What a GPS satellite does
A GPS satellite broadcasts a time signal. A receiver that can see at least 4 satellites at once can work out where it is and what time it is. That's why the headline count isn't the number a user needs: the system has to be big enough that four are above the horizon from anywhere on Earth, and the 37 that GCAT lists as active or possibly transmitting is more than that, as the notes at the end of this page explain. The count also depends on what you call a GPS satellite. GCAT names 75 satellites GPS in its launch log, starting on July 14, 1983. The 7 earlier ones, launched from 1978 to 1981, were named Navstar and aren't counted. 37 of the 75 are still listed as active, which leaves 38 that have been retired.
From Navstar to a working system
The first Block I satellite launched in 1978. The first of the operational Block II satellites followed on February 14, 1989, and the launch log shows the build-out in the years after: six GPS launches in each of 1992 and 1993. Wikipedia gives 1993 for initial operational capability, declared in December, and April 1995 for full operational capability.
The three generations still flying
| Block | Active satellites | Launched |
|---|---|---|
| Block IIF | 12 | 2010 to 2016 |
| Block III | 10 | 2018 to 2026 |
| Block IIR | 15 | 1997 to 2009 |
Block IIR satellites are the oldest of the three still listed as active. Block IIF followed, and Block III is the newest, with the latest launch on April 21, 2026.
How GPS compares with other navigation systems
GLONASS satellites are catalogued under Kosmos names, so they can't be counted separately here. These counts include satellites that are active or may still be transmitting, which is more than the number a system needs to work.
When they were launched
The day the error shrank
Civilian receivers weren't always as accurate as the ones in a phone. The US military deliberately degraded the public signal, a policy called selective availability, and switched it off on May 1, 2000. Wikipedia gives the typical error it added as about 50 meters horizontally and 100 meters vertically. On September 19, 2007 the US Department of Defense said the next generation, GPS III, wouldn't be able to do it at all, and the capability was gone for good.
Three generations still flying
The active satellites come from three blocks. Block IIR has 15 satellites launched between 1997 and 2009, Block IIF has 12 launched 2010 to 2016, and Block III has 10. The oldest active satellite launched in 1997, and the median age of the active group is 13 years. The first GPS III satellite launched on December 23, 2018 with a design life of 15 years, according to Wikipedia. It took until April 21, 2026 to launch the tenth, just over 7 years later, a pace of about 1.4 a year. Wikipedia lists nine of the ten as operational, while GCAT lists all ten as active. The two counts follow different rules: GCAT lists what's active or possibly transmitting.
What the count hides
37 is a catalogue number. It includes satellites that are active or may still be transmitting, which is more than the system needs to work. It leaves out GLONASS entirely, because Russia's satellites are catalogued under Kosmos names and can't be separated. The comparison below needs the same care. ESA describes a Galileo constellation of 28 satellites, while GCAT lists 33 under the Galileo name. GCAT lists 56 BeiDou satellites, against the 30 of the global BeiDou-3 system, because it also holds the older regional satellites.
Three systems, one sky
Galileo, Europe's system, flies at 23,222 kilometers at an inclination of 56 degrees, and its initial services began on December 15, 2016. China's BeiDou launched its first satellite on October 30, 2000, started regional service in December 2012 and was completed by the launch described on the 2020 page. Its 30 BeiDou-3 satellites are split into 24 in medium Earth orbit, 3 in inclined geosynchronous orbit and 3 in geostationary orbit, the last of which sit on the arc described on the geostationary page. GPS, with 37 active, is owned by the United States, and the United States page puts it in the context of everything else the country flies. China's side is on the China page.
Launches by decade
The log has 9 GPS launches in the 1980s, 26 in the 1990s, 18 in the 2000s, 14 in the 2010s and 8 so far in the 2020s. The busiest decade was the 1990s. The years since 2010 with no GPS launch at all were 2017 and 2022. A constellation that's replenished slowly stays old, which the next figures show.
Block III launches by year run 2018, 2019, 2020, 2021, 2023, 2024, 2025, 2026, with two in each of the busiest years. Block IIF, by comparison, was finished in 12 satellites over 6 years.
27 of the 37 active satellites, 73%, belong to the two older blocks, IIR and IIF. The newest IIR satellite launched in 2009, so every one of the 15 is at least 17 years old as of 2026. Block III is the only group still being added to. The satellite count shows where navigation sits among the other jobs satellites do.
What to watch
As of October 17, 2026, the most recent GPS launch in the log is April 21, 2026, and there have been 2 in 2026. The Block IIR group is the oldest and the first to retire. If launches stay at one or two a year, the count of 37 will drift down as they do. The satellites and the launches that carry them are tracked together on the satellites page.