How to bring satellite interoperability down to Earth

The United States Department of Defense has said that it wants the armed forces to use satellite networks that are owned and operated by several different companies. It makes perfect sense. If an adversary jams one network, troops could switch to another. If one supplier falters, the military can rely on others. But the ability of the United States to do this depends on whether or not they can move easily from one network to another from the ground.

The Pentagon has already made considerable progress towards this goal, not least through the work of the Space Development Agency. The SDA is developing the Proliferated Warfighter Space Architecture, which will comprise hundreds of satellites in low Earth orbit. The United States Space Force also intends to connect commercial satellite systems through its Space Data Network.

Together, these programmes could give U.S. forces access to far more satellites and suppliers. The next opportunity is to build on this progress by making ground equipment equally flexible.

Consider a forward base, where troops could have access to three, five or even ten satellite networks. If each requires its own terminal, antenna and software, personnel have to install and maintain every system. They must also learn how to use each one and keep it up to date.

On ships, aircraft and small bases, where space and power are scarce, this can become expensive. Every additional system may also need spare parts and its own supply chain. Beyond a certain point, adding another satellite supplier can give troops more equipment to support without necessarily providing much more useful capacity.

Considerable progress has already been made in radio-frequency communications, where some antennas can support several constellations. Different frequency bands and proprietary systems, however, can still require additional hardware.

Cost is one thing; what happens during an attack is another. Suppose troops normally use one commercial satellite network and an adversary jams it. Another company may have working satellites overhead, but the troops can't use them if their ground equipment can't connect to that company’s network. The value of having several networks therefore depends partly on how easily troops can reach them.

This is precisely the kind of problem that the SDA has already helped to solve in space. By publishing a common optical communications standard and making it available to companies, the agency has helped to create an ecosystem of compatible optical communications terminals.

Different suppliers can build equipment to the same requirements, making interoperability a foundation of the PWSA rather than an afterthought. It’s an achievement, and one that offers a model for ground networks.

Satellite companies need not build identical networks. Different designs give the military more choice and reduce its dependence on any one technology. But common standards can allow equipment from different suppliers to work together, without requiring the networks themselves to be identical. The same principle could help ground stations connect to several satellite networks.

The next step is to extend this approach to the ground. Indeed, wherever possible, one ground station should connect to several networks. Operators shouldn't have to install new hardware whenever the military adds another satellite provider. Nor should they need a team of specialists to move from one network to another during a crisis. Troops should be able to make the change quickly with equipment already in place.

Encouragingly, the SDA is already exploring greater flexibility on the ground. In September, the agency asked industry how it could make the PWSA ground network more open, so that equipment from different suppliers could work together more easily. It is also buying ground stations for later stages of the programme.

These are welcome developments and provide an opportunity to extend the benefits of interoperability to connections with other military and commercial satellite networks.

Optical ground stations hold particular promise because, unlike radio-frequency equipment, which depends on hardware designed for particular frequency bands, optical ground stations can be designed to accommodate a range of optical waveforms without replacing their underlying optical hardware. This could make it easier to connect to different satellite systems as technology and operational requirements change.

There is another advantage to concentrating on the ground: equipment on Earth can be upgraded, replaced and adapted far more easily than hardware already in orbit. As new suppliers enter the market and technology improves, operators could gain access to new networks without having to replace their ground stations.

The United States has sound reasons to spread military communications across many satellites and suppliers. When there are more networks, it’s far harder for an enemy to cut communications and the Pentagon has more ways to add capacity.

The SDA has already demonstrated what common standards can achieve in space. Its work offers a valuable foundation for the next stage: developing flexible optical ground networks that can connect military users to an increasingly diverse range of satellites.

By extending the principle of interoperability from orbit to Earth, the United States can make still greater use of the investments it is already making in space.