Wireless Communication onboard Spacecraft: Draadloze Communicatie aan boord van Ruimtevaartuigen

This dissertation focuses on intra-spacecraft wireless communication as a solution for reducing the spacecraft onboard harness. Despite outstanding advances in aerospace industry, the cost of accessing space is still very high and the amount of engineering work required for spacecraft design and development is enormous. The key elements which increase the development and launch cost of a spacecraft are size, mass, and the necessity of a tailored design for each mission. Studies show that the contribution of onboard harness to spacecraft mass is about 6% to 10%. Any effort to reduce harness can directly result in reducing the launch cost and arriving to a more modular and flexible design.
This thesis aims to answer the following questions:
1. What are the problems of onboard wired standards and what are the benefits and characteristics of wireless network onboard spacecraft?
2. Which spacecraft subsystems could benefit most from a wireless onboard communication paradigm?
3. What is the major challenge regarding employing a wireless standard onboard a spacecraft?
4. How can we solve the identified system level design challenge?

To answer these questions, this dissertation reviews the existing wired spacecraft data bus standards and major commercial off the shelf (COTS) wireless communication solutions to identify and characterize their architectures. These wireless standards are Wi-Fi, Bluetooth and ZigBee. Categorizing different onboard data types aids to identify a suitable COTS wireless communication solution for each application category. Specifically, sensors of attitude determination and control system (ADCS) can greatly benefit from a low power and low data rate wireless communication solution such as ZigBee, however, the major challenge is conserving energy on the sensors to enable a wireless architecture and achieve an adequate battery life without compromising the system performance. This dissertation proposes two onboard energy managers based on sensor scheduling schemes to tackle the energy conservation challenge. These solutions are tailored to ADCS and aim to reduce the overall ADCS energy consumption without affecting the required accuracy of attitude determination. Both energy managers use similar design elements and decision making algorithms while one of them presents a centralized scheme and the other one employs a decentralized architecture. A unique characteristic of these designs is that the energy management solution is fully integrated with the onboard attitude determination system of the spacecraft. Simulation results show that enabling the energy managers result in total energy saving between 20.9% to 51% (depending on the scenario) without compromoising accuracy of attitude determination.