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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Lunar ephemeris and selenographic coordinates of the earth and sun for 1983 and 1984

Ephemeris data are presented in sections for each month for 1983 and 1984 to provide a time history of lunar coordinates and related geometric information. A NASA Manned Spacecraft Center modification of an ephemeris tape was used to calculate and plot coordinates of the earth, moon, and sun. The ephemeris is referenced to the mean vernal equinox at the nearest beginning of a Besselian year. Therefore, the reference equinox changes from one year to the next between 30 June and 1 July. The apparent discontinuity in the data is not noticeable in the graphical presentation, but can be observed in the digital output. The mean equator of epoch is used in all cases. The computer program used to compute and plot the ephemeris data is described in the appendix.

Hartung, A. D.↗
NASA NTRS1973

Hybrid coordinate formulation used for the design of attitude control systems for flexible spacecraft

Formulation combines certain advantages of discrete and distributed coordinates by using both simultaneously. In report summarizing method, theoretical development is extended as necessary for applications of practical interest. Explicit analyses are presented in sufficient detail to establish utility in flexible space vehicle control system of hybrid coordinate formulation.

Likins, P. W.↗
NASA NTRS1972

Tracking-station coordinates from Geos 1 and Geos 2 optical flash data.

Center-of-mass coordinates for 28 NASA MOTS and SAO Baker-Nunn camera sites have been obtained from optical flash data from Geos 1 (1965 89A) and Geos 2 (1968 002A). More than 25,000 observations in about 100 two-day arcs were used in dynamical solutions (SAO 1969 AGU gravity model). Comparison of results with local survey solutions and with solutions from deep-space vehicle tracking suggests accuracy of about 2 meters in longitude and height and 5 meters in latitude. The relatively larger error in latitude arose from propagation of gravity-model error largely along the track of these high-inclination satellites. The results have also been compared with the solutions of the SAO 1969 standard earth for station coordinates on the North American datum. The solution obtained in the present work is much closer to the survey results in chord length between stations.

Marsh, J. G.↗
NASA NTRS1974

Magnetic coordinates for the Pioneer 10 Jupiter encounter

The magnetic coordinates of the Pioneer 10 spacecraft and the five innermost satellites are reported for the Jupiter encounter. The D sub 2 offset is used to make the calculations. Magnetic coordinates are needed for the interpretation of the trapped particle measurements, including the absorption effects of the satellites. Contours of constant field magnitude and magnetic latitude are given at the surface of Jupiter for the D sub 2 model. The system 3 longitude of a spacecraft at Jupiter is derived, and formulas given for the relationships between system 1, 2, and 3 longitudes. The longitude of the magnetic dipole increases by about 3 deg per year, due to the inaccurate rotation rate used to define system 3 longitude.

Mead, G. D.↗
NASA NTRS1974

Derivation of transformation formulas between geocentric and geodetic coordinates for nonzero altitudes

Four formulas, for the nonzero altitude transformation from geodetic coordinates (geodetic latitude and altitude) to geocentric coordinates (geocentric latitude and geocentric distance) and vice versa, are derived. The set of four formulas is expressed in each of the three useful forms: series expansion in powers of the earth's flattening; series expansion in powers of the earth's eccentricity; and Fourier series expansion in terms of the geodetic latitude or the geocentric latitude. The error incurred in these series expansions is of the order of one part in 3 x 10 to the 7th power.

Long, S. A. T.↗
NASA NTRS1973

Which electromagnetic equations apply in rotating coordinates

It was discovered some years ago by Schiff that two equations for fields in vacuum do not carry over without change from an inertial frame to a frame with rotating axes of space coordinates, even for a region with all velocities much lower than the speed of light. However, the belief that all four of the field equations are invariant under such conditions is still prevalent and causes misconceptions in physical applications, including astrophysical and geophysical ones. The purpose of the present paper is therefore to call attention to Schiff's discovery, discussing its basis and its extension to fields in material media, and to interpret the additional terms that must be added to the equations in order to obtain valid transformations to rotating axes of coordinates.

Webster, D. L.↗
NASA NTRS1973

Coordinate systems and lunar observing station positions

Satellite geodesy has yielded the locations of more than fifty stations in a single coordinate system referred to the earth's center of mass with accuracies in the five to ten meter range. The different methods used at Goddard to accomplish this are described, and estimates of the accuracies of the satellite determinations are discussed. Theoretical aspects of coordinate systems associated with the earth and the moon are also considered.

Siry, J. W.↗
NASA NTRS1974

Magnetic coordinates for the Pioneer 10 Jupiter encounter

The magnetic coordinates of the Pioneer 10 spacecraft and the five innermost satellites are given around the time of Jupiter encounter, Dec. 1-8, 1973. The D sub 2 offset dipole model of Smith et al. (1974) is used to make the calculations. Magnetic coordinates are needed for the interpretation of the trapped particle measurements, including the absorption effects of the satellites. Contours of constant field magnitude and magnetic latitude are given at the surface of Jupiter for the D sub 2 model. The system III longitude of a spacecraft at Jupiter is derived, and formulas are given for the relationships between system I, II, and III longitudes. The longitude of the magnetic dipole increases by about 3 deg/yr, owing to the inaccurate rotation rate used to define system III longitude.

Mead, G. D.↗
NASA NTRS1975

Secular variations of L, B-coordinates

The calculation results of L, B-coordinates for different years from 1957 to 1967 are given. Periodic calculations of the geomagnetic coordinates for different epochs are considered to be very urgent.

