reported threshold dose (LTD) and the 25-percent change dose level are found to vary widely among the different insulators (used as spacecraft components). The LTD is tabulated to indicate the levels where radiation effects become apparent. These level are of use in setting a lower limit where changes can be expected, and could be used to exempt synthetic insulation and dielectrics from radiation considerations when the environments are substantially below this limit. Cautions to be observed in applying the data to current problems are presented.

Bouquet, F. L.↗
NASA NTRS1984

Magneto-atmospheric waves from a localized source

A technique developed by Lighthill (1960, 1965, and 1967) for finding the asymptotic solution of an inhomogeneous wave equation with constant coefficients is applied to the study of wave propagation in magneto-atmospheres. The geometry of the wavenumber surface plays an important role in determining the generation and propagation of various types of magneto-atmospheric waves from a localized forcing region. Examples of these wavenumber surfaces are exhibited for various magnetic-field strengths and wave frequencies. The asymptotic far field is tabulated for a time-harmonic spatially Gaussian localized forcing term.

Adam, J. A.↗
NASA NTRS1985

Rocket spectrogram of a solar flare in the 10-100 A region

The soft (10-100 A) X-ray spectrum of an M-class solar flare was observed with a high-resolution (0.02 A) rocket-borne spectrograph on 1982 July 13. The spectrum samples an area of 600/sq arcsec on the sun, centered on or near the brightest X-ray feature of the flare. Several hundred emission lines characteristic of temperatures from about 0.5 to 7 x 10 to the 6th K have been photographically recorded. All but three of the stronger lines have been identified. It is argued that previous identification of the line at 17.62 A as iron Ly-alpha is incorrect. Spectral lines from nickel, iron, chromium, calcium, sulphur, silicon, aluminium, magnesium, neon, oxygen, nitrogen, and carbon are tabulated and discussed with extensive reference to earlier work. Absolute line intensities are given and the calibration of the telescope-spectrograph is discussed.

Acton, L. W.↗
NASA NTRS1985

The microwave and far-infrared spectra of the SiH radical

Consideration of Si's cosmic abundance leads to the expectation that the related molecule SiH may be detected in extraterrestrial sources. A tabulation is presented of frequencies, wavelengths, and line strengths for SiH molecule transitions at microwave and far-IR wavelengths, on the basis of an analysis of its laser magnetic resonance spectrum. It is hoped that the frequencies presented will be useful to both laboratory spectroscopists and astrophysicists.

Brown, J. M.↗
NASA NTRS1986

Equations for Annular-Heat-Transfer Coefficients

Tables of coefficients converted to algebraic expressions. Plot of Equation for Nusselt number agrees closely with points from tabulated data. Equation for Nusselt number and those for coefficients A and B obtained by regression analysis of data. Other plots also show close agreement for radius of 0.1 and 0.2. In equation form, coefficients incorporated into mathematical models more readily than as tabular data. Equations simplify design and analysis of heat exchangers.

Yao, B.↗
NASA NTRS1986

List of Preferred Electronic Parts

Components passed stringent qualification tests tabulated and described. Destructive and nondestructive qualification testing confirmed parts capable of withstanding spacecraft environments without excessive degradation and have stable characteristics during operating lives. Testing assessed effects of electrical, environmental, and mechanical stresses in various levels and time durations.

Covey, R. E.↗
NASA NTRS1985

High-rate convolutional code construction with the minimum required SNR criterion

New short constraint length, high-rate convolutional codes which minimize the required signal to noise ratios (SNR) are found and tabulated for rates 2/3, 3/4, and 4/5, and for constraint length K up to 10. When compared with previously reported codes, most of the new codes reduce the required SNR only slightly. However, there are some pairs of K and code rate for which the new codes require considerably less SNR. The most significant one is the new K = 8, ate 4/5 code which requires 1.2 dB less SNR than the known code with the same parameters, for a desired bit error rate of 0.000001.

Lee, P. J.↗
NASA NTRS1985

Planetary Waves

The mean temperature field at various pressure levels for January and July for both hemispheres are given. In summer (July in the Northern Hemisphere, January in the Southern Hemisphere) the fields are nearly zonally symmetric, but in winter large longitudinal variations are evident. These are mainly of low wave number, i.e., they may be represented by Fourier analysis around the globe using just a few (one or two) waves. This is the basis for representing the climatology of longitudinal variation in terms of wave components, since the fields may be defined with fewer values than by using a grid in longitude that has a sufficiently small interval to adequately represent the smooth variations. The amplitude and phase of temperature and geopotential height for wave numbers one and two, with In(pressure) as the vertical coordinate are given. The fields were calculated and plotted at pressure intervals of 0.2 in In(pressure) and at latitude intervals of 4 deg, but were interpolated to intervals of 0.5 in In(pressure) (approximately 3.5 km) and 10 deg latitude for tabulation. Tables and figures give wave coefficients for the monthly mean temperature fields. Thus they represent the quasi-statinary planetary waves.

Barnett, J. J.↗
NASA NTRS1985

An unbiased X-ray sampling of stars within 25 parsecs of the Sun

A search of all of the Einstein Observatory IPC and HRI fields for untargeted stars in the Woolley, et al., Catalogue of the nearby stars is reported. Optical data and IPC coordinates, flux density F sub x, and luminosity L sub x, or upper limits, are tabulated for 126 single or blended systems, and HRI results for a few of them. IPC luminosity functions are derived for the systems, for 193 individual stars in the systems (with L sub x shared equally among blended components), and for 63 individual M dwarfs. These stars have relatively large X-ray flux densities that are free of interstellar extinction, because they are nearby, but they are otherwise unbiased with respect to the X-ray properties that are found in a defined small space around the Sun.

