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How many GPS satellites are there? Height and how GPS works

The U.S. Space Force counted 32 operational GPS satellites in April 2026, about 20,200 km up. How GPS works, and how Galileo, GLONASS and BeiDou compare.

By the WatchSat editors · · 8 min read

A JPL chart of ripples in the ionosphere recorded by GPS, GLONASS, Galileo and BeiDou signals after the January 2022 Hunga Tonga eruption, spreading out from the volcano across the Pacific
Image: NASA/JPL-Caltech/GDGPS · Public domain

The U.S. Space Force counted 32 operational GPS satellites in April 2026. Its Space Systems Command gave that figure on April 21, the day the last satellite of the GPS III generation, space vehicle 10 or SV10, launched on a SpaceX Falcon 9. Older answers to how many GPS satellites there are say 31, which was right when they were written. GPS.gov listed 31 operational satellites as of July 3, 2023. The Space Force said the constellation reached 31 active satellites on January 22, 2025, when GPS III SV-07 was set healthy, a status that clears receivers to use a satellite's signal.

The 32 also counted SV10 from launch day, before the satellite had finished its checkout in orbit. Live status comes from the U.S. Coast Guard's Navigation Center, whose September 2026 advisories listed two satellites, PRN 11 and PRN 25, as unusable until further notice. A PRN, short for pseudorandom noise, is the code number receivers use to tell one satellite's signal from another's.

GPS was designed around 24 slots, four in each of six orbital planes, the separate rings around Earth that the satellites follow. GPS.gov describes a commitment to keep at least 24 operational satellites available 95 percent of the time. In June 2011 three of the slots were expanded and six satellites repositioned, which made three extra satellites part of the baseline. Satellites beyond those fly as spares, so coverage holds when one is serviced or retired.

At the April launch, Spaceflight Now reported a fleet of 38 GPS spacecraft in medium Earth orbit, the middle band of altitudes between low orbits and the geostationary belt. Of the 38, 32 were active and the rest in reserve. The Space Force's 2nd Navigation Warfare Squadron flies them from Schriever Space Force Base in Colorado.

Our October 8 snapshot of CelesTrak's list of active satellites, the data behind our live satellite map, contains 40 GPS satellites, all under the catalog name NAVSTAR. The list doesn't separate spares from working satellites, so 40 is a count of listed objects, not of operational GPS satellites.

How does GPS work?

A GPS receiver finds its position by timing radio signals from satellites that carry atomic clocks. In NASA's explanation, multiplying each signal's travel time by the speed of light gives the distance to that satellite. Once a receiver knows its distance from four or more satellites, it knows where you are, usually to within a few yards.

The delays are short. By our arithmetic, a signal from a satellite straight overhead arrives about 67.3 milliseconds after it leaves, and one from a satellite on the horizon, 25,783 km away, takes about 86.0 milliseconds.

Three distances would pin down a point in space if the receiver's clock were perfect. Finding a point from its distances to known points is called trilateration, and GPS.gov's trilateration tutorial uses three satellites to show the geometry. The tutorial calls the exercise simplified, though, and says it isn't exactly how GPS works. The catch is the receiver's own clock, which is far less accurate than the atomic clocks in orbit. A timing error of one microsecond becomes about 300 m of error in distance. So the receiver treats its clock error as a fourth unknown beside its three coordinates, and four satellites give it the four measurements it needs. In practice it has many more than four to choose from, as our counts below show.

How high are GPS satellites?

GPS satellites orbit about 20,200 km (12,550 miles) above Earth, in medium Earth orbit, and each circles the planet twice a day, according to GPS.gov. Our snapshot agrees. Of our 40, the 38 in the main shell, the height band where nearly all of them fly, have a median altitude of 20,182 km (12,541 miles). Like CelesTrak's catalog, we measure altitude above Earth's equatorial radius of 6,378 km. The orbits of those 38 are tilted about 55 degrees to the equator, an angle called the inclination. The other two, NAVSTAR 52 at 21,018 km and NAVSTAR 53 at 20,902 km, orbit higher, and both are older satellites.

One lap takes 11 hours 58.0 minutes in our data, half of a sidereal day. That's the 23 hours 56 minutes Earth takes to spin once relative to the stars. It's a few minutes shorter than the solar day our clocks keep, because the solar day also has to make up for Earth's movement around the Sun. Because two orbits fit into one turn of the planet, each satellite repeats its path over the ground every day. The mismatch between the two kinds of day means it passes over a given spot about four minutes earlier each day.

The six orbital planes show up in the data as well. Each orbit crosses the equator heading north at a point called the ascending node. The direction of that crossing, measured against the stars, is the right ascension of the ascending node, or RAAN, and satellites in the same plane share it. When we sort the 40 NAVSTAR satellites by RAAN, they fall into six clusters spaced 55 to 65 degrees apart, close to the even 60 degrees of the design. Each cluster holds five to eight satellites. Our page for NAVSTAR 86, the catalog name for SV10, shows where the newest one is in its plane right now.

