The geodetic applications of satellites
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Date
1964-06
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Publisher
Ohio State University. Division of Geodetic Science
Abstract
The geodetic applications of satellites may be divided into geometric and dynamic applications. In the geometric applications the general method is to compare the predicted position of the satellite, based on the assumed parameters of the orbit and the geocentric coordinates of the observer, with the observed positions. The comparisons, if made in sufficient numbers, may yield corrections to both the orbital elements and the coordinates of the observer, thus enabling simultaneous determinations of the orbit and the locations of the observers. There are simplified cases, when the orbit is known, and when the orbit is not needed, both of which will be discussed here. The result of the geometrical application is a set of observing stations whose coordinates refer to the same, possibly geocentric, geodetic datum. By this method, triangulation systems located on different datums may be tied together, or be brought to the same, possibly best fitting geocentric, system. In the dynamic applications the coefficients of the spherical harmonic expansion of the earth's gravitational potential function are determined from observing the perturbations of the elements. From these directly determined coefficients, several indirect but geodetically significant results may be calculated, such as the shape of the earth ellipsoid, the regional undulations of the geoid, regional surface gravity anomalies, etc. It is also possible to determine the Gaussian gravitational constant which, through the application of Kepler's third law, may yield information on the equatorial radius of the earth.
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Prepared for Air Force Cambridge Research Laboratories, Office of Aerospace Research, United States Air Force, Bedford, Massachusetts: Contract No. AF 19(628)1628, Project No. 7600, Task No. 760002