GBAS Flight Trials for Multi-Constellation / Multi-Frequency GBAS Concept Validation

Abstract

In recent publications the use of different Global Navigation Satellite Systems (GNSS) such as the Global Positioning System (GPS, USA), Glonass (Russia) or Galileo (Europe) for improving the Ground Based Augmentation System (GBAS) had been described [1][9]. Even if not specified in the relevant standards (ICAO Annex 10 [6] and RTCA specifications [3][4][5]) yet, these additional signals can have a tremendous potential for improvements regarding GBAS availability, continuity and especially integrity. The current planning of GBAS manufacturers and certification agencies foresees a type certificate for GBAS Approach Service Type (GAST) D ground stations in two to three years’ timeframe. GAST D will then offer CAT-III approach capabilities based on GPS L1 C/A as sole usable GNSS signal. The main challenges for this GBAS CAT-III service, called GAST D, are ionospheric anomalies threatening the integrity. GAST D will thus require a combination of extensive airborne and ground monitoring algorithms. However, with the availability of modern GNSS signals from different core constellations (Multi-Constellation, MC) and on different frequencies (Multi-Frequency, MF), the ionospheric threat can be mitigated almost completely. Within the European SESAR 15.3.7 project, a VDB message definition for MC/MF GBAS has been proposed [1], targeting towards an additional MF service for GBAS CAT-III operations. This paper describes MC/MF GBAS concepts and discusses the results of initial MC/MF flight trials performed in autumn 2015 at the Research Airport of Braunschweig (Germany). It will give a brief description of the MC/MF GBAS concept, its experimental implementation by TU Braunschweig as well as the setup for the flight trials. The paper will close with the discussion of the results and an outlook to planned future steps.