The Loran terrestrial radionavigation system might well be pulled back from its 12-year-long dance on the brink of extinction, while the Nationwide Differential GPS (NDGPS) radiobeacon-based augmentation system may have finally been pushed over the edge.

An independent assessment team (IAT) is scheduled to brief U.S. Department of Transportation (DoT) and Department of Homeland Security (DHS) officials in December on its recommendations for whether an enhanced Loran (eLoran) system could serve as a U.S. backup to GPS (or GNSS in general).

The DoT and DHS are charged by President Bush’s 2004 national security directive on space-based positioning, navigation, and timing (PNT) to develop and maintain backup position, navigation, and timing capabilities within the United States, in the event of a disruption of GPS or other GNSSes.

Despite being stiffed by Presidential budget proposals since 1994, written out of the Federal Radionavigation Plan in 2004, its 2007 budget zeroed out by the U.S. Coast Guard (USCG) commandant earlier this year, overshadowed by GPS for the past decade, and practically devoid of North American users, Loran still appears likely to find new life as a hedge against the potential failure of space-based PNT systems.

It is, in fact, the last of these increasingly critical infrastructures — precise timing for telecommunications, banking, and electric power systems — that may put eLoran back in the game.

While every safety-critical mode of transportation has individual means to survive a temporary loss of GPS, timing systems would now have to depend on disparate and unnetworked atomic clocks and crystal oscillators that would lose synchronization at various and unpredictable rates.

Despite its routine absence from administration budget proposals, Loran has been rescued by congressional advocates who have provided $160 million since 1997 to enhance the Loran system and conduct research to make eLoran a viable backup to GPS.

Those funds have helped modernize and add to the network of Loran transmitters that cover the United States, equipping every station with three cesium clocks, while encouraging miniaturization of Loran receiver technology able to use new all-in-view techniques that provide positioning and timing accuracy approaching that of GPS.

Coming together. All this is leading to a convergence of forces and activities that bode well for Loran.

In a paper presented at the International Loran Association Convention and Technical Symposium in October, timing experts from the U.S. Naval Observatory, the National Institute of Standards and Technology, and a timing instrument manufacturer wrote, “[W]e have identified eLoran as potentially the best available backup provider to GPS as a reference source for precise time synchronization and frequency control.”

Meanwhile, in August a white paper prepared for the Federal Aviation Administration, “GPS Backup For Position, Navigation and Timing,” endorsed eLoran as well.

The 11-member Loran IAT, which is headed by Brad Parkinson, a Stanford University professor and founding program director for the GPS Joint Program Office, has held a series of meetings with PNT equipment manufacturers and users to assess their ideas and sentiments about eLoran.

Parkinson himself appears to be leaning toward Loran. In comments to the European Journal of Navigation in October, he said, “I am a supporter of having a backup radionavigation system, and the only backup system I can see is Loran.”

NDGPS in trouble. Meanwhile, NDGPS appears to be losing its equally long battle to remain on the air. The recent transfer of the program from Federal Railroad Administration (FRA) sponsorship to the new U.S. Department of Transportation’s (DoT’s) Research & Innovative Technology Administration (RITA) failed to secure operational funding from the White House Office of Management and Budget (OMB).

Currently, the FY07 operating plan halts all new NDGPS site construction and allocates only $2 million to decommission the program beginning in FY08. Absent the intervention of Congress or a reversal of administration plans, NDGPS will go off the air in October 2007.

Pressure from private companies, which argue the system provides an unfair taxpayer-supported alternative to their services, apparently struck a chord with advocates of privatization in the Bush administration.

Copyright 2006 Gibbons Media and Research LLC

The post Loran Revives; NDGPS Fades appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

China has confirmed what many have been expecting for some time: it will construct the world’s fourth GNSS system — joining the systems operated by the United States, Russia, and Europe.

Given the defense implications of GNSS technology, the development was probably inevitable; however, the timing still came as a surprise for many, especially in Europe where Chinese participation in the Galileo program had been seen as a way to pre-empt China’s creation of an independent system.

