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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 235 records · Page 13
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NASA NTRS1976

Results from the IMP-J violet solar cell experiment and violet cell balloon flights

The Interplanetary Monitoring Platform-J violet solar cell experiment was flown in an orbit with mild thermal cycling and low hard-particle radiation. The results of the experiment show that violet cells degrade at about the same rate as conventional cells in such an orbit. Balloon flight measurements show that violet solar cells produce approximately 20% more power than conventional cells.

Gaddy, E. M.↗
NASA NTRS1977

Explorer 45 and Imp 6 observations in the magnetosphere of injected waves from the Siple Station VLF transmitter

Results are reported for an experiment in which VLF waves from a transmitter in Antarctica were injected into the magnetosphere along geomagnetic field lines and detected near the magnetic equatorial plane by high-altitude spacecraft. The purpose of this experiment was to conduct a controlled in situ study of VLF wave-particle interactions and to determine the propagation characteristics of the injected waves in the magnetosphere, the regions where VLF emissions are produced, and the effective volume of the magnetosphere illuminated by the transmitter. The results indicate that: (1) the bulk of the satellite receptions occurred during periods of quieting following magnetic disturbances, (2) receptions generally occurred inside the plasmapause, (3) the spacecraft detected predominantly unducted waves, (4) the injected signals could illuminate a large volume of the magnetosphere, and (5) VLF emissions were triggered by nonducted transmitter pulses.

Inan, U. S.↗
NASA NTRS1978

Comparison of 74-MHz interplanetary scintillation and IMP 7 observations of the solar wind during 1973

Solar wind velocities measured by earth-orbiting spacecraft are compared with velocities determined from interplanetary scintillation (IPS) observations for 1973, a period when high-velocity streams were prevalent. The spacecraft and IPS velocities agree well in the mean and are highly correlated. No simple model for the distribution of enhanced turbulence within streams is sufficient to explain the velocity comparison results for the entire year. Although a simple proportionality between density fluctuation level and bulk density is consistent with IPS velocities for some periods, some streams appear to have enhanced turbulence in the high-velocity region, where the density is low.

Coles, W. A.↗
NASA NTRS1976

IMP: Interactive mass properties program. Volume 1: Program description

A method of computing a weights and center of gravity analysis of a flight vehicle using interactive graphical capabilities of the Adage 340 computer is described. The equations used to calculate area, volume, and mass properties are based on elemental surface characteristics. The input/output methods employ the graphic support of the Adage computer. Several interactive program options are available for analyzing the mass properties of a vehicle. These options are explained.

Stewart, W. A.↗
NASA NTRS1979

Interplanetary particles and fields, November 22 - December 6, 1977: Helios, Voyager, and IMP observations between 0.6 AU and 1.6 AU

The principal interplanetary events observed are described and analyzed. Three flow systems were observed: (1) a corotating stream and a stream interface associated with a coronal hole; (2) a shock wave and an energetic particle event associated with a 2-B flare; and (3) an isolated shock wave of uncertain origin. Data from 28 experiments and 6 spacecraft provide measurements of solar wind plasma, magnetic fields, plasma waves, radio waves, energetic electrons, and low energy protons.

Burlaga, L. F.↗
NASA NTRS1980

Simultaneous measurements of magnetotail dynamics by IMP spacecraft

Changes in tail energy density during substorms in the magnetotail are given. In addition to plasma sheet thinnings seen prior to substorm onsets, a gradual decrease in plasma beta was detected in the deep tail which precedes onset and the more prominent plasma disappearance that typically accompanies it. The frequency of thinnings and the regions over which they occurred indicate that drastic changes in plasma sheet thickness are common features of substorms which occur at all locations across the tail.

