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    Mars Entry, Descent, and Landing Trajectory and Atmosphere Reconstruction
    (Georgia Institute of Technology, 2010-05-05) Dutta, Soumyo
    Flight data from an entry, descent, and landing (EDL) sequence can be used to reconstruct the vehicle’s trajectory as well as compute the associated uncertainty. The atmospheric profile encountered by the vehicle can similarly be estimated from the flight data. Past Mars missions have contained instruments, such as accelerometers, gyroscopes, and radar altimeters that do not provide direct measurement of the free-stream atmospheric conditions. Thus, uncertainties in the atmospheric reconstruction and the aerodynamic database knowledge cannot be separated. However, the upcoming Mars Science Laboratory (MSL) will take measurements of the pressure on the aeroshell forebody during entry. These measurements will provide means to determine the free-stream conditions and to separate the atmospheric and aerodynamic uncertainties. In this paper, analytical methods to statistically estimate trajectories and free-stream conditions from flight data and to quantify uncertainties in these parameters are discussed. A sample data set from a ballistic range test of an Orion Crew Exploration Vehicle (CEV) model is then used to demonstrate results from applying these procedures. This approach utilizes the same techniques and toolset planned for subsequent application for the reconstruction of MSL’s EDL sequence in 2012.
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    Manufacturing, Integration, and Testing of the Green Monopropellant Propulsion System for NASA’s Lunar Flashlight Mission
    (Georgia Institute of Technology, 2020-12) Talaski, Ali
    NASA’s Lunar Flashlight is a 6U CubeSat that will be investigating the Lunar South Pole for water-ice. Propelling the spacecraft is a 2.5U green monopropellant propulsion system developed by the Georgia Tech Space Systems Design Laboratory in partnership with the NASA Marshall Spaceflight Center and NASA Jet Propulsion Laboratory. Lunar Flashlight will be the first interplanetary CubeSat to use green propulsion, and will be the first CubeSat to place itself into orbit around another planetary body. Utilizing a mix of traditional and additive manufacturing techniques to manufacture the propulsion system presented unique challenges for the project. In addition, the integration of precision flight hardware has required rapid design changes to parts to ensure that the system fits together as intended. However, as a pathfinder mission for future small satellite propulsion systems, the Lunar Flashlight Propulsion System will establish flight heritage of various components, including additively manufactured hardware, microfluidic components, custom-designed electronics, and unique cleanliness specifications.
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    Payload System Design of a CubeSat Distributed Telescope
    (Georgia Institute of Technology, 2020-12-10) Thatavarthi, Rohan
    The Virtual Super-Resolution Optics with Reconfigurable Swarms (VISORS) mission is a novel CubeSat formation distributed telescope mission that aims to investigate the underlying energy release mechanisms in the solar corona. VISORS is a mission that was initially conceived in the National Science Foundation (NSF) CubeSat Innovations Ideas Lab workshop held in 2019. The mission will observe the corona in extreme ultra-violet (EUV) at an angular resolution of less than 0.2 arcseconds using two 6U CubeSats that align and fly 40 meters apart to form a distributed telescope. Achieving such a mission requires key technologies in the fields of diffractive optics, inter-satellite communication, CubeSat propulsion, and relative navigation. The development of any single one of these technologies is novel but all of them working in conjunction truly enables the VISORS mission. The consolidation of these technologies into the Cubesat form factor poses a mechanical and systems design challenge. This paper focuses on the preliminary payload design of the VISORS CubeSats, the challenges inherent with combining the key technologies into a 6U form factor, and the key next steps to mature the payload design. Working in conjunction with 10 different universities and a projected launch in late 2023, the VISORS mission will demonstrate the capabilities of CubeSats to perform high precision coronal imagery and will pave the path forward for future CubeSat swarm missions.
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    Deployment of Microcells by integrating LTE-U with LTE
    (Georgia Institute of Technology, 2014) Panchal, Deven
    With increasing data requirements of users, cellular operators are finding new ways to fulfil these requirements. These attempts involve the practice of deploying Wi-Fi access points nearer to the user and backhauling it to the nearest eNB (in case of LTE and LTE-A). The paper studies LTE-U, an extension of LTE which works in the unlicensed spectrum, as a potential solution to this problem. It is based on the idea of densification. Network deployments incorporating LTE-U will be able to better cater to the growing data rate demand of voice and video, thus reducing the load on eNB. Further we explore the possibility of LTE-U as an alternative to Wi-Fi or co-existing with Wi-Fi deployments and issues revolving around this idea. We show that LTE-U deployment solves the problem of capacity in both cases.
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    Unveiling air pollution-related health inequality in China’s food system
    (Georgia Institute of Technology, 2024-03) Zheng, Lianming ; Adalibieke, Wulahati ; Zhou, Feng ; He, Pan ; Chen, Yilin ; Guo, Peng ; He, Jinling ; Zhang, Yuanzheng ; Xu, Peng ; Wang, Chen ; Ye, Jianhuai ; Zhu, Lei ; Shen, Guofeng ; Fu, Tzung-May ; Yang, Xin ; Zhao, Shunliu ; Hakami, Amir ; Russell, Armistead G. ; Tao, Shu ; Meng, Jing ; Shen, Huizhong
    Food consumption contributes to the degradation of air quality in regions where food is produced, giving rise to an often-neglected form of environmental inequality, i.e., the contrast between the environmental health burden caused by the food consumption of a specific population and that they encounter as a consequence of food production activities. Herein, we explore this inequality within China’s food system, by linking air pollution–related health burden from the production side to the consumption side at high levels of spatial and sectorial granularity. Our findings reveal that low-income groups bear a 70% higher air pollution-related health burden from the food production than is caused by their food consumption, while high-income groups benefit from a 29% lower health burden relative to their food consumption. This discrepancy can be primarily attributed to the significant concentration of the low-income population residing in food production areas, thereby exposing them to higher emissions from agricultural activities. Our study indicates that comprehensive interventions targeting both production and consumption sides can effectively reduce health damages and concurrently mitigate associated inequalities, while singular interventions exhibit limited efficacy. This emphasizes the need for a combination of measures to establish a sustainable and equitable food system.
