By John Rhea
WASHINGTON - A decision expected this month from U.S. Transportation Department officials will do more than decide the fate of the RF ground-based Long-Range Aide to Navigation system known as LORAN-C.
The decision also will mean life or death for what could be an emerging industry to produce systems incorporating LORAN and the Global Positioning System (GPS) for a broad spectrum of aviation and maritime users.
At issue now is a relatively small budget item of $106 million over the next five years to permit the U.S. Coast Guard to operate LORAN past its Dec. 31, 2000, planned cutoff date. The request, if it receives Transportation Department approval, would become part of the department`s fiscal year 2000 draft budget.
The underlying issue, how- ever, is a desperate attempt by LORAN industry leaders to keep the system alive long enough to apply new technologies.
Specifically, LORAN system makers want to add digital signal processing to create a new generation of receivers to combine the World War II-era LORAN tech-nology and GPS in a system containing built-in backup.
Fueling the industry`s drive are two recent incidents, both involving Continental Airlines commercial flights, in which GPS signals were jammed.
The first incident occurred last October in France while French military forces were conducting GPS jamming exercises. Then in December, in what the Air Force described as a faulty antenna test at its Research Laboratory Information Directorate at Rome, N.Y., another Continental jet-liner lost its GPS signal while approaching the New York metropolitan area.
Langhorne Bond, an aviation consultant in Pittsboro, N.C., says these incidents prove GPS is vulnerable to jamming, inadvertent interference, and even to atmospheric effects. Industry representatives displayed a 4-watt GPS jammer at last year`s Moscow Air Show, which they said is effective to ranges of at least 100 miles.
Bond, who led the Federal Aviation Agency (FAA) from 1977 to 1980, says commercial and military users should not depend on a single-thread navigation system. The technology now exists, he insists, to upgrade LORAN at a reasonable cost.
LORAN industry officials are pushing the so-called Eurofix system, originally pioneered at the Technological University of Delft in the Netherlands. Eurofix uses the 100 KHz LORAN signal as a carrier to transmit corrections to the GPS signals over long distances. Because its long wavelengths follow the curvature of the earth, a LORAN signal can be received to distances of greater than 250 miles.
Twenty-nine LORAN transmitters exist in North America - 24 in the U.S. and five in Canada - which cover the heavily traveled North Atlantic air routes. These transmitters also work together with 16 LORAN transmitters in Russia, Japan, South Korea, and China to cover the principal Pacific air routes.
There are 55 LORAN receivers worldwide, which cover about one-third of the world`s surface and most of the heavily traveled air corridors, says William Roland, president of Megapulse in Bedford, Mass., the major transmitter producer. There is no LORAN coverage in the Southern Hemisphere.
U.S. officials are committed to maintain LORAN until 2015. Nevertheless, a Federal Radionavigation Plan approved in 1996 mandated the earlier cutoff date. The major Northern European countries (Norway, Denmark, Germany, Netherlands, France, Ireland, and the United Kingdom) inherited the nine U.S. LORAN receivers in Europe, which they have turned into the Northwestern European LORAN Service.
Now, to keep LORAN alive, the Europeans have developed a way to modulate the LORAN transmitter to carry the updated time standard. The alternative for them is depending solely on foreign military satellite-based navigation systems, either the U.S. GPS or the Russian Global Navigation Satellite System.
The Eurofix approach operated for tests on five days during the first week of April at the Coast Guard LORAN site at Wildwood, N.J. Roland says LORAN sets received the signals at distances as far away from the transmitters as 600 miles. Megapulse engineers conducted the tests under a $10,000 Coast Guard contract, using the Delft university as a subcontractor.
LORAN evolved out of the World War II LORAN-A, operating at 2 MHz. Operating the system costs between $17 million to $27 million a year. Roland contends that number can drop to $8 million to $10 million by upgrading the transmitters and introducing automation.
Furthermore, mobile LORAN transmitters can deploy to areas of military conflict (as they were in Vietnam) for situations such as urban warfare and jungle fighting, when GPS signals are not readily available. Experts from the Defense Advanced Research Projects Agency, in cooperation with the U.S. Navy, last fall sent out feelers to transmitter and receiver manufacturers to see what such systems would cost.
FAA officials last year also sought an independent appraisal of LORAN and commissioned a study by Booze Allen & Hamilton in McLean, Va. The results of that study have not been released. The project leader, Ron Davis, says his group found reasons for continuing LORAN beyond its planned cutoff date, but he could not elaborate. Another study by the Washington-based Radio Technical Commission for Aeronautics is due to be released in early October.
The issue is extremely politically charged, even by Washington standards, with the major airlines lining up against any continuation of LORAN because of the user charges. Military leaders are somewhat ambivalent since they can fall back on inertial navigation systems except in urban and jungle warfare.
The other user groups have generally favored LORAN without taking any firm stands, although the Aircraft Owners and Pilots Association, an organization of private aircraft operators based in Frederick, Md., did come out in favor of it last December.
The company that would benefit most from continuing LORAN is Locus Inc. in Madison, Wis., which makes today`s receivers and is developing an advanced model known as Linear Averaging Digital LORAN (LAD-LORAN).
Locus officials could sell their LAD-LORAN devices either separately or, more likely, as a card for GPS receivers. Linn Roth, president of Locus, has been evaluating DSPs from Texas Instruments in Houston and Analog Devices in Norwood, Mass., which would be the heart of the new receivers.
Representatives of the major GPS receiver manufacturers and avionics systems companies have also looked into this possibility but have not pursued this effort until they could get a clearer signal from DOT on the future of the Loran transmitters.
Bill Brogdon, president of the International Loran Association in Santa Barbara, Calif., concedes that LORAN and GPS have their gaps, but says a combined system would provide coverage for all but about 0.7 seconds per day.
Lightning causes the most problems for LORAN, says Brogdon, who is based in Cape Carteret, N.C. But the selective availability feature of GPS means that for 72 minutes a day GPS errors may increase from their normal 110 yards to 330 yards, he points out Differential GPS will get that down to five to 10 yards using radio beacons, but it is not yet operational. Also, FAA officials are developing the Wide Area Augmentation System, which will alert users when GPS is not working, but that system will not be operational for several years.
More than commercial aviation and military use is at stake, Brogdon notes. Maritime users constitute the majority of the LORAN installed base - about a million receivers vs. 200,000 on aircraft - and the investment in LORAN receivers amounts to $500 million.
The commercial aviation industry has its own backups, such as VHF Omni Range beacon, Distance Measuring Equipment, and the Instrument Landing System, but maritime users often depend exclusively on LORAN.
Another user group affected by the Transportation Department LORAN decision, says Roth at Locus, is the telecommunications industry, which needs an assured means of synchronizing its cellular phone base stations.
This LORAN-C transmitting tower in Seneca, N.Y., is one of 29 such sites in North America. Systems designers house the electronics that run the LORAN transmitter, inset, in several cabinets.
