Satellites use radio waves, a type of electromagnetic radiation, to send and receive nearly all their data. These radio waves travel at the speed of light and span a wide range of frequencies, from about 1 GHz up to 86 GHz depending on the satellite’s job. A smaller but growing number of satellites also use laser beams operating at infrared wavelengths for high-speed links between spacecraft.
Why Radio Waves Work for Space
Earth’s atmosphere has a natural “radio window” that lets electromagnetic waves pass through with minimal interference. This window stretches from about 5 MHz up to around 300 GHz, covering wavelengths from nearly 100 meters down to about 1 millimeter. Below that range, the ionosphere absorbs the signal. Above it, water vapor and carbon dioxide in the atmosphere block transmission. Satellite engineers pick frequencies inside this window so signals can travel between ground stations and orbit without being swallowed by the atmosphere.
The Main Frequency Bands
Satellite frequencies are grouped into lettered bands, each suited to different tasks. The European Space Agency defines the primary ones as:
- L-band (1–2 GHz): Used for GPS and other navigation satellites, plus some mobile phone services. The relatively low frequency penetrates clouds and light foliage well, making it reliable for positioning signals.
- S-band (2–4 GHz): Common for weather satellites and some spacecraft telemetry. Also used by certain navigation systems at around 2,498 MHz.
- C-band (4–8 GHz): A workhorse for traditional satellite TV distribution and long-distance phone networks. It resists rain interference better than higher bands.
- X-band (8–12 GHz): Primarily reserved for military communications, radar imaging, and deep-space missions.
- Ku-band (12–18 GHz): The most widely deployed band for direct-to-home satellite TV and broadband internet. It offers over 7,000 leasable transponder units worldwide, far more than any other band.
- Ka-band (26–40 GHz): Carries higher data rates in tighter beams. Used by newer high-throughput internet satellites but more susceptible to signal loss during heavy rain.
Higher frequencies carry more data per second but are more easily disrupted by weather. Lower frequencies are more resilient but offer less bandwidth. This tradeoff is the core reason different satellite services cluster around different bands.
What Starlink and OneWeb Use
Modern mega-constellations in low Earth orbit rely heavily on Ku-band and Ka-band. Starlink’s gateway stations communicate with satellites using frequencies between roughly 17.8 and 30 GHz, covering both Ka-band uplinks and downlinks. Starlink has also been authorized to use extremely high frequencies between 71 and 86 GHz for some gateway links, pushing into what’s called the E-band or W-band range.
OneWeb operates its gateways in similar Ka-band ranges (around 17.8–30 GHz) and uses Ku-band frequencies between 10.7 and 14.5 GHz for its fixed earth stations. The user terminals you’d have on your roof generally communicate in Ku-band, which keeps the dish size manageable and the signal reasonably weather-resistant.
GPS and Navigation Frequencies
Navigation satellites like GPS broadcast in the L-band, using very specific carrier frequencies. The primary civilian signal, L1, transmits at exactly 1,575.42 MHz. A second frequency, L5, operates at 1,176.45 MHz. Your phone or car GPS receiver picks up both of these.
Using two frequencies at once isn’t just a backup plan. Radio waves slow down slightly as they pass through the ionosphere, and the amount of delay depends on the frequency. By comparing the arrival times of two different frequencies, a receiver can calculate and cancel out that ionospheric error. This dual-frequency approach is what makes high-precision positioning possible, bringing accuracy from several meters down to centimeters in professional-grade systems.
Deep Space Communication
Talking to a probe millions of kilometers away is a different challenge entirely. NASA’s Deep Space Network, a set of giant dish antennas in California, Spain, and Australia, uses three bands. S-band (2,110–2,300 MHz) was the original deep-space frequency and is still used on some legacy missions. X-band (7,145–8,450 MHz) is now the standard for most interplanetary spacecraft. Ka-band (31,800–34,700 MHz) provides the highest data rates and is used on newer missions that need to send back large volumes of science data, like high-resolution images from Mars orbiters.
The tradeoff in deep space is the same as closer to home: higher frequencies move more data but require more precise antenna pointing. At distances where a signal can take over 20 minutes to arrive, every bit of efficiency matters.
Laser Links Between Satellites
The newest development in satellite communication isn’t radio at all. Laser links, sometimes called free-space optical communication, use infrared light at wavelengths around 1,550 nanometers. That’s invisible to the human eye but travels in an extremely tight beam, allowing satellites to exchange data at high speeds without interfering with radio traffic.
These optical links work best between satellites in orbit, where there’s no atmosphere to scatter the beam. Several companies now build laser terminals small enough to fit on satellites weighing just a few kilograms, achieving data rates of 100 megabits per second or more at wavelengths between about 1,537 and 1,563 nanometers. Laser crosslinks are already part of the Starlink constellation’s architecture, letting satellites relay data to each other across the network before sending it down to a ground station via radio.
Laser communication to the ground is harder because clouds, rain, and turbulence distort the beam. For now, satellite-to-ground links still rely almost entirely on radio waves, while laser handles the satellite-to-satellite backbone.
How Data Gets Encoded on the Wave
A radio wave by itself is just a carrier. To transmit actual information, satellites modulate the wave, changing its properties in precise patterns that represent digital ones and zeros. The most common approach shifts the phase of the wave, essentially nudging the wave’s timing in small, controlled steps that a receiver can decode. More advanced versions combine phase and amplitude changes to pack even more data into each signal, which is particularly useful for low-orbit satellites where the link time with any ground station is short and every second counts.
The encoding method matters because satellite transmitters aren’t perfectly linear. Pushing more data into the same slice of radio spectrum requires modulation techniques that tolerate the slight signal distortion introduced by onboard amplifiers. Getting this balance right is what allows a Ku-band satellite to deliver hundreds of TV channels or gigabits of internet traffic from the same orbital slot.