A report describes a series of computational models conceived as an improvement over prior models for determining effects of solar-radiation pressure on orbits of Global Positioning System (GPS) satellites. These models are based on fitting coefficients of Fourier functions of Sun-spacecraft- Earth angles to observed spacecraft orbital motions. Construction of a model in this series involves the following steps:
- Form 10-day "truth" orbit arcs from precise daily GPS orbit data gathered during more than four years.
- Construct a model of the solar-radiation pressure and estimate model parameter values that make a least squares best fit of the model-predicted trajectory to each of the "truth" 10-day orbit arcs.
- Using a least-squares procedure and utilizing the full covariance information from each 10-day fit, combine the estimates from all satellite arcs into a single set of model parameters for the two GPS constellations of the satellites now or soon to be placed in service.
- Evaluate the model thus derived by means of orbit-data-fit and orbit-prediction tests.
In evaluations performed thus far, these models have been found to offer accuracies significantly greater than those of the prior models.
This work was done by Yoaz Bar-Sever and Da Kuang of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Information Sciences category. NPO-41395
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Improved Solar-Radiation Pressure Models for GPS Satellites
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Overview
The document is a Technical Support Package for "Improved Solar-Radiation Pressure Models for GPS Satellites," referenced as NPO-41395 from NASA Tech Briefs. It outlines advancements in modeling solar radiation pressure effects on GPS satellites, which are crucial for accurate positioning and navigation.
The analysis is based on a comprehensive review of daily orbit solutions from January 1, 1998, to July 1, 2002. Researchers selected consecutive 10-day arcs with daily 3D orbit overlap RMS better than 20 cm, resulting in a total of 2,414 arcs. These arcs were categorized into two groups: Block IIA and Block IIR satellites. The study emphasizes the importance of solar radiation pressure modeling, particularly during eclipse seasons, which will be addressed in a follow-up paper. Eclipsing arcs were excluded from the analysis to ensure the quality of the data.
The document serves as a resource for aerospace-related developments with potential technological, scientific, or commercial applications. It is part of NASA's Commercial Technology Program, aimed at disseminating research findings to a broader audience. The Technical Support Package includes information on how to access further assistance and additional resources from NASA's Scientific and Technical Information (STI) Program Office.
The document also contains a disclaimer stating that the U.S. Government and its representatives do not assume liability for the use of the information provided, nor do they guarantee that such use will be free from privately owned rights. It clarifies that any trade names or manufacturers' names mentioned are for identification purposes only and do not imply official endorsement by NASA.
Overall, the document highlights the significance of improved solar radiation pressure models in enhancing the accuracy of GPS satellite orbits, which is vital for various applications in navigation and positioning. The findings and methodologies presented are expected to contribute to ongoing research and development in aerospace technology, ensuring better performance and reliability of GPS systems.
