This thesis presents an approximate solution of second order relative motion equations. The equations of motion for a Keplerian orbit in spherical coordinates are expanded in Taylor series form using reference conditions consistent with that of a circular orbit. Only terms that are linear or quadratic in state variables are kept in the expansion. A perturbation method is employed to obtain an approximate solution of the resulting nonlinear differential equations. This new solution is compared with the previously known solution of the linear case to show improvement, and with numerical integration of the quadratic differential equation to understand the error incurred by the approximation. In all cases, the comparison is made by computing the difference of the approximate state (analytical or numerical) from numerical integration of the full nonlinear Keplerian equations of motion. / Master of Science

This thesis presents an analysis of CubeSat orbits for both Low Earth Orbit (LEO) and Sun-Synchronous Orbit (SSO) missions using Systems Tool Kit (STK). The study focuses on analyzing communication, power generation, and radiation exposure while considering various factors. The analysis is based on the 3U CubeSat called UT-ProSat-1, developed by students at Virginia Polytechnic Institute and State University (VT) for an upcoming mission. The orbit size and mass adjustments were made for the LEO mission to enhance communication performance. The influence of solar activity on CubeSat lifetime and access time was examined, highlighting the significance of mass and solar activity. The impact of increasing orbit size on communication time was analyzed, emphasizing the trade-offs between mass, orbit size, and communication performance. The SSO mission prioritized power generation optimization resulted in generating sufficient power for the nominal phase of the mission. It also considered the effects of the South Atlantic Anomaly (SAA) on radiation exposure. Effective risk management of increasing the shielding for the avionics were emphasized which consequently will stabilize the orbit and prolong its lifetime. Additionally, temperature dynamics were investigated, indicating the need for further analysis considering heat dissipation and utilizing a more accurate CubeSat model. The insights gained from this study contribute to the improved the performance of CubeSats and validate the mission results, providing valuable information for successful missions in the future. / Master of Science / This project explored the trajectories that small satellites, known as CubeSats, follow around Earth. Two main paths were investigated: the Low Earth Orbit (LEO), which is close to the Earth's surface, and the Sun Synchronized Orbit (SSO), which aligns with the Sun's movement. The software called Systems Tool Kit (STK) served as the simulation tool, helping to analyze the satellites' abilities to communicate, generate power, total space radiation, and satellite's temperature throughout the missions. The study was conducted on the satellite called UT-ProSat-1, a design by students from Virginia Polytechnic Institute and State University (VT). For the LEO path, changes to the satellite's size and weight were applied to analyze its effect on the communication capabilities. Also the Sun's effect on the satellite's operational life and communication windows was assessed. Changes in the satellite's orbit can influence its communication duration, and this necessitates a balance between its weight, trajectory, and communication capacity. Regarding the Sun-aligned path, SSO, the power generated from the Sun was sufficient for the satellite's power needs throughout its mission. A particular space zone with high radiation, the South Atlantic Anomaly (SAA), was evaluated. The majority of total radiation build up on the satellite was determined to came from this area. However, risks associated with this radiation can be minimized by enhancing protection for the satellite's electronics. Such measures not only safeguard the satellite but also increase its stability and longevity in space. The temperature behavior of the satellite was analyzed, underscoring the need for a deeper examination of its thermal patterns. Insights from this study will bolster CubeSat performance and provide valuable information for future successful space missions.

No description available.

Cubesats are picosatellites that have a mass of less than 1.3kg and have a shape of acube. As a result of their low cost of development and launch, cubesats are gainingpopularity in industry and academia. These satellites are also a cost-efective way forspace technology demonstrations. University of Würzburg has a longstanding cubesatprogram started with the launch of UWE-1 in 2005. This was followed by UWE-2 andUWE-3. Several technologies were tested and validated using the UWE platform. Thelast mission UWE-3 has successfully tested an attitude control system.In the next mission, UWE-4 will demonstrate an orbit control system. Being a picosatellite as small as this one (10 x 10 x 10cm 3 and 1kg) brings new challenges intodi↵erent aspects of satellite design, development, control and operation. The orbit con-trol of such a satellite is one of the problems that should be tackled. Being such a smallsatellite means having less propellant mass and much smaller thrusters than conventionalsatellites. These should be addressed in the orbit control. UWE-4 will take advantage of four NanoFEEP thrusters, on one side. Because of theiraccuracy and functionality, these thrusters can be used to implement a continuous thrustsystem. They are also a good choice because of their low energy usage. This work startswith the preparation that was needed to implement a control system. Then explains thestate of the art for continuous thrust control systems. Implements two di↵erent methods,based on perfect control and discusses the outcome. It discuses the limiting factors, likefuel mass, available electrical energy and their e↵ect on the controller performance andconcludes with recommendation for the future researches. / UWE-4

No description available.

