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At least 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

The proper weighting function for retrieving temperatures from satellite measured radiances

One class of methods for converting satellite measured radiances into atmospheric temperature profiles, involves a linearization of the radiative transfer equation: delta r = the sum of (W sub i) (delta T sub i) where (i=1...s) and where delta T sub i is the deviation of the temperature in layer i from that of a reference atmosphere, delta R is the difference in the radiance at satellite altitude from the corresponding radiance for the reference atmosphere, and W sub i is the discrete (or vector) form of the T-weighting (i.e., temperature weighting) function W(P), where P is pressure. The top layer of the atmosphere corresponds to i = 1, the bottom layer to i = s - 1, and i = s refers to the surface. Linearization in temperature (or some function of temperature) is at the heart of all linear or matrix methods. The weighting function that should be used is developed.

Arking, A.↗
NASA NTRS1976

Investigations with satellite data temperature retrievals

A method is presented for using satellite measurements to interpolate vertical temperature soundings between radiosonde stations. The method finds a set of coefficients, which when multiplied by corresponding measured radiance quantities, yield zero temperature error at a radiosonde station. This derived set of coefficients is then applied to satellite radiance measurements at places between radiosonde stations. The computations show, for example, that the average absolute error in the layer 1000-800 mbs is only 0.3K when the corresponding 'minimum-information' method error was 2.9K. The method may be most applicable to measurements from geostationary satellites, but should also be applicable to measurements from polar orbiting satellites under certain conditions.

Fritz, S.↗
NASA NTRS1975

A new approach to radiative transfer theory using Jones's vectors. I Fundamentals

Radiative transfer of partially polarized radiation in an anisotropically scattering, inhomogeneous atmosphere containing an arbitrary polydispersion of particles is described using Jones's (1941) amplitude vectors and matrices. This approach exploits the close analogy between the quantum-mechanical states of spin 1/2 systems and the polarization states of electromagnetic radiation described by Jones's vector. The complete equivalence between the transport equation for Jones's vectors and the classical radiative-transfer equation for Stokes's intensity vectors is demonstrated in two independent ways after deriving the transport equations for the polarization coherency matrices and for the quaternions corresponding to the Jones's vectors. A compact-operator formulation of the theory is provided and used to derive the necessary equations for both a local and a global description of the transport of Jones's vectors. The integro-differential equations for the amplitude reflection and transmission matrices are derived and related to the usual corresponding equations.

Fymat, A. L.↗
NASA NTRS1975

Micropulsations in the morning sector. II - Satellite observations of 10to 45-s waves at synchronous orbit, ATS 1

A study of 13 wave events having 10- to 45-s periods and observed by ATS 1 in the morning sector reveals that these events, which have been called band-limited pulsations and are thought to be related to Pi 1, appear actually to be Pc 3. Digital power-spectral and coherency analysis was used to determine the characteristics of the wave activity. The average peak frequency of the events (about 0.04 Hz) and their generally narrow-band nature correspond closely with the characteristics of Pc 3. The local-time distribution of the events (peaking at 0900 LT) and their less than complete association with substorms also correspond more closely with Pc 3 characteristics. The orientation of the major axis of the polarization ellipse for these events was predominantly azimuthal, which agrees more closely with the east-west polarization of Pi 1 observed on the ground. However, some examples of radial orientation were observed in the satellite data.

Arthur, C. W.↗
NASA NTRS1975

Uranian methane abundance, rotational temperature, and effective pressure from the 6800 A band

Measurements of the methane absorption features at 6800 A in two spectrograms of Uranus have been analyzed on the working hypothesis that the features are the R branch of the 5 mu(3) rotation-vibration overtone. Internal and external consistencies in temperature calculations from the measurements give increased confidence that the band identification and rotational-quantum-number assignments to band members are correct. Parametric fitting of synthetic reflecting-layer and homogeneous scattering-layer spectra to the spectrograms is attempted. The best-fit methane abundances, taken with recent estimates of the molecular hydrogen abundance, correspond to an average C:H ratio between 1.5 and 25 times larger than the solar ratio. Even greater enrichment of the C:H ratio may occur below the visible cloud boundary. High spectroscopic resolution of the present data permits direct measurement of the methane line halfwidth in Uranus's spectrum. The halfwidth corresponds to an effective pressure greater than 3 atm, depending on the mixture of atmospheric gases. Pressure in this range, at the methane rotational temperature of between 93 and 100 K, is inconsistent with current Uranus atmosphere models having solar elemental-abundance ratios. It is consistent with models which are considerably enriched in 'heavier' constituents.

Bergstralh, J. T.↗
NASA NTRS1975

ATS-6 - Quartz-Crystal Microbalance

The Quartz-Crystal Microbalance Experiment provided data on the possible return of contaminants to the exterior surfaces of the spacecraft. The experiment measures the change in resonant frequency of the crystal due to deposition of material on the surface. There has been no mass accretion corresponding to the firing of hydrazine thrusters to unload the spacecraft momentum wheels. There have been accretions corresponding to the firing of the cesium ion engines.

