It is heartening to see a burgeoning constellation and its operators move on from doubt to certainty, as Galileo prepares for fuller operational capability and the expectations that scope elicits.
To pick up the thread from last month’s column covering keynote speeches at the European Navigation Conference: plenaries subsequent to the opening session focused respectively on “GNSS for Aeronautical Applications: from GPS to Multi-Constellation with Galileo,” and “GNSS Resilience for Terrestrial & Naval Applications.”
Avionics. Benoit Roturier, GNSS and Performance-Based Navigation program head for the French air traffic control agency, Direction des Services de la Navigation Aérienne (DSNA), reviewed the rather complex assembly of air navigation systems gradually coming together. Not quite — or not nearly — a system of systems, as I understand it, more a conglomeration of systems.
Multi-constellation GNSS combos, with added context from satellite-based augmentation systems (SBAS), target provision of performance-based navigation (PBN) in all phases of flight, with increased robustness and availability, as well as escalating categories of precision approach and landing. Roturier presaged the SBAS message agreement that also took place in April with his observation that “[The] most benefits are achieved with two constellations — but which ones?” As four constellations and two frequencies deliver “many, many potential navigation modes,” how can air traffic controllers limit complexity while achieving maximum benefits? At the very least, there is a need to agree on main mode and reversion modes.
He gave an overview of upgrades planned, in progress, and completed at airports around France. 141 runways are as of January 2015 equipped with PBN, with GNSS and often EGNOS approaches, compared with 260 still relying on older systems. He concluded with a summary of DSNA views, including “SBAS/EGNOS is seen as a free of charge, performing, mature and here to stay technology, supporting navigation and surveillance (ADS-B) performance requirements.”
By the way, June’s EAGER enewsletter column will cover a recent EGNOS demonstration flight and the current state of runway approaches in Europe. Subscribe here for free.
GNSS Resilience. The second plenary, on resilience, brought forth some of the most pointed commentary of the conference. Ignacio Fernández Hernández of the European Commission spoke on Galileo differentiators for resilience: its authentication plans for the Open Service, Commercial Service, and Public Regulated Service, respectively. “The proposed GNSS authentication services are 100 percent backward compatible and interoperable with other receiver-based technologies.”
Hernandez proferred the caveat that “some of the required changes to deliver these services (particularly OS authentication) are pending on an impact analysis by industry/ESA and are not yet in the baseline. We hope however to have them in the baseline soon and we’re working hard for it.”
Matteo Paonni of the EC’s Joint Research Centre addressed spectrum management and regulatory issues, specifically the hot-button topic pseudolites. The EC is working closely with the United States and others to limit potential in-band interference risks. Outdoors, pseudolites are clearly undesirable; indoors, they offer some potential, but must be controlled.
Paonni stressed that there is a clear need to protect GNSS spectrum, and that the EC and its member states are doing their utmost to install such protections, and are also promoting GNSS radio-frequency interference detection and mitigation initiatives. Galileo’s PRS is more robust and resilient, but it is not invulnerable. GNSS vulnerabilities should be appreciated and backups put in place for critical systems; backups such as eLORAN, mini atomic clocks, GSM network, and so on.
Michel Monnerat of Thales Alenia Space focused on resilience in the road and LBS sectors. With a wide range of environments, devices and applications coming into play, “we need standardization” to specify levels of integrity and levels of performance for each different set of parameters. Thales Alenia is developing just such a set of performance requirements and references, with a first version set for release and discussion soon.