By Randy Saunders
50th Space Wing historian
The GPS is arguably America’s best known satellite system. Its satellites provide positioning, navigation, and timing services that affect our lives daily, and in ways in which we may not be aware. More than a military system, GPS helps us navigate America’s roadways, trails, and waterways, it provides the time stamp on our ATM and other banking transactions, and makes surveying, farming, and many other commercial activities more efficient. The GPS has been recognized internationally for its contributions to humanity. Few know, however, that the concept behind GPS dates to the early days of America’s efforts to develop satellite systems.
On Oct. 4, 1957, the Soviet Union launched Sputnik I, the first man-made object to orbit Earth. They followed quickly with Sputnik II, which carried the first live being, a dog named Laika, into orbit. While the Soviet launches surprised Americans, the United States was not that far behind, launching its first artificial satellite Explorer I Jan. 31, 1958.
Scientists at Massachusetts Institute of Technology noted the rate of the signals from Sputnik increased as the satellite neared and decreased as the satellite moved away from MINITRACK sites proposed, designed and built by Roger L. Easton and the Naval Research Laboratory. Scientists concluded that if satellites could be tracked based on their distance from ground receivers, then the reverse would also hold true. The location of ground receivers could be tracked by their known distance from the satellite.
Using this concept, the U.S. Navy built the first navigation satellite system, named TRANSIT, to locate submarines. This system had limited capabilities, due in part to the small number of orbiting satellites. Still, it demonstrated the validity of the concept that led to the development of GPS.
In 1964, the Naval Research Laboratory began developing TIMATION satellites to broadcast highly accurate time signals to ground receivers. The first satellite launched in 1967, and the program continued with a second satellite launch in 1969. The knowledge gained from TIMATION was important in the development of GPS. Meanwhile, in 1963, the Aerospace Corporation, under the direction of Dr. Ivan Getting, completed a study for the Department of Defense that proposed a satellite constellation that continuously sent signals to ground receivers, and that could locate fast-moving objects in the air and on the ground.
Work on the proposed satellite navigation system began, and the first developmental NAVSTAR Global Positioning System satellite launched in 1978. Between 1978 and 1985, the U.S. Air Force launched 10 Block I developmental satellites. In 1989, the deployment of the first generation of operational satellites, designated Block II, began and continued until Oct. 1, 1990. One month later, the Air Force began launching the Block IIA satellites. On Dec. 8, 1993, Secretary of Defense Les Aspin announced the achievement of initial operational capability for the 24-satellite GPS. Gen. Joseph W. Ashy, Air Force Space Command commander, declared full operational capability April 27, 1995.
In the two decades since, the Air Force has continued to improve GPS. The newest Block IIF satellites provide improved capabilities. Today, crews of the 2nd and 19th Space Operations Squadrons maintain and control 38 GPS satellites. These advancements, and the largest ever constellation, give GPS unprecedented accuracy.