the ground systems that control the satellites. More than two dozen Boeing employees provide on-site support, examining data and offering technical advice. Vandenberg Air Force Base near Lompoc, Calif., supplies an alternative GPS control station. Four ground antennas are located globally, mostly in remote island locations. Six Air Force monitor stations, eight Air Force Satellite Control Network tracking stations and nine National Geospatial Intelligence Agency monitor stations, strategically placed across the world, fill out the network. In 1991, GPS was first used militarily during the Gulf War. Fifteen satellites were overhead when American troops launched the “Left Hook” mission, where an armored brigade, guided through the vast, featureless terrain by the navigational tool, rushed around the Iraqis’ left flank to help defeat enemy ground forces. “They would do a quick GPS read, fire off rounds, pack up everything and go, with everything done in a 10th of the time it would have taken to do it without GPS,” said Marc Drake, GPS Space Vehicle Operations manager at Shriever Air Force Base. “It had an enormous impact on the Gulf War.” The final IIF satellite replaces the last operational IIA, which was built by Rockwell and has been in orbit for 25 years—since the Gulf War. The new GPS constellation will consist of Boeing’s 12 IIFs and Lockheed Martin’s 19 2Rs. The IIF satellite is similar in size to a sports utility vehicle, only taller. It is designed for 12 years of operation, yet has the ability to double or triple that. Each new satellite block pursues stronger military coding to prevent adversaries from jamming or spoofing GPS signals, according to Boeing experts. Allies are permitted to use portions of the U.S. military signal in certain circumstances. Anyone can freely use the American civilian signal. The GPS benefit to the American economy is estimated to be $55 billion per year, said Larry Davidoff, Boeing sales and marketing lead for navigation. “We don’t take the performance of these satellites lightly,” said Doug Skinner, Boeing GPS program manager. “They’re counted on by a large portion of the population, and not just the United States but around the world. They have to be accurate and always be there.” The IIF was the first reprogrammable satellite, with new software uploaded to its memory bank while it orbited overhead. In the future, GPS satellites might be completely modified in space, reducing the amount of new satellites built, said Harry Brown, GPS IIF program chief engineer. Brown has worked on GPS satellites for 32 years for Rockwell and Boeing. He’s been involved in all but the original Block I program. He never envisioned that he was building anything other than a military resource. He’s witnessed GPS receivers shrink from the size of a brick to a postage stamp and all of the electronics become miniaturized, the satellite production line convert from two work cells to something similar to a jetliner pulse line, and the atomic clocks double in power. He sees unlimited potential in GPS. Long-haul aircraft navigation over oceans and uninhabited terrain currently relies on gyro-based “inertial” and GPS systems, or close to land, radio beacons. Over the next decade, he expects GPS to become the sole guiding system for aviation and air traffic control. “With new civil signals,” Brown explained, “we’ll someday be able to take off and land airplanes anywhere in the world using a GPS signal alone.” • DANIEL.W.RALEY@BOEING.COM Photo: The 12th Boeing-built GPS IIF satellite lifts off from Cape Canaveral Air Force Station in Florida aboard a United Launch Alliance Atlas V rocket in February. UNITED LAUNCH ALLIANCE MARCH 2016 | 29
Frontiers March 2016 Issue
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