A satellite’s orbital period depends almost entirely on its altitude above Earth’s surface. At the lowest practical orbits, roughly 160 to 2,000 kilometers up, a satellite circles the planet in about 90 to 120 minutes. At geostationary altitude, around 36,000 kilometers, the trip takes exactly one sidereal day, so the satellite appears to hover over a single point on the equator. Between those extremes lies a continuous range of orbital periods, and the physics behind that range explains a great deal about how we use space.
Why Higher Means Slower
The basic relationship is simple: the farther a satellite is from Earth, the longer each orbit takes. Gravity weakens with distance, so a satellite at high altitude does not need to travel as fast to avoid falling back to the surface. A slower speed combined with a much larger circle to trace means the orbital period increases dramatically with altitude. Double the altitude and you more than double the period. Triple it and the period grows even more. This is not a linear slide; it follows a steep curve rooted in the way gravity scales with distance.
That curve means the practical range of satellite orbits is enormous. At one extreme, a satellite skimming just above the atmosphere completes a full revolution in roughly an hour and a half. At the other, satellites positioned tens of thousands of kilometers away take the better part of a day. Altitude can be as low as about 160 kilometers for a low Earth orbit or over 36,000 kilometers for a geostationary orbit.1SAMRIDDHI: A Journal of Physical Sciences, Engineering and Technology. A Comparative Study of Satellite Orbits as Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) Every communications satellite, weather satellite, GPS unit, and space station sits somewhere along this altitude-period curve, chosen for the job it needs to do.
Low Earth Orbit and the 90-Minute Trip
The International Space Station orbits at about 400 kilometers altitude and completes one full revolution every 92 minutes or so. That makes it a good reference point for low Earth orbit, the zone from roughly 160 kilometers up to about 2,000 kilometers. At these altitudes, orbital speeds run around 7.5 to 8 kilometers per second, which is fast enough to cross the entire continental United States in under ten minutes.
Most of the satellites launched in recent years fly in this zone. SpaceX’s Starlink constellation sits at altitudes between roughly 340 and 550 kilometers, giving each satellite an orbital period near 90 to 96 minutes. The Hubble Space Telescope orbits at about 540 kilometers with a period close to 95 minutes. Earth-observation and reconnaissance satellites also tend to favor low Earth orbit because the closer vantage point gives sharper imagery.
The speed at which these satellites move has a curious consequence for anyone aboard: the crew of the ISS witnesses roughly 16 sunrises and 16 sunsets every 24 hours. That relentless light-dark cycling creates real problems for human biology. Astronauts on Space Shuttle missions experienced circadian rhythm disruptions, reduced body-temperature rhythms, and measurable drops in cognitive performance tied to the mismatch between their scheduled rest periods and the rapid alternation of light and dark aboard the spacecraft.2PubMed. Sleep, performance, circadian rhythms, and light-dark cycles during two space shuttle flights The ISS now uses tunable LED lighting designed to help regulate crew sleep cycles, but the fundamental challenge of living on a 90-minute “day” persists.
Medium Earth Orbit and Navigation Satellites
Between low Earth orbit and the geostationary belt sits medium Earth orbit, generally defined as altitudes from about 2,000 to 35,786 kilometers. The satellites most people interact with every day without realizing it occupy this zone: the GPS constellation flies at roughly 20,200 kilometers altitude, giving each satellite an orbital period of about 12 hours. That means a GPS satellite completes exactly two orbits per sidereal day, a deliberate design choice that places each satellite over the same ground track once every day and simplifies the geometry needed to calculate your position.
Other navigation constellations operate at similar altitudes. Europe’s Galileo system orbits near 23,222 kilometers with a period of about 14 hours. Russia’s GLONASS flies at approximately 19,100 kilometers with a period just under 11 hours and 16 minutes. China’s BeiDou includes satellites in both medium Earth orbit and geostationary orbit. In all cases, the altitude was chosen to balance coverage area, signal travel time, and the number of satellites needed to guarantee that at least four are visible from any point on the ground at any given moment.
Geostationary Orbit and the Stationary Illusion
At an altitude of about 35,786 kilometers above the equator, a satellite’s orbital period matches Earth’s rotation exactly. From the ground, the satellite appears to hang motionless in the sky. This is geostationary orbit, and it has been one of the most commercially valuable pieces of real estate in space since the 1960s. Weather satellites like those in the GOES series, direct-broadcast television satellites, and many communications relays sit in this band.
