It’s dusk in Afghanistan and a Joint Terminal Attack Controller (JTAC) crouches behind cover halfway up a mountainside. He’s equipped with a weapon, helmet mounted display, universal tactical display, and an AN/PRC-161 Battlefield Awareness and Targeting System-Dismounted (BATS-D) radio.
The JTAC is tasked with directing airborne reconnaissance and precision strike assets in support of a ground offensive against Taliban combatants in the valley below. Observing the ongoing battle, the JTAC operates the AN/PRC-161 to communicate with a Link 16-enabled Low Earth Orbit (LEO) satellite passing overhead at an altitude of 550km and a speed of 8km per second.
Within seconds, the JTAC receives an updated Common Operating Picture (COP) of the battlespace, which enables them to task multiple air assets to find, fix, and destroy enemy mortar positions.
Once enemy mortar positions have been destroyed and the target area has been successfully secured by coalition forces, the JTAC uses the AN/PRC-161 to communicate with the satellite to update the COP before instructing supporting air assets to stand down and return to base.
Despite being fictional, this operational vignette provides an insight into a next-generation Link 16 capability now on the verge of becoming available to U.S. and partner forces. It’s expected to be made possible from the development of the world’s first Link 16 LEO satellite.
Viasat, which was selected to lead the U.S. Air Force Research Laboratory (AFRL) Space Vehicles XVI program, is scheduled to deliver the first 50-pound XVI satellite to Vandenberg Air Force Base, California in in the spring of 2021, with launch anticipated the following fall.
Craig Miller, Viasat’s Chief Technology Officer for Government Systems, explained that the AFRL’s XVI program will push the boundaries of what can be achieved with Link 16 communications protocol.
“We’re working at distances that are far greater than have ever been demonstrated with Link 16 before and we have gone from a science project to a space launch. It’s a really exciting time,” he said.
The XVI satellite comprises a 12U spacecraft bus manufactured by Blue Canyon Technologies and features a Viasat Link 16 payload as well as Roccor L-Band antenna.
Operating from a 95-degree orbital inclination, the XVI satellite will have an on-orbit lifetime of at least six months. Benefiting from immediate interoperability with legacy Link 16 terminals already fielded across the Department of Defense, the satellite will support multiple demonstrations due to be undertaken by the AFRL, Marine Corps and Special Operations Command.
According to Miller, demonstrations will test the spacecraft’s ability to help create and share COPs with ground users across extended ranges. Designed to enhance situational awareness, COPs generally indicate the position of friendly and enemy forces as well as other points of interest across a map or satellite image of the battlespace.
“The COP means ground users, aircraft, and ships know exactly where everyone is within a local theater or battlespace,” he said. “XVI will turn Link 16 into an interconnected and global capability in addition to providing an exit point into external IP and broadband internet networks, allowing users to share target tracks and access data anywhere in the World. We are really excited about the program and the increased capabilities it will offer to warfighters, which will drive increased Link 16 Concepts of Operations (CONOPS).”
Beyond Line of Sight capability
According to Miller, demonstrations will see two ground users talking to each other via the XVI satellite, in addition to a ground user communicating with an aircraft a about a hundred miles away.
“This will demonstrate a massive range extension for Link 16,” Miller said.
Additional objectives include proving XVI’s ability to work with a variety of end user terminals including Viasat’s Small Tactical Terminal (STT), AN/PRC-161, and the Move Out/Jump Out (MOJO) tactical gateway system.
“Demonstrations will also prove Link 16’s Beyond Line of Sight capability (BLoS) capability to take data from a terminal, relay it through the XVI satellite, and send it back to another terminal; or relay data via S-Band to another user on the ground and then into a wider global communications network,” Miller said.
During tests, the AFRL will be responsible for primary satellite operations with Viasat providing “shadow” operations from its Space Center in Carlsbad, CA.
The XVI satellite has already completed laboratory tests to simulate orbital velocity, time delays, and Doppler effect. The latter refers to just one of the challenges of making a radio connection from a warfighter on the ground to a satellite racing overhead at over 7km/s.
As Viasat’s XVI program manager, Don Gants, said: “The real proof is going to be in the operational environment. The geometries of simply working in the BLoS Link 16 network are going to be an exciting challenge, but we think we’ve solved those. There are also timing sensitive protocols with Link 16, and because we are working at geometries far beyond what it was originally designed to work at — at ranges in the hundreds to over a thousand miles — we have to do some clever things to make that work.”
Looking beyond the XVI demonstration, Viasat remains in discussions with the AFRL regarding further enhancements in a follow-on program. Areas of interest include more efficient use of bandwidth and scheduling; optimized dynamic network entry and exit; as well as the ability to operate BLoS Link 16 in extreme environments.
“Viasat is a company that works in multiple orbits and regimes, providing communications, sensors in space, and tactical data links,” Miller said. “It’s a very wide portfolio. XVI LEO is just another area we’re entering into and building steam. We’re really excited by this.”
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