This research effort is concerned with the methods of simplified orbit determination and orbit representation and their applications for Low Earth Orbit (LEO) satellite missions, particularly addressing the operational needs of the FedSat mission. FedSat is the first Australian-built satellite in over thirty years. The microsatellite is approximately 50cm cubed with a mass of 58 kg. The satellite was successfully placed into a low-earth near-polar orbit at an altitude of 780km by the Japanese National Space Development Agency (NASDA) H-IIA launch vehicle on 14, December 2002. Since then, it has been streaming scientific data to its ground station in Adelaide almost daily. This information is used by Australian and international researchers to study space weather, to help improve the design of space computers, communication systems and other satellite technology, and for research into navigation and satellite tracking. This research effort addresses four practical issues regarding the FedSat mission and operations. First, unlike most satellite missions, the GPS receiver onboard FedSat operates in a duty-cycle mode due to the limitations of the FedSat power supply. This causes significant difficulties for orbit tracking, Precise Orbit Determination and scientific applications. A covariance analysis was performed before the mission launch to assess the orbit performance under different operational modes. The thesis presents the analysis methods and results. Second, FedSat supports Ka-band tracking experiments that require a pointing accuracy of 0.03 degree. The QUT GPS group is obligated to provide the GPS precise orbit solution to meet this requirement. Ka-band tracking requests satellite orbital position at any instant time with respect to any of the observation stations. Because orbit determination and prediction software only provide satellite orbital data at a discrete time point, it is necessary to find a way to represent the satellite orbit as a continuous trajectory with discrete observation data, able to obtain the position of the satellite at the time of interest. For this purpose, an orbit interpolation algorithm using the Chebyshev polynomial was developed and applied to Ka-band tracking applications. The thesis will describe the software and results. Third, since the launch of FedSat, investigators have received much flight GPS data. Some research was invested in the analysis of FedSat orbit performance, GPS data quality and the quality of the onboard navigation solutions. Studies have revealed that there are many gross errors in the FedSat onboard navigation solution (ONS). Although the 1-sigma accuracy of each component is about 20 m, there are more than 11 %positioning errors that fall outside +/-50m, and 5% of the errors are outside the 100mbound. The 3D RMS values would be 35m, 87m, and 173m for the above three cases respectively. The FedSat ONS uncertainties are believed to be approximately three times greater than those from other satellite missions. Due to the high percentage of outlier solutions, it would be dangerous to use these without first applying data detection and exclusion procedures. Therefore, this thesis presents two simplified orbit determination methods that can improve the ONS. One is the &quotgeometric method", which makes use of delta-position solutions derived from carrier phase differences between two epochs to smooth the code-based navigation solutions. The algorithms were tested using SAC-C GPS data and showing some improvement. The second method is the &quotdynamic method", which uses orbit dynamics information for orbit improvements. Fourth, the FedSat ground tracking team at Adelaide use the NORAD TLE orbit for daily FedSat tracking. Research was undertaken to convert an orbit trajectory into these Two Line Elements (TLE). Algorithms for the estimation of TLE solutions from the FedSat onboard GPS navigation solutions are outlined. Numerical results have shown the effects of the unmodelled forces/perturbations in the SPG4 models for the FedSat orbit determination would reach a level of ±1000m. This only includes the orbit representation errors with TLE data sets. The total FedSat orbit propagation should include both the orbit propagation and orbit representation terms. The analysis also demonstrates that the orbit presentation error can be reduced to ±200m and ±100mlevels with the EGM4x4 and EGM10x10 gravity field models respectively. This can meet the requirements for Ka-band tracking. However, a simplified tracking program based on numerical integration has to be developed to replace the SPG4 models.

Doctor of Philosophy / Traditional military descriptions of conflict tend to focus on the movement of soldiers and armies across battlefields. When the airplane emerged, it forced military theorists to contend with a new, vertical, dimension of conflict. In America, the United States Air Force assumed an important role in this vertical dimension as the country's delivery mechanism for nuclear weapons. However, at the same time that politicians, academics, and military officials debated the offensive uses for aircraft a second debate occurred describing how best to use military means to defend the North American continent. Those who advocated for a defensive system to protect North American, including the President Eisenhower, strongly advocated for a continent-wide test of the new air defense system. That test was conducted once a year between 1960 and 1962 during which all civilian air travel across the U.S. and Canada was suspended. The tests were called the "Sky Shield" exercises. This research shows how a prevailing mood of fear and vulnerability gave air defense proponents the political capital to build a continental air defense network and test it during the Sky Shield exercises. Further, it describes the enduring legacy of this domestically-focused Cold War defense program. The research finds that America's approach to Cold War continental defense was strong when it was aligned with the White House's nuclear strategy, but when successive political leaders changed nuclear strategies that decision negatively influenced continental defense programs. This research is useful because it examines a relatively under-explored area of Cold War defense programs. Traditionally these studies focus on offensive capabilities far from American shores. This study instead examines homeland defense and how it changed during the Cold War as a function of changing nuclear programs and changing threats to the United States.

This thesis asks why the North American Aerospace Defense Command (NORAD) continues to exist and remain relevant in the defence of North America following the disappearance of the threat of the Soviet Union at the end of the Cold War. This thesis argues that NORAD’s binational nature is key to understanding the command’s continued role in continental defence. By employing the international relation theories of functionalism and neoliberal institutionalism as a lens of analysis to understand binational defence cooperation, NORAD’s origins as a binational defence command tasked with the air defence of North America, and its acquisition of its responsibilities for drug interdiction, the continental interior, and for maritime warning are analyzed. NORAD’s longevity and continued relevance can be attributed to the command’s binational nature, which has allowed the command to focus on and institutionalize specific functional-technical solutions to select issues of mutual concern in continental defence and security for Canada and the U.S. / May 2016