Target Pillar: Earth Observation and Satellites
Introduction
Not all satellites live in the same neighborhood. A weather satellite that seems to hover permanently over the Pacific and a Starlink satellite zipping overhead in a few minutes are both “in orbit,” but they’re doing fundamentally different jobs from fundamentally different altitudes. The choice of orbit isn’t arbitrary — it’s one of the first and most consequential decisions in designing any satellite mission, because it determines coverage, latency, cost, and even how long the satellite will last.
The two orbits people run into most often are low Earth orbit (LEO) and geostationary orbit (GEO). Understanding the tradeoff between them explains a lot about how modern satellite internet, weather forecasting, GPS, and TV broadcasting actually work.
Low Earth Orbit: Close, Fast, and Crowded
LEO covers roughly 160 to 2,000 kilometers (about 100 to 1,200 miles) above Earth’s surface, according to NASA’s Earthdata orbit guide. That’s close enough that satellites here move fast just to avoid falling back down — around 17,000 mph, completing a full trip around the planet in roughly 90 minutes to two hours.
That speed has a practical consequence: a single LEO satellite only stays above any given spot on Earth for a few minutes before disappearing over the horizon. To provide continuous coverage of one location, you need many satellites working in relay, which is exactly why LEO satellite internet services like Starlink require thousands of satellites rather than a handful.
The upside is proximity. Because LEO satellites are so close to Earth compared to other orbits, signals travel a much shorter round trip — this is the main reason Starlink and similar services can offer internet latency closer to cable broadband than older satellite internet ever managed. Proximity also makes LEO the preferred altitude for Earth-imaging satellites, since being closer to the ground means sharper images without needing enormous optics. According to aerospace industry analysis, more than half of all operational satellites currently sit in LEO, making it the single most crowded orbital regime around Earth.
The International Space Station itself orbits in LEO, at roughly 250 miles up — which is also why it circles the planet about 16 times a day.
Geostationary Orbit: Far, Slow (Relatively), and Fixed
GEO sits at a very specific altitude: 35,786 kilometers (about 22,236 miles), according to the European Space Agency. At exactly that height, directly above the equator, a satellite’s orbital period matches Earth’s rotation almost perfectly — one full orbit takes 23 hours, 56 minutes, and 4 seconds, the length of a sidereal day. The result: from the ground, the satellite appears to hang motionless in the same patch of sky, permanently.
That fixed position is GEO’s entire appeal. A ground antenna pointed at a geostationary satellite never needs to move or track — it just stares at one spot forever. This is why satellite TV dishes are bolted in place rather than motorized, and why weather satellites like NOAA’s GOES series can stare continuously at the same third of the planet, tracking a hurricane’s entire development without ever losing the view.
GEO satellites also see an enormous amount of Earth at once — a single one can cover roughly a third of the globe, which is why as few as three well-spaced geostationary satellites can provide near-total coverage outside the polar regions, per ESA.
The tradeoff is distance-related latency. A round trip to GEO and back takes a radio signal roughly half a second — barely noticeable for broadcast TV, but enough to be irritating in a live phone call and genuinely disruptive for anything requiring fast back-and-forth communication, which is one reason GEO was never a serious contender for consumer internet the way LEO constellations are now.
Why Not Just Pick One?
Because the physics reward different altitudes for different jobs, and no single orbit does everything well:
Need constant coverage of one region with no satellite handoffs? GEO wins — weather monitoring, TV broadcast, and regional communications relay all favor it.
Need low latency or high-resolution imaging? LEO wins — internet constellations and Earth-observation imaging satellites both favor it.
Need to watch the poles? Neither GEO nor standard LEO works particularly well. GEO satellites sit over the equator and view polar regions at a useless, glancing angle, while a single LEO satellite’s coverage of any one spot is too brief. This is part of why polar-orbiting satellites — a variant of LEO that crosses over both poles on each pass — exist as their own category, and why Russia historically used a specialized, highly elliptical path called a Molniya orbit specifically to loiter over high northern latitudes, as NASA’s Earth Observatory explains.
The Middle Ground: MEO
Sitting between the two is medium Earth orbit (MEO), roughly 2,000 to 35,500 kilometers up. This is prime real estate for GPS and other navigation satellites — high enough that a modest-sized constellation can cover the globe, but low enough to avoid GEO’s half-second latency penalty and orbital slot competition. Europe’s Galileo navigation system, for instance, orbits at roughly 23,222 km, comfortably inside the MEO band, according to NASA Earthdata. GPS satellites orbit at a similar altitude for the same reasons — enough coverage per satellite to keep the constellation size manageable, without the round-trip lag that would make real-time positioning sluggish.
What This Means for the Satellites You Actually Use
Next time you watch a hurricane forecast built from a satellite image that never seems to blink, that’s GEO. Next time your phone streams video over Starlink from a rural cabin, that’s LEO — and specifically a very low, densely packed slice of it, since Starlink satellites orbit at only around 340–570 km, near the bottom of the LEO range, trading satellite lifespan and coverage-per-satellite for lower latency and easier deorbiting at end of life. And every time your phone quietly calculates its own position in the background, that’s MEO, running the GPS system described here.
None of these orbits is “better” in the abstract — each is a deliberate engineering tradeoff between coverage, latency, cost, and satellite count, chosen to match the job the satellite actually needs to do.
Frequently Asked Questions
Is the ISS in geostationary orbit?
No — the International Space Station orbits in low Earth orbit, about 250 miles up. If it were in GEO, it would need to sit far higher and directly over the equator, and astronauts would experience much higher radiation exposure outside the partial protection of Earth’s inner magnetosphere.
Why do geostationary satellites need to be over the equator?
Because a stable geostationary orbit requires the satellite’s orbital plane to align with Earth’s equatorial plane. A satellite in a similarly high orbit but tilted relative to the equator is technically “geosynchronous” (matching Earth’s rotation period) but traces a figure-eight path in the sky rather than staying fixed — useful for some applications, but not the same as true geostationary.
How long do satellites last in each orbit?
LEO satellites, especially at very low altitudes, experience atmospheric drag that eventually pulls them back to Earth, often within 5–15 years without active reboosting — which is actually a feature for constellations like Starlink, since it guarantees dead satellites deorbit rather than becoming permanent debris. GEO satellites, at much higher altitude with negligible drag, can remain operational for 15 years or more and, once retired, are typically nudged into a “graveyard orbit” slightly above GEO rather than deorbited.
Why does Starlink need thousands of satellites if GPS only needs about 30?
Because GPS satellites sit in MEO, far higher than Starlink, so each one covers a huge swath of Earth and only needs to broadcast a timing signal, not carry two-way internet traffic. Starlink sits deep in LEO for low latency, meaning each satellite covers a much smaller area and moves out of range within minutes — so thousands are needed to keep continuous broadband coverage available everywhere.