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Articles 1 - 30 of 35
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Design, Development, And Testing Of Embedded Computing On Afit's Control & Autonomy Space Proximity Robot (Caspr), Collin A. Gwaltney
Design, Development, And Testing Of Embedded Computing On Afit's Control & Autonomy Space Proximity Robot (Caspr), Collin A. Gwaltney
Theses and Dissertations
This thesis reviews RPO algorithm testbeds and discusses the development of the Control and Autonomy Space proximity Robot (CASpR) kinematic testbed housed at the Air Force Institute of Technology (AFIT). CASpR operates on a rail system to propagate the trajectories of two satellites using the Hill-Clohessy-Wiltshire (HCW) Equations of Motion (EOMs). In this study, the implementation of a Jetson TX2i as an onboard flight computer is discussed and accomplished. Each hardware component used in the process of adding embedded computing as well as the software and paths of communication are all discussed in detail. Tests are conducted to assess the …
A Comparison Of Sporadic-E Occurrence Rates Using Ionosondes And Gps Radio Occultation Measurements, Rodney A. Carmona Jr.
A Comparison Of Sporadic-E Occurrence Rates Using Ionosondes And Gps Radio Occultation Measurements, Rodney A. Carmona Jr.
Theses and Dissertations
Sporadic-E (Es) occurrence rates from Global Position Satellite radio occultation (GPS-RO) measurements have shown to vary by nearly an order of magnitude between studies, motivating a comparison with ground-based measurements. In an attempt to find an accurate GPS-RO technique for detecting Es formation, occurrence rates derived using five previously developed GPS-RO techniques are compared to ionosonde measurements over an eight-year period from 2010-2017. GPS-RO measurements within 170 km of a ionosonde site are used to calculate Es occurrence rates and compared to the ground-truth ionosonde measurements. Each technique is compared individually for each ionosonde site and then combined to determine …
Evaluation Of The Impact Of An Additive Manufacturing Enhanced Cubesat Architecture On The Cubesat Development Process, Rachel E. Sharples
Evaluation Of The Impact Of An Additive Manufacturing Enhanced Cubesat Architecture On The Cubesat Development Process, Rachel E. Sharples
Theses and Dissertations
Additive manufacturing (AM) is a fabrication method ideally suited to low-quantity, highly customized builds, leading to interest in its application to satellite development and manufacturing, where each build is unique. Due to the issues of long development schedules and high development and manufacturing costs, methods are needed in the CubeSat development process to reduce the weight and volume of subsystems and decrease integration time. The work develops an architecture for an AM-augmented CubeSat and examines the AM techniques of embedded electronics, embedded thrusters, and custom radiation-hardened materials can impact the subsystems of a CubeSat. The AM-augmented architecture shows a shift …
Military Applications Of High-Altitude Satellite Orbits In A Multi-Body Dynamical Environment Using Numerical Methods And Dynamical Systems Theory, Meredith M. Wilmer
Military Applications Of High-Altitude Satellite Orbits In A Multi-Body Dynamical Environment Using Numerical Methods And Dynamical Systems Theory, Meredith M. Wilmer
Theses and Dissertations
The circular restricted three-body problem (CR3BP) is a simplified dynamical model for a satellite under the gravitational influence of both the Earth and the Moon, maintaining closer fidelity to the gravitational environment experienced by a high-altitude Earth-orbiting spacecraft than modeling in the Earth-satellite two-body problem. Resonant orbit arcs are used to determine an initial guess to input into an algorithm that computes a trajectory solution with specific design requirements and constraints. A test case uses this method to compute a lunar fly-by transfer solution requiring less than two-body transfer methods and offers an unusual pathway that adds an unpredictability element …
Key Detection Rate Modeling And Analysis For Satellite-Based Quantum Key Distribution, Jonathan C. Denton
Key Detection Rate Modeling And Analysis For Satellite-Based Quantum Key Distribution, Jonathan C. Denton
Theses and Dissertations
