Definition
The constellation of U.S. Department of Defense satellites that broadcast the radio signals used by GPS receivers to determine position, velocity, and time. Each Navstar satellite continuously transmits coded signals from medium Earth orbit, and a GPS receiver uses signals from at least four of them to calculate a three-dimensional fix.
Plain English
Navstar satellites are the actual satellites that make GPS work. They circle the Earth and send out signals that your GPS receiver listens to in order to figure out where you are.
Context Anchor
Seen in GPS system descriptions, especially when learning how an aircraft GPS gets position information from the space part of the GPS system.
Derivation
Navstar comes from 'Navigation System with Timing and Ranging.' The name reflects what the system actually does: it uses precise timing of signals from satellites to measure ranges (distances), which the receiver turns into a position.
Why Pilots Care
These satellites supply the signals that enable GPS navigation, allowing precise position fixes during instrument flight when visual references are unavailable.
Analogy
Think of several distant clocks all sending out time-stamped signals. Your GPS compares when those signals arrive and uses the differences to work out where you are.
Intuition Check
Navstar satellites are not general radio or weather satellites. Here, they are the GPS satellites that provide timing and position signals for navigation.
Example Sentence 1
The GPS receiver locked onto signals from several Navstar satellites and produced a position fix within seconds of power-up.
Example Sentence 2
During an instrument approach the pilot monitors signal strength from the Navstar satellites to confirm GPS integrity.