[2] Global Positioning System (GPS) was developed by the U.S. Department of Defense to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces.

Since its implementation, GPS has also become an integral asset in numerous civilian applications and industries around the globe, including recreational used (e.g., boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying.

They had S-band communications for control and telemetry and Ultra high frequency (UHF) cross-link between spacecraft.

They were manufactured by Rockwell Space Systems, were 5.3 meters across with solar panels deployed, and had a design life expectancy of 5 years.

[2] It broadcast the PRN 04 signal in the GPS demonstration constellation, and was retired from service on 17 July 1985.