A satellite QKD model was developed and validated, that allows a user to determine the optimum wavelength for use in a satellite-based QKD link considering the location of ground sites, selected orbit and hardware performance. This thesis explains how the model was developed, validated and presents results from a simulated year-long study of satellite-based quantum key distribution. It was found that diffractive losses and atmospheric losses define a fundamental trade space that drives both orbit and wavelength selection. The optimal orbit is one which generates the highest detection rates while providing equal pass elevation angles and durations to multiple ground …
Space Object Self-Tracker On-Board Orbit Determination Analysis, Stacie M. Flamos
Space Object Self-Tracker On-Board Orbit Determination Analysis, Stacie M. Flamos
Theses and Dissertations
Due to the United States' growing dependence on space based assets and the in- creasing number of resident space objects (RSO), improvement of Space Situational Awareness (SSA) capabilities is more necessary than ever. As a way to aid in this need, the Air Force Institute of Technology (AFIT) is developing the Space Object Self-Tracker (SOS) as a proof-of-concept experimental satellite for RSO precision tracking and collision avoidance system in Low Earth Orbit (LEO). Specifically, SOS will use Global Positioning System (GPS) position estimates for on-board orbit de- termination. Currently, SOS will use the Simplified General Perturbations-4 (SGP4) algorithm as its …
Modular Heat Dissipation Technique For A Cubesat, Melih Eken
Modular Heat Dissipation Technique For A Cubesat, Melih Eken
Theses and Dissertations
In recent years, due to their many advantages, interest in larger scale CubeSats, such as 3U and 6U, has been increased. Correspondingly, dissipating the heat from the heat generating components in the CubeSat has become a challenge for thermal control. In this research, a modular approach was developed to dissipate heat from the overheating components in a CubeSat. To accomplish this, both experimental and computational methodologies were used. A 6U CubeSat was computationally modeled and the model correlated by experimental test results. Subsequently, validated CubeSat thermal model was used to design a modular heat dissipater. Validation and performance experiments of …
Modeling Navigation System Performance Of A Satellite-Observing Star Tracker Tightly Integrated With An Inertial Measurement Unit, Scott J. Pierce
Modeling Navigation System Performance Of A Satellite-Observing Star Tracker Tightly Integrated With An Inertial Measurement Unit, Scott J. Pierce
Theses and Dissertations
This dissertation evaluates a navigation system using satellite observations from a star tracker tightly-integrated with an inertial measurement unit (IMU) and a barometric altimeter using an extended Kalman filter. The star tracker measurement accuracy of a satellite is derived. Several system configurations are simulated comparing the performance of the estimate with respect to system parameters of the IMU, and star tracker, as well as comparing performance when providing a remote sensor satellite ephemeris error correction. Experimental observations are used to evaluate the model performance. Additionally, power requirements were calculated for a satellite signal operating in imaging bands, such that a …
Low Earth Orbit Satellite Tracking Telescope Network: Collaborative Optical Tracking For Enhanced Space Situational Awareness, Victor A. Salvador
Low Earth Orbit Satellite Tracking Telescope Network: Collaborative Optical Tracking For Enhanced Space Situational Awareness, Victor A. Salvador
Theses and Dissertations
The Air Force Institute of Technology has spent the last seven years conducting research on orbit identification and object characterization of space objects through the use of commercial-off-the-shelf hardware systems controlled via custom software routines, referred to simply as TeleTrak. Year after year, depending on the research objectives, students have added or modified the system's hardware and software to achieve their individual research objectives. In the last year, due to operating system and software upgrades, TeleTrak became inoperable. Furthermore, due to a lack of student overlap, knowledge of the basic operation of the TeleTrak deteriorated. This research re-establishes the basic …
Improving The Performance Of The Space Surveillance Telescope As A Function Of Seeing Parameter, Jae H. Jeon
Improving The Performance Of The Space Surveillance Telescope As A Function Of Seeing Parameter, Jae H. Jeon
Theses and Dissertations
