Organizational Unit:

Daniel Guggenheim School of Aerospace Engineering

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https://hdl.handle.net/1853/70742

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College of Engineering

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Aerospace Design Group

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Aerospace Systems Design Laboratory (ASDL)

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Air Transportation Laboratory

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Cognitive Engineering Center

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Space Systems Design Laboratory (SSDL)

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https://finding-aids.library.gatech.edu/agents/corporate_entities/106

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Publication Search Results

Now showing 1 - 10 of 273

The Design, Assembly, and Testing of Magnetorquers for a 1U CubeSat Mission

(Georgia Institute of Technology, 2019-12-12) Amin, John

Over the next few years Georgia Tech’s Space System Design Lab (SSDL) will design and develop several 1U CubeSat missions starting with GT-1. These missions will include an Attitude Determination and Control Systems (ADCS) utilizing torque rods to control detumble and orbital attitude. This paper describes the design and construction and testing of GT-1’s torque rods and will serve as a resource to help guide future torque rod iterations. The first section details the equations and mathematics behind torque rods. Next, the design section considers factors influencing the magnetic dipole moment including core material, part length, and radius. It then describes the manufacturing and assembly process of torque rods involving core shaping and layer winding. It then describes the test setup to test the torque rod’s magnetic dipole moment and later indicates topics of future work.
Design of a Green Monopropellant Propulsion System for the Lunar Flashlight Mission

(Georgia Institute of Technology, 2019-12-12) Andrews, Dawn ; Lightsey, E. Glenn

The Lunar Flashlight Mission is a lunar-bound small satellite that will investigate the Moon’s poles for water ice. Aboard the spacecraft is a green monopropellant propulsion system that has been designed by the Georgia Institute of Technology under sponsorship and guidance by the NASA Marshall Space Flight Center. Green monopropellant propul sion is a forthcoming technology that promises improvements in performance and safety over existing monopropellant systems such as Hydrazine, making it a very desirable new technology, and Lunar Flashlight will be the first mission to utilize this propulsion on a CubeSat platform. The design solution for the Lunar Flashlight Propulsion System will be shared, as well as the story behind its evolution through the design process. Additionally, several key aspects of its design that are fundamental to green monopropellant propul sion will be collected in contribution to a design methodology for future iterations. This project is intended to continue on to launch with the Artemis-1 Mission, at which point the propulsion system would complete its objectives of contributing flight heritage to this technology while acting as a critical component for the Lunar Flashlight Mission.
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
Mahalanobis Shell Sampling (MSS) method for collision probability computation

(Georgia Institute of Technology, 2019-12-01) Núñez Garzón, Ulises E.

Motivated by desire for collision avoidance in spacecraft formations, and by the need for accurately computing low kinematic probabilities of collision (KPC) in spacecraft collision risk analysis, this work introduces an algorithm for sampling from non-degenerate, multidi mensional normal random variables. In this algorithm, the analytical relationship between certain probability density integrals of such random variables and the chi-square distribution is leveraged in order to provide weights to sample points. In so doing, this algorithm allows direct sampling from probability density “tails” without unduly penalizing sample size, as would occur with Monte Carlo-based methods. The primary motivation for the development of this algorithm is to help in the efficient computation of collision probability measures for relative dynamic systems. Performance of this method in approximating KPC waveforms is examined for a low-dimensionality dynamic example. However, this method could be applied to other dynamic systems and for probability density integrals other than collision probability measures, allowing for efficient computation of such integrals for problems where analytical results do not exist. Therefore, this method is suggested as an alternative to random sampling algorithms such as Monte Carlo methods or the Unscented Transform.
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.
Localizing in Urban Canyons using Joint Doppler and Ranging and the Law of Cosines Method

(Georgia Institute of Technology, 2019-09) Jun, William W. ; Cheung, Kar-Ming ; Lightsey, E. Glenn ; Lee, Charles

The performance of Global Navigation Satellite System (GNSS) based navigation can be limited in urban canyons and other regions with narrow satellite visibility. These regions may only allow for less than the minimum of four satellites to be visible, leading to a decay of positional knowledge. A scheme with Joint Doppler and Ranging (JDR) and relative positioning, known as the Law of Cosines (LOC) method, is introduced in this paper that utilizes Doppler and pseudorange measurements from a minimum of two GNSS satellites to obtain a position fix. The user’s GNSS receiver was assumed to output both corrected pseudorange and Doppler shift measurements for each tracked satellite. The velocity vector of each satellite was calculated using broadcast satellite ephemerides. Additionally, the location of the reference station was known and Doppler measurements from the GNSS receiver at the reference station were transmitted to the user. Ephemerides from eight GNSS satellites were simulated with the user and reference station approximately 12 km apart in San Francisco. Gaussian error sources were modelled and randomized in Monte Carlo simulations, adding error to the receiver’s known satellite ephemeris, satellite velocity, Doppler, and pseudorange measurements. Each unique pair of 2 satellites was employed for the positioning of the user using the LOC method for over 10,000 Monte Carlo simulations. With reasonable assumptions on measurement error, the average 2D topocentric Root-Mean-Square-Error (RMSE) performance of all pairs of satellites was 23 meters, reducing to 10 meters by removing specific pairs with poor geometry. However, with a new technique called Terrain Assisted – JDR (TA-JDR), which uses accurate topographic information of the user’s region as a faux pseudorange measurement, the average RSME of the satellite pairs was reduced to approximately 7 meters. The use of the JDR-LOC scheme and its variants may not only be useful in urban canyons, but also in other GPS-denied unfriendly environments. Ultimately, the JDR-LOC scheme was capable of achieving navigational solutions with an RMSE as low as 7 meters for users with limited GNSS satellite visibility, with only the use of a GNSS receiver and a reference station.
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.