Technologies and methodologies for CubeSat performances improvement

The importance of small satellites, and in particular of nano-satellites (e.g. CubeSats) has increased during last years thanks to major improvements in the field of electrical and mechanical miniaturisation. Another important factor is represented by the interest of national and international space agencies, which has led to the creation of many scientific small satellites programmes, beyond several educational ones. "Small satellites" term shall not be considered referring only to mass, but it describes also a new approach to building, operating, and managing risk for satellite systems; in fact, CubeSat standard (whose reference design was proposed in 1999, and first launch occurred in 2003) is becoming a concrete realisation of a new way of thinking space systems, which is changing the way to access the space. Commercial components, rapid scheduling, risk tolerance and lean testing are just some of features behind the success and spread of CubeSats among universities, space agencies, research and scientific centres, and private companies. Current CubeSat and small satellite missions are mostly developed for Low Earth Orbit (LEO) application, and the number of scientific goals/tasks that they can perform is still limited. CubeSats are nowadays a mature technology to perform Earth observation with low-to-medium performance, and they are a valid educational tool to train young engineers and students in the process of conceiving, implementing and operating a space mission. However, it is possible to say we are entering a new CubeSat Era, in which CubeSats will be called to carry out real missions of the future. Within the new framework, they may represent new test-beds for future bigger missions or allow independent and unprecedented new applications. This research aims at contributing to advance the state of the art in CubeSat missions design and implementation by enhancing some technologies that will support those missions and by defining some innovative approaches for CubeSat development. This main objective has been addressed and pursued from two different points of view: -design perspective, to contribute at improving one specific technology in one technical domain of interest at sub-system level. A subsystem, specifically the Attitude Determination and Control Subsystem (ADCS), has been chosen and the attitude determination process is the function that has been specifically analysed -development perspective, to contribute at improving the development process of a CubeSat mission. This activity has been carried out at system-level, and addresses specifically the Assembly, Integration and Test/Verification (AIT/V) process of a CubeSat for which a new approach has been proposed based on lessons learned from past missions and innovative simulation methodologies and tools. The problem definition for this thesis has been expressed with the following questions: "How and to what extent can the CubeSat platform support future space missions for science purposes, technology demonstration, and service applications?", and "What features of CubeSat platforms and their missions shall be improved to meet the emerging needs and requirements?". To answer these questions, the whole CubeSat life-cycle has been considered, analysed and eventually adapted to the rising needs. Both design aspects and development processes have been addressed, which might help improving overall CubeSat quality, extend CubeSat applications range, and finally increase mission success. The major results are represented by improvements attainable at different phases of the CubeSat life-cycle, such as design, development and verification phase, and at different levels (i.e. subsystem level and system level), through the use of In-the-Loop (IL) simulator and leveraging lessons learned and heritage from previous missions. The methodology adopted is the Model Based System Engineering (MBSE), which provides a wonde