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At least 1,711 records · Page 95
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Observations of low-energy electrons upstream of the earth's bow shock

Observations of electron fluxes with a lunar-based electron spectrometer when the moon was upstream of the earth have shown that a subset of observed fluxes are strongly controlled by the interplanetary magnetic field direction. The fluxes occur only when the IMF lines connect back to the earth's bow shock. Observed densities and temperatures were in the ranges 2-4 x 0,001/cu cm and 1.7-2.8 x 1,000,000 K. It is shown that these electrons can account for increases in effective solar wind electron temperatures on bow-shock connected field lines which have been observed previously by other investigators. It is further shown that if a model of the bow shock with an electrostatic potential barrier is assumed, the potential can be estimated to be 500 volts.

Reasoner, D. L.↗
NASA NTRS1974

Protonospheric columnar electron content determination. II - Observations

The results of over 300 hours of measurements of the quantity I sub w - the difference between total columnar electron content, derived from the differential phase-path data, and Faraday electron content - is presented. The interpretation of the measurements in terms of protonospheric content is discussed in the light of a previous analysis which demonstrates that good protonospheric content measurements can only be obtained under certain geometries of observations unless information on the shape and height of the ionospheric layer is available. A strong correlation between I sub w and the ionospheric content is observed in most of the Arecibo data, because they were collected under unfavorable conditions. The Stanford data, on the other hand, yield good measurements of the protonospheric content. The May 1969 observations show a strong depletion of protonospheric content during a magnetic storm and its subsequent recovery. This is in general agreement with flux tube content behavior observed by the whistler technique during similar conditions.

Almeida, O. G.↗
NASA NTRS1974

Light flashes observed by astronauts on Apollo 11 through Apollo 17

The crew members on the last seven Apollo flights observed light flashes that are tentatively attributed to cosmic ray nuclei (atomic number equal to or greater than 6) penetrating the head and eyes of the observers. Analyses of the event rates for all missions has revealed an anomalously low rate for transearth coast observations with respect to translunar coast observations.

Pinsky, L. S.↗
NASA NTRS1974

Cosmic ray scintillations. III - The low-frequency limit and observations of interplanetary scintillations

Statistically significant broad-band fluctuations, or 'scintillations', in the high-energy (about 1 GeV) cosmic ray intensity observed by neutron monitors are interpreted. The scintillations are caused by fluctuations in the interplanetary magnetic field. The theory of the scintillations is presented for the low-frequency limit, below .0001 Hz, including the effects of the earth's rotation on the fluxes observed by the neutron monitors. The observations and the theory are in good agreement. The shapes and amplitudes of the observed spectra and, in particular, a broad enhancement in the power spectrum of the Deep River neutron monitor flux near 1 cpd are related to the interplanetary magnetic field power spectrum and the cosmic ray anisotropy.

Owens, A. J.↗
NASA NTRS1974

Stabilization of nonlinear systems using linear observers

It is shown that a linear observer can always be employed to stabilize a nonlinear system which contains a true Popov type nonlinearity in the closed interval from 0 to k, where k is finite, provided the nonlinear function and a completely observable output of the linear portion are available as inputs to the observer. Taking into consideration the case in which a completely observable output is not available from the linear portion, stabilization is shown to be possible if the original linear approximation of the system is asymptotically stable.

Strane, R. E.↗
NASA NTRS1974

Corotating particle fluxes observed with the Pioneer 7 and IMP 4 spacecraft

Observations are reported of the time development of 17-MeV proton fluxes in four corotating particle streams during the five days required for corotation from Pioneer 7, about 70 E of earth in 1968, to IMP-4 at earth. The azimuthal width of the particle streams was observed to remain constant over the five days. Assuming either continuous or impulsive injection of particles at the sun, this observation is shown to imply that the azimuthal diffusion coefficient was significantly less than the value derived from recent solar flare observations (McKibben, 1972).