This research paper investigates ways to improve the detection capability and predict the performance of the Space Surveillance Telescope (SST) system when it's relocated to Exmouth, Australia. The dataset collected by the SST observing the Geosynchronous Earth Orbit (GEO) satellite, ANIK-F1, entering the earth's eclipse is used to test the performance of the three existing and one new detection algorithm. The three existing algorithms are the point detection (Binary Hypothesis Test (BHT)), correlation detection (CD-BHT), and Multi-hypothesis Test using ten hypotheses (MHT10), and the new detection algorithm is the Multi-hypothesis Test using six hypotheses (MHT6). To improve the accuracy and …
Satellite Capabilities Mapping - Utilizing Small Satellites, David A. Grigsby
Satellite Capabilities Mapping - Utilizing Small Satellites, David A. Grigsby
Theses and Dissertations
The cost and schedule advantages small satellites have over larger legacy systems have been studied, but there has been very little experimentation performed to determine whether small satellites can actually deliver the capabilities of larger spacecraft. To date, a desired operational capability has not been fully realized by a scalable satellite design. Advances in sensor technology have led to significant reductions in size, weight, and power (SWaP) presenting an opportunity to exploit the evolution of space operations by using small satellites to perform specific missions. This paper describes a methodology that maps a specific set of large space vehicle capabilities …
Assembly, Integration, And Test Methods For Operationally Responsive Space Satellites, Lisa A. Baghal
Assembly, Integration, And Test Methods For Operationally Responsive Space Satellites, Lisa A. Baghal
Theses and Dissertations
Current government and industry standards in spacecraft testing result in an Assembly, Integration, and Test (AIT) timeline greater than six months. These standards will not support the vision of Operationally Responsive Space (ORS) to deploy a satellite within six days to fill an urgent need. Using the Air Force Research Laboratory’s Plug-and-Play Satellite (PnPSat), multiple Rapid AIT trials were conducted. By exercising the AIT process with various spacecraft configurations and personnel, methods for reducing or modifying traditional testing regimen were investigated.
Fatigue Evaluation Of Nanocomposites As Lightweight Electronic Enclosures For Satellites' Applications, Javier Rodriguez
Fatigue Evaluation Of Nanocomposites As Lightweight Electronic Enclosures For Satellites' Applications, Javier Rodriguez
Theses and Dissertations
Existing nanocomposite materials used for satellite applications don't offer the required conductivity and electromagnetic shielding protection, requiring metal shields in order to survive in space. The AFRL Materials and Manufacturing Directorate in conjunction with the private sector have developed a material that promises to blend the attributes of nanocomposites and metal materials. The M55J/RS3 material consists of carbon fibers combined with a polyisocyanate matrix, in which Nickel nanostrandsTM are added. The research effort investigated the changes in the EMI and ESD of the material after being subjected to cyclic loads. Four configurations of a symmetric layup with fibers oriented …
A Constraint Based Approach For Building Operationally Responsive Satellites, Mesut O. Kahraman
A Constraint Based Approach For Building Operationally Responsive Satellites, Mesut O. Kahraman
Theses and Dissertations
The Operational Responsive Space (ORS) program requires flexible and responsive satellites to meet user’s needs. Traditional satellite design methods are typically iterative processes that optimize individual components, subsystems, and ultimately the entire satellite. This study focuses on developing a new approach for creating Responsive Satellites (RS) from Plug-and-Play (PnP) components. The aim is to create an approach that quickly evaluates a wide variety of possible satellite configurations and identify the best configurations that meet the user’s needs and constraints. Satellite configurations are created by matching locations on the satellite structure with PnP components. Various constraints are derived from the user’s …
Operationally Responsive Space (Ors): An Architecture And Enterprise Model For Adaptive Integration, Test And Logistics, Jeff A. Alexander, Martha Charles-Vickers, Talbot L. Smith, Michael L. Vickers
Operationally Responsive Space (Ors): An Architecture And Enterprise Model For Adaptive Integration, Test And Logistics, Jeff A. Alexander, Martha Charles-Vickers, Talbot L. Smith, Michael L. Vickers
Theses and Dissertations
