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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 19 records

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NASA NTRS1984

The motion of the earth-moon system in modern tabular ephemerides. II - Inertial motion, mean longitude of the sun, and general precession in longitude

Properties of astronomical time scales (ET and UT) are considered, with particular emphasis on correctly determining of-date longitude as the sum of inertial mean longitude of the sun relative to the mean equinox of a fixed epoch (1950.0), and the general precession in longitude accumulated since the epoch. The inertial mean longitude and motion (relative to the mean equinox) are derived from tabular ephemerides such as the Jet Propulsion Laboratories' DE 102 and DE 96, by comparisons with subroutines based on Newcomb's perturbation theory. An unresolved inconsistency of approximately 1 second per century among the mean inertial motion of DE 102, IAU precession speed (1976), and the classical Newcomb of-date mean motion is found. Interpretation difficulties arising from the use of different systems of Ephemeris Time are also discussed.

Stumpff, P.↗

NASA NTRS1972

Stable longitudes for 12-hr eccentric orbit satellites.

The accelerated longitude drift regimes of eccentric 12-hr orbits are considered, due to the resonant geopotential. These quasi-stationary orbits are under investigation at NASA for large payload earth surveillance spacecraft in the small applications technology satellite (SATS) program. Inclinations near 'critical' are especially attractive because of their possible long term stability, and these are examined in detail. 'Stable' equator crossing longitudes for these satellites are found as functions of the argument of perigee. As long as the argument of perigee is between plus or minus 100 deg, these stable longitudes lie within a narrow range. Maximum 'east-west' stationkeeping requirements for these satellites at nonequilibrium positions are in the range of 0.3 to 3 m/sec/yr.

Wagner, C. A.↗

NASA NTRS1974

Solar longitude dependence of some characteristics of type III radio bursts from metric to hectometric wavelengths

Using the observed data for metric and hectometric type III radio bursts, the dependence of burst characteristics on the solar longitude has been examined over a wide frequency range. It is found that there exists and east-west asymmetry for the extension of metric type III bursts into the hectometric wavelength range. In particular, hectometric bursts are rarely observed for solar flares associated with metric bursts east of 60 E solar longitude. Furthermore, for east longitudes, the low-frequency radio observations show a large dispersion in drift time interval.

Sakurai, K.↗

NASA NTRS1977

Preferred solar wind emitting longitudes on the sun

During the 11 1/2-year period from July 1964 through December 1975, high- and low-speed solar wind flows originated from preferred solar longitudes. The preferred longitude effect was most pronounced from 1970 onward but was also evident in the years preceding 1970. The most pronounced modulation in average solar wind speed with longitude (approximately 20%) was obtained when it was assumed that the synodic rotation period of the sun is 27.025 days. Some deep internal structure in the sun must ultimately be responsible for these long-lived longitudinal effects, which appear to rotate rigidly with the sun.

Gosling, J. T.↗

NASA NTRS1978

A nearly complete longitude-velocity map of neutral hydrogen

A longitude-velocity map based on two recent 21-cm neutral hydrogen surveys and covering all but 42 deg of galactic longitude is presented. Latitude information between -2 and +2 deg is included as an integrated quantity by averaging the observed brightness temperatures over latitude at constant longitude and velocity to produce intensity information corresponding to a surface density distribution of neutral hydrogen in the galactic plane. The northern and southern rotation curves of the Galaxy within the solar galactic orbit are derived from the maximum radial velocities by the usual tangent-point method. Five interesting features of the map are discussed: (1) the scale of density variations in the neutral hydrogen; (2) a region of very high brightness centered at 81 deg and 0 km/s which is probably due to the spiral arm with which the sun is associated; (3) a region of very low brightness centered at 242 deg and 39 km/s; (4) negative-velocity features visible in the anticenter direction; and (5) a strong absorption feature at 289 deg having a kinematic distance of about 4 kpc.

Waldes, F.↗

NASA NTRS1979

M2 ocean tide parameters and the deceleration of the moon's mean longitude from satellite orbit data

An estimation is made of the principal long-period spherical harmonic parameters in the representation of the M2 ocean tide from the orbital histories of the three satellites 1967-92A, Starlette, and GEOS 3. The data used are primarily the evolution of the orbital inclinations of the satellites in conjunction with the longitude of the ascending node from GEOS 3. Analysis procedure and analytic formulation, as well as ocean tidal parameter estimation and deceleration of the lunar mean longitude are outlined. The credibility of the M2 ocean tide solution is further enhanced by the close accord between the computed value for the deceleration of the lunar mean longitude and other recently reported estimates. It is evident from the results presented that studies of close earth satellite orbits are able to provide important information about the tidal forces acting on the earth.

