GBAS Interoperability and Multi-constellation/Multi-frequency Trials

This paper summarizes GBAS tests conducted by the Technische Universität Braunschweig (TUBS), the Electronic Navigation Research Institute (ENRI) and European Organisation for the Safety of Air Navigation (EUROCONTROL) in the frame of the Single European Sky ATM Research Programme (SESAR, subproject 15.3.7). For these tests, an experimental GBAS ground facility transmitted VDB data for current and future approach services. On the one hand, this paper summarizes the efforts to ensure backward compatibility and interoperability. To this end, existing GBAS hardware receivers were tested and compared with different software solutions. These tests confirmed that the proposed VDB formatting does not interfere with existing GBAS implementations. On the other hand, these tests were intended to support the development of future Multi-Constellation and Multi-Frequency GBAS services. GNSS data recorded at the ground reference receivers and the research aircraft D-IBUF was used to calculate an experimental ionosphere-free GBAS solution not threatened by ionospheric gradients. This paper presents initial results for the proposed GAST-F service, demonstrating that (despite the low number of L1 and L5 capable GNSS satellites currently available) this kind of processing could be a candidate for a future MC/MF CAT-II/III GBAS service.