Engineering topics

Eanes, R. J.

Publications and source records attributed to Eanes, R. J..

23 records · Page 2

NASA NTRS1985

Station coordinates, baselines, and earth rotation from Lageos laser ranging - 1976-1984

The orbit of the Lageos satellite is well suited as a reference frame for studying the rotation of the earth and the relative motion of points on the earth's crust. The satellite laser measurements can determine the location of a set of tracking stations in an appropriate terrestrial coordinate system. The motion of the earth's rotation axis relative to this system can be studied on the basis of the established tracking station locations. The present investigation is concerned with an analysis of 7.7 years of Lageos laser ranging data. In the first solution considered, the entire data span was used to adjust a single set of station positions simultaneously with orbit and earth rotation parameters. Attention is given to the accuracy of earth rotation parameters which are determined as an inherent part of the solution process.

Tapley, B. D.↗

NASA NTRS1983

Secular variation of earth's gravitational harmonic J2 coefficient from Lageos and nontidal acceleration of earth rotation

Analysis of 5.5 years of Lageos satellite range data reveal significant residual nodal signatures: an acceleration and annual and semiannual periods. These signatures primarily reflect variations in the zonal gravitational harmonic J2 coefficient and hence the polar moment of inertia. The implied decrease of J2 = -3 x 10 to the -11th/yr is consistent with both historical observations of the nontidal acceleration of the earth's rotation and models of viscous rebound of the solid earth from the decrease in load due to the last deglaciation.

Yoder, C. F.↗

NASA NTRS1983

Comparison of earth rotation as inferred from radio interferometric, laser ranging and astrometric observations

Results of measurements of the earth's rotation vector for a 400-day period from late September 1980 to December 1981, for which date from VLBI, satellite laser ranging (SLR), and lunar laser ranging (LLR) were available, are compared. The acquisition of the data and their evaluation are described. VLBI, SLR, and classical astrometric determinations of the X-parameter required to describe the location of the rotation pole on the earth's surface are shown, and VLBI, LLR, and classical astrometric determinations of the angle of rotation about this pole (UT1) are presented. The results indicate that VLBI and SLR, at their present stages of development, yield standard errors under 20 cm in the determinations of X, about twofold smaller than obtained from classical measurements, and that VLBI and LLR yield determination of UT1 with standard errors less than 40 cm, somewhat smaller than that of the corresponding determinations from classical observations. Methods for improving these types of intercomparisons are suggested.

Robertson, D. S.↗

NASA NTRS1982

Earth rotation from a simultaneous reduction of LLR and LAGEOS laser ranging data

As the techniques of lunar and artificial satellite laser ranging mature, emphasis is being placed upon the use of these observations to monitor the earth's rotation. It is important to note, however, that at the present time neither technique alone can furnish all three components of this rotation to an accuracy which surpasses those results obtained from classical techniques. The present study represents the first stages of an investigation which has the objective to combine Lageos satellite and lunar laser ranging observations. It is hoped that the proper implementation of such a process might eliminate the shortcomings inherent in each technique, while accentuating the advantages of each. Attention is given to data and model compatibilities, analysis techniques, and numerical results. The presented results are indicative of the great progress which has been realized recently concerning an appropriate combination of Lageos and lunar laser ranging results

Shelus, P. J.↗

NASA NTRS1980

Precision orbit determination software validation experiment

This paper presents the results of an experiment which was designed to ascertain the level of agreement between GEODYN and UTOPIA, two completely independent computer programs used for precision orbit determination, and to identify the sources which limit the agreement. For a limited set of models and a seven-day data set arc length, the altitude components of the ephemeris obtained by the two programs agree at the sub-centimeter level throughout the arc.

Schutz, B. E.↗