Rogers, J. F.↗
NASA NTRS1975

Open-loop response of a burning liquid monopropellant

A direct comparison was obtained between the theoretical and experimental response of a burning liquid monopropellant surface to imposed pressure oscillations. The comparison extended beyond the quasi-steady frequency regime into the range where the combustion process interacts with the thermal wave in the liquid phase. The theory considered both gas and liquid-phase transient effects, involving a numerically integrated, first-order perturbation analysis. The experiment employed hydrazine as the test fuel, burning as a strand. With kinetic parameters fixed by steady burning rate measurements, the model gave good predictions of liquid-phase temperature distributions during steady combustion as well as the amplitude and phase of the oscillatory component of the burning rate in the presence of imposed pressure oscillations. The combustion response tends to peak in two frequency ranges; one corresponding to interaction with liquid-phase transient effects, which could be verified both theoretically and experimentally; the second corresponding to gas-phase transient effects, which could only be examined theoretically. Both ranges provide conditions where the amplifying power is sufficient to drive combustion instability.

Allison, C. B.↗
NASA NTRS1976

Correlated observations of several auroral substorms on February 17, 1971

The purpose of this study is to correlate in detail auroral activity with the corresponding disturbances in the magnetotail. The auroral data were recorded by optical instruments aboard an airplane flying over the Arctic Ocean along the Alaska meridian and by the Alaska meridian chain of all-sky cameras. The corresponding magnetotail observations were made by various instruments on Vela 6A and Imp 5; the interplanetary magnetic field was monitored concurrently by Explorer 35. Three successive substorms were observed on February 17, 1971. Each substorm was readily identified by the classical auroral and magnetic signatures which accompanied its onset. The observed variations of plasma and magnetic field in the magnetotail were consistent with the idea that a neutral line formed in the range X sub SM between -12 and -18 R sub E at the onset of each substorm expansive phase and then moved tailward past X sub SM = -18 R sub E some tens of minutes afterward. The Z component of the tail magnetic field decreased rather steadily for a period of 1-2 1/2 hours after each substorm and until the onset of the next expansive phase, reaching a minimum value just before each onset.

Hones, E. W., Jr.↗
NASA NTRS1976

Minor planets and related objects. XX - Polarimetric evidence for the albedos and compositions of 94 asteroids

Polarimetric observations are presented and analyzed for a total of 94 asteroids. The data include numerical parameters describing the polarization-plane curve, the maximum depth of the negative branch, geometric albedo, and diameter. With few exceptions, the polarizations are found to be repeatable from hour to hour, night to night, and apparition to apparition at the same solar phase angle within an observational accuracy of plus or minus 0.05%. It is shown that over a range of more than a factor of 50 in diameter or a factor of 100,000 in mass, all the asteroids seem to have microscopically very rough or particulate surface textures. In terms of their polarimetric properties, the asteroids are classified as follows: 48 in the broad S class, with compositions corresponding to stony-iron meteorites or ordinary chondrites; 34 in the C class, probably corresponding to carbonaceous chondrites; three to five M asteroids with surfaces rich in free metal; two with low-opacity surfaces (class E) attributable to pure enstatite; and five of other types.

Zellner, B.↗
NASA NTRS1976

The effects of trailing vorticity on the flow through highly loaded cascades

This paper presents a procedure whereby three-dimensional inviscid flow through a highly loaded turbomachinery cascade of lifting lines can be treated by methods corresponding to classical aerodynamic theory. In contrast to earlier linearized (thin airfoil) three-dimensional theory, the present study allows analysis of the flow corresponding to the large turning and/or large pressure ratios induced by practical rotors or stators. For the sake of simplicity, the present paper is limited to incompressible flow through a highly loaded rectilinear cascade and to the design problem; i.e., given blade loading. Formulas are derived for both the mean and the three-dimensional components of the flow; in particular, the velocities at the blades induced by the trailing vorticity associated with nonuniform blade circulation are determined.

Mccune, J. E.↗
NASA NTRS1976

Sterols of a contemporary lacustrine sediment

Results are reported for detailed sterol analyses of several depths (corresponding to between zero and about 150 yr in age) in a contemporary lacustrine sediment from a freshwater lake of postglacial origin in England. Delta 5-, delta 22-, and delta 5,22-sterols are identified along with 5 alpha- and 5 beta-stanols as well as a C26 stanol with a C7 side chain. Solvent extraction yields carbon number distributions for the 5 alpha- and 5 beta-stanol sediment constituents that parallel the corresponding delta 5-sterol distributions. The amounts of 5 alpha-stanols are found to exceed those of 5 beta-stanols in the sediment, and variations in the ratio of 5 alpha- to 5 beta-stanol between sediment samples from similar depths are shown to suggest an inhomogeneity of the sediment. It is found that the sterol composition of sediment cores varies markedly with depth, reflecting both the effects of a sterol hydrogenation process and a changing input to the sediment. It is concluded that C29 sterols, of probable higher-plant origin, predominate at lower sediment depths while C27 sterols, possibly derived from autochthonous sources, are more abundant in the surface sediment.