Mckibben, R. B.↗
NASA NTRS1974

Pulsar observations and neutron star models

Information about the physical parameters of neutron stars is obtained from pulsar observations. The energy balance of the Crab Nebula and the Vela X remnant allows one to derive limits for the masses of the Crab and Vela pulsars. Glitch observations provide further clues on the masses of these two pulsars. The degree of confidence with which one should believe the derived numbers is pointed out. The possibility of observing neutron stars in binary systems as pulsating X-ray sources is discussed. Finally, the importance of observing redshifted gamma ray lines from the surface of neutron stars, and thus directly measuring either individual or statistical properties of these objects, is pointed out.

Boerner, G.↗
NASA NTRS1974

A reduced adaptive observer for multivariable systems

An adaptive observer for multivariable systems of order n having p output measurements is developed. The adaptive observer allows both the generation of the state of the system and - at least - the partial identification of the unknown parameters of the system. The order of this adaptive observer is n - p plus 1. The adaptive algorithm, based upon Liapunov synthesis, may be implemented in real time without the use of derivative operators. Eigenvalues of the observer may be arbitrarily or almost arbitrarily located. With some mild restriction upon the structure of the multivariable system, and upon the command system input, both generation of state and identification of parameters is guaranteed globally.

Carroll, R. L.↗
NASA NTRS1974

Observations at Mercury encounter by the plasma science experiment on Mariner 10

A fully developed bow shock and magnetosheath were observed near Mercury, providing unambiguous evidence for a strong interaction between Mercury and the solar wind. Inside the sheath there is a distinct region analogous to the magnetosphere or magnetotail of earth, populated by electrons with lower density and higher temperature than the electrons observed in the solar wind or magnetosheath. At the time of encounter, conditions were such that a perpendicular shock was observed on the inbound leg and a parallel shock was observed on the outbound leg of the trajectory, and energetic plasma electron events were detected upstream from the outbound shock crossing. The interaction is most likely not atmospheric, but the data clearly indicate that the obstacle to solar wind flow is magnetic, either intrinsic or induced.

Ogilvie, K. W.↗
NASA NTRS1974

Visual observations from space

A visual observations project was established as part of the Skylab experimental program in order to optimize the collection of scientific data during the 84-day Skylab 4 mission. One objective of this project was the determination of the capabilities of the crewmen in the visual identification of various types of surface, air, and water phenomena of the earth which may be observed from the Skylab orbit. Another objective was a study of the possibilities provided by visual observations, supplemented by photographs, in the support of scientific investigations. Aspects of premission preparations are considered along with details concerning the equipment to be used and questions of mission operations. The results of the project show that the presence of man in an earth-observations program contributes a significant additional capability which is not available with a totally automated program.

Lenoir, W. B.↗
NASA NTRS1975

Precision selenodesy and lunar libration through VLBI observations of ALSEPs

Data from 500 observation series, each one representing about five hours' continuous observation of a pair of ALSEPs by differential very long baseline interferometers (VLBI) have been compiled on magnetic tape. The theoretical models used to calculate the rotation of the earth, the orbit of the moon, the libration of the moon, and the basic VLBI observable were improved substantially. Analysis of data from long spans of VLBI observations was begun.

Counselman, C. C., III↗
NASA NTRS1974

Infrared, radio, and X-ray observations of Cygnus X-3

Infrared observations of Cyg X-3 are presented along with X-ray and radio data. A study of the data shows evidence for several types of behavior in the infrared flux variations of Cyg X-3. It is pointed out that a lack of periodic variations observed can be due either to a real absence of these variations or to a masking by an outburst preceding the observation time. There is no simple radio-infrared correlation, although both radio and infrared emissions were observed during the same period of time.

Becklin, E. E.↗
NASA NTRS1974

Skylab observations of Comet Kohoutek

This paper summarizes the special operational procedures developed to observe the Comet Kohoutek from Skylab and the scientific results from these observations. Emphasis is placed on results from Skylab experiments S052, White Light Coronagraph; S201, Far UV Electronographic Camera; S233, Kohoutek Photometric Photography; S019, UV Stellar Astronomy; S183, Ultraviolet Panorama Telescope; and S082B, Ultraviolet Spectrography. Visual observations by the astronaut crew and the significance of these observations are discussed.

