Figuring out whether the addition of a European global navigation satellite system (GNSS) in the next few years will enhance worldwide aviation safety depends on whom you ask.

The officials Air Safety Week interviewed in the United Sates, where the global positioning system (GPS) was developed and remains under the firm control of the U.S. military, mostly downplay any potential advantages expected from the new Galileo system. Meanwhile, some officials in Europe, where Galileo is being developed and deployed, are more bullish on the new system’s potential in improving signal accuracy and reliability.

Meanwhile, a U.S.-based “knowledgeable expert,” who wants to remain anonymous, calls the advent of Galileo a “terrific” development for civil navigation and aviation safety.

While GPS increasingly reaches into all sorts of applications around the globe, its U.S. masters retain full discretion to shut it off or scramble its signals at a moment’s notice, carrying the potential of partially shutting down some foreign economies, this same source points out. U.S. officials have repeatedly avoided taking any opportunity to change that possible scenario, even as they have reasserted their authority to interrupt GPS signals.

The main problem is that GPS was originally developed more than 30 years ago only for defense purposes, but since then has been adopted for numerous civilian uses from people’s cars to their cell phones, as well as for aviation. Galileo, by contrast, which launched its first satellite late last year, will be a fully civilian-controlled system.

Meanwhile, the aviation community and the FAA are becoming increasingly reliant on navigational and situational awareness technologies, and other aviation-related safety systems that depend on reliable GPS signals. GPS is a part of the latest efforts to improve weather forecasting (Air Safety Week, Feb. 27). It’s also an integral component of North America’s first runway debris detection system being installed in Vancouver, Canada (Air Safety Week, Feb. 6), and plays a key role in the FAA’s and Alaskan Airlines‘ rollout of a new technique to safely navigate approaches through bad weather or hazardous terrain (Air Safety Week, Jan. 30).

Besides GPS and Galileo, there’s Russia’s already operating Global Orbiting Navigation Satellite System (GLONASS). But cooperation seems to be developing most rapidly between the U.S. and European systems.

For aviation safety, the two biggest advantages of Galileo would derive from a doubling of the orbiting satellites (from about 30 to 60) and by having two signals (one more than GPS has had) for avionics, our anonymous expert explains (although the FAA says that GPS also is adding a second signal). Both developments, all sources concur, will improve the redundancy and robustness of satellite-based systems, thereby enhancing air safety.

GPS still has a lot of signal gaps, the anonymous source adds. Three satellites are needed to provide the most accurate signals. In landing a plane with your nose close to the ground, GPS signals can be blocked by hilly terrain or by the horizon. Having twice as many satellites will help immensely.

Moreover, there’s a lot of electromagnetic phenomena from lightning, sunspots, or from storms that can disturb signal transmissions. These phenomena coupled with GPS’s fairly weak signals means there is a high degree of susceptibility to such disruptions. But once a second frequency is added, it’s highly unlikely that both signals would be affected by the same cause at the same time.

Greater two-signal accuracy also could mean that wide area augmentation system (WAAS) technology is not needed to better pinpoint locations (from GPS’ 10-15 meters down to a couple of meters with WAAS). But this is a development that “they don’t like to talk about in the U.S.,” the same source says, because of the FAA’s and the U.S. general aviation industry’s heavy investment so far in WAAS technology.

Galileo will provide signals with a sufficient-enough accuracy level so neither WAAS or the European equivalent of WAAS, the European Geostationary Navigation Overlay Service (EGNOS), will be needed, says Dominique Detain, communications manager for the European Space Agency (ESA) in Paris. Under either WAAS or EGNOS, pilots are warned within a few seconds’ time if the incoming signals are not clear enough to proceed with landing. Galileo has a similar feature — known as “Safety of Life” (SOL). With it, there will be no need for the filters supplied by WAAS or EGNOS, Detain tells Air Safety Week.

Meanwhile, in the Brussels, Belgium, offices of Eurocontrol (or, the European Organisation for the Safety of Air Navigation), officials aren’t so sure that the SOL alert is needed. Once both Galileo and GPS are up and running, the signals should be quite robust, says Roland Rawlings, Eurocontrol’s navigation domain manager.

Eurocontrol’s basic position is that Galileo is certainly necessary for aviation, and has certain advantages over GPS, but will not necessarily increase aviation safety on the continent, Rawlings tells Air Safety Week. That is because it is Eurocontrol’s policy not to promote the use of anything that isn’t fully safe.