Johnson, H. M.↗
NASA NTRS1985

Pressure distributions from high Reynolds number tests of a Boeing BAC 1 airfoil in the Langley 0.3-meter transonic cryogenic tunnel

A wind-tunnel investigation designed to test a Boeing advanced-technology airfoil from low to flight-equivalent Reynolds numbers has been completed in the Langley 0.3-Meter Transonic Cryogenic Tunnel. This investigation represents the first in a series of NASA/U.S. industry two-dimensional airfoil studies to be completed in the Advanced Technology Airfoil Test program. Test temperature was varied from ambient to about 100 K at pressures ranging from about 1.2 to 6.0 atm. Mach number was varied from about 0.40 to 0.80. These variables provided a Reynolds number (based on airfoil chord) range from 4.4 X 10 to the 6th power to 50.0 X 10 to the 6th power. All the test objectives were met. The pressure data are presented without analysis in plotted and tabulated formats for use in conjunction with the aerodynamic coefficient data published as NASA TM-81922. At the time of the test, these pressure data were considered proprietary and have only recently been made available by Boeing for general release. Data are included which demonstrate the effects of fixed transition. Also included are remarks on the model design, the model structural integrity, and the overall test experience.

Johnson, W. G., Jr.↗
NASA NTRS1986

PROFILE user's guide

User information for program PROFILE, an aerodynamics design utility for refining, plotting, and tabulating airfoil profiles is provided. The theory and implementation details for two of the more complex options are also presented. These are the REFINE option, for smoothing curvature in selected regions while retaining or seeking some specified thickness ratio, and the OPTIMIZE option, which seeks a specified curvature distribution. REFINE uses linear techniques to manipulate ordinates via the central difference approximation to second derivatives, while OPTIMIZE works directly with curvature using nonlinear least squares techniques. Use of programs QPLOT and BPLOT is also described, since all of the plots provided by PROFILE (airfoil coordinates, curvature distributions) are achieved via the general purpose QPLOT utility. BPLOT illustrates (again, via QPLOT) the shape functions used by two of PROFILE's options. The programs were designed and implemented for the Applied Aerodynamics Branch at NASA Ames Research Center, Moffett Field, California, and written in FORTRAN and run on a VAX-11/780 under VMS.

Collins, L.↗
NASA NTRS1986

Low-speed stability and control characteristics of a transport model with aft-fuselage-mounted advanced turboprops

A limited experimental investigation was conducted in the Langley 4- by 7-Meter Tunnel to explore the effects of aft-fuselage-mounted advanced turboprop installations on the low-speed stability and control characteristics of a representative transport aircraft in a landing configuration. In general, the experimental results indicate that the longitudinal and lateral-directional stability characteristics for the aft-fuselage-mounted single-rotation tractor and counter-rotation pusher propeller configurations tested during this investigation are acceptable aerodynamically. For the single-rotation tractor configuration, the propeller-induced aerodynamics are significantly influenced by the interaction of the propeller slipstream with the pylon and nacelle. The stability characteristics for the counter-rotation pusher configuration are strongly influenced by propeller normal forces. The longitudinal and directional control effectiveness, engine-out characteristics, and ground effects are also presented. In addition, a tabulated presentation of all aerodynamic data presented in this report is included as an appendix.

Applin, Z. T.↗
NASA NTRS1986

A Monte Carlo study of Weibull reliability analysis for space shuttle main engine components

The incorporation of a number of additional capabilities into an existing Weibull analysis computer program and the results of Monte Carlo computer simulation study to evaluate the usefulness of the Weibull methods using samples with a very small number of failures and extensive censoring are discussed. Since the censoring mechanism inherent in the Space Shuttle Main Engine (SSME) data is hard to analyze, it was decided to use a random censoring model, generating censoring times from a uniform probability distribution. Some of the statistical techniques and computer programs that are used in the SSME Weibull analysis are described. The methods documented in were supplemented by adding computer calculations of approximate (using iteractive methods) confidence intervals for several parameters of interest. These calculations are based on a likelihood ratio statistic which is asymptotically a chisquared statistic with one degree of freedom. The assumptions built into the computer simulations are described. The simulation program and the techniques used in it are described there also. Simulation results are tabulated for various combinations of Weibull shape parameters and the numbers of failures in the samples.

Abernethy, K.↗
NASA NTRS1986

Unsteady transonic flow calculations for wing-fuselage configurations

Unsteady transonic flow calculations are presented for wing-fuselage configurations. Calculations are performed by extending the XTRAN3S unsteady transonic small-disturbance code to allow the treatment of a fuselage. Details of the XTRAN3S fuselage modeling are discussed in the context of the small-disturbance equation. Transonic calculations are presented for three wing-fuselage configurations with leading edge sweep angles ranging from 0 deg to 46.76 deg. Simple bending and torsion modal oscillations of the wing are calculated. Sectional lift and moment coefficients for the wing-alone and wing-fuselage cases are compared and the effects of fuselage aerodynamic interference on the unsteady wing loading are revealed. Tabulated generalized aerodynamic forces used in flutter analyses, indicate small changes in the real in-phase component and as much as a 30% change in the imaginary component when the fuselage is included in the calculation. These changes result in a 2 to 5% increase in total magnitude and a several degree increase in phase.

Batina, J. T.↗
NASA NTRS1982

JPL preferred parts list: Reliable electronic components

The JPL Preferred Parts List was prepared to provide a basis for selection of electronic parts for JPL spacecraft programs. Supporting tests for the listed parts were designed to comply with specific spacecraft environmental requirements. The list tabulates the electronic, magnetic, and electromechanical parts applicable to all JPL electronic equipment wherein reliability is a major concern. The parts listed are revelant to equipment supplied by subcontractors as well as fabricated at the laboratory.

Covey, R. E.↗