The capability to rapidly deploy tactical satellites to meet a Joint Force Commander's immediate battlespace requirements is a well-documented joint capability need. Key U.S. strategic documentation cites the need for the capability to maintain persistent surveillance or an "unblinking eye" over battlespace and to rapidly reconstitute critical space capabilities to preserve situational awareness. The warfighter requires a tactical space-based deployment capability which employs a request to launch and operational deployment window of 90 to 120 days. This master's thesis executed two (2) major areas of work: apply, and reinforce the Operationally Responsive Space (ORS) mission tasks using the Joint Capabilities …
Anisotropy In The South Atlantic Anomaly, Shaun M. Easley
Anisotropy In The South Atlantic Anomaly, Shaun M. Easley
Theses and Dissertations
From June 2000 through July 2006, the TSX-5 satellite measured proton fluxes in the Earth’s magnetosphere using its CEASE instrument. A review of the satellite data by scientists at AFRL/VSBX revealed an unanticipated, recurring bi-modal structure in histograms of the proton counts. This research identified the bi-modal behavior as anisotropic in nature, and the result of two separate processes. At low altitudes the anisotropy was well described by the classic “East-West Effect.” Comparisons of the satellite data to simple analytical models are presented. At high altitudes, the anisotropy was the result of the detector measuring protons at different pitch angles …
Prioritizing Satellite Payload Selection Via Optimization, Benjamin S. Kallemyn
Prioritizing Satellite Payload Selection Via Optimization, Benjamin S. Kallemyn
Theses and Dissertations
This thesis develops optimization models for prioritizing payloads for inclusion on satellite buses with volume, power, weight and budget constraints. The first model considers a single satellite launch for which the budget is uncertain and constellation requirements are not considered. Subsequently, we include constellation requirements and provide a more enhanced model. Both single-launch models provide a prioritized list of payloads to include on the launch before the budget is realized. The single-launch models are subsequently extended to a sequence of multiple launches in two cases, both of which incorporate an explicit dependence on the constellation composition at each launch epoch. …
Dynamics And Control Of Tethered Satellite Formations For The Purpose Of Space-Based Remote Sensing, Kurt A. Vogel
Dynamics And Control Of Tethered Satellite Formations For The Purpose Of Space-Based Remote Sensing, Kurt A. Vogel
Theses and Dissertations
This dissertation assesses the utility of tethered satellite formations for the space-based remote sensing mission. Energy dissipation is found to have an adverse effect on foundational rigid body (Likins-Pringle) equilibria. It is shown that a continuously earth-facing equilibrium condition for a fixed-length tethered system does not exist since the spin rate required for the proper precession would not be high enough to maintain tether tension. The range of required spin rates for steady-spin motion is numerically defined here, but none of these conditions can meet the continuously earth-facing criteria. Of particular note is the discovery that applying certain rigid body …
Optimizing Mean Mission Duration For Multiple-Payload Satellites, John A. Flory
Optimizing Mean Mission Duration For Multiple-Payload Satellites, John A. Flory
Theses and Dissertations
This thesis addresses the problem of optimally selecting and specifying satellite payloads for inclusion on a satellite bus to be launched into a constellation. The objective is to select and specify payloads so that the total lifetime utility of the constellation is maximized. The satellite bus is limited by finite power, weight, volume, and cost constraints. This problem is modeled as a classical knapsack problem in one and multiple dimensions, and dynamic programming and binary integer programming formulations are provided to solve the problem. Due to the computational complexity of the problem, the solution techniques include exact methods as well …
Optimal Maintenance For Stochastically Degrading Satellite Constellations, Timothy J. Cook
Optimal Maintenance For Stochastically Degrading Satellite Constellations, Timothy J. Cook
Theses and Dissertations
This thesis develops a methodology to determine an optimal policy for maintaining a satellite constellation that degrades over time. Previous work has developed a methodology to compute an optimal replacement policy for a satellite constellation in which satellites were viewed as binary entities, either operational or failed. This research extends the previous models by developing an optimal maintenance policy for satellite constellations in which each satellite may operate in a finite number of degraded states. The constellation is assumed to consist of a finite number of satellites, each with a finite number of functions with distinct failure mechanisms. Assuming each …
