Design, Development and Testing of a GPS-Based Navigation sub-System for Microsatellites Missions

The topic of spacecraft navigation can be addressed using different approaches, which can be grouped in ground based or space-based techniques. Previous space missions demonstrated that GPS-based navigation brings several advantages in terms of costs reduction of the whole mission and the possibility to obtain the position information in real-time on-board. While major spacecraft missions can easily host any model of the several spaceborne receivers, finding a GPS-based navigation solution for small satellite platforms is not an easy task, due to the limited budget, development time and available volume, typical of this kind of missions. Following the design philosophy of sub-systems for small satellites, this thesis presents the development process of a GPS-based navigation device for future low-cost missions, which aims at representing an ideal trade-off between high quality positioning in space and fast and cost effective manufacturing. The entire PhD work was carried out in the framework of the ESEO project, a microsatellite mission sponsored by ESA education office, and this thesis covers the entire design process of the GPS receiver, which will be launched as secondary payload on-board of this spacecraft. As part of a real space mission, this thesis describes all steps of the development, following the tight ESEO spacecraft schedule. Hardware and software design is described, focusing on the main solutions adopted to meet the typical reliability requirements of space applications. The GPS-based navigation payload underwent a long test campaign to assess its capability to operate in the space environment and the navigation algorithm was validated with the support of GPS signal simulators. The results of the development and testing phases shown herein indicate that accurate and autonomous real-time orbit determination is a viable option also for microsatellite platforms. It is expected that this findings will eventually become flight proven during the ESEO in-orbit operations.