SATCOM, short for satellite communications, is the use of orbiting satellites to relay signals between points on Earth that a cable or a cell tower cannot reach. A ground antenna sends a signal up to the satellite. The satellite catches it, shifts it to a new frequency, amplifies it, and beams it back down to a receiver somewhere else. That relay lets a ship at sea, a plane over the ocean, a field team after a hurricane, or a home far from any fiber line stay connected. Every SATCOM link, from a satellite phone to a broadband dish, works on that same up-and-down path.
How a SATCOM Link Works: Uplink, Downlink, and Transponders
Every satellite link has two halves that use separate frequencies. The uplink is the signal traveling from a ground station up to the satellite. The downlink is the signal coming back down to a receiver. Splitting them across two frequencies keeps the strong outgoing signal from drowning the faint incoming one.
The device that ties the two halves together is the transponder. A transponder receives the uplink, converts it to the downlink frequency, amplifies it, and retransmits it toward Earth. One satellite carries dozens of transponders, and operators such as Intelsat and SES lease that capacity to broadcasters and network providers. Because the amplified downlink covers a wide footprint, a single transponder can serve a whole region at once, which is why satellite is the cheapest way to send one television feed to millions of homes.
The small dishes at the customer end have a name of their own: VSATs, short for very small aperture terminals. These are the compact antennas bolted to gas stations, bank branches, and remote offices that run their data over satellite instead of a wired line. A VSAT sends its uplink to the satellite, and the satellite relays it to a central hub dish that connects to the wider network. That hub-and-spoke shape lets one operator tie together hundreds of scattered sites that no single cable could reach.
GEO, MEO, and LEO: The Three Orbits That Carry SATCOM
SATCOM runs from three altitude bands, and the altitude sets the tradeoff between coverage and delay. A higher orbit sees more of the planet at once but adds distance, and distance adds lag.
| Orbit | Altitude | Coverage per satellite | Round-trip delay | Typical use |
|---|---|---|---|---|
| GEO (geostationary Earth orbit) | ~35,786 km | About a third of the globe | ~500 ms | Broadcast TV, weather, wide-area links |
| MEO (medium Earth orbit) | ~2,000 to 35,786 km | Large regions | ~125 to 250 ms | Regional broadband, navigation |
| LEO (low Earth orbit) | ~160 to 2,000 km | A small moving patch | Tens of ms | Broadband constellations, phones |
A geostationary Earth orbit (GEO) satellite circles at the same rate the planet turns, so it appears fixed in the sky. A dish points at it once and never moves again. That makes GEO ideal for television and for reaching remote sites, but the long path adds about half a second of delay, which frustrates video calls.
A medium Earth orbit (MEO) satellite sits closer, so its delay falls to a quarter second or less. The O3b network run by SES uses MEO for regional broadband, and the satellites behind GPS navigation also live in this band. A low Earth orbit (LEO) satellite flies lowest of all, which cuts delay to tens of milliseconds. The catch is coverage: a LEO satellite is overhead for only a few minutes, so a network needs many of them working as a fleet. That tradeoff is the whole story behind modern LEO satellites.
The Frequency Bands: L, C, Ku, and Ka
SATCOM uses several radio frequency bands, and each band trades data rate against how well it punches through rain and how big an antenna it needs. Naming a band tells an engineer roughly how a link will behave.
- L band (1 to 2 GHz): low data rate but rugged. It works with small handheld antennas and shrugs off rain, so it carries satellite phones, aircraft safety links, and emergency beacons.
- C band (4 to 8 GHz): resists rain fade well but needs a large dish. It carried television distribution for decades because a heavy downpour rarely knocks it out.
- Ku band (12 to 18 GHz): works with dishes small enough for a rooftop, which made it the standard for satellite TV and business networks.
- Ka band (26 to 40 GHz): carries far more data through small terminals, so today’s broadband constellations lean on it. The tradeoff is that heavy rain weakens a Ka signal more than a lower band, so systems fade the data rate to hold the link.
Civil Versus Military SATCOM
Civil and commercial SATCOM sells connectivity as a service. Broadcasters, airlines, shipping lines, and rural internet providers lease capacity from operators such as Viasat and the companies above, then resell it to end users. The priority is cost per bit and wide coverage.
Military SATCOM, often written MILSATCOM, protects the link itself. A battlefield radio has to keep working when an adversary jams the frequency, spoofs the signal, or tries to listen in. So military systems add encryption, frequency hopping, and hardened ground control that commercial services usually skip. The United States runs dedicated fleets for this: the Wideband Global SATCOM system for high-capacity data, Advanced Extremely High Frequency satellites for protected strategic traffic, and the Mobile User Objective System for narrowband voice on the move. The distinction is not the physics, which is identical, but how much protection is built around the link.
Why SATCOM Matters
SATCOM reaches the places terrestrial networks cannot. Roughly two-thirds of the planet is ocean, and no fiber line crosses open water to a moving ship or a transoceanic flight. Fiber and towers also stop at the edge of dense population, leaving farms, mountains, and polar research stations without a link. When an earthquake or storm flattens the local network, a portable satellite terminal is often the first thing that restores communication for rescue crews.
The technology has widened fast. A GEO dish once meant a fixed installation and a costly monthly bill. Low-orbit fleets now push satellite broadband toward laptop-sized terminals and, as of 2026, toward ordinary phones through direct-to-cell service. For a fuller picture of the low-orbit shift reshaping SATCOM economics, read our explainer on LEO satellites.