Spacecraft and Payload Pointing

Spacecraft and Payload Pointing focuses on development of the attitude determination and control system (ADACS) for a spacecraft, including payload pointing. Such systems can require knowledge of a large diversity of disciplines for two reasons. First, the ADACS itself is a broad subject, including the dynamics of the spacecraft and payloads, the physics and engineering of the ADACS sensor and actuator hardware, control and filtering theory, plus systems engineering. Second, many disciplines are involved since the ADACS must interface with several other subsystems (notably payload, structure, and command and data handling [C&DH]) and because ADACS performance translates into key mission performance parameters such as pointing control. When mission requirements are flowed down to the spacecraft and then to its subsystems, the engineer must be able to translate these requirements into appropriate terms at each level. Mission requirements are customer related (such as the ability to broadcast a TV signal or transmit data); they must be translated into spacecraft system concepts (orbits, transmitted power levels), then to subsystem requirements (available power, antenna gain, antenna pointing accuracy), and further down to the level of components. Rather than treat each of the subject areas involved in ADACS design in great depth, this book aims to show how they fit together. The subject can be examined from two basic points of view. The first is that of the systems engineer. This view focuses on requirements, requirements flowdowns, and verification. In it, the onboard hardware and software are regarded as black boxes, defined by their functions, reliability, etc. The other standpoint is that of the physicist or engineer who focuses on what is involved in actually getting these items to work. This view includes actions such as quantifying feasible performance levels, learning how they can be improved, and understanding their fundamental limitations.