Definition
The constellation of orbiting spacecraft that broadcast precisely timed radio signals used by GPS receivers on the ground, in aircraft, and at sea to determine position, velocity, and time. The system is operated by the U.S. Space Force and consists of at least 24 active satellites arranged in six orbital planes at roughly 12,550 nautical miles altitude, ensuring that several satellites are in view from any point on Earth at any time.
Plain English
These are the spacecraft circling the Earth that constantly send out signals telling receivers where they are and what time it is. A GPS receiver listens to several of them at once and uses that information to work out its own location.
Context Anchor
Seen in GPS navigation, instrument procedures, and NextGen discussions about how aircraft position is determined.
Derivation
GPS stands for Global Positioning System. 'Satellite' comes from the Latin 'satelles,' meaning attendant or companion -- something that travels alongside a larger body. In this case, the satellites are companions of Earth, orbiting it continuously.
Why Pilots Care
They provide the foundation for area navigation and GPS approaches, allowing precise guidance independent of ground-based navigation aids.
Grounding Statement
A GPS receiver in the aircraft does not know where it is by itself; it works out its position by comparing signals from multiple GPS satellites overhead.
Intuition Check
GPS satellites do not watch or track your airplane. They broadcast signals, and the receiver in the aircraft uses those signals to calculate its own position.
Example Sentence 1
The receiver lost lock on two GPS satellites as the aircraft passed through the canyon, and the position display flagged degraded accuracy.
Example Sentence 2
Before beginning the GPS approach the pilot verifies that enough satellites are in view to meet the required navigation performance.