In the generation of the standard GRACE gravity fields, the K-Band Ranging (KBR) system data is used in its range-rate mode. Because time derivatives attenuate the gravity signal relative to the data noise at the lower frequencies, it is thought that solutions using range data might have better low-degree (low-frequency) characteristics. The purpose of this work is to detail the methods required to generate range-based solutions, to determine some of the properties of these solutions and then to compare them to range-rate based solutions. It is demonstrated that the range-based solutions are feasible. Different subarc lengths and parameterizations were considered. Although, the most effective combination of subarc lengths and parameterizations are not picked, it is concluded that estimating the mixed periodic term along with bias, bias-rate, bias-acceleration and periodic terms degrades the quality of the range based solution and therefore should not be used. Further study is necessary to pick the optimal combination of subarc length and parameterization which would be used in the time-series analysis. / text

Thesis (M.S. in Space Systems Operations)--Naval Postgraduate School, September 2002. / Thesis advisor(s): Stephen A. Whitmore, Michael G. Spencer. Includes bibliographical references (p. 73-74). Also available online.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: orbital trajectory, ion collection, turning point method, spherical probes, turning angle, ion scattering, cylindrical probes. Includes bibliographical references (p.60-63).

abstract: Solar system orbital dynamics can offer unique challenges. Impacts of interplanetary dust particles can significantly alter the surfaces of icy satellites and minor planets. Impact heating from these particles can anneal away radiation damage to the crystalline structure of surface water ice. This effect is enhanced by gravitational focusing for giant planet satellites. In addition, impacts of interplanetary dust particles on the small satellites of the Pluto system can eject into the system significant amounts of secondary intra-satellite dust. This dust is primarily swept up by Pluto and Charon, and could explain the observed albedo features on Pluto's surface. In addition to Pluto, a large fraction of trans-neptunian objects (TNOs) are binary or multiple systems. The mutual orbits of these TNO binaries can range from very wide (periods of several years) to near-contact systems (less than a day period). No single formation mechanism can explain this distribution. However, if the systems generally formed wide, a combination of solar and body tides (commonly called Kozai Cycles-Tidal Friction, KCTF) can cause most systems to tighten sufficiently to explain the observed distributions. This KCTF process can also be used to describe the orbital evolution of a terrestrial-class exoplanet after being captured as a satellite of a habitable-zone giant exoplanet. The resulting exomoon would be both potentially habitable and potenially detectable in the full Kepler data set. / Dissertation/Thesis / Ph.D. Astrophysics 2013

A key challenge in low-thrust trajectory design is generating preliminary solutions that simultaneously detail the evolution of the spacecraft position and velocity vectors, as well as the thrust history. To address this difficulty, a dynamical model that incorporates a low-thrust force into the circular restricted 3-body problem (CR3BP), i.e., the CR3BP+LT, is constructed and analyzed. Control strategies that deliver specific energy changes (including zero energy change to deliver a conservative system) are derived and investigated, and dynamical structures within the CR3BP+LT are explored as candidate solutions to seed initial low-thrust trajectory designs. Furthermore, insights from dynamical systems theory are leveraged to inform the design process. In the combined model, the addition of a low-thrust force modifies the locations and stability of the equilibrium solutions, resulting in flow configurations that differ from the natural behavior in the CR3BP. The application of simplifying assumptions yields a conservative, autonomous system with properties that supply useful insights. For instance, "forbidden regions" at fixed energy levels bound low-thrust motion, and analytical equations are available to guide the navigation through energy space. Linearized dynamics about the equilibria supply hyperbolic and center manifold structures, similar to the ballistic CR3BP. Low-thrust periodic orbits in the vicinity of the equilibrium solutions also admit hyperbolic and center manifolds, providing an even greater number of dynamical structures to be employed in preliminary trajectory designs. Several applications of the structures and insights derived from the CR3BP+LT are presented, including several strategies for transit and capture near the smaller CR3BP primary body. Finally, an interactive trajectory design framework is presented to explore and utilize the structures and insights delivered by this investigation.