WASHINGTON — Each of the satellites in the Space Development Agency’s mesh network known as the Transport Layer could have as many as five laser links so they can talk to other satellites, airplanes, ships and ground stations.
Realizing that goal will require “affordable” optical terminals that can be mass produced and comply with basic technical standards, said Derek Tournear, director of the Space Development Agency.
Speaking via video April 21 at a conference hosted by C4ISRNET, Tournear said he is soliciting information from commercial suppliers about the state of the technology and their ability to mass produce small laser links for SDA’s satellites.
Tournear last year identified laser intersatellite links as one of the most critical technologies in SDA’s constellation.
Laser links use optical technologies to route data traffic. They provide much higher transmission data rates than traditional radio-frequency links and are harder to intercept. A network of laser-link satellites also reduces the dependence on ground stations and extends coverage to remote areas where ground stations are not available.
The first iteration of SDA’s network is known as Transport Layer Tranche 0. The agency will launch 28 Tranche 0 communications and missile tracking satellites in 2022 and is now planning to order 150 communications satellites for Tranche 1 to be launched in 2024.
Tournear said SDA revised the optical crosslinks standards for Tranche 1 satellites to make sure the government can leverage systems that the commercial sector is buying in large quantities.
“Those 28 satellites in Tranche 0 are just there to do the demonstration, but Tranche 1 is a completely different ballgame,” he said. Tranche 1 is an operational system, he said. “We’re looking at 150 satellites, and we’re looking at something on the order of three to five optical crosslinks per satellite, and we want those crosslinks to not only be satellite-to-satellite but satellite-to-air, satellite-to-ground and satellite-to-maritime assets.”
To ensure SDA can tap into a broad base of vendors, the agency adopted the 1550 nanometers standard, which is the most widely used wavelength in optical communication systems.
SDA satellites’ laser links also have to be compatible with the most common waveforms used by the fiber optics industry, said Tournear.
These decisions were made based on “what we think the current state of the art is for technology to be able to buy very affordable optical crosslinks that can be mass produced,” he said.
Another key requirement is pointing, acquisition and tracking, the technology that makes it possible to establish and maintain the laser links. “That is a space based problem,” said Tournear. “You don’t have that with fiber optics on the ground.”
