Plain English Meaning

These are the names for different versions of GPS satellites that have been launched over the years. Each version improved on the one before it, with better clocks, stronger signals, and new features. Together they made up the working GPS constellation that pilots have relied on for navigation.

Full Definition

Successive generations of GPS satellites built by the U.S. Department of Defense and operated by the U.S. Space Force as part of the GPS satellite constellation. Block II was the first operational generation, Block IIA added improved data storage and longer autonomous operation, Block IIR (Replenishment) provided on-orbit replacements with better atomic clocks and inter-satellite ranging, and Block IIR-M (Modernized) added a second civil signal (L2C) and new military M-code signals.

Context Anchor

Seen in GPS system descriptions, especially when explaining the satellite portion of GPS.