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Aviation History
1998
1998 - 3396.PDF
AIR NAVIGATION Jriines are being called into the fight to protect the frequency band used by satellite navigation systems CHRIS YATES/MANCHESTER HE AERONAUTICAL community must pool its resources and protect its strategic interests ii it is to avoid losing the hundreds of millions of dollars invested in :llite navigation. The threat comes from an Inmarsat-sponsored proposal, currently before the International Telecommunications Union- World Radio Council (TTU-WRC), to share frequencies in the global navigation satellite system/radio navigation satellite system ((IXSS/RNSS) band of 1,559-1,610MHz. The GNSS/RNSS band has until now been designated for exclusive use by the aeronautical and maritime communities, but the proposal - originally put lorward at last year's WRC 97 meeting and due to be considered more seri ously at WRC 2000 - would allow mobile satel lite service (MSS) users access to a subset of frequencies in the lower portion of the band, between 1,559 and 1,567MHz. If the pro- accepted at WRC 2000, the ITU risks compro mising critical aeronautical safety-of-life ser vices that rely on GNSS/RNSS signals because they will have no protection from interference by odier band users. "The spectrum protection issue is as time crit ical and potentially damaging as die Year 2000 flaw, and suffers from die same lack of foresight, understanding and resources to correct it," says James Miller, a senior analyst with United Airlines. He believes the fact that the spectrum problem is seen as a strategic issue has caused inertia among airline lobby groups such as the Air Transport Association (ATA) and International Air Transport Association (IATA). "We may not be using [the Spectrum) now, but if you look at the studies done, by 2005 we're going to be looking at air traffic control grid lock," says Miller. "Once that spectrum is gone, it's gone. Airlines have to step up to the plate and put resources into this, because the ATA and IATA are not going to do it unless we say this is important to us." In economic terms alone, the issue is vitally important. United, for example, has been equipping its fleet with GNSS functionality to comply with Federal Aviation Administration and International Civil Aviation Organisation (ICAO) infrastructure modernisation plans. By the end of 1998, 35 Boeing 747-400s, 34 777s, four 767-300s, 20 Airbus A319s and one McDonnell Douglas DC-10 operated by United will be able to use the GNSS. If spectrum sharing becomes a reality, that investment is lost, says Miller, and even greater losses will be incurred from the operational impact of not being able to take advantage of satellite navigation technology. As recendy as October, the battle to protect the GNSS/RNSS band from encroachment by A1SS users appeared to be swinging in favour of die aeronautical community, with a suggestion emanating from the ITU that the frequency- sharing proposal would be turned down. But there was a sting in the tail: to retain exclusive use of die GNSS/RNSS band, die aeronautical commu nity must present at WRC 2000 a concise and detailed plan for its utilisation . Currendy, the GNSS/RNSS band supports the US global positioning system (GPS) and Russia's GLONASS. Future plans foresee a multitude of uses. As well as supporting the US Wide Area Augmentation System, the European Geostationary Navigation Overlay System and Japan's MSAS augmentation sys tem, the band may be needed for "...ADS-B [automatic dependent surveillance-broadcast] and pseudo-satellites for die LAAS [local area augmentation system], so we can do Cat 3 land ings," says Miller. "We don't know yet what fre quencies those systems are going to use, yet they're forcing us to make decisions on that right away just to fill die band." There are conflicting views on die efficacy of sharingthe band. A study conducted outside the framework of the ITU Radiocommunication Sector, but presented at WRC 97, suggested that appropriate power limits for the MSS would protect GPS and GLONASS as well as future navigation satellite systems, such as the E-NSS-1. "They're trying to minimise die threat to GPS-based applications," says Miller. "Once they [the MSS] get their foot in the door, it's obvious they're not going to get good ser vice unless they crank the power up." If this happened, die fear is that the selectivity of airborne systems would not be great enough to pick out die the weak signals from navigation satellites. Current genera tion GPS receivers cannot deal FLIGHT INTERNATIONAL 16 - 22 December 1998
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