Gaskell, S. J.↗
NASA NTRS1976

Jupiter at five microns

The paper summarizes the information obtained in recent maps of Jupiter at 5 microns, a frequency at which the gases in Jupiter have a relatively low opacity. It is highly possible that 5-micron hot spots are breaks in the cloud deck permitting observation of the hot lower layers of the atmosphere. Many 5-micron sources coincide with blue visual features, but the details of the correspondence need further investigation. Large-scale changes in the appearance of the planet occur at 5 microns on time scales of months; these changes are sufficiently dramatic to produce detectable variations in the whole-disk flux from the planet. Their correspondence to large-scale changes in visual features is not yet determined.

Armstrong, K. R.↗
NASA NTRS1978

Obtaining a tomographic image from transmission projections

Technique for obtaining tomographic images work directly in signal space and is used to find object configuration by simple summation of density values. Image is reconstructed by precise inverse of scanning. Signal values corresponding to density of projection are added as constant terms along line corresponding to original path between two probes that give rise to that density value.

Heyser, R. C.↗
NASA NTRS1976

Seismic effects on the rotational dynamics of the earth and its gravitational field

The effects of earthquakes on the rotational motion of the earth were studied. The connection between the fault parameters and the corresponding changes in the moments and products of inertia were analytically developed. The reciprocal theorem of elasticity and Volterra's formula were applied as well as the displacement and stress fields for the second degree static response of the earth model being used. The numerical results of the investigation yield the magnitude and direction of the pole shift as well as the change in the length of the day. The changes in the second degree coefficients of the geopotential were computed. Source parameters corresponding to the Alaskan earthquake on March 28, 1964 were used to generate numerical results.

Sanchez, B. V.↗
NASA NTRS1977

Analytical prediction of the performance and stability of a J85-13 compressor with distorted inlet flow

The parallel compressor concept was studied using a compressor model based on the overall clean-inlet performance map obtained from experimental tests in an altitude chamber using a General Electric J85-13 turbojet engine. The model, which includes a static-pressure balance calculation at compressor discharge, was exercised at conditions corresponding to 10 different screen-induced distortion patterns included in the experimental data base. The spoiled area of these patterns ranged from 30 deg to 180 deg, and the distortion screen density, or the area blocked by the screen wire per unit area of screen, varied from 26 to 69 percent. The study indicates that at the higher corrected speeds, the analytical surge lines obtained are good representations of the corresponding experimental surge lines and are independent of distortion angle or distortion angle or distortion level.

Milner, E. J.↗
NASA NTRS1977

Gamma rays from the de-excitation of C-12 resonance 15.11 MeV and C-12 resonance 4.44 MeV as probes of energetic particle spectra

The flux of 15.11 MeV gamma rays relative to the flux 4.44 MeV gamma rays was calculated from measured cross sections for excitation of the corresponding states of C-12 and from experimental determinations of the branching ratios for direct de-excitation of these states to the ground state. Because of the difference in threshold energies for excitation of these two levels, the relative intensities in the two lines are particularly sensitive to the spectral distribution of energetic particles which excite the corresponding nuclear levels. For both solar and cosmic emission, the observability of the 15.11 MeV line is expected to be enhances by low source-background continuum in this energy range.

Crannell, C. J.↗
NASA NTRS1977

Utility of correlation techniques in gravity and magnetic interpretation

Internal correspondence uses Poisson's Theorem in a moving-window linear regression analysis between the anomalous first vertical derivative of gravity and total magnetic field reduced to the pole. The regression parameters provide critical information on source characteristics. The correlation coefficient indicates the strength of the relation between magnetics and gravity. Slope value gives delta j/delta sigma estimates of the anomalous source. The intercept furnishes information on anomaly interference. Cluster analysis consists of the classification of subsets of data into groups of similarity based on correlation of selected characteristics of the anomalies. Model studies are used to illustrate implementation and interpretation procedures of these methods, particularly internal correspondence. Analysis of the results of applying these methods to data from the midcontinent and a transcontinental profile shows they can be useful in identifying crustal provinces, providing information on horizontal and vertical variations of physical properties over province size zones, validating long wavelength anomalies, and isolating geomagnetic field removal problems.

Chandler, V. W.↗
NASA NTRS1977

Analog to digital converter for two-dimensional radiant energy array computers

The analog to digital converter stage derives a bit array of digital radiant energy signals representative of the amplitudes of an input radiant energy analog signal array and derives an output radiant energy analog signal array to serve as an input to succeeding stages. The converter stage includes a digital radiant energy array device which contains radiant energy array positions so that the analog array is less than a predetermined threshold level. A scaling device amplifies the radiant signal levels of the input array and the digital array so that the radiant energy signal level carried by the digital array corresponds to the threshold level. An adder device adds the signals of the scaled input and digital arrays at corresponding array positions to form the output analog array.

Shaefer, D. H.↗