The “stationary” part is an illusion, of course. The satellite is moving at about 3.07 kilometers per second, tracing a circle of roughly 265,000 kilometers in circumference. It only appears fixed because it is keeping pace with the ground beneath it. And maintaining that illusion takes work. Natural forces, including gravitational tugs from the Sun and Moon, irregularities in Earth’s own gravitational field, and solar radiation pressure, constantly nudge the satellite away from its assigned longitude.3Acta Astronautica. The scientific and technical aspects of the geostationary orbit Left alone, a geostationary satellite would slowly drift east or west and tilt its orbital plane, eventually wandering far from its intended position.
Station-Keeping and Why Geostationary Satellites Need Constant Correction
To stay on station, geostationary satellites perform regular small thruster firings known as station-keeping maneuvers. These fall into two categories: east-west corrections to hold the satellite at its assigned longitude, and north-south corrections to keep the orbital plane aligned with the equator. North-south corrections consume the lion’s share of fuel because the gravitational pull of the Sun and Moon steadily tilts the orbit. The combined velocity change needed for both types of correction runs on the order of tens of meters per second per year.4Progress in Astronautics and Rocketry. Synchronous Satellite Station-Keeping
The practical consequence is that a geostationary satellite’s usable lifespan is almost always limited by fuel rather than by hardware failure. Once the station-keeping propellant runs out, the satellite can no longer hold position and must be moved to a “graveyard orbit” a few hundred kilometers above the geostationary belt. Modern electric propulsion systems have stretched fuel budgets considerably compared to older chemical thrusters, pushing operational lifetimes of some geostationary satellites past 20 years.
One engineering concern is what happens if ground controllers lose contact with the satellite. Research into station-keeping robustness has shown that pre-loading east-west maneuvers for automatic onboard execution significantly extends the window during which a satellite can stay within its assigned position box without ground intervention. Shortening the cycle between maneuvers also helps, roughly doubling the time a satellite can maintain its tighter position window compared to longer cycles.5Journal of Astronomy and Space Sciences. Geostationary Satellite Station Keeping Robustness to Loss of Ground Control These backup strategies matter because a drifting geostationary satellite can interfere with its neighbors, and slots in the geostationary arc are internationally coordinated resources.
Atmospheric Drag and Why Low Orbits Shrink Over Time
The period of a satellite in low Earth orbit is not perfectly stable. At altitudes below about 600 to 800 kilometers, the outermost wisps of Earth’s atmosphere produce measurable drag. The effect works the same way air resistance slows a car: molecules collide with the satellite’s surface, transferring momentum and gradually bleeding off orbital energy. As the satellite loses energy, it drops to a slightly lower orbit, where the atmosphere is denser, which increases drag further, creating a feedback loop that accelerates the decay.6Acta Astronautica. Decay time estimate for LEO spacecraft
How quickly this happens depends on a satellite’s mass, its cross-sectional area, and how active the Sun is at the time. During solar maximum, increased ultraviolet radiation heats the upper atmosphere, causing it to expand and pushing denser air to higher altitudes. This dramatically increases drag. The effect is large enough that it influences how long pieces of space debris remain in orbit; debris tracked during solar maximum periods loses altitude markedly faster than the same objects during solar minimum.7arXiv. Deciphering Solar Cycle Influence on Long-Term Orbital Deterioration of Space Debris in LEO and MEO orbits The ISS, for instance, must periodically boost its altitude using onboard thrusters or visiting cargo vehicles to counteract drag. Without those boosts, it would reenter the atmosphere within a few years.
At higher altitudes, atmospheric drag becomes negligible. A satellite at 1,000 kilometers might take centuries to decay naturally, and anything above about 1,500 kilometers can remain in orbit for thousands of years without correction. Geostationary satellites experience essentially zero atmospheric drag.
How Earth’s Shape Tweaks Orbital Timing
Earth is not a perfect sphere. It bulges at the equator and is slightly flattened at the poles, and it has lumpy mass concentrations beneath the surface. These asymmetries affect satellite orbits in subtle but important ways. The equatorial bulge, in particular, causes the orbital plane of a satellite to slowly rotate, a phenomenon called nodal precession. It also shifts the point in each orbit where the satellite is closest to Earth, causing that point to migrate around the orbit over time.
These effects are altitude-dependent and inclination-dependent. Early satellite tracking efforts recognized that precise measurement of a satellite’s orbital period could actually be used in reverse to map Earth’s gravitational field. The relationship between orbital period variations and Earth’s oblateness was formalized in the late 1950s.8PubMed. Earth Oblateness in Terms of Satellite Orbital Periods Today, the same principle underpins an entire class of orbits. Sun-synchronous orbits, for example, are chosen so that the nodal precession caused by Earth’s bulge rotates the orbital plane by exactly one degree per day, matching the rate at which Earth moves around the Sun. This keeps the satellite crossing any given latitude at the same local solar time year-round, which is invaluable for consistent Earth-observation lighting.