One advantage for Galileo is that its ground-based control centers seem to be better positioned than those currently in place for GPS, he adds. Currently, U.S. satellites can fail and be out of sight for some time before it’s noticed by a GPS ground-based relay center, which then normally sends a warning to all operators.

Galileo also addresses a long-standing concern of Eurocontrol. If GPS fails, its signal accidentally goes dead somewhere, or it’s jammed by terrorists, Galileo can provide a back-up.

While Galileo could serve as back-up if GPS experienced a “systemic failure,” it’s important to recall that there has been no such failure now in 30-plus years, says Michael Swiek, executive director of the U.S. GPS Industry Council.

Some claims by Galileo’s proponents about its benefits “get a little overboard,” he tells Air Safety Week. Galileo, GPS, and GLONASS all use “very similar signals” and could have the same interference problems.

Galileo’s real advantages, Swiek adds, mostly will be in combination with GPS, particularly by doubling the number of orbiting satellites. In the area of aviation safety, there still are some questions outstanding as to how the systems will someday work together, Swiek says. One big question regards the type of receivers required for U.S. aircraft – “Will they have to pick up both systems, or will operators have a choice?,” he asks. That’s an area that’s “hopefully being discussed.”

In fact, it is. FAA’s prime concern with Galileo and GPS is standardization across the two systems, because the agency wants aviation operators to regularly tap into both. But without sufficient standardization, operators might need extra receivers or more expensive receivers to get up to three signals now, Dave Hempe, manager of the Aircraft Engineering Division within the FAA’s Aircraft Certification Division, tells Air Safety Week.

So, for FAA, it’s not a matter of choice. It’s a matter of ensuring that operators do use both systems. More than one system is only useful if they can be used together, says Bruce DeClene, an FAA navigation program manager who works under Hempe. Two years ago, the U.S. State Department and the EU laid some groundwork with an agreement between them setting some broad principles to make the systems compatible.

Although he agrees that adding Galileo to GPS will make signals more reliable, DeClene doubts that Galileo’s performance capabilities will add anything to aviation.

Moreover, it’s also too early to say what aviation safety enhancements Galileo might bring. So far, there are few proposed standards from the Europeans for “us to sink our teeth into,” he adds. “A lot of stuff is still in flux.”

So FAA maintains its focus on ensuring that receiver costs remain low. Historically, GPS has had one frequency for civilian use, DeClene explains to Air Safety Week. Soon GPS will add a second signal. Galileo, meanwhile, is planning on using three signals; with two at the same frequencies that GPS will use, but with a third for the SOL service. The FAA wants Galileo to switch SOL to one of the other frequencies, so the Europeans and the Americans would be on the same frequencies for aviation-safety purposes.

Generally speaking, Galileo-GPS coordination is “working well” with the Europeans, DeClene also says, adding that this matter with Galileo’s third signal is the “only open issue from our point of view.” But GJU would say it’s a closed issue.

When we asked GJU’s Detain to respond, he said the costs are minimal for receivers that get three signals.

Eurocontrol’s Rawlings admits that the FAA has a point about more signals increasing receiver cost, but not a particularly big one. There’s a trade-off. Either an operator just foregoes the extra expenses, or gets the most reliable and robust signals possible.

ESA’s Detain adds that Galileo’s “Search and Rescue’ feature will be a service currently not provided by GPS. Galileo satellites will pick up signals from emergency beacons carried by airplanes, ships or people (like backpackers), which will send these signals back to national rescue centers, providing the precise location of accidents or emergencies. At least one satellite will be in view of any point on Earth, so near real-time alerts will be possible. In some cases, signals may travel the other way.

One advantage Galileo has as a civilian managed system, as opposed to being under military control, is that its service providers will guarantee the integrity of their system, Detain adds. If a bad signal gets through without an alert to operators, the latter will be able sue the system’s operating company, which has yet to be selected. In some cases, liability would also be assumed by the GNSS Supervisory Authority.

A big reason Galileo will be more technologically advanced, besides coming online much later than GPS and taking advantage of recent advancements, is that the latter’s satellites have lasted far longer than was first anticipated, our unanimous source says. This unexpected reliability has slowed down GPS modernization. There’s also quite a pile of unused GPS satellites, manufactured a while ago, that are still sitting on the ground.

>>Contacts: Lucia Pasquini, Eurocontrol, +32 2 729 34 20, [email protected]; Dominique Detain, ESA, +33 1 53 69 77 26, [email protected]; Michael Swiek , USGIC, (202) 223-7683, [email protected]<<