| Knowledge of the earth's gravity field is an important aspect of many disciplines. On a localized scale, many engineering and surveying projects depend on knowledge of equipotential surfaces. At longer wavelengths, knowledge of the acceleration due to gravity affecting satellite orbits is a necessary component of precision orbit determination. Improved knowledge of salellite orbits results in decreasing error in interpreting data from satellite instrumentation, which has far reaching effects on several scientific disciplines. Further, temporal variations of the gravity field can result from deformations of the earth's solid surface due to time-varying loading factors and re-distribution of mass in the atmosphere and the oceans. A better understanding of these variations can help explain the physical phenomena that are causing them, phenomena which are intimately related to climatological changes on our planet.;The Explorer Platform (EP) has the potential for enhancing the gravity model by adding data to spatially weak components of present models. To do so, however, requires deconvolving the EP orbit errors to the component due to gravity signal and to everything else. This research focuses on achieving this gravity model improvement. The single-frequency Global Positioning System tracking data from EP is used to assess their strength in improving the gravity model. This is important as many future spacecraft may carry similar inexpensive receivers whose data will then become a valuable data set for science, even if the original intent of the instruments was for navigation purposes only. Evaluation of the results includes comparison of the orbits to those generated from various external sources as a means of validating our methods. Comparisons of the resulting gravity models with current models and independent ground truth are made and evaluated. The remaining errors and their residual effect on the geodetic results is quantified. |