For the typical reader wondering about orbital periods, the practical takeaway is that two satellites at the same altitude but different inclinations will not have exactly the same period once these gravitational effects are accounted for. The differences are small, typically seconds rather than minutes, but they matter for precision applications like GPS timing and satellite rendezvous.
Orbits That Are Not Circles
Everything discussed so far assumes roughly circular orbits, but many satellites follow elliptical paths. An elliptical orbit has a low point (perigee) and a high point (apogee), and the satellite’s speed varies constantly, moving fastest at perigee and slowest at apogee. The orbital period of an elliptical orbit depends on the size of the ellipse, specifically the length of its longest axis, not on how circular or elongated the shape is. Two orbits with the same semi-major axis have the same period regardless of eccentricity.
Highly elliptical orbits are used when you want a satellite to spend most of its time over a particular region of the globe. Russia’s Molniya orbit, for example, has a period of about 12 hours, with an apogee over the Northern Hemisphere so high that the satellite lingers there for roughly eight of those hours before swooping quickly through perigee over the Southern Hemisphere. This design provides coverage to high-latitude regions that geostationary satellites cannot serve well because the geostationary belt sits directly above the equator and is visible only at low elevation angles from places like Moscow or northern Canada.
Tundra orbits take the same idea further with a 24-hour period and extreme eccentricity, keeping the satellite over a chosen region for most of each day. These orbits require active management because gravitational perturbations from Earth’s oblateness and lunar-solar gravity change the orbit’s orientation over time, but they fill a genuine coverage gap that no circular orbit can address.
Beyond Earth Orbit Entirely
Some spacecraft associated with Earth are not orbiting the planet at all in the traditional sense. The James Webb Space Telescope, for instance, sits at the second Lagrange point (L2), a gravitational balance point about 1.5 million kilometers from Earth on the side away from the Sun. Rather than orbiting Earth, JWST follows a roughly 180-day loop around L2 while the L2 point itself orbits the Sun in lockstep with Earth.9Publications of the Astronomical Society of the Pacific. The Design, Verification, and Performance of the James Webb Space Telescope In a sense, JWST orbits the Sun with a one-year period, just like Earth does, while wobbling around L2 on a much shorter cycle. Asking “how long does it take to orbit Earth” does not quite apply to JWST, and that is by design: L2 provides a stable thermal environment and an unobstructed view of deep space that no Earth orbit could match.
Several other observatories have used L2 or its sunward counterpart L1, including the Solar and Heliospheric Observatory (SOHO) at L1 and the former Planck and Herschel missions at L2. These Lagrange-point missions illustrate that the question of orbital period becomes genuinely more complicated once you step outside the neat hierarchy of low, medium, and geostationary Earth orbits.
How Orbital Period Shapes Everyday Technology
The choice of orbital period is not academic; it directly determines what a satellite can do and how many you need. A low-orbit imaging satellite with a 90-minute period can revisit any given spot on the ground roughly every few days, depending on its specific orbit and the width of its camera’s field of view. Constellations like Planet Labs’ fleet of small satellites compensate for the narrow view of each pass by fielding hundreds of spacecraft, ensuring daily global coverage.
GPS satellites with their 12-hour period are spaced so that at least four are above the horizon from any point on Earth at any time. The 12-hour period means each satellite’s ground track repeats daily, which simplifies system design and makes signal-availability patterns predictable. If those satellites were in low orbit instead, you would need many more of them to achieve the same continuous coverage, and the faster motion would complicate the precision timing on which GPS depends.
Geostationary satellites with their 24-hour period are irreplaceable for applications that need a fixed point in the sky. A home satellite dish pointed at a geostationary transponder never needs to move. A weather satellite watching a hurricane from geostationary altitude can stare at the same patch of ocean continuously rather than catching a brief glimpse every 90 minutes. The trade-off is distance: geostationary altitude means weaker signals and a communication latency of about 240 milliseconds for a round trip, which is noticeable during a phone call and unacceptable for some real-time applications. Low-orbit constellations like Starlink accept the complexity of thousands of fast-moving satellites in exchange for latencies closer to 20 to 40 milliseconds.
In short, there is no single answer to how long a satellite takes to orbit Earth. The answer is engineered, not discovered. Mission designers pick the altitude and therefore the period that best fits what they need the satellite to do, then build around the constraints that choice imposes.