Cal Poly’s PolySat CubeSat satellites have begun to conduct more complex and scientifically significant experiments. The large data products generated by these missions demonstrate the necessity for higher data rate communication than currently provided by the PolySat UHF radio. This thesis leverages the proliferation of consumer wireless monolithic transceivers to develop a 250kbps to 2000kbps, 2W CubeSat radio operating within the 2.45GHz Industrial, Scientific, and Medical (ISM) radio band. Estimating a link budget for a realistic CubeSat leads to the conclusion that this system will require a large deployable CubeSat antenna, large earth station satellite dish, and a fine-pointing attitude control system. Noise floor measurements of a CubeSat ground station demonstrate that terrestrial ISM interference can be minimized to below the thermal noise floor by carefully choosing the operating frequency. The radio is specifically designed as a daughter board for the PolySat System Board with a direct interface to the embedded Linux microprocessor. A state-of-the-art ZigBee transceiver evaluation board is measured to confirm its suitability for a CubeSat radio. A schematic is developed, which integrates the transceiver, power amplifier, low noise amplifier, amplifier protection circuitry, switching regulators, and RF power measurement into a single printed circuit board assembly (PCBA). The circuitry is then squeezed into a high-density, 1.4” x 3.3” layout. The PCBA is then manufactured, troubleshot, tuned, and characterized.

With the rising popularity of small satellites, such as CubeSats, many smaller institutions previously incapable of developing and deploying a spacecraft have starting to do so. Institutions with a history of space flight, such as NASA JPL, have begun to put projects on CubeSats that would normally fly on much larger satellites. As a result, the institutions with space flight heritage have begun to port spacecraft software that was previously designed for much larger and more complex satellites to the CubeSat platform. Unfortunately for universities, who are the majority of all institutions devel- oping CubeSats, these ported systems are too large and complex to be a practical control solution. Student teams have a high turnover rate due to graduation and when a student becomes an expert on the control system, they graduate; most students get a maximum of two or three years of experience before graduating. This thesis proposes the Generic Decision Making Framework for Autonomous Systems (GDMFAS) as an accessible, easily extensible, component-based executive system architecture. The architecture is designed for Linux distributions, including the custom Linux distribution used by PolySat, and is implemented using C++. The proposed framework provides much of the same functionality as systems designed for larger satellites in a smaller, more straightforward pack- age, which includes both scheduling and executive components. This thesis also provides validation for the prototype implementation and evaluates the system according to six metrics. The metric analysis for this work is then compared with the metric analyses of previous works.

Following the successful launch of CP3 and CP4, the PolySat team noticed an unreliable uplink to both satellites. A significant problem with the PolySat COMM system is poor receive sensitivity of the communications system. Efforts have been made to improve the uplink margin, but without proper characterization of the receiver sensitivity, the problem cannot be fully addressed. By developing an accurate method of measuring receive sensitivity, a methodical approach can be used to properly diagnose the communication system and link budget. Two revisions of the PolySat COMM system will be measured and compared. An in-depth study of the PolySat COMM system will be performed, providing an interesting look at possible causes of the inconsistent uplink and methods of improving the COMM system. For future bus development, this test setup can be used to accurately measure the receive sensitivity.

CubeSat designers are increasingly looking to incorporate delicate structures and optics into their payloads. These delicate payloads, however, may not survive the required absolute-worst-case launch vibration testing needed for flight certification. To help address this problem, and to better match testing conditions to real-world launch environments, this thesis introduces Sync, a compact 1/4U CubeSat payload designed to collect data on the vibrations and thermal environments CubeSats experience inside a deployer on the way to orbit. This data can be used to better understand the launch environment for different vehicles, and help develop new, more realistic testing guidelines that could enable more delicate payloads to be launched.

