Space Systems for Optical Communications

The rapid development and miniaturization of technologies has progressively allowed for the integration of spaceborne applications in the context of privately led scientific and commercial activities. This groundbreaking trend has recently caused the emergence of a new approach commonly referred to as “New Space”, which aims at providing a faster and more cost-effective access to space technologies and services for small and medium businesses. This necessarily requires the further development of a variety of new satellite technologies, among which telecommunications will play a decisive role. Satellite telecommunication has been historically dominated by Radio Frequency (RF) transmission. Although this technology has shown remarkable improvements, at this point a considerable increase in data rate can only be obtained at the expense of an increase in transmitted RF power. Free Space Optical Communication (FSOC) is a technology that promises to increase the available data rate by at least one order of magnitude at the same transmitted power, thanks to the small width of the transmitted beam translating into a high antenna gain. The narrow beam also guarantees extreme directivity of transmission, which represents a crucial advantage in terms of band regulation flexibility and data security. Although satellite optical communication feasibility has been widely proven during in-orbit demonstrations carried out on larger satellites during the last decades, several challenges remain open to make this technology reliable, cost- effective and available at large scale. The research presented in this work has specifically aimed at advancing the technological state of the art of satellite optical communications, focusing on small size satellites. The work has been carried out in the context of the activities related to the development of LaserCube, an optical communication terminal compatible with CubeSat standards developed by Stellar Project. After a preliminary survey of the applications that will benefit the most from increased satellite communications capabilities and of the state of the art of optical communication technologies (Chapter 2), the research has been focused on the development of the main building blocks that will enable the large scale adoption of space optical communications: the analysis and design of innovative applications based on satellite network configurations supported by optical communications (Chapter 3); and the design and development of the optical communications space segment (Chapter 4) and ground segment (Chapter 5). The general context of these developments is the in-orbit demonstration of LaserCube, whose launch has taken place on 30th June 2021. The activities specifically related to the preparation and operations management of the in-orbit demonstration mission are presented in Chapter 6: these include the space qualification of the system, a preliminary ground-to-ground test performed to assess system functional compliance, the description of the planned orbital operations and the detailed orbital determination analysis required for the link acquisition procedure.