How Satellites Work: Orbits, Signals and Global Connectivity Explained

A satellite is simply an object moving fast enough sideways that it falls around the Earth instead of into it. Orbital mechanics describes this balance between gravity pulling a satellite down and its velocity carrying it forward; the result is a curved path that repeats, called an orbit. The altitude of that orbit sets the orbital period — the time for one full trip around the planet — according to the relationship that period grows with the square root of the cube of the orbital radius, as described by eoPortal, the European Space Agency-linked satellite reference site.

Three orbital bands, three different jobs

Engineers group satellites by altitude because altitude dictates speed, coverage and signal delay. According to eoPortal's classification of Earth orbits, Low Earth Orbit (LEO) sits below 2,000 km, with satellites completing a full orbit in roughly 90 minutes at about 7.8 km/s; this proximity gives sharper imagery and frequent revisits, which is why LEO hosts most Earth-observation satellites, broadband constellations and the International Space Station.

Medium Earth Orbit (MEO) runs from 2,000 km up to just below geostationary altitude. eoPortal notes that MEO offers a balance of wide ground coverage and lower signal delay than higher orbits, which is why navigation constellations such as GPS and Galileo use it; eoPortal gives Galileo's orbital altitude as about 23,222 km. GPS.gov explains how a receiver uses timed signals from GPS satellites to calculate position, but the GPS.gov page reviewed for this article does not state the constellation's orbital altitude.

Geostationary Earth Orbit (GEO), at 35,786 km above the equator, has an orbital period matching Earth's rotation, so a satellite there stays fixed over the same point on the ground. eoPortal describes this as ideal for weather monitoring and telecommunications, though the greater distance means a longer round-trip signal delay and lower image resolution than LEO.

How GPS finds a location

GPS.gov explains that satellite navigation relies on trilateration: a receiver on the ground measures how long a radio signal took to arrive from each satellite, multiplies that time by the speed of light, and gets the distance to that satellite. With distances from at least three satellites, the receiver can calculate a three-dimensional position; GPS.gov notes a fourth satellite is used in practice to also help correct the receiver's own clock error. Because the calculation depends on precise timing signals, each satellite carries a highly accurate clock.

Watching the weather from two different heights

The US National Oceanic and Atmospheric Administration (NOAA) operates two types of weather satellites that illustrate the LEO/GEO trade-off directly. NOAA's JetStream education site states that geostationary GOES satellites orbit at 22,236 miles (35,786 km) and can capture a new image of the same hemisphere as often as once a minute, making them suited to tracking storms in real time. Polar-orbiting satellites fly far lower, around 520 miles (833 km), completing 14.1 orbits a day and crossing near both poles; NOAA says this gives sharper detail and better polar coverage but only a handful of usable passes over any one location per day.

Getting the signal to and from orbit

Communication with a satellite travels on radio frequencies, which are a shared and limited global resource. The International Telecommunication Union (ITU), the United Nations body that runs this system, assigns frequency bands and orbital slots to countries and operators under its Radio Regulations treaty, according to the ITU's own account of the process. An operator must publish its planned satellite's technical details, have them checked against the treaty, negotiate with any administration whose existing systems could suffer interference, and finally register the assignment in the ITU's Master International Frequency Register.

Low orbit, global broadband

The clearest recent example of orbit choice shaping a service is the growth of LEO broadband constellations. On 9 January 2026, the US Federal Communications Commission authorized SpaceX to deploy 7,500 additional second-generation Starlink satellites, doubling its approved Gen2 fleet to 15,000 spacecraft, according to the FCC decision as reported by TechCrunch. The regulator deferred action on a further 14,988 satellites SpaceX had also requested. SpaceX must have half the authorized fleet launched and operating by 1 December 2028, with the rest in place by December 2031, per the same reporting. The approval also lets Starlink satellites use five frequencies to provide direct-to-cell connectivity outside the United States, along with supplemental coverage within the US, according to TechCrunch's report.

Why this matters for everyday connectivity

The same orbital-mechanics trade-offs that eoPortal describes for spacecraft design directly shape consumer experience: a GEO-based satellite TV link has noticeable lag because of the distance signals must travel, while a LEO broadband terminal has far less delay but needs a large, coordinated fleet of satellites to keep a given spot on Earth continuously covered as individual satellites move quickly out of view. Navigation apps rely on MEO satellites whose orbits are tuned for a balance of coverage and timing accuracy rather than for speed of light alone. Each layer — orbit, frequency band and ground infrastructure — is governed by its own physical limits and, in the case of spectrum, by the ITU's international coordination process.