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Master's Projects

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Now showing 1 - 10 of 31

A Technical Evaluation of Integrating Optical Inter-Satellite Links into Proliferated Polar LEO Constellations

(Georgia Institute of Technology, 2019-12-01) Ingersoll, Joshua

This study evaluates the technical requirements, benefits, and limitations of integrating optical inter-satellite links into a proliferated polar LEO constellation. When compared to traditional radio frequency (RF) links, optical links can transmit orders of magnitude more data at much lower powers in a far more secure method. However, these benefits come with stiff coarse and fine pointing requirements, complex thermal and vibrational satellite bus interfaces, as well as sensitivities to atmospheric conditions for LEO-ground connections. This study breaks optical inter-satellite links (OISL’s) into three distinct categories; in-plane, out-of-plane (crosslink), and LEO-ground. General commercial off the shelf (COTS) state of the art OISL terminal parameters are established. Based on these parameters, varying constellation level implementation strategies are assessed based on latency, bandwidth and technical feasibility using Model Based Systems Engineering principles. These assessments were then re-run at different OISL bandwidths, latencies and costs to evaluate whether the optimal integration technique will change in the future as OISL terminal capability increases. The study finds that the methodology outlined gives crucial insight into future OISL integration and implementation strategies for both current and future mega-constellation architects. Using both current OISL performance parameters as well as future improvements, this study finds that an RF-reliant in-plane architecture is the optimal integration architecture given the constellation configuration constraints. This assessment can help drive the trade space for both OISL vendors producing COTS terminals as well as commercial and military customers looking to integrate OISL terminals into their future constellations.
X-Ray Pulsar Navigation Instrument Performance and Scale Analysis

(Georgia Institute of Technology, 2019-12-01) Payne, Jacob Hurrell

This thesis investigates instruments for autonomous satellite navigation using measurements of X-ray emissions from millisecond pulsars. A manifestation of an instrument for this purpose, called the Neutron star Interior Composition Explorer (NICER), was launched to the International Space Station in 2017. The NICER instrument was designed to observe X-ray emissions from neutron stars for astrophysics research, and is out of scale in terms of volume, power consumption, mass and mechanical complexity to be useful for small satellite missions. This work surveys the range of existing X-ray observation missions to tabulate collecting areas, focal lengths, and optical configurations from milestone missions which describe the evolution of the state of the art in X-ray observatories. A navigation demonstration experiment, called the Station Explorer for X-ray Timing and Navigation Technology (SEXTANT), was conducted using the NICER instrument. The experimental performance observed from NICER through the SEXTANT navigation demonstration is compared to theoretical predictions established by existing formulations. It is concluded that SEXTANT benefits from soft band (0.3-4 keV) exposure to achieve better accuracy than predicted by theoretical lower bounds. Additionally, investigation is presented on the readiness of a navigation instrument for small satellites using compound refractive lensing (CRL) and derived designs. X-ray refraction achieves a much shorter focal length than grazing incidence optics at the expense of signal attenuation in the lens material. Performance estimates and previous experimental results are presented as a baseline for physical prototypes and ix hardware testing to support future development of a physical instrument. The technological hurdle that will enable this tool is manufacturing precise lenses on a 3- micron scale from materials like beryllium with low atomic mass. Recent X-ray concentrator concepts demonstrate progress towards an implementation that can support a CubeSat scale navigation instrument optimized for soft band (0.3-4 keV) X-rays
CubeSat Inter-satellite Tracking Using Remote Sensing and Trajectory Estimation

(Georgia Institute of Technology, 2019-12) Bewley, Logan E. A.
A Technical Evaluation of Integrating Optical Inter- Satellite Links into Proliferated Polar LEO Constellations

(Georgia Institute of Technology, 2019-12) Ingersoll, Joshua E.
Autonomous Control of Small Satellite Formations using Differential Drag

(Georgia Institute of Technology, 2019-08) Groesbeck, Daniel, S.
Lunar Laser Ranging from Low Earth Orbit

(Georgia Institute of Technology, 2019-08) Henley, Brandon R.
Precise Tracking of UAVs using LiDAR and Computer Vision

(Georgia Institute of Technology, 2019-06) Subagia, Rachmat
Application of Self-Healing Materials to Leak Repair in Inflatable Structures

(Georgia Institute of Technology, 2019-05-03) Simmons, Emily Erin

As the duration of crewed spaceflight missions increases, so does the need for habitable volume. Inflatable structures have been proposed as one solution, but they face challenges in in terms of their resilience and repair of leaks. This study examines the use of self-healing materials as a method to repair damage to the inflatable structures, without any human intervention. The study used the finite element analysis software Abaqus to evaluate the effects of thickness, crack size, and initial stresses on the healing efficiency of both microvascular and microencapsulated self-healing materials. The analysis showed that cracks up to 0.2 mm can be healed effectively for the materials explored; however, the healing requires a significant increase in necessary volume of healing agent over the nominal, unloaded case. As a result, the microvascular system is considered to be superior to the microencapsulation method for use in inflatable structures, as it can deliver a continuous supply of the healing agent.
Autonomous Control of Small Satellite Formations using Differential Drag

(Georgia Institute of Technology, 2019-05-01) Groesbeck, Daniel

This study develops a methodology for the autonomous control of multiple small satellites, to include CubeSats, designed to operate in a formation or constellation in Low Earth Orbit (LEO). The satellites are assumed to have no onboard propellant and will rely solely on changing the orientations of the satellites, creating a differential drag force that will be the control mechanism. The control systems that were developed account for the reduction of inter-satellite distance drift and maneuver controls such that two satellites could change the mean relative distance between them while not imparting an additional drift rate. These systems were developed on the assumption of identical satellites operating in similar, near circular coplanar orbits. Simulations were run to validate the functionality of the control systems developed and to find optimal user defined parameters. The final simulations achieved both distance drift reduction and inter-satellite relative distance changes
Processing Strategy for GNSS-based Orbit Determination of Small Satellites

(Georgia Institute of Technology, 2019-05) Elarbee, Jairus H.