July 19, 1977 — The First GPS Signal Was Received

Today, GPS feels like an everyday technology, but it took decades to develop. The summer of 1977 marked two major milestones: first, the experimental NTS-2 satellite was launched into orbit, and then its navigation signal was successfully received on Earth for the first time.

On June 23, 1977, the Navigation Technology Satellite 2 (NTS-2) was launched. It was not part of the future GPS constellation but served as a test platform for key technologies, including highly accurate atomic clocks, navigation signals, and satellite positioning techniques.

Less than a month later, on July 19, 1977, engineers at Rockwell Collins successfully received and decoded a GPS signal from NTS-2 for the first time. The experiment demonstrated that satellite navigation could achieve high accuracy in practice and became a major milestone in the development of the NAVSTAR GPS program.

The next step came on February 22, 1978, with the launch of Navstar 1, the first operational Block I GPS satellite. It marked the beginning of the satellite constellation that would eventually become the Global Positioning System.

Deployment continued for nearly two decades. In 1995, the U.S. Department of Defense declared GPS fully operational after the complete satellite constellation had been deployed. Since then, GPS has become a global navigation infrastructure used by billions of people and devices every day.

Sources

• NTS-2 launch (June 23, 1977): Naval Research Laboratory — NRL GPS Bibliography
• First GPS signal received (July 19, 1977): GPS World — First GPS Signal Received 40 Years Ago This Month
• Navstar 1 launch (February 22, 1978): NASA — Navstar 1