Felsentreger, T. L.↗

NASA NTRS1980

Inverting x,y grid coordinates to obtain latitude and longitude in the vanderGrinten projection

The latitude and longitude of a point on the Earth's surface are found from its x,y grid coordinates in the vanderGrinten projection. The latitude is a solution of a cubic equation and the longitude a solution of a quadratic equation. Also, the x,y grid coordinates of a point on the Earth's surface can be found if its latitude and longitude are known by solving two simultaneous quadratic equations.

Rubincam, D. P.↗

NASA NTRS1995

Hot spots and active longitudes: Organization of solar activity as a probe of the interior

In order to investigate how solar activity is organized in longitude, major solar flares, large sunspot groups, and large scale photospheric magnetic field strengths were analyzed. The results of these analyses are reported. The following results are discussed: hot spots, initially recognized as areas of high concentration of major flares, are the preferred locations for the emergence of big sunspot groups; double hot spots appear in pairs that rotate at the same rate separated by about 180 deg in longitude, whereas, single hot spots have no such companions; the northern and southern hemispheres behave differently in organizing solar activity in longitude; the lifetime of hot spots range from one to several solar cycles; a hot spot is not always active throughout its lifetime, but goes through dormant periods; and hot spots with different rotational periods coexist in the same hemisphere during the same solar cycle.

Bai, Taeil↗

NASA NTRS2012

DC and Structured Electric Fields Observed on the C/NOFS Satellite and Their Association with Longitude, Plasma Density, and Solar Activity

Observations of DC electric fields and associated E x B plasma drifts gathered by the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite are presented. We show statistical averages of the vector fields and resulting E x B plasma flows for the first three years of operations as a function of season, longitude, local time, and Fl 0.7 conditions. Magnetic field data from the VEFI science magnetometer are used to compute the plasma flows. Although typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night, the data from DC electric field detector often reveal variations from this pattern that depend on longitude, solar activity, and plasma density. Clear "wave-4" tidal effects in both electric field components have been detected and will be presented. Zonal plasma drifts show a marked variation with solar activity and may be used as a proxy for neutral winds at night. Evidence for pre-reversal enhancements in the meridional drifts that depend on solar activity is present for some longitudes, and are corroborated by clear evidence in the plasma density data that the spacecraft journeyed below the F-peak during evenings when the rise in the ionosphere is most pronounced. In addition to DC electric fields, the data reveal considerable electric field structures at large scales (approx 100's of km) that are usually confined to the nightside. Although such electric field structures are typically associated with plasma density depletions and structures, what is surprising is the number of cases in which large amplitude, structured DC electric fields are observed without a significant plasma density counterpart structure, including their appearance at times when the ambient plasma density appears relatively quiescent. We investigate the mapping of structured electric fields along magnetic field lines from distant locations and consider tropospheric thunderstorm sources to explain some of the observations. The dependence of the structuring on season and solar activity will be reported and discussed.

Pfaff, Robert↗

NASA NTRS1968

Longitude variations in the earth's gravity field as sensed by two Russian 12 hour satellites.

Low order longitude harmonics derived from long term amplified oscillations of semimajor axis and orbit longitude of two 12-hr Soviet satellites

Wagner, C. A.↗

NASA NTRS1975

Modulation of Jovian interplanetary electrons and the longitude variation of decametric emissions

The relationship between modulation of the intensity and energy spectrum of relativistic interplanetary electrons originating from Jupiter's magnetosphere and longitudinal asymmetry in decametric radio emissions from the surface is discussed. Modulation minima are correlated with the time when the subsolar point on Jupiter is near the longitude of the most frequent non-Io-related decametric emissions. The probability of observing such emissions is graphed as a function of the System III central meridian longitude of an observer and the angle of Io past superior conjunction. It is suggested that the modulation of interplanetary electrons and the longitudinal asymmetry of decametric emissions may be due to the same unknown longitudinally asymmetric feature on Jupiter.

