Precise Orbit Determination of CubeSats

CubeSats are faced with some limitations, mainly due to the limited onboard power and the quality of the onboard sensors. These limitations significantly reduce CubeSats' applicability in space missions requiring high orbital accuracy. This thesis first investigates the limitations in the precise orbit determination of CubeSats and next develops algorithms and remedies to reach high orbital and clock accuracies. The outputs would help in increasing CubeSats' applicability in future space missions

Europe's Space capabilities for the benefit of the Arctic

In recent years, the Arctic region has acquired an increasing environmental, social, economic and strategic importance. The Arctic’s fragile environment is both a direct and key indicator of the climate change and requires specific mitigation and adaptation actions. The EU has a clear strategic interest in playing a key role and is actively responding to the impacts of climate change safeguarding the Arctic’s fragile ecosystem, ensuring a sustainable development, particularly in the European part of the Arctic. The European Commission’s Joint Research Centre has recently completed a study aimed at identifying the capabilities and relevant synergies across the four domains of the EU Space Programme: earth observation, satellite navigation, satellite communications, and space situational awareness (SSA). These synergies are expected to be key enablers of new services that will have a high societal impact in the region, which could be developed in a more cost-efficient and rapid manner. Similarly, synergies will also help exploit to its full extent operational services that are already deployed in the Arctic (e.g., the Copernicus emergency service or the Galileo Search and rescue service could greatly benefit from improved satellite communications connectivity in the region).JRC.E.2-Technology Innovation in Securit

Looking Back and Looking Forward: Reprising the Promise and Predicting the Future of Formation Flying and Spaceborne GPS Navigation Systems

A retrospective consideration of two 15-year old Guidance, Navigation and Control (GN&C) technology 'vision' predictions will be the focus of this paper. A look back analysis and critique of these late 1990s technology roadmaps out-lining the future vision, for two then nascent, but rapidly emerging, GN&C technologies will be performed. Specifically, these two GN&C technologies were: 1) multi-spacecraft formation flying and 2) the spaceborne use and exploitation of global positioning system (GPS) signals to enable formation flying. This paper reprises the promise of formation flying and spaceborne GPS as depicted in the cited 1999 and 1998 papers. It will discuss what happened to cause that promise to be mostly unfulfilled and the reasons why the envisioned formation flying dream has yet to become a reality. The recent technology trends over the past few years will then be identified and a renewed government interest in spacecraft formation flying/cluster flight will be highlighted. The authors will conclude with a reality-tempered perspective, 15 years after the initial technology roadmaps were published, predicting a promising future of spacecraft formation flying technology development over the next decade

Starlink receiver prototyping for opportunistic positioning

openTraditional GNSS systems for positioning (PNT), such as GPS and Galileo, use Medium Earth Orbits (MEO). Recently, the possibility to use Low Earth Orbit (LEO) orbits for PNT has been investigated, which offer several advantages over the traditional MEO, e.g., higher power and wider band. Among the available signals of opportunity (SOOPs), this thesis project investigates the feasibility of utilizing Starlink signals, primarily designed for global Internet coverage, for positioning purposes. The Starlink signal structure is not publicly available, but the literature suggests the presence of nine equidistant spectral peaks within a band of approximately 1 MHz in the signal spectrum of each satellite, centered at frequency 11,325 GHz. The method proposed in this thesis involves the acquisition and tracking of these peaks, on a signal sampled at a lower frequency than the estimated bandwidth for the entire Starlink channel of 240 MHz, in order to reduce receiver complexity. For the acquisition phase, once the IQ components have been extracted from the signal, the optimal acquisition window length is selected as the trade-off between noise and Fast Fourier Transform (FFT) computational performance. The peak detection threshold is chosen based on the Gaussian distribution of noise and a predefined false alarm probability. This enables the selection of peaks above the noise floor in each acquisition instance, facilitating the detection of potential satellites. Then, similar to standard GNSS receivers, a tracking loop (a third-order PLL assisted by a second-order FLL) is implemented to estimate the Doppler frequency shift of the peaks over the entire captured window. However, as opposed to standard GNSS signals, Starlink does not use a PRN code to identify the individual satellites. To resolve the ambiguity in satellite identification, a method is proposed to compare the Doppler frequency shifts estimated from peak tracking with the Doppler frequency shifts predicted by a visibility prediction tool, which provides the ability to associate each identified peak with a specific Starlink satellite. The tool uses Two-Line Element Sets (TLEs) data and a simplified perturbation model (SGP4) to propagate the satellite orbits. The method is applied to a signal captured using a basic configuration with a Ku-band Low Noise Block (LNB) converter, and the data acquired consist of raw In-phase and Quadrature-phase (IQ) samples with a bandwidth of 4,096 MHz around 11,325 GHz. The results show that the method allows to acquire several satellites in the captured signal, and to track the corresponding peaks for positioning purposes