The GPS OCX control system is set to increase the number of satellites supported by the current GPS network and improve its overall targeting and tracking capabilities Image courtesy of ThinkStock

Update: GPS III Control System Boosts Navigational Accuracy

Dec. 2, 2015
Having maintained the Global Positioning System (GPS) since it was invented, the Department of Defense is again looking to upgrade it with a new satellite control system.

Raytheon recently completed three exercises with its Launch and Checkout System (LCS), a system designed to support GPS III satellites through launch and early operational tests. The first exercise successfully demonstrated several capabilities that would support the satellites during launch, including transferring orbits, configuration procedures, and handling unexpected events that might occur in orbit.

The other exercises focused on internal communications within the GPS III ground control system. The second exercise marked the first time that the system was able to switch contacts between multiple simulated Air Force Satellite Control Network ground sites. In the third exercise, the system demonstrated that it could acquire the satellite after launch, carrying out transfer orbit configurations, simultaneous contacts, and hand-offs from multiple command sites.

Having maintained the Global Positioning System (GPS) since it was introduced almost five decades ago, the Department of Defense is again seeking to upgrade the system for both military and civilian usage. Through a series of operational tests, Raytheon is in the process of demonstrating the latest ground control system for the GPS satellite network—a critical feature of the department’s GPS Modernization Program. The Next Generation Operational Control System (GPS OCX) is set to increase the number of satellites supported by the current network and improve its overall targeting capabilities.

The GPS OCX system shifts the main GPS control features, which used to be carried out manually, to software. That software can provide accurate tracking information in spite of interference. The system observes the signals uploaded to the GPS monitor stations and then measures the overall system variance.

As a result, the system can recursively update the location of vehicles and devices equipped with GPS receivers. Designed for the next generation of navigational satellites - the GPS III series - the software is designed to improve the precision of the GPS network in areas like urban canyons and mountainous terrain.

Further improving accuracy is the system's compatibility with other navigational satellites in orbit. The GPS was the only one of its kind for several years. But as satellite networks with similar capabilities have emerged, like the European Union’s Galileo satellite project and Russia’s GLObal NAvigation Satellite System (GLONASS), the GPS OCX system is using them to increase signal reliability.

The control system is capable of assimilating both legacy signals from the current satellite network and new types of signals, including the jam-resistant military M-code and civil signals such as L1C, L2C, and L5. Working together in support of the system, these signals eliminate atmospheric distortions and provide signal redundancy to mitigate radio-frequency interference.

According to Raytheon, the resulting measurements are almost ten times more precise than those using the previous satellite constellation.

The GPS OCX will be delivered in several phases or blocks. The Block 0 Launch and Checkout System (LCS) was recently installed at the Shriever Air Force Base in Colorado, the eventual home of the GPS OCX Master Control Station. This version will introduce the full capabilities of the L2C navigation signal. GPS OCX Block 1, which will fully introduce the new control system, is scheduled to enter service in 2018.

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