Vasyliunas, V. M.↗

NASA NTRS1975

The motion of a satellite in resonance with the longitude-dependent harmonics

The solution to the motion of a satellite in an eccentric orbit and in resonance with one or more of the longitude-dependent harmonics of the central planet is developed. The method of solution parallels the well known von Zeipel method of general perturbations. The solution consists of expressions for the variations of the Delaunay variables. These expressions are composed of the perturbations developed by Brouwer in 1959 for the motion of an artificial satellite plus first-order resonant perturbations due to longitude-dependent harmonics (in terms of Legendre normal elliptic integrals of the first and second kind).

Dallas, S. S.↗

NASA NTRS1976

The motion of a satellite in resonance with the longitude-dependent harmonics

Dallas, S. S.↗

NASA NTRS1977

Evaluation of Jupiter longitudes in System III/1965/

Commission 40 of the International Astronomical Union has adopted a new longitude system for Jupiter, labelled System III(1965), to replace the provisional System III(1957.0). The specification of the prime meridian and epoch for the new system differs slightly from that recently published. Its rotation rate implies a period of 9 hr 55 min 29.711 (plus or minus 0.04) sec, consistent with recent determinations from decimetric and decametric data. For both the new and older systems, equations are provided which are useful in the evaluation of longitudes for the analysis of Jupiter radio, particle, and field data from earth and spacecraft observations.

Seidelmann, P. K.↗

NASA NTRS1981

A comparison of the radio data and model calculations of Jupiter's synchrotron radiation. I - The high energy electron distribution in Jupiter's inner magnetosphere. II - East-west asymmetry in the radiation belts as a function of Jovian longitude

A comparison has been made between detailed model calculations of Jupiter's synchrotron radiation and the radio data at wavelengths of 6, 21, and 50 cm. The calculations were performed for a Jovian longitude of 200 deg and were based on the multipole field configurations as derived from the Pioneer data. The electron distribution in the inner magnetosphere was derived as a function of energy, pitch angle, and spatial coordinates. In addition, the hot region or east-west asymmetry in the radiation belts is investigated. It is suggested that this asymmetry is due to the combined effect of an overabundance of electrons at jovicentric longitudes of 240-360 deg and the existence of a dusk-to-dawn directed electric field over the inner magnetosphere generated by the wind system in the upper atmosphere.

De Pater, I.↗

NASA NTRS1981

Multi-spacecraft observations of heliographic latitude-longitude structure in the solar wind

The heliographic latitude-longitude structure of high speed solar winds observed prior to the maximum of sunspot cycle 20 is investigated by multi-spacecraft comparisons. It is shown that differences in solar wind structures are due to two different kinds of spatial structures. One structure is found to be consistent with the simultaneous existence of a single, broad stream at latitudes above 7 deg N and a series of narrow streams at lower latitudes, while the other is consistent with the existence of a latitudinally sloping stream boundary near the solar equator. For latitude separations less than 3.5 deg, cross-correlations of Explorer-Mariner velocities show only previously reported systematic increases in velocity with latitude, and for latitude separations from 3.5 to 6.2 deg, differences in high speed streams shift in longitude and/or amplitude are also identified on a timescale of one solar rotation.

Rhodes, E. J., Jr.↗

NASA NTRS1987

Mercury - Wavelength and longitude dependence of polarization

The polarization-time variations noted in the present linear polarization observations of the integrated Mercury disk, with filters covering the 0.3-1.0 micron bandpass and between 53-130 deg of phase angle, may be accounted for in terms of longitude dependence through the variation of brightness or other properties over the surface. Kepler's equation for the eccentric anomaly was solved for each observation, and the true anomaly was used to find the subsolar longitude. The difference found in the polarization-albedo relations of Mercury and the moon indicates a difference in surface texture and/or composition.

Gehrels, T.↗

NASA NTRS1990

The longitude dependence of the dayside F region trough - A detailed model-observation comparison

The nighttime main F-region trough extends into the sunlit afternoon sector. This trough feature exhibits both a strong magnetic-activity dependence and a longitude (UT) dependence. Whalen (1987), using IGY ionosonde data, showed that both of these effects are readly extracted from f0F2 observations. This study shows that the longitude effect is the same as that contained in the Utah State University time-dependent ionospheric model. It arises from the offset of the geomagnetic axis from the geographic axis. The magnetic-activity dependency is associated with the westward convection in the afternoon sector. It is also contained in the ionospheric model via the empirical magnetospheric convection model.

Sojka, J. J.↗