In an announcement made through the government news agency, Xinhua, the People’s Republic of China (PRC) National Space Administration said the nation will build its own 35-satellite GNSS system, known as Beidou or Compass. The system would include five geostationary Earth orbit (GEO) satellites and 30 medium Earth orbiting (MEO) satellites in six orbital planes, the latter operating near the GPS and Galileo altitude of 20,000 kilometers.

According to People’s Daily Online, Compass will offer two levels of service: an open, commercial service with real-time autonomous positioning accuracy of 10 meters and 50-nanosecond timing accuracy as well as a safer “authorized” service — probably similar to Galileo’s publicly regulated service (PRS) or the encrypted GPS military signals.

Beidou (or “North Dipper,” referring to the seven stars in the constellation Ursa Major also known as the Big Dipper) alludes to the navigational role long associated with the compass or Pole-star — stella polaris — found in that grouping of stars.

By May 2003, the program had launched three Beidou GEOs transmitting signals in the S-band radio spectrum. The next stage of development will begin early in 2007 with launch of two satellites, although the news reports did not indicate whether they would be additional GEOs or MEOs.

The plan behind the program. China’s government approved the implementation of the system in September 2003 with a capital investment of 15 billion renminbi (US$1.9 billion) and completion of the system by 2010, according to a May 28, 2004, commitment letter to the ITU, from Zhu Sanbao, deputy director general of the Radio Regulatory Department of the PRC’s Ministry of Information Industry. According to Zhu’s communication, the Compass satellites will be developed, manufactured, and launched by the China Aerospace Science and Technology Corporation (CASTC).

PRS, M-code overlay threat? Frequency filings made by China for radio bands in which to transmit Compass signals indicate that it would overlay both the Galileo Public Regulated Service (PRS) and military GPS M-code at L1, as well as L2. That could reignite the controversy that arose with the Galileo program’s initial proposal for PRS to overlay the M-code, which is a new capability on the modernized GPS Block IIR satellites now being launched – including the third one put into orbit on November 17.

Those requests have gone to the International Telecommuncations Union (ITU), a United Nations affiliate responsible for achieving consensual harmony in use of radio spectrum worldwide. ITU working groups are currently evaluating the potential interference with existing or approved GNSS signal allocations. The issue is certain to come up at the World Radiocommunication Conference 2007 set for Geneva, Switzerland, next October/November.

Cooperation, Competition, or Cooptition? China is willing to cooperate with other countries in developing its satellite navigation industry to allow the Compass system to operate with other global satellite positioning systems, according to an “informed source” cited by Xinhua.

The proposal to overlay the M-code — effectively preventing the U.S. military from jamming Compass transmissions without jamming its forces’ own signals — will undoubtedly raise the same alarm in the Department of Defense as did the original PRS design. More immediate consternation will probably occur in the European Union (EU), which has sought to engage China’s support for years in the Galileo program.

The Galileo Joint Undertaking (GJU) signed a cooperation agreement in October 2003 — reportedly the largest EU/PRC science & technology effort — that included China’s €200 million contribution to the Galileo program, primarily in the form of applications development and regional monitoring capabilities.

The National Remote Sensing Center of China (NRSCC) was designated as the European Union’s Chinese partner on the Galileo Project and a state company established, China Galileo Industries Ltd., owned by CASTC, China Electronics Technology Group Corporation, China Satcom and China Academy of Space Technology.

The European Commission, the EU’s executive branch, signed an agreement with China that assured Chinese “participation” in the GNSS Supervisory Authority (GSA) slated to take over Galileo program responsibilities from the GJU in 2007. However, that participation apparently will not stake the form of full membership that China wants.

Rainer Grohe, GJU executive director, told Inside GNSS recently that Europe still hopes to involve China further in Galileo. “You can’t exploit the Chinese market without a Chinese partner,” he said. “We hope that they continue to participate [in Galileo] in an appropriate way.”

Copyright 2006 Gibbons Media and Research LLC

The post Compass: And China’s GNSS Makes Four appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.