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    Prox-1 Guidance, Navigation & Control Formulation and Algorithms
    (Georgia Institute of Technology, 2013-05-01) Zappulla, Richard, II
    Beginning with the manned Gemini missions, proximity operations and rendezvous between two (2) spacecraft have significantly evolved from human-in-the-loop to ground-in-the-loop to more autonomous vehicles, such as the Japanese ETS-VII and the Russian Progress vehicles. Prior to the proposal for the Prox-1 mission, numerous other missions—such as XSS-10, XSS-11, DART, and Orbital Express—have demonstrated varying levels of autonomy. Unlike previous missions, the Prox-1 mission will utilize a completely autonomous GN&C system driven by an on-board GPS receiver, an uncooled infrared microbolometer, a three-axis magnetometer, an inertial measurement unit (IMU), and sun sensors. The GN&C algorithms and strategies discussed in this paper are designed around robust formulations that are shown to guarantee asymptotic stability and aid in mitigating risk involved with passive, autonomous proximity operations
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    Strategic Planning of Abort Trajectories for Manned Lunar Missions
    (Georgia Institute of Technology, 2018-05-01) Yuricich, Jillian
    A resurgence in manned lunar missions is on the horizon with private space companies and nation states alike competing to be the first to return to the Moon since the Apollo program ended in 1972. Technology and mission planning abilities have expanded im mensely in the almost half century of time that has elapsed since Apollo 11 first landed on the Moon. It is therefore necessary to evaluate and update how abort procedures should be strategized given the increase in volume of crewed missions planned for the Moon and beyond. This research seeks to investigate three abort strategies for space vehicles in or bit around the Moon and provide a high-level road map of options based on their fuel costs and time of flight to return to the Earth. By investigating previous historic works in combination with more recent research, this paper intends to capitalize on previous math ematical derivations and combine multiple abort strategies into a coherent simulation tool. It is expected that given the nominal trajectory of a circular lunar orbit, a specific abort strategy with options ranging from single to triple-impulse requirements can be selected as the optimal trajectory for a return to Earth. This research provides a high-level road map of contingency plans and fills a gap in understanding abort strategies from lunar orbit.
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    Trajectory Animator Java Applet
    (Georgia Institute of Technology, 2001-08-01) Weglian, John E.
    Low thrust trajectories allow for very complicated, programmable thrust profiles to shape the orbit. Also it is often desirable or necessary to only apply thrust at a certain point in a trajectory such as at periapsis. The Trajectory Animator allows the user to program complicated thrust profiles based on the position in the orbit (specified by true anomaly or mean anomaly), and then see how the orbit develops over time. Trajectory Animator is a Java applet that can be run from any windows browser that supports Java. The HTML code for the applet will prompt a user to automatically download the Java plug-in if it is not already installed on the user’s machine.
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    Automated Proximity Operations Using Image Based Relative Navigation
    (Georgia Institute of Technology, 2012-05-01) Walker, Luke
    This paper will describe a system for relative navigation and automated proximity operations for a small spacecraft about another spacecraft using continuous thrust propulsion and low cost imagers. Novel image processing algorithms provide range estimates in addition to traditional spherical angle estimates using knowledge of the target spacecraft’s geometry. A differential correction batch filter is used to provide relative navigation and state estimation. These state estimates are used to provide input for the automated control of the chaser spacecraft via a Linear Quadratic Regulator. Propulsive maneuvers are accomplished using several low-thrust, non-throttleable thrusters using pulse-width modulation and thrust vectoring. A waypoint logic controller is used to define intermediate goals to reach the final goal in order to limit operational risk from an error in estimation of the spacecraft’s relative state. The system is described and then initial simulation test results are shown.
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    SPORE Parachute Design and Selection
    (Georgia Institute of Technology, 2012-12-01) Stout, Stephanie E.
    Eleven parachute types are investigated to determine the best option for the SPORE 1U LEO and 2x2U LEO configurations. The 1U LEO configuration must meet a 5 meters per second impact velocity requirement, and the 2x2U LEO configuration must meet a 40g acceleration limit throughout its trajectory, constraining both the impact deceleration and the parachute opening deceleration due to inflation. The suggested parachute types for the 2x2U LEO configuration are the ringslot, disk-gap-band, extended skirt 14.3% full, and conical ribbon parachutes, due to their low opening forces. The parachute should be deployed at a Mach number less than 0.65 to minimize opening decelerations. However, these designed parachutes do not consistently meet the impact deceleration requirement in a Monte Carlo simulation and should be oversized to account for variability. This strategy is applied to the 1U LEO configuration and results in approximately 49% confidence of meeting the impact velocity requirement with doubling the parachute area. Only 63% confidence is achieved by tripling the parachute area, indicating significantly diminished returns with increasing area. These approximate confidence levels are present with all eleven parachute types.