Inter-Satellite Link

Author: CislunarSpace

Website: https://cislunarspace.cn

Definition

An Inter-Satellite Link (ISL) is a direct communication link established between two or more satellites for tracking, telemetry, command, data transmission, and information exchange. ISLs are the core infrastructure for satellite constellation networking, enabling the constellation to operate as a coordinated whole.

Technology Regimes

ISLs primarily employ two technology regimes:

  • Operating bands include Ka-band (~23-26 GHz) and V-band (~70 GHz)
  • Use phased-array antennas for beam scanning and agile control
  • BeiDou-3 employs Ka-band phased-array agile microwave ISLs
  • The DRO three-satellite constellation uses K-band for inter-satellite measurement and communication
  • Compared to microwave, laser communication payloads offer light weight, small size, low power consumption, and strong data transmission capability
  • BeiDou-3 satellites are equipped with laser ISL payloads
  • The DRO-A satellite carries a laser communication payload, achieving the world's first verified inter-satellite communication link exceeding 1 million kilometers

Applications in Cislunar Space

ISLs play a critical role in cislunar communication architecture:

  • Intra-constellation: Laser-microwave hybrid links maintain long-term stable, uninterrupted connections between satellites, forming a constant satellite network
  • User spacecraft access: ISLs provide all-time seamless communication services for catalogued cislunar user spacecraft
  • Dynamic routing: Onboard network information devices perform dynamic link planning and routing across the entire constellation

References

  • Duan Z, Wang J, Fan Y. Research on the Development of Beidou Satellites Based on Full-Time Communication and Navigation in the Earth-Moon Space[J]. Journal of Telemetry, Tracking and Command, 2026.
  • Chinese Academy of Sciences. Symposium on DRO Exploration in Cislunar Space[C]. Beijing, 2025.