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Communications

The Communications section focuses on radio communication systems used in CubeSats, including transceivers, antennas, modulation schemes, and ground station interfaces. It covers both UHF/VHF amateur radio systems and higher-bandwidth S-band and X-band setups. Optical communication is not yet common in CubeSats, but emerging concepts will be added here as they develop.

Radio Frequency Communications (RF)

CubeSats typically employ RF communication for uplink (commands) and downlink (beacon, telemetry and payload data), operating in both amateur and licensed frequency bands. TT&C is a commonly used abbreviation:

A special case is the beacon: a low-data-rate, always-on (during commissioning) signal that periodically transmits basic telemetry (e.g. battery voltage, temperature, timestamp, ID). Beacons help confirm the satellite is alive and can be used to aid tracking. The SatNOGS network has become a de facto standard for receiving and sharing beacon data in open-source and academic missions, enabling global signal tracking and community-supported downlink coverage.

CubeSat beacons are most commonly found in the UHF amateur band (~437 MHz) and typically use simple modulation schemes like AFSK, BPSK, or GMSK. They often conform to protocols such as AX.25 for compatibility with amateur ground stations.

Telemetry, Tracking, and Command (TT&C) refers to the fundamental communication link between a spacecraft and its ground segment.

  • Telemetry: Downlinked data about the spacecraft’s health, status, and environment (e.g. temperature, voltage, position).
  • Tracking: Ground-based tracking of the satellite’s orbit and signal, often using Doppler shift and time-of-flight data.
  • Command: Uplinked instructions that control the satellite’s behavior, such as mode changes, resets, or payload activation.

TT&C is typically implemented on a robust, low-data-rate RF link—often in UHF or VHF—to ensure reliability even under degraded conditions. It operates independently from high-bandwidth payload downlinks and remains active throughout the mission lifecycle, often independently of high-bandwidth payload links.

Amateur Bands
Used primarily by university and research missions under IARU coordination:

  • UHF
  • Uplink: 435–438 MHz

  • Downlink: ~437 MHz (very common)

  • VHF

  • Uplink: 145.9–146.0 MHz

  • Downlink: 144.0–146.0 MHz

  • L-band

  • Occasionally used (e.g. 1.2–1.3 GHz); less common in CubeSats

Licensed Scientific and Commercial Bands
Require coordination through ITU and national regulatory agencies:

  • S-band (2–4 GHz)

  • Common for high-data-rate downlinks (e.g. 2.2–2.3 GHz)

  • X-band (8–12 GHz)

  • Used for high-rate payload data and remote sensing missions

  • Ka-band (26–40 GHz)

  • Rare in CubeSats due to pointing precision and power constraints