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Planetary exploration has always been a very complex and risky engineering problem. Building on the past successes, more missions are currently being considered and investigated for the near future. One of the cornerstones of a successful lander-based planetary mission is the Entry, Descent and Landing System (EDLS) on which this work concentrates. The Entry, Descent and Landing sequence is introduced in the broader context of planetary exploration and the various systems involved in delivering safely a payload on the surface are presented. The literature review concentrates on a number of studies that emphasised the need to understand the whole EDL sequence to help designing better systems. It also introduces the reader to the current state-of-the-art both in term of EDLS technologies and design methods as well as identifying a need to design EDL systems in a more integrated and streamlined manner. From the conclusions of the literature review, the main drivers of the EDLS are identified and a new integrated computational framework, SPADES, is developed that provides analysis and design of entry systems. Current and new methods are built into the framework to size all the main EDL systems and provide realistic simulated scenario validated against past missions data. From this point onward, new mission data is generated in the form of the proposed 140 kg astrobiology-focused Vanguard Mars Mission, for which both a parachute and an inflatable-based EDLS is produced. In addition, an ESA mars lander concept is investigated, focusing on the scalability of powered landing systems up to the scale of the future Mars Sample Return vehicle. Finally, building on the case studies and additional mission scenarios, the influence of spatial and atmospheric variables on the performance of EDLS is systematically assessed to provide planet- wide access maps for specific EDL systems and characterise the impact of low-density atmospheric profiles on a number of mission parameters.

The topic of this research focuses on developing analytic models, simulations and relative orbit control for multiple spacecraft in constellations or formations in Low Earth Orbits (LEO). The motivation for this research lies in the recent development and focus on describing the relative motions of spacecraft flying in LEO and also the numerous advantages proposed formation flying missions could provide. Since the complexity of modelling, the dynamics and executing control on a group of satellites is far greater than that of one satellite, this research only investigates a small number of very specific problems in this area. The focus of the approach is to develop the orbit modelling of a single satellite, to describe the relative motion of multiple satellites in neighbouring orbits, using the analytical epicycle equations. The first part of the thesis focuses on the problem of formation and constellation assembly, where inclination differences in the initial conditions causes drift in the relative phases of the satellites. After deriving an analytical model and executing firings, real world data is shown to prove the accuracy of the method. In the second part, the modelling of relative orbits of kilometre-sized satellite formations is investigated. Such formations could only be viable if accurate description and prediction of the relative orbits of the spacecraft is available. The analytic formulation also gives a better understanding of ways to establish formations and maintain them with the least fuel requirement. Finally, in the third part, the orbit acquisition, phasing and maintenance of constellations of satellites is discussed in the context of Surrey's Disaster Monitoring Constellation. The centralized control scheme allows for global optimization and fuel balancing algorithms, which can also be used for formation flying as well. The results presented show that small satellite formations and constellations benefit significantly from an analytical description. Reformulating the epicycle equations for multi-satellite applications provides satisfactory accuracy for most small satellite formation missions. Key words: spacecraft formation flying, satellite constellations, epicycle.

Single Gimbal Control Moment Gyroscopes (CMGs) are thought to be efficient actuators for the attitude control of the new generation of small and agile satellites. CMGs belong to a class of actuators known as momentum exchange devices. This thesis presents a detailed formulation of three-axis attitude dynamics and control of a satellite equipped with a cluster of n momentum exchange devices (which include CMGs and reaction wheels).