Getselev, I. V.↗
NASA NTRS1975

Accuracy of site coordinates obtainable by a mobile lunar laser station

The accuracy with which a mobile lunar laser station can be located was the subject of a modeling study. The influence of the number and accuracy of fixed lunar ranging stations, the uncertainty in polar motion, and data loss due to weather and similar factors were considered, and the results are given in a cartographic form. In general, all three coordinates (for coordinates to latitude + or - 60 deg) were determined to better than the pole uncertainty, given three or more fixed sites and reasonable weather. This result indicates that one or more mobile stations would be suitable for the study of geotectonics.

Loumos, G. L.↗
NASA NTRS1975

Transonic airfoil flowfield analysis using Cartesian coordinates

A numerical technique for analyzing transonic airfoils is presented. The method employs the basic features of Jameson's iterative solution for the full potential equation, except that Cartesian coordinates are used rather than a grid which fits the airfoil, such as the conformal circle-plane or 'sheared parabolic' coordinates which were used previously. Comparison with previous results shows that it is not necessary to match the computational grid to the airfoil surface, and that accurate results can be obtained with a Cartesian grid for lifting supercritical airfoils.

Carlson, L. A.↗
NASA NTRS1975

On the use of a coordinate transformation for the solution of the Navier-Stokes equations

The equations of fluid motion have been formulated in a generalized noncartesian, nonorthogonal coordinate system. A particular coordinate transformation, which transforms a domain with an irregular lower boundary into a cube, has been constructed. The transformed system, unlike the original one, has flat boundaries and homogeneous boundary conditions. Where the topography is flat, the original and transformed system are identical, and extra terms do not appear. A finite difference scheme for solving the transformed equations has been constructed and will be described later.

Gal-Chen, T.↗
NASA NTRS1975

Surface coordinates and cartography of Mercury

A control net of Mercury has been established photogrammetrically by using the Mariner 10 pictures; coordinates of 1328 points are given. The Mariner 10 coordinate system uses a system of longitudes in which the twentieth meridian passes through the center of the small crater Hun Kal and the spin axis is assumed normal to the orbital plane. A reference mosaic of Mercury has been published, and a series of 1:5,000,000 maps is now being produced.

Davies, M. E.↗
NASA NTRS1975

Averaged initial Cartesian coordinates for long lifetime satellite studies

A set of initial Cartesian coordinates, which are free of ambiguities and resonance singularities, is developed to study satellite mission requirements and dispersions over long lifetimes. The method outlined herein possesses two distinct advantages over most other averaging procedures. First, the averaging is carried out numerically using Gaussian quadratures, thus avoiding tedious expansions and the resulting resonances for critical inclinations, etc. Secondly, by using the initial rectangular Cartesian coordinates, conventional, existing acceleration perturbation routines can be absorbed into the program without further modifications, thus making the method easily adaptable to the addition of new perturbation effects. The averaged nonlinear differential equations are integrated by means of a Runge Kutta method. A typical step size of several orbits permits rapid integration of long lifetime orbits in a short computing time.

Pines, S.↗
NASA NTRS1976

Extending the Lorentz transformation by characteristic coordinates

The problem considered is that of rectilinear motion with variable velocity. The paper gives, by an elementary construction, a system of coordinates which is conformal in a restricted region near the axis of the motion. In such coordinates the velocity of light remains invariant even for observers moving with variable velocity. By a particular choice of the scale relation the restricted conformal transformations can be made to reduce to the Lorentz transformation everywhere in the case of constant velocity and locally in the case of variable velocity.

Jones, R. T.↗
NASA NTRS1976

Space telescope coordinate systems, symbols, and nomenclature definitions

The major coordinate systems as well as the transformations and transformation angles between them, for the Space Telescope are defined. The coordinate systems were primarily developed for use in pointing and control system analysis and simulation. Additional useful information (on nomenclature, symbols, quaternion operations, etc.) is also contained.

Kennel, H. F.↗
NASA NTRS1975

Computer-developed construction of analytic expressions for the coordinates and partial derivatives of Jupiter's Galilean satellites

A method for improving Sampson's (1910, 1912, 1921) original work in developing series expressions for accurate coordinates of the Galilean satellites is discussed. The method, which utilizes computer-based algebraic manipulation software, was developed to reconstruct Sampson's theory, remove existing errors, introduce neglected effects, and provide analytic expressions for the coordinates as well as for the partial derivatives with respect to orbital parameters, Jupiter's mass and oblateness, the satellite masses, and Jupiter's pole and rotation period. The software system, capable of handling Poisson series with up to 73 polynomial variables and 28 trigonometric arguments, is described. The preliminary solution is presented, and procedures are outlined for calculating perturbations and eliminating auxiliary parameters.

Lieske, J. H.↗
NASA NTRS1975

Station coordinates in the Standard Earth III system derived by using camera data from ISAGEX

Simultaneous and individual camera observations of Geos 1, Geos 2, Pageos, and Midas 4 obtained during the International Satellite Geodesy Experiment are used to determine station coordinates. The Smithsonian Astrophysical Observatory Standard Earth III system of coordinates is utilized to tie the geometrical network to a geocentric system and as a reference for calculating satellite orbits. The normal systems for geometrical and dynamical solutions are combined.

Gaposchkin, E. M.↗