The GPS Constellation, Live
GPS is the American satellite navigation system, operated by the US Space Force. Its satellites sit far higher than the broadband fleets — around 20,200 km up — and AstroSat renders the whole constellation live in 3D.
The numbers right now
As of August 3, 2026, AstroSat is tracking 73 satellites in this constellation — about 0.4% of every active satellite currently tracked, out of 18,436 active satellites in total.
This is a live catalogue count, not a fixed design figure: it includes retired and spare satellites that are still in orbit and still being tracked, which is why it can differ from the “official” constellation size. Refreshed automatically from Space-Track every two hours.
How GPS actually works
You need four satellites
Three give you a position in space; the fourth solves for the clock error in your receiver. That is why a fix needs four satellites in view, not three.
Twice around, once a day
Each GPS satellite orbits at about 20,200 km with a period close to 11 hours 58 minutes — so it laps Earth twice for every rotation, passing over the same spot at the same time each day.
Six orbital planes
The satellites are spread across six planes inclined 55° to the equator, arranged so at least four are above the horizon from anywhere on Earth at any time.
Atomic clocks in orbit
Each satellite carries atomic clocks, and the timing has to account for relativity — clocks up there tick faster than clocks on the ground, and uncorrected that error would break positioning within minutes.
GPS — formally NAVSTAR GPS — has been operational since 1993 and is the reason satellite navigation became ordinary. The constellation is designed around a baseline of 24 operational satellites, though more are usually flying: newer blocks are launched before older ones are retired, and decommissioned satellites often stay in orbit as tracked objects long after they stop broadcasting. That is why a live catalogue count is higher than the "24 satellites" figure most articles quote — the number below counts every GPS-series object currently carrying a fresh orbital element set, working or not. GPS sits in medium Earth orbit, a compromise: high enough that each satellite sees a huge area of the planet, low enough that the signal still arrives usable. Galileo, GLONASS and BeiDou all use the same broad approach at similar altitudes, and most modern receivers listen to several of them at once.
Frequently asked questions
How many GPS satellites are there?
The system is designed around 24 operational satellites, but more are usually in orbit at once — replacements launch before older ones retire, and retired satellites remain tracked. The live count on this page reflects every GPS-series object currently being tracked.
How high do GPS satellites orbit?
About 20,200 km up, in medium Earth orbit — roughly 50 times higher than the International Space Station and far above Starlink.
Why do you need four satellites for a fix?
Three satellites pin down your position in three dimensions, but your receiver's clock is not accurate enough on its own. The fourth satellite lets the receiver solve for its own clock error at the same time.
Can you see GPS satellites from the ground?
Not with the naked eye. At 20,200 km they are far too distant and faint — unlike the ISS or a fresh Starlink batch in low Earth orbit.