CubeSat satellites have redefined the standard solution for conducting missions in space due to their unique form factor and cost. The harsh environment of space necessitates examining features that improve satellite robustness and ultimately extend lifetime, which is typical and vital for mission success. The CubeSat development team at Cal Poly, PolySat, has recently redefined its standard avionics platform to support more complex mission capabilities with this robustness in mind. A significant addition was the integration of the Linux operating system, which provides the flexibility to develop much more elaborate protection mechanisms within software, such as support for remote on-orbit software updates. This thesis details the design and development of such a feature-set with critical software recovery and multiple-mission single-CubeSat functionality in mind. As a result, features that focus on software update usability, validation, system recovery, upset tolerance, and extensibility have been developed. These include backup Linux kernel and file system image availability, image validation prior to boot, and the use of multiple file system devices to protect against system upsets. Furthermore, each feature has been designed for usability on current and future missions.

Currently, the CubeSat spacecraft is predominantly used for missions at Low- Earth Orbit (LEO). There are various limitations to expanding past that range, one of the major ones being the lack of sufficient radiation shielding on the Poly-Picosatellite Orbital Deployer (P-POD). The P-POD attaches to a launch vehicle transporting a primary spacecraft and takes the CubeSats out into their orbit. As the demand for interplanetary exploration grows, there is an equal increase in interest in sending CubeSats further out past their current regime. In a collaboration with NASA’s Jet Propulsion Laboratory (JPL), students from the Cal Poly CubeSat program worked on a preliminary design of an interplanetary CubeSat deployer, the Poly-Picosatellite Deep Space Deployer (PDSD). Radiation concerns were mitigated in a very basic manner, by simply increasing the thickness of the deployer wall panels. While this provided a preliminary idea for improved radiation shielding, full analysis was not conducted to determine what changes to the current P-POD are necessary to make it sufficiently radiation hardened for interplanetary travel. This thesis develops a tool that can be used to further analyze the radiation environment concerns that come up with interplanetary travel. This tool is the connection between any geometry modeled in CAD software and the radiation tool OLTARIS (On- Page iv Line Tool for the Assessment of Radiation In Space). It reads in the CAD file and converts it into MATLAB, at which point it can then perform ray-tracing analysis to get a thickness distribution at any user-defined target points. This thickness distribution file is uploaded to OLTARIS for radiation analysis of the user geometry. To demonstrate the effectiveness of the tool, the radiation environment that a CubeSat sees inside of the current P-POD is characterized to create a radiation map that CubeSat developers can use to better design their satellites. Cases were run to determine the radiation in a low altitude orbit compared to a high altitude orbit, as well as a Europa mission. For the LEO trajectory, doses were seen at levels of 102 mGy, while the GEO trajectory showed results at one order of magnitude lower. Electronics inside the P-POD can survive these doses with the current design, confirming that Earth orbits are safe for CubeSats. The Europa- Jovian Tour mission showed results on a higher scale of 107 mGy, which is too high for electronics in the P-POD. Additional cases at double the original thickness and 100 times the original thickness resulted in dose levels at orders of about 107 and 104 mGy respectively. This gives a scale to work off for a “worst case” scenario and provides a path forward to modifying the shielding on deployers for interplanetary missions. Further analysis is required since increasing the existing P-POD thickness by 100 times is unfeasible from both size and mass perspectives. Ultimately, the end result is that the current P-POD standard does not work too far outside of Earth orbits. Radiation-based changes in the design, materials, and overall shielding of the P- POD need to be made before CubeSats can feasibly perform interplanetary missions.

As science instruments on CubeSats become more sensitive to the attitude of the spacecraft, better methods must be employed to provide the accuracy needed to complete the planned mission. While systems that provide the accuracy required are available commercially, these solutions are not cost-effective, do not allow the design to be tailored to a specific mission, and most importantly, do not give students hand-on experience with attitude control actuators. This thesis documents the design, modeling, and simulation of a low-cost, student-fabricated, reaction wheel system for use in 3U CubeSat satellites. The entire design process for the development of this reaction wheel is based on fundamental design principles and can be replicated for either larger or smaller spacecraft as needed. Additionally, plans for bringing this design up to a prototyping and testing phase are outlined for continued use of this design in the Cal Poly CubeSat Laboratory.