Assured PNT A path to resilient positioning, navigation and timing by Mr. Kevin Coggins P


ositioning, navigation and timing (PNT) has been at the foundation of military capability for centuries, required for functions ranging from navigating the seas to coordinating actions on the battlefield. Instruments such as the sextant, sundial, pocket watch and compass—using the reliable properties of celestial objects, mechanical springs and the Earth’s magnetic fields—have been critical in the battles that have shaped our history.


Tese instruments were ingenious discoveries that continue to prove useful today, with a certain degree of skill and training required to maintain proficiency. Te sextant, first built in 1757 and still in use today on Navy warships, and the Davis quad- rant, invented in 1594, allowed us to use the stars for navigation, the stars providing an extremely reliable positional reference. Te map and compass, a staple of land navigation, are still used by some in the Army. Te requirement is, and has always been, access to PNT information that you can trust—assured PNT.


A revolutionary change in PNT occurred with the invention and fielding of satellite-based navigation systems. Scientists at Johns Hopkins University, monitoring radio transmissions from Sputnik in 1957, ascertained a method to pinpoint an object’s location based on radio transmissions. Years of hard work ensued, and the first satellite navigation system, Transit, was tested by the Navy in 1959 and became operational in 1964. Transit eventu- ally provided position accuracy of 200 meters and time accuracy


86 Army AL&T Magazine January–March 2015


of 50 microseconds—an amazing capability used by thousands of warships and seagoing vessels until 1991. Tis technology matured into the present-day GPS, one of the most complex technological innovations the world has ever seen. GPS, with a position accuracy of better than 1 meter and time accuracy better than 100 nanoseconds, has become a ubiquitous technology in consumer electronics and the U.S. critical infrastructure, from cellphones to the power grid, and is the PNT gold standard for military and civil users worldwide. GPS has become so prevalent and easy to use that most forget its underpinning enablers—and their vulnerabilities.


Te next version of military GPS capability, known as Mili- tary Code (M-code), is presently in development, undergoing technology maturation and risk reduction. Te M-Code signal is much improved over the present P(Y)-code precision mili- tary signal, offering additional signal power and a new signal structure. Under Public Law 111-383, Section 913, effective Jan. 7, 2011, procurement funds cannot be used after FY17 to purchase GPS receivers that are not capable of receiving the M-code signal, unless granted a waiver by the secretary of defense. Te Chairman of the Joint Chiefs of Staff Instruction 6130.01E, “Master Position, Navigation, and Timing Plan (MPNTP),” effective May 1, 2013, requires the use of M-code- capable user equipment by the time the 24th M-code-capable GPS satellite is declared operational, which is estimated to occur in a five- to seven-year time frame.


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