Experimental Demonstration Of An Algorithm To Detect The Presence Of A Parasitic Satellite, Vincent J. Dabrowski
Experimental Demonstration Of An Algorithm To Detect The Presence Of A Parasitic Satellite, Vincent J. Dabrowski
Theses and Dissertations
Published reports of microsatellite weapons testing have led to a concern that some of these "parasitic" satellites could be deployed against US satellites to rendezvous dock and then disrupt, degrade disable or destroy the system. An effective detection method is essential. Various sensing solutions were investigated including visual, impact, and dynamic techniques. Dynamic detection, the most effective solution, was further explored. A detection algorithm was constructed and validated on the Air Force Institute of Technology's ground-based satellite simulator, SIMSAT. Results indicate that microsat microsatellites rigidly connected to a satellite can be detected with a series of small identical maneuvers utilizing …
Optimal Replacement Policies For Satellite Constellations, Bradley R. Sumter
Optimal Replacement Policies For Satellite Constellations, Bradley R. Sumter
Theses and Dissertations
This work considers the problem of finding optimal replacement policies that minimize the expected total cost of maintaining a satellite constellation. The problem is modeled using discrete-time Markov decision processes to determine the replacement policy by allowing the satellite constellation to be in one of a finite number of states at each decision epoch. The constellation stochastically transitions at each time step from one state to another as determined by a set of transition probabilities. At each decision epoch, a decision maker chooses an action from a set of allowable actions for the current system state. A cost associated with …
An Examination Of Latency And Degradation Issues In Unmanned Combat Aerial Vehicle Environments, Shane A. Dougherty
An Examination Of Latency And Degradation Issues In Unmanned Combat Aerial Vehicle Environments, Shane A. Dougherty
Theses and Dissertations
Since the multidimensional knapsack problems are NP-hard problems, the exact solutions of knapsack problems often need excessive computing time and storage space. Thus, heuristic approaches are more practical for multidimensional knapsack problems as problems get large. This thesis presents the results of an empirical study of the performance of heuristic solution procedures based on the coefficients correlation structures and constraint slackness settings. In this thesis, the three representative greedy heuristics, Toyoda, Senju and Toyoda, and Loulou and Michaelides methods, are studied. The purpose of this thesis is to explore which heuristic of the three representative greedy heuristics perform best under …
Estimation Of Relative Satellite Formation Elements In Near Circular Orbits, Ralph E. Bordner Iii
Estimation Of Relative Satellite Formation Elements In Near Circular Orbits, Ralph E. Bordner Iii
Theses and Dissertations
Precise relative position determination of satellite formation elements in near circular orbits is the focus of this thesis. A Bayes filter is used for the estimator with the dynamics solution obtained by solving the time periodic, linearized system via Floquet theory. This approach is similar to that of the traditional Clohessy-Wiltshire treatment, however much more of the system's behavior is retained by using a linear, time periodic system. The dynamics model includes all zonal harmonics of the Earth as well as sectoral, tesseral, and air drag perturbations. The filter algorithm was fed three types of simulated measurements: relative Carrier-Phases Differential …
Structural Emergence And The Collaborative Behavior Of Autonomous Nano-Satellites, Daniel J. Petrovich
Structural Emergence And The Collaborative Behavior Of Autonomous Nano-Satellites, Daniel J. Petrovich
Theses and Dissertations
The collaborative behavior of nano-satellites in a zero-gravity environment is explored, and satellite characteristics are proposed that maximize constellation robustness and minimize manufacturing costs. Behavioral algorithms are proposed to facilitate both swarming and structural formation and are validated using the Structural Emergence Simulator (STEMS) Graphical User Interface (GUl). A payload of multiple satellites is placed in a zero-gravity environment and released to re-configure autonomously into a pre-designed structure. Data transmission between satellites is not permitted during the swarming phase of the structure formation mission. A binary behavior algorithm is invented that produces a direction and magnitude solution to the satellite …
