SDA's Transport Layer will provide assured, resilient, low-latency military data and connectivity worldwide to the full range of warfighter platforms.

SDA's Transport Layer is envisioned, modeled, and architected as a constellation varying in size from 300 to more than 500 satellites in Low Earth Orbit (LEO) ranging from 750km to 1200km in altitude. With a full constellation, 95% of the locations on the Earth will have at least two satellites in view at any given time while 99% of the locations on the Earth will have at least one satellite in view. This will ensure constant world-wide coverage around the globe. The constellation will be interconnected with Optical Inter-Satellite Links (OISLs) which have significantly increased performance over existing radio frequency crosslinks. LEO orbits in conjunction with OISLs will reduce path loss issues but more importantly offer much lower latencies, which are deemed critical to prosecute time sensitive targets in today's wartime environment.

This SDA constellation is expected to operate over Ka band, have stereo coverage and be dynamically networked for simpler hand-offs, greater bandwidth and fault tolerance. Initially, the Tranche 0 constellation consisting of 20 space vehicles is expected to have a limited networked capability. Future enhancements (Tranche 1 and beyond) will significantly increase the routing of data across a larger network of space vehicles. The constellation will also have the capability to integrate with both Link-16 and the Integrated Broadcast System (IBS). Link-16 and IBS integration on the Transport Layer will modernize current capabilities to better support warfighter needs for worldwide timely threat warning and situational awareness information across the range of military operations.

SDA's Transport Layer is exploring technical areas including, but not limited to:

  • Optimized control of modulation techniques (including wide-band or narrow-band operations),
  • Simultaneous transmit and receive technologies,
  • Communications security functions (e.g. frequency hopping),
  • Unique state of the art waveforms,
  • Space implementation of tactical data links,
  • Automated dynamic networking and routing techniques,
  • Commercial cryptographic systems,
  • Blockchain technologies,
  • Multiband phased array antennas, and
  • Multi-level security (MLS).