Now military leaders are looking for the technologies that can fill the gaps in PNT that occur in GPS signal – challenged conditions . changing the Game changer The Way Ahead for military PnT

n o v e m b e r / d e c e m b e r 2 0 1 0 www.insidegnss.com W ith thanks to Yogi Berra, it’s “déjà vu all over again” for the Global Positioning System, but this time with a twist. Twenty-five years ago, the question asked by U.S. military commanders and combat personnel in the field was, “Why should I go to the trouble to use this space-based system called GPS?” Today, the question being asked is, “GPS is vital to the success of my mission; so, why are you asking me to consider using something else?” The original question has been answered in countless ways for military users beginning with Operation Desert Shield/Storm and continuing through Operation Enduring Freedom/New Dawn. Today’s question arises from recent concerns about U.S. military dependence on GPS and the vulnerabilities that may affect mission success if GPS is not available — even if only for the briefest of periods. Those concerns also underpin a growing Defense Department interest over the last few years in alternate sources of positioning, navigation, and timing (PNT) to augment or complement GPS. Studies by U.S. Strategic Command (STRATCOM) and by an interagency group that recently produced a proposal for implementing an enterprise-level National PNT Architecture have highlighted the fact that even a modernized GPS cannot satisfy all the military’s PNT needs all the time. As a result, efforts are now underway to characterize the full spectrum of possible PNT sources and assess their capability, in combination with GPS, to meet those needs. Those efforts will be discussed in some detail later in this article. First, some additional background. . . . Air Force Chief of Staff, General Norton Schwartz directly addressed the concern about GPS dependency in a February 2010 speech to the Air Force Association’s Air Warfare Symposium and Technology Exposition meeting in Orlando, Florida. In that speech, Gen. Schwartz noted, “[O]ur dependency on the Global Positioning System has also created certain vulnerabilities that our adversaries can exploit through jamming and other tactical denial techniques. While we remain unequivocally committed to proper stewardship and use of the world’s unparalleled standard in precision navigation and timing, as well as advancing enhanced capabilities with new GPS Block IIF satellites and next-generation GPS III concepts, we also recognize the need to be able to continue to operate effectively, through improvement to GPS and other methods, in a denied or degraded localized environment.” Gen. Schwartz’s comments reflect the full spectrum of issues regarding use of GPS by the military as well as throughout the civilian infrastructure. It’s almost a “can’t live with it, can’t live without it” dichotomy. GPS-based positioning, navigation, and timing (PNT) have profoundly changed how the U.S. Defense Department carries out command and control in the electronic battlespace — from a reactive to a real-time mode of continuous situational awareness. Now military leaders are looking for the technologies that can fill the gaps in PNT that occur in GPS signal–challenged conditions. changing the Game changer The Way Ahead for military PnT Jules mcneff OverlOOk SyStemS technOlOgieS GNSS forum