Agreement on Galileo seen as enhancing GPS

 - December 18, 2007, 7:47 AM

It took several years for the U.S. and the European Union to reach agreement about satellite navigation systems, but the cooperation agreement the parties signed in June that paves the way for the Galileo and GPS satellite navigation systems should be beneficial to both sides, and to aviation worldwide.

Essentially, the agreement says that while each system will be owned and managed independently, the two systems will be compatible and interoperable, so that users anywhere can choose to use either, or a combination of both, based on their needs. And despite fears to the contrary, neither the U.S. nor the European Union will mandate use of its own system in its own airspace.

The State Department’s Ralph Braibanti discussed these and other published aspects of the agreement at the September meeting of the Civil GPS Service Interface Committee (CGSIC), held in conjunction with the Institute of Navigation’s (ION’s) GNSS 2004 Conference in Long Beach, Calif. The CGSIC is a component of the DOT’s Transportation Policy Branch, and acts as the policy conduit between the civil user community and the various government agencies with domestic and international GPS interests.

Braibanti did not describe the long and fairly rocky road that led to the agreement. In fact, many on both sides of the Atlantic scoffed at the idea that there could ever be any U.S.-EU agreement on satellite navigation.

When the Europeans announced interest in developing their own satnav system in the early 1990s, reaction in the U.S. was unfavorable. Some argued that the Europeans didn’t need or couldn’t afford satnav; others argued that they weren’t capable of developing a satnav system or, finally, shouldn’t be allowed to create one. At the time, one satellite magazine editorialist even described the nations behind the proposal as “rebellious” and accused them of being “renegade states.”

And the DOD and the U.S. GPS industry were equally displeased: the DOD because the nation’s adversaries could use a foreign-controlled global system with GPS capabilities against the U.S., and the industry because it feared lower-priced competitors would flood the multi-billion dollar market for satnav equipment and services.

Enhanced Satnav Performance
The Europeans’ view, of course, was quite different. They saw, perhaps more clearly than those in the U.S., just how pervasive a high-accuracy positioning system would become in the affairs of industrialized nations, and how disruptive it would be if the system’s owners decided to remove or degrade it.

It is probably fair to say that in the past 20 years in Europe, as in the U.S., most major construction, surveying, navigation, communications and even banking activities have come to depend on GPS in one form or another, providing a classic case of “sole means,” except that the Europeans didn’t control the means. U.S. State Department efforts to convince Europeans of America’s best intentions fell mainly on deaf ears since DOD would not–and still does not–guarantee GPS service to anyone except itself and certain allied military forces.

So will Galileo, when it enters operation at the end of the decade, be a competitor to GPS? Some might still feel that way, but they were notably absent from the ION GNSS Conference. Almost all manufacturers and service providers polled at the show told AIN that Galileo would not only enhance satnav performance when combined with GPS but would also enhance business opportunities for the same reason.
And the same is expected to be true for aviation, where the combined GPS/Galileo constellation will have as many as 60 satellites orbiting the earth, providing significant improvements in availability, accuracy and overall performance.

Observers might therefore conclude that Galileo was inevitable. That’s partly true, but its arrival would likely be much further away without U.S. technology. Satellite navigation depends on super-precise timing, where incorrect fractions of seconds can create miles of navigation error. As a result, each GPS satellite carries three cesium atomic clocks for long-term accuracy and redundancy, and so will the Galileo satellites.

But space-capable, semi-classified cesium clock technology is available only from U.S. laboratories and is under extremely tight export control. So why did the U.S. provide cesium clocks to the Europeans? The clocks and other advanced technology considerations were part of the undisclosed horse trading that went on behind the June agreement. The agreement does, however, forbid technology transfers to any third parties without the originating party’s permission–a U.S.-imposed condition possibly based on the Galileo partnership investments of China, India and other nations.

In return, the U.S. got a major, and rather startling, concession. GPS transmits signals on several different frequencies, as will Galileo. But only one of the GPS signals is available to civil users, with the others restricted to the military, including the secret and highly encrypted M Code. As it happened, Galileo’s designers, unaware of the M Code’s frequency and characteristics, selected the same frequency for one of its main signals. Mutual interference was guaranteed, but each side wanted the other side to move to different, less optimal, frequencies. For Galileo, it was an interference issue, but the DOD had a greater imperative. In a conflict theater, the DOD would want to jam both the civil GPS and all the Galileo signals to prevent enemy use. But jamming Galileo would also jam the M Code on that common frequency.

Under the negotiated solution leading to the agreement, the Galileo authorities rearranged their signals’ frequencies to closely bracket, but not overlap, the M Code, thereby allowing the DOD, under specific protocols, to jam Galileo yet maintain the military GPS and the M Code, an outcome that would have been inconceivable not too many years ago.

European officials expect that the full, 30-satellite Galileo constellation will be operational by 2010. The DOD expects–unofficially–that its next-generation 24- to 30-satellite GPS III constellation will be in orbit by 2015. Their combined performance should be remarkable.