Determination of satellite orbits and the global positioning system
An artificial satellite orbit determination (OD) computer program is the most essential tool in satellite geodesy. Such a program has been developed at Nottingham as part of this research and was tested with Satellite Laser Ranging (SLR) observations of the Laser Geodynamics Satellite (LAGEOS). This thesis describes the basic theory behind orbit determination and the software development at Nottingham. It includes details of the adopted force model, coordinate reference frames, and numerical integration and interpolation techniques. It is also explained how several geodetic parameters can be determined. The thesis discusses the results of two separate determinations of the LAGEOS orbit with an emphasis on the solutions for station coordinates and for earth rotation and polar motion. The NAVSTAR Global Positioning System (GPS) is on schedule to replace Transit as the most important satellite navigation system. When fully operational, in 1988, it will consist of 18 satellites which will provide continuous global coverage. This thesis describes the Global Positioning System and outlines the theory behind the most accurate techniques of adjustment of the CPS observables. It derives the equations for interferometric techniques and shows that, by differencing the observations, several undesirable unknowns can be eliminated. GPS data from the NAVSTAR Geodetic Receiver System (NGRS) have been provided for Nottingham by the US Defence Mapping Agency (DMA). The thesis describes the software development to analyse these data and gives the results of several solution schemes to derive the absolute coordinates of the NGRS antenna. It is also shown how the software can be modified to incorporate interferometric techniques. Significant improvements over the NGRS solutions can be expected when GPS is fully operational, with refinements in both receiver hardware and software.