By Kristen Beckman, Assistant Editor

 

The global positioning system (GPS) is undergoing a modernization effort that will result in increased accuracy and reliability, as well as advanced applications that could impact public-safety and mission-critical communications.

 

The U.S. Air Force awarded a contract to Lockheed Martin Space Systems in 2008 to develop the next generation of GPS satellites in an effort to replace aging GPS equipment and introduce new capabilities. The initial contract included development of two space vehicles (SV) with an option for up to 10 additional space vehicles. In 2012, the U.S. Air Force contracted with Lockheed Martin for production of two additional satellites.

 

The company has been working toward designing, testing and building the GPS III space vehicle with plans for the first launch in 2014. Lockheed Martin is cooperating with Raytheon, which won the contract to build the Next Generation GPS Operational Control System (OCX) in 2010.

 

The U.S. Air Force plans to build up to 32 GPS III satellites.

 

The first iteration of the GPS system — GPS Block I — was initiated in 1974 with launches beginning in 1978. The last Block I satellite was taken out of service in 1995. Block I satellites were designed to last five years.

 

GPS Block II was initiated in 1983, and the first satellite was launched in 1989. Block II includes several series of upgraded satellites and follow-on satellites that continue to be added to the GPS constellation. The most recent launch was a GPS IIF satellite on Oct. 4, 2012.

 

The current GPS system includes a constellation of at least 24 operating satellites at any time. During the past few years, 31 operational satellites have been in service in addition to three or four decommissioned satellites that can be reactivated if necessary.

 

The GPS III modernization effort was launched in an effort to maintain the existing GPS constellation and improve positioning, navigation and timing (PNT) services. GPS III will include a new civilian signal, higher signal power, greater accuracy, longer SV lifetime and higher signal availability than Block II.

 

The first GPS III satellites are expected to deliver signals three times more accurate than current GPS satellites and provide three times more power for military users. The satellites also will have an increased design life of 15 years and add a civil signal that will be able to interoperate with international global navigation satellite systems (GNSS).

 

The new civilian signal will be interoperable with other navigation systems, including Europe’s Galileo (link to http://www.radioresourcemag.com/onlyonline.cfm?OnlyOnlineID=303), Japan’s Quasi-Zenith Satellite System (QZSS) and potentially China’s BeiDou system (link to http://www.radioresourcemag.com/onlyonline.cfm?OnlyOnlineID=291). The signal provides improved acquisition and tracking, faster data download and a more accurate ranging signal.

 

Another planned application of the GPS III system is the Distress Alerting Satellite System (DASS) payload that will relay distress signals from emergency beacons to search-and-rescue operations.

 

GPS has important applications in the public-safety communications arena, as well as the public-safety market as a whole.

 

GPS provides precision timing for synchronization and operational efficiency of communications systems, including wireless telephone and data networks, and electrical power grids. GPS is used in some mobile handsets to determine location information that can be provided to emergency dispatchers. In addition, GPS can be used to accurately determine the locations of landmarks, streets, buildings, emergency service resources and disaster relief sites, reducing response times for first responders.

 

GPS is widely used in emergency vehicles and specialty fleets both to help guide first responders and to provide an overview of responders to dispatchers and incident commanders. GPS can also be combined with infrared scanners to identify wildfire boundaries and hot spots for firefighters.

 

Scientists are using GPS to study earthquake-prone areas in an attempt to predict earthquake activity. Meteorologists use GPS to track storms and predict floods, and the Federal Aviation Administration (FAA) uses GPS to synchronize reporting of hazardous weather from its Terminal Doppler Weather Radars throughout the United States.

 

Rail systems use GPS to track the movement of trains, rail cars, maintenance vehicles and wayside equipment. In addition, some forthcoming positive train control (PTC) systems may use GPS to determine whether a train has changed tracks after going through a switch. GPS also synchronizes the timing of railroad communications systems, including data transmissions for PTC, voice contact between locomotive engineers and dispatchers, and intermodal communications among trains, rail stations, ports and airports, according to GPS.gov.

 

In the aviation industry, GPS offers satellite navigation services, three-dimensional position determination for all phases of flight and area navigation, which allows aircraft to fly user-preferred routes from waypoint to waypoint.

 

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