Snoddy, W. C.↗
NASA NTRS1974

Extensive summer upwelling on Lake Michigan during 1973 observed by NOAA-2 and ERTS-1 satellites

Two studies are presented that utilize data from the NOAA-2 and ERTS-1 satellites. The studies are concentrated on two summer upwelling episodes in Lake Michigan when considerable contrast was observed in both surface water temperature as observed by NOAA-2 and surface water color as observed by ERTS-1. Physical, biological and chemical processes support the hypothesis that much of the observed 'whitening' is calcium carbonate precipitating as an immediate result of the upwelling.

Strong, A. E.↗
NASA NTRS1975

Observations of low-energy electrons upstream of the earth's bow shock

Observations of electron fluxes with a lunar-based electron spectrometer when the moon was upstream of the earth have shown that a subset of observed fluxes are strongly controlled by the interplanetary magnetic field (IMF) direction. The fluxes occur only when the IMF lines connect back to the earth's bow shock. Observed densities and temperatures were in the ranges 0.002 to 0.004 per cu cm and 1,700,000 to 2,800,000 K. It is shown that these electrons can account for increases in effective solar wind electron temperatures on bow shock connected field lines, which have been observed previously by other investigators. It is further shown that if a model of the bow shock with an electrostatic potential barrier is assumed, the potential can be estimated to be 500 V.

Reasoner, D. L.↗
NASA NTRS1974

Observations and calculations of atmospheric helium 10830 emission

Observations and computer model calculations of helium excitation and transport were carried out. The following conclusions can be drawn: (1) the dawn helium density in the thermosphere is greater than the dusk helium density by 50 per cent or more, in contrast to the static diffusion models but in agreement with the dynamic models; (2) the computed He 10830 intensities are inconsistent with the observations when use of the new Penning ionization cross section for loss of atomic oxygen is used; (3) conjugate photoelectron precipitation is responsible for excitation of atmospheric helium at middle latitudes, but it is not evident in the observations at the equator or Brazil (L equals 1.1); (4) the computations predict greater conjugate effects than observed, leading to the possibility of strong interhemispheric absorption.

Christensen, A. B.↗
NASA NTRS1975

Direct observations of higher frequency density fluctuations in the interplanetary plasma

Direct observations from the plasma spectrometers on Pioneer 6 at 1 AU in December, 1965, have been used to obtain the power associated with fluctuations in the number density of solar-wind protons in the frequency range from .001 to .01 Hz. A power-law spectrum is obtained in this frequency range. The extension of the power-law density spectrum based on direct observations to these higher frequencies is consistent with previous extrapolations of both spacecraft and interplanetary scintillation observations and with the dominance of large-scale turbulence in the solar wind. This result is also consistent with direct observations of the solar-wind proton speed and the interplanetary magnetic field.

Intriligator, D. S.↗
NASA NTRS1975

Observations of OI 7774 emission excited by conjugate photoelectrons

Observations and computer calculations of O I 7774 A airglow emissions excited by conjugate photoelectrons have been carried out. The observations were made at McDonald Observatory, Texas using a 2 m grille spectrometer from December 1972 to June 1973. The zenithal emission intensity during conjugate photoelectron precipitation was fairly constant at 2-4 R until conjugate sunset, after which it diminished steadily and ceased near a conjugate solar zenith angle of 105 (plus or minus 3) deg. A predawn enhancement in both O I 7774 A and forbidden O I 6300 A was observed to commence near 102 deg. The computations utilize the two-stream technique of Nagy and Banks (1970) to obtain the escaping photoelectron flux and the local excitation rates of the oxygen emissions. Good agreement with the observations is obtained for the dependence of the emission rate on conjugate solar zenith angle.

Christensen, A. B.↗