The History of GPS Tracking

The United States Department of Defense developed the Global Positioning System. GPS satellites broadcast two signals, one for civilians and one for military use. The system has four active-tracking and five passive-tracking ground receiver stations around the world.

Predecessors

The Navy system Transit was two-dimensional. The Navy system Timation had atomic clocks. The Air Force System 621B provided three-dimensional information. The Department of Defense created a steering committee in 1968 from the Navy, Air Force and Army to coordinate efforts.

First GPS

The first satellite for the Navigation System with Timing and Ranging Global Positioning System was a refurbished Timation satellite, launched in 1974. The first true GPS satellites, known as Block Is, launched in 1978.

Modern GPS

The first Block II satellite launched in 1989. Block IIs have an improved security system and radiation-hardened electronics. President Ronald Reagan ordered GPS made available for civilian national and international use, and commercial GPS equipment for surveying appeared on the market in the mid-1980s. The Persian Gulf crisis in 1990-91 was the first military test of the system. In 2000, the military ended its practice of fuzzing the signal.

References

• Rand Corporation: GPS History, Chronology and Budgets
• NASA Mission and Spacecraft Library: Global Positioning System
• The National Academy of Sciences: GPS:The Role of Atomic Clocks
• "Time" magazine; A Brief History of GPS; Randy James; May 26, 2009