While it may be hard to believe that the global positioning system (GPS) is already more than a quarter century old, it may be equally difficult to imagine that by 2020 there will be more than 100 navigation satellites crisscrossing in outer space, high above us. Yet the first is true and, barring unforeseen eventualities, the second will also be true.
For most of today’s GPS users, now estimated to be in the tens of millions, the 27 or so GPS satellites would seem to be more than adequate. Why then does the world need more than 100? Basically, it’s because GPS is solely owned and controlled by the U.S. military and, while the U.S. has offered its service free of charge and has pledged never to degrade or remove its satellites’ signals except in times of national emergency, other nations would prefer to control their own satellite destinies.
This is not simply xenophobia, but it is because GPS is more than just a navigation system. For example, one of its lesser known functions is its super-accurate time signals that are now used by virtually every modern society for the precise control of key functions, among them: communications, transportation, power distribution and financial transactions. Long-term dependence on a foreign source–regardless of how friendly it is–as a reliable control of such key services can make nations a little nervous.
And for those opting for independence, or semi-independence, from GPS there are important economic benefits in the development of their own space technology industries, and in producing income from their own systems. For these and other reasons, Russia, Europe and Japan are active in fielding their own, GPS-like navigation satellite constellations.
Russia is the pioneer in this realm, primarily because the former Soviet Union had developed its global navigation satellite system (GLONASS) as a counter to the U.S. GPS during the Cold War. The 24-satellite GLONASS dwindled to just seven satellites during the 1980s and 1990s because of financial restraints, but it is being built up again, with three satellites having been simultaneously launched on Dec. 25, 2005, and with an edict from President Vladimir Putin that the full number will again be in orbit by 2008. Russian speakers at recent international conferences stressed that the country intends to be a major competitor in the future satellite navigation business.
Europe’s entry into the field occurred in 1992, when European Union members decided to proceed with their own system, called Galileo (after the early Italian astronomer), which would be funded through a joint public/private partnership. While signal-compatible with GPS, Galileo would be technically more advanced and more accurate.
The operational date for Galileo was originally forecast for 2008, but it has subsequently slipped to 2010. A test satellite, called Giove-A, was launched in December aboard a Russian booster rocket and results so far have been encouraging enough that the planned autumn launch of a follow-on Giove-B test satellite has been indefinitely postponed. Currently, 25 EU member states are Galileo participants, plus China, Israel and South Korea; other nations are expected to join later.
Unlike GPS and GLONASS, Galileo is primarily a commercial system, with a range of services, some of which are fee- bearing. The operators foresee tracking highway vehicles for toll collection as a major revenue earner, as well as collecting fees for aircraft landing guidance.
The GPS, GLONASS and Galileo constellations have generally similar configurations, with their satellites following circular, 11,000-mile high orbital “trains” around the earth. GPS and GLONASS have 24 satellites (the three extra GPS units are operating spares), while Galileo is expected to have 30, some of which may have elliptical orbits. It seems probable that the next generation GPS will adopt the Galileo configuration.
Japan’s planned systems will be very different. The four satellites of its Quasi-Zenith Satellite System (QZSS) will follow a figure-eight shaped path, arranged to give vehicles in the urban canyons of Japan’s cities better satellite visibility than is presently available from the lower elevation GPS units. Japanese automobile makers intend to install satellite navigators in all of the four to five million cars they sell domestically each year.
QZSS can be used for other applications, but automobile navigation is its prime purpose. Japan’s second proposed network is the three-satellite Japan regional air navigation system (JRANS) which is designed for more conventional use over a much larger area.
GPS, GLONASS, Galileo, QZSS and JRANS share one common characteristic. All will use the same basic signal frequencies, to allow worldwide seamless compatibility. And above them, spaced around the earth’s circumference and apparently motionless in 23,000-mile geostationary orbits above the equator, will be as many as 10 satellites to provide a protective performance umbrella sending down alerts and accuracy corrections to users on or above the earth’s surface. Called geostationary augmentation satellites, or GEOs, some are in operation over the U.S. and Europe, shortly to be joined by others operated by India and Japan.
Yet while each of the systems is a competitor to the others, they are each mutually complementary. GPS users today know of coverage holes interference and other anomalies. With 100 signal sources in the sky, future satellite navigation system availability, reliability and accuracy will unquestionably be, to coin a phrase, “out of this world.”
