Down to Earth: Satellite Technologies, Industries, and Cultures

Chapter 5: The NAVSTAR Global Positioning System: From Military Tool to Global Utility

5 @ The NAVSTAR Global Positioning System From Military Tool to Global Utility rick w. sturdevant The NAVSTAR Global Positioning System (GPS), which enabled users to determine their precise location in three dimensions and time within billionths of a second, evolved from concept to operational system in slightly more than two decades.1 Colonel Bradford Parkinson, U.S. Air Force (USAF) director of the newly formed GPS Joint Program Office in 1973, directed his team to synthesize a design from several competing programs.2 The USAF launched the first operational GPS satellite in 1989 and declared a twenty-four satellite constellation fully operational in April 1995.3 The Department of Defense (DoD) needed GPS primarily to deliver weapons on target, but recognized the system’s nonmilitary potential. To withhold full accuracy from enemies but provide GPS service to civilian users, the USAF designed the system with a protective feature called “selective availability” (SA) that, when used, gave U.S. and allied forces significantly more precise signals than other users received. In September 1983, after Korean Airline Flight 007 went astray and was shot down by Soviet fighters, President Ronald Reagan assured the world that once GPS became operational , the coarser signal that could have saved the Korean flight would remain continually and universally accessible at no cost. As GPS approached operational status in the early 1990s, civilian and commercial users, who already had ten times as many GPS receivers as the military, mounted an increasingly vocal campaign for unrestricted access to the more precise signals . Finally, in May 2000 President Bill Clinton acknowledged the global utility of GPS and directed immediate discontinuation of the SA feature.4 With increasing demand for accuracy, users found ways to augment GPS. For small areas, those included pseudolites (ground-based transmitters that could be configured to emit GPS-like signals) and differential GPS (DGPS), which required a high-quality GPS “reference receiver” at a surveyed location. The Wide Area Augmentation System (WAAS), one type of Wide Area DGPS, used reference receivers at multiple monitor stations and a master-control hub to achieve similar results over a larger region.5 Other countries and regions developed their own GPS augmentation systems . Russia had its own Global Orbiting Navigation Satellite System (GLONASS). China launched its first Beidou prototype navigation satellite in October 2000. Europe followed suit with GIOVE-A in December 2005, the first step toward an operational system called Galileo. Even as GPS’s global utility manifested itself, integrating all the systems into a single Global Navigation Satellite System (GNSS) remained possible. Participants in the International GNSS Service (IGS), a voluntary federation of more than 200 agencies worldwide, contemplated just such a possibility at meetings like the IGS Analysis Center Workshop in Miami, Florida, in June 2008.6 Since a full accounting of GPS’s impact would require hundreds of pages, what follows is merely illustrative. Military Applications The first use of GPS-guided weapons occurred in Operation Desert Storm, the first Gulf War, in 1991. During the initial hours of the air campaign, bombers delivered AGM-86C Conventional Air-Launched Cruise Missiles, each containing GPS loosely coupled with an existing inertial navigation system , and achieved several exact hits. During the 1990s, the U.S. military converted fundamentally “dumb” bombs into GPS-guided Joint Direct Attack Munitions (JDAMs), high-precision ordnance capable of destroying multiple targets in a single sortie at any time of day or night, in any kind of weather. During Operation Allied Force in 1999, U.S. B-2 “Spirit” stealth bombers delivered 650 JDAMs against Serbia with devastating accuracy. Munitions manufacturers strove to put GPS into smaller projectiles, and, in 2008, army artillery in Afghanistan first fired a 155 mm GPS-guided howitzer round during combat. These new projectiles offered greater lethality and lower collateral damage.7 In 2004, U.S. Marines in Iraq witnessed the first combat use of a GPSassisted parafoil, a key component of the Joint Precision Airdrop System (JPADS). The first operational use of JPADS in Southwest Asia supplied ammunition and water to troops in Afghanistan in 2006. By enabling accurate delivery of cargo pallets from release altitudes above 25,000 feet, these systems protected aircraft and crews from inexpensive surface-to-air missiles.8 Meanwhile, paratroopers obtained GPS-equipped helmets. French forces had rick w. sturdevant 100 the Operational Paratroopers Navigation System in 2005, and U.S. Marines contracted for helmet-mounted ParaNav units in 2008...