Fairfield, D. H.↗
NASA NTRS1980

Deceleration of the solar wind in the Earth foreshock region: ISEE 2 and IMP 8 observations

The deceleration of the solar wind in the region of the interplanetary space filled by ions backstreaming from the Earth bow shock was studied using a two spacecraft technique. This deceleration, which is correlated with the "diffuse" but not with the "reflected" ion population, depends on the solar wind bulk velocity: at low velocities (below 300 km/sec) the velocity decrease is about 5 km/sec, while at higher velocities (above 400 km/sec) the decrease may be as large as 30 km/sec. Along with this deceleration, the solar wind undergoes a deflection of about 1 deg away from the direction of the Earth bow shock. The energy balance shows that the kinetic energy loss far exceeds the thermal energy which is possibly gained by the solar wind, therefore, at least part of this energy must go into waves and/or into the backstreaming ions.

Bonifazi, C.↗
NASA NTRS1981

Magnetic loop behind an interplanetary shock: Voyager, Helios and IMP-8 observations

The shock was followed by a turbulent sheath in which there were large fluctuations in both the strength and direction of the magnetic field. This in turn was followed by a region (magnetic cloud) in which the magnetic field vectors were observed to change by rotating nearly parallel to a plane, consistent with the passage of a magnetic loop. This loop extended at least 30 deg in longitude between 1-2 AU, and its radial dimension was approximately 0.5 AU. In the cloud the field strength was high and the density and temperature were relatively low. Thus, the dominant pressure in the cloud was that of the magnetic field.

Burlaga, L.↗
NASA NTRS1980

Deceleration of the solar wind in the earth's foreshock region - Isee 2 and Imp 8 observations

The deceleration of the solar wind in the region of the interplanetary space filled by ions backstreaming from the earth's bow shock and associated waves is studied using a two-spacecraft technique. This deceleration depends on the solar wind bulk velocity; at low velocities (below 300 km/s) the velocity decrease is about 5 km/s, while at higher velocities (above 400 km/s) the decrease may be as large as 30 km/s. The energy balance shows that the kinetic energy loss far exceeds the thermal energy which is possibly gained by the solar wind; therefore at least part of this energy must go into waves and/or into the backstreaming ions.

Bonifazi, C.↗
NASA NTRS1981

Magnetic loop behind an interplanetary shock - Voyager, Helios, and IMP 8 observations

The flow behind an interplanetary shock was analyzed through the use of magnetic field and plasma data from five spacecraft, with emphasis on the magnetic cloud identified by a characteristic variation of the latitude angle of the magnetic field. The size of the cloud was found to be about 0.5 AU in radial extent and greater than 30 deg in azimuthal extent, with its front boundary almost normal to the radial direction. Because the field direction of the magnetic cloud as it moved past the spacecraft was observed to rotate nearly parallel to a plane, it is thought that the field configuration of the cloud was essentially two-dimensional. These results further suggest that the lines of force in the magnetic cloud formed loops, but it could not be determined whether these loops were open or closed.

Burlaga, L.↗
NASA NTRS1979

Evaluation of the IMP-16 microprocessor orbit determination system filter

The results of the numerical tests performed in evaluating the interplanetary monitoring platform-16 orbit determination system are presented. The system is capable of performing orbit determination from satellite to satellite tracking data in applications technology satellite range and range rate format. The estimation scheme used is a Kalman filter, sequential (recursive) estimator. Descriptions of the tests performed and tabulations of the numerical results are included.

Shenitz, C. M.↗
NASA NTRS1983

Latitudinal and field-aligned cosmic ray gradients 2 to 5 AU Voyagers 1 and 2 and IMP 8

Results are presented showing that the contemporary picture of a relatively small heliocentric radial gradient is generally correct. They emphasize that such a gradient should really be thought of in terms of field-aligned structures since the cosmic ray populations tend to 'corotate' locally with the interplanetary field structure. Nonuniform latitudinal gradients of approximately 2 to 5 percent/deg in structures lasting 10 to 30 days are identified unambiguously. Additional evidence is seen for somewhat smaller latitudinal gradients often north to south and probably mixed with small field-aligned gradients of less than 1 percent/AU that persist for several solar rotations. It is suggested that these smallest ephemeral latitudinal gradients manifest themselves by affecting the degree of irregularity in diurnal variations of high latitude neutron monitors.

Roelof, E. C.↗