Next time your automobile calmly announces that “You have arrived at your destination,” pause for a moment. That quiet confidence is not the result of ordinary engineering. It is the legacy of a young Air Force colonel who, over one long Labor Day weekend in 1973, found his presence in the drearily empty Pentagon suddenly interrupted by a cascade of insights that would forever rewrite the future of navigation.
Long before he ever set foot in those corridors, Bradford Parkinson had covered the walls of his boyhood bedroom with large maps of the Boundary Waters in northern Minnesota — the lakes, streams and, mosquitoes notwithstanding, the wilderness he loved to explore by canoe. “It was easy to get lost,” he later recalled. “You had to keep your wits about you.” That early fascination with knowing exactly where you are would shape the rest of his life.
In 1973 Parkinson had been handed a program that was going nowhere. Bureaucracy, competing military services, conflicting technical approaches, and deep institutional skepticism had left the idea of a global satellite navigation system in a classic state of FUBAR — close to collapse. Yet in three intense days he and a small team of officers replaced haze and indecision with architectural clarity. They stripped the concept back to its essentials, rebuilt it around a constellation of satellites carrying atomic clocks, and emerged with a design that would eventually place precise time and position in the hands — literally — of almost every person on Earth.
Parkinson was able to do two decisive things: he identified the fundamental simplicity of cause and effect that lay buried beneath the history of competing projects, and, with that understanding of causation, he swiftly joined those essential points into a single, coherent design.
The roots of that simplicity stretched back nearly two decades. When the first practical atomic clock came online in 1955, the concept of a global positioning system was not even a science-fiction dream. That changed with startling speed only two years later.
This brings us to the first fundamental: the decisive catalyst represented by the launch of Sputnik on 4 October 1957. Within days, physicists at the Johns Hopkins Applied Physics Laboratory had tracked the satellite’s radio signal through its Doppler shift; almost immediately afterward, Frank McClure inverted the problem and realized that a satellite of known position could locate a receiver on Earth. The intellectual ignition was so rapid and decisive that it invites a modest comparison with Einstein’s annus mirabilis.
The second fundamental relates to the atomic clock itself.
While we covered its mechanics in our previous blog, a short restatement is useful here. An atomic clock measures the passage of time by counting the extraordinarily stable oscillations of atoms rather than the vibration of a quartz crystal. In the world’s first practical version, a beam of caesium-133 atoms is exposed to microwave radiation. When the microwaves are tuned to exactly 9,192,631,770 cycles per second, the atoms absorb and re-emit energy as they flip between two specific energy states (the hyperfine transition). The clock continuously adjusts its microwave source to stay locked on that natural resonance and simply counts the cycles. Without it, GPS could never have happened.
Parkinson and his small team did not, of course, invent either breakthrough. What they did was recognize that the geometric insight born from Sputnik (passive ranging from satellites of known position) and the timing precision supplied by atomic clocks were not merely complementary — they were two halves of the same fundamental solution. When they locked those two elements together in the 1973 redesign, the entire global positioning concept suddenly became simple and robust. All that was necessary was for each satellite to carry a much smaller version of the 1955 atomic clock so that the exact moment a signal left the spacecraft was known. That done, any distance could be calculated with extreme precision by resolving a basic equation: distance = speed of light × time. In modern GPS the satellites therefore carry redundant atomic clocks; receivers use the precisely timed signals for ranging and exploiting residual Doppler information to determine velocity.
What began as a desperate redesign in a quiet corridor of the Pentagon is today the invisible utility that guides aircraft, ships, tractors, emergency services, the phone in your hand, and the car that you drive. This is the story of how one determined engineer, standing on the shoulders of that rapid post-Sputnik insight, turned a failing military project into the most widely used navigation system in human history.
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Dr. Anthony O'Sullivan
Palomar Technologies
Senior Director of Strategic Marketing