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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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ItemHigh-Speed, Low-Power, Low-Profile Design Fiber-Optic Communication System for CubeSat(Georgia Institute of Technology, 2022-06-08) Kotani, KoheiToday, the demand for big data, such as high-resolution images, has been rapidly increasing in space missions. However, the means to achieve multi-Gbps transmission is limited to ethernet, coax, or FFC in CubeSat design. This research describes the development of a lightweight and low-power consumption high-speed communication system suitable for small satellites. A high volume of data from two high-resolution cameras is transmitted to a Raspberry Pi Compute Module 4 running Linux using a fiber-optic link as an interconnect, and the dual images are displayed on a monitor. The FPGA with a high-speed transceiver is extensively used to achieve high-speed communication. It is also verified that the fiber-optic module operates at up to 6.25 Gbps with a power consumption of 90 mW. This research includes the hardware and software development details. All the materials, including the schematics, PCB design, and programming codes, can be found in the Github repository. Furthermore, this thesis includes the discussion of fiber-optic module usage in the space environment and comparing fiber-optic with ethernet, coax, and FFC, along with the selection guides CubeSat developers can refer to. The final deliverable of this research is the high-speed fiber-optic interconnection designed to fit into a CubeSat platform, demonstrating the dual-image display from two HD cameras. The prototype can be extended to implement high-volume data applications such as stereo imaging for proximity operations, free-space inter-satellite links, and high-speed intra-satellite communications for CubeSat platforms.
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ItemThe Improvement of Multi-Satellite Orbit Determination Through the Incorporation of Intersatellite Ranging Observations(Georgia Institute of Technology, 2021-12-14) Davis, Byron TaylorFor many satellite remote sensing and communications missions, particularly those involving a formation or constellation of satellites, having precise knowledge of the satellites’ positions in both an absolute and relative sense is essential. However, the capabilities of Global Navigation Satellite Systems (GNSS)-based precise orbit determination (POD) alone may not be enough to fulfill the mission’s requirements. This thesis examines potential gains to POD when additional Intersatellite Range (ISR) observations (range magnitude only, not range direction or rate) are combined with standard GNSS observables. These ISR observations can be obtained from simple radio frequency (RF) or optical sensors. The methodology behind the combination approach is described and illustrated through a series of simulated case studies involving multiple satellites in low Earth orbit (LEO) using realistic hardware-derived (where possible) measurement noise. The results demonstrate that substantial improvements (factor of two or better) in the POD of the constellation satellites can be obtained with even intermittent ranging measurements, and with only millimeter-level ranging precision. This improved positioning capability enables new mission concepts for small-satellite constellations and formations, and makes these multi-satellite systems resilient to disruptions in GNSS signal availability. This GNSS-denial could be due to a variety of factors, such as intermittent or total hardware failure, power-related duty cycling, or ground-based jamming. Results show that under appropriate phasing of periodic GNSS-denial, combined with the new information from the ISR observations, POD levels approaching the non-GNSS-denied case can be achieved. For the cases of region-specific or single-satellite total GNSS-denial, constellations with ISR capability can be designed to completely compensate for the loss of GNSS observations and perform at levels better than with GNSS alone. Furthermore, the GNSS-denied case has an extended application for providing ISR-only POD for constellations around planetary bodies through the inversion of the invariant non-spherical gravity fields. Case studies are presented using high resolution invariant Earth and lunar gravity fields. In these example cases, ISR-only POD is demonstrated at the sub-meter level with the same millimeter precision of ISR. This research provides opportunities for new mission concepts that require precise positioning, improvements to mission operations, and enables new paradigms for orbit determination without access to GNSS.
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ItemOptimal Phasing and Performance Mapping for Translunar Satellite Missions across the Earth-Moon Nodal Cycle(Georgia Institute of Technology, 2020-01-10) Hunter, Richard Anthony JohnFast, high-cadence translunar pathfinder missions hold great promise for advancing NASA's scientific observation, prospecting, and technology validation objectives through increased lunar exploration. This research applies high-performance computing to characterize direct injection lunar trajectories over a broad parameter space, and in so doing, demonstrates the viability of lunar pathfinder missions using the near-future commercial launch market. The results are intended to provide mission designers with an accurate, versatile reference for preliminary planning, including optimal departure epochs, and pertinent performance dependencies. Characterized herein are statistical distributions for the performance demands of optimally phased translunar missions, over an 18.6 year Earth-Moon nodal cycle, to a range of tailored lunar arrival architectures, for 0 – 24 kg small satellite payloads capable of supporting pathfinder objectives. This characterization is based upon a TLI stage with flight proven propulsion technology, high fidelity orbital dynamics, and direct injection flyby, orbit insertion and landing architectures compatible with both dedicated and ride share commercial launches.