Analysis Of Radio Frequency Interference Effects On A Modern Coarse Acquisition Code Global Positioning System (Gps) Receiver, Kenneth D. Johnston
Analysis Of Radio Frequency Interference Effects On A Modern Coarse Acquisition Code Global Positioning System (Gps) Receiver, Kenneth D. Johnston
Theses and Dissertations
The purpose of this thesis was to investigate the performance of a twelve channel Standard Positioning Service (SPS) based (Global Positioning System (GPS) receiver using an eight state Kalman filter in a hostile radio frequency (RF) environment and to develop instructional tools for teaching RF interference on GPS receivers. The two types of jamming signals generated included Continuous Wave (CW) and Swept CW. Actual GPS and jamming signals were used in the research. The signals received from GPS satellites exhibit a Doppler shift which vary between approximately plus six Kilohertz. The Doppler shift frequency can be reasonably predicted for a …
Whole Spacecraft Vibration Isolation, Gregory G. Karahalis
Whole Spacecraft Vibration Isolation, Gregory G. Karahalis
Theses and Dissertations
The Department of Defense identified launch vibration isolation as a major research interest. Reducing the loads a satellite experiences during launch will greatly enhance the reliability, lifetime, and payload to structure ratio. DoD satellite programs stand to benefit significantly from advances in vibration isolation technology.
Singularity Avoidance Strategies For Satellite Mounted Manipulators Using Attitude Control, Nathan A. Titus
Singularity Avoidance Strategies For Satellite Mounted Manipulators Using Attitude Control, Nathan A. Titus
Theses and Dissertations
Control concepts for satellite mounted manipulators (SMM) are examined. The primary focus is on base actuated concepts, which eliminate singularity problems associated with free floating SMMs. A new form of the equations of motion for an n-link SMM is developed using a quasi coordinate form of Lagrange's Equation. Alternative free floating SMM designs are presented which eliminate dynamic singularities, but still experience difficulties due to the unactuated base. A new generic SMM controller is developed as a framework for various control concepts with and without base actuation. Momentum constrained Jacobians are shown to produce better SMM tracking than fixed base …
A Performance Analysis Of The Iridium Low Earth Orbit Satellite System, Carl E. Fossa Jr.
A Performance Analysis Of The Iridium Low Earth Orbit Satellite System, Carl E. Fossa Jr.
Theses and Dissertations
This thesis provides a performance evaluation of the IRIDIUM Low Earth Orbit Satellite system. It examines the system's ability to meet real time communications constraints with a degraded satellite constellation. The analysis is conducted via computer simulation. The simulation is run at low, medium, and high loading levels with both uniform and non-uniform traffic distributions. An algorithmic approach is used to select critical satellites to remove from the constellation. Each combination of loading level and traffic distribution is analyzed with zero, three, five and seven non-operational satellites. The measured outputs are end-to-end packet delay and packet rejection rate. In addition …
Evaluation Of Satellite Microwave Derived Surface Temperature Algorithms For The Period August 1996 To February 1997, Charles H. Harris
Evaluation Of Satellite Microwave Derived Surface Temperature Algorithms For The Period August 1996 To February 1997, Charles H. Harris
Theses and Dissertations
The Air Force Weather Agency (AFWA) has two operational algorithms that derive surface temperatures from microwave observations taken by the Special Sensor Microwave Imager (SSM/I) which rides aboard space platforms of the Defense Meteorological Satellite Program (DMSP). The algorithm called Temperature from Satellite Microwave Imager (TS) is used to analyze global cloud coverage. The second algorithm is fittingly called Calibration and Validation (CV), as it was the algorithm used to calibrate and validate the first SSM/I in 1987. Multiple linear regression defined the algorithms from empirically gathered brightness temperatures and simultaneous surface temperatures. The key questions were how much data …