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Papo, H. B.

Publications and source records attributed to Papo, H. B..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

A new parameterization of polar motion

The rotational motion of the earth is decomposed into spin, polar motion and local motions. The rotation vector components are associated to phenomena such as precession, nutation, diurnal spin, polar motion and local motions. The above decomposition is accomplished without refering to an earth-fixed CIO pole or BIH zero meridian. The time-like variations of the coordinates of a surface point in a geocentric equatorial reference frame are presented as a function of the rotation vector components. In the rigid earth approximation three scalar parameters are necessary for evaluating point coordinate variations, namely spin rate of the earth, polar motion magnitude and spin rate of the polar motion vector. Two numerical examples are given as an illustration.

Papo, H. B.↗
NASA NTRS1979

Investigations on the hierarchy of reference frames in geodesy and geodynamics

Problems related to reference directions were investigated. Space and time variant angular parameters are illustrated in hierarchic structures or towers. Using least squares techniques, model towers of triads are presented which allow the formation of linear observation equations. Translational and rotational degrees of freedom (origin and orientation) are discussed along with and the notion of length and scale degrees of freedom. According to the notion of scale parallelism, scale factors with respect to a unit length are given. Three-dimensional geodesy was constructed from the set of three base vectors (gravity, earth-rotation and the ecliptic normal vector). Space and time variations are given with respect to a polar and singular value decomposition or in terms of changes in translation, rotation, deformation (shear, dilatation or angular and scale distortions).

Grafarend, E. W.↗
NASA NTRS1979

Concepts for reference frames in geodesy and geodynamics - The reference directions

The paper discusses a study that establishes a reference frame, moving with the earth (in some average sense), in which the geometric and dynamical behavior of the earth can be monitored, and whose motion with respect to inertial space can also be determined. Emphasis is placed on the fact that the reference directions at an observation point on the earth surface, are defined by fundamental vectors for both space and time. The interrelationships between this space- and time-variant angular parameter are illustrated in a commutative diagram and tower of triads. Although the model tower is also space- and time-variant, its variations are described by adopted parameters using our current knowledge of the earth.

Grafarend, E. W.↗
NASA NTRS1973

Orientation of the moon by numerical integration

The differential equations of rotational motion of the moon are solved by numerical integration methods. Euler's dynamical equations transformed to a convenient form are treated by techniques analogous to ordinary orbit determination procedures. The proposed method is fully consistent with the ephemeris of the moon and can utilize a variety of observational material for the solution of the selected parameters. Examples are given of comparison between the proposed method and Eckhardt's 1970 model of the physical librations of the moon. The merits of the new method are discussed in the light of conventional data sources like earth-based or satellite-based photography as well as newly available data types like laser ranging to retroreflectors on the moon.

Papo, H. B.↗
NASA NTRS1973

The influence of laser ranging on selenodetic control.

A mathematical model for performing an adjustment, using laser distances to improve coordinates of points on the earth and on the moon, as well as the orientation of these two bodies in space, is presented. The observation equations are given, and the orientation of the earth and the moon are defined in terms of three Eulerian angles. Numerical experiments were performed to investigate the expected accuracies of parameters in the adjustment model under differing conditions. The results indicate that the statistics both for the coordinates of points on earth and on the moon, and for the orientation parameters of the two bodies are favorable. However, very high correlations exist between some of the parameters; therefore, the recovery of these parameters from a simultaneous adjustment is questionable.

Mueller, I. I.↗
NASA NTRS1972

The influence of laser ranging on selenodetic control.

In this paper, a mathematical model is presented which can be used to perform an adjustment using laser distances to improve coordinates of points of the earth and on the moon. The observation equations are given and the orientation of the earth and the moon is defined in terms of three Eulerian angles. Parameters related to the orientation of the two bodies are the six initial conditions in each case, for the numerical integration of the three angles and their time derivatives. Numerical experiments were performed for the purpose of investigating the expected accuracies of the various parameters in the adjustment model under differing conditions. The results of the experiments indicate that the statistics for both the coordinates of points on earth and on the moon, and for the orientation parameters of the two bodies, are favorable.

Mueller, I. I.↗