GPS, Galileo, GLONASS and BeiDou in our data

In the same October 8 snapshot, the four global navigation systems have 157 satellites between them, made up of 40 GPS, 29 GLONASS, 32 Galileo and 56 BeiDou. They're a small slice of everything in orbit. We worked out each group's typical orbit from its two-line element sets, or TLEs, the compact blocks of orbit numbers explained in our guide to TLEs.

System Run by In our snapshot Median altitude Median inclination Orbital period
GLONASS Russia 29 19,130 km 65.0° 11 h 15.7 min
GPS United States 40 20,182 km 54.9° 11 h 58.0 min
BeiDou (medium orbit) China 33 21,528 km 54.4° 12 h 53.2 min
Galileo European Union 32 23,222 km 55.6° 14 h 4.7 min
BeiDou (geosynchronous) China 23 35,787 km 0.4° to 62.6° 23 h 56.1 min

Every system has more satellites on the list than its design calls for. Galileo was designed as 30 satellites, 24 active and six spares, in three planes, according to ESA. In our data the Galileo satellites sit at 23,222 km, exactly the height ESA gives, except for two early ones, Galileo 5 and 6. Those two fly an eccentric, or stretched-out, orbit that swings between about 16,870 and 26,320 km.

In 2022 the China Satellite Navigation Office described BeiDou-3 to a UN-hosted committee as 24 satellites in medium orbit, three geostationary and three in inclined geosynchronous orbits. A geosynchronous satellite circles once for every turn of the Earth. A geostationary one does it over the equator, so it seems to hang still in the sky, while an inclined one is tilted and swings north and south. Our 56 BeiDou objects include 17 from the older BeiDou-2 system and four experimental BeiDou-3S satellites, alongside 35 BeiDou-3. Russia's GLONASS was planned as 24 satellites, according to a 2019 working paper filed with ICAO, the UN's civil aviation agency, and our list has 29.

Japan's QZSS and India's NavIC, which aren't among the four global systems, have six and eight satellites in our snapshot, all in geosynchronous orbits about 35,787 km up. They bring the navigation total to 171. Our navigation satellites page shows the four global systems, 157 satellites, on a live globe, and lists QZSS and NavIC among other satellites. An earlier version of that page counted 174. Some Galileo satellites have catalog names starting with GSAT, and our rule for spotting them also caught 17 of India's GSAT communications satellites. We've fixed it.

To see what a receiver on the ground gets, we computed the positions of all 157 every five minutes for 24 hours from midday UTC on October 10. Then we counted those more than 10 degrees above the horizon at six cities. Because the list holds more than the operational satellites, these counts are upper limits. GPS alone gave between 7 and 18 at any moment, averaging 11 to 13 depending on the city. With all four systems, Ann Arbor, Michigan, had 32 to 48 in view and Tromsø, in northern Norway, 40 to 58. Singapore had the most, 61 to 74, with BeiDou alone averaging 33.8 there because its geosynchronous satellites sit over Asia and the Pacific.

GLONASS, whose orbits are tilted more steeply, did better in the far north. It averaged 9.9 satellites over Tromsø against 8.1 over Quito, on the equator, while GPS was nearly level at 13.0 and 12.7.

GPS also has the oldest fleet of the four. Twenty of our 40 NAVSTAR satellites, half the list, launched in 2011 or earlier, and the oldest, NAVSTAR 43, has been in orbit since 1997, 29 years. On average a GPS satellite on the list is 14.8 years old, against 9.9 years for GLONASS, 8.7 for Galileo and 9.5 for BeiDou. The newest arrivals are there too. All ten GPS III satellites, launched from 2018 to 2026, are on the list, and so are two GLONASS-K1 satellites launched this year, including COSMOS 2619.

What's next for GPS and Galileo

SV10 was the last of ten GPS III satellites, and all four launched since December 2024 flew on SpaceX's Falcon 9. The first of those, SV07, had been moved off United Launch Alliance's Vulcan for an expedited launch, Spaceflight Now reported. The next generation, GPS IIIF, is in production at Lockheed Martin. On April 29, 2026, the company completed core mate, an assembly milestone, on the first IIIF satellite, SV11, but the first IIIF launch has no firm date.

Galileo's next pair is planned for the end of 2026 on Ariane 6, according to ESA, which said on July 24, 2026, that four first-generation satellites remain to be launched. Launch Library, the public launch database that feeds our launch schedule, carries that flight with a placeholder date of December 31. The same feed lists India's next NavIC satellite, NVS-03, for no earlier than October 31, with the date still marked to be determined.

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