GAC
Galileo Advanced Concepts

The work was directed towards three distinct sectors. The signal studies were the most urgent and provided independent assessment and consolidation of the Galileo signals. The short-term development studies were aimed at optimising resources as SAR payloads were not required on every Galileo satellite and a complementary messaging mission was investigated which would be compatible with the first generation satellites. The long-term development studies were clearly aimed at second-generation Galileo satellites and the envisaged Galileo infrastructure.

The major axes of investigation included:

• assessment of the Galileo signals, codes and navigation data message;
• short-term developments, implementation of a messaging mission;
• long-term developments, technology advancements and future complementary missions.

Description

Task 2000: Signals, Codes, Navigation Message The work on this task was arranged in three study cycles. During the first study cycle the baseline signals, codes and navigation messages were reassessed. The consortium performed some specific, urgent analysis of the proposed modifications to the SIS ICD as directed by ESA and the Signal Task Force (STF).

The work on the second and third study cycles continued the first cycle work looking at other modulation types and focused on signals achieving the MBOC spectrum. In addition a study on the feasibility of a higher data rate E6 signal was performed as a complement to the messaging task. Apart from the signals work, the second cycle of activities also involved simulations and analysis of receiver performance with optimised L1 signals.

The work on optimisation of spreading codes included further testing of some newly proposed chaotic codes. Also consolidation of the navigation data message was performed with comparisons of GPS and Galileo navigation data messages and a catalogue of potential innovations to the navigation data message was produced.

Task 3000: Short-term developments – implementation of the messaging mission Recommendations were made on the number of satellites required for the SAR mission and hence the number of SAR payloads that could be replaced by a new, optional messaging payload. In fact studies have led to the selection of a dual-mode architecture as the optimum solution in which both SAR and messaging payloads are incorporated on each satellite with a switch allowing either payload to be operable as required. Feasibility studies and an assessment of system boundary constraints were completed for the dual mode payload with a review of the overall system architecture.

Maritime applications such as LRIT, LRR, VMS, etc. were retained as the primary choice applications. The messaging system network architecture was proposed and the air interface has been studied in detail.

The study also addressed a preliminary definition of the terminal for maritime users. A messaging payload accommodation study was completed which addressed the issues of payload implementation on the Galileo satellites.

Task 4000: Long-term evolutions The GNSS technology advancements task addressed the current status and trends in electronic components like ASIC/FPGA, processors and memory devices in satellite payload and user receiver applications. Architecture and performance of such devices was assessed as well as radiation hardening issues for space applications.

The Galileo Flexible Payload Architecture task studied a novel concept based on the use of common intermediate frequencies for all of the payload’s RF interfaces. It also assessed possible future use of a digital receiver to the maximum possible extent replacing analogue equipment. A further study line addressed possible future Galileo-complementary missions. An Earth atmospheric gases monitoring mission was proposed. This mission assumed implementation of optical sensors operating at various wavelengths on the Galileo satellites.

Objectives

The objective of GAC was to develop new ideas and to conduct activities to evolve and/or to consolidate the critical aspects of the Galileo system in order to anticipate the future context of the satellite navigation technology and to sustain Galileo’s competitiveness.