DARPA Developing Universal Translator for Satellites

The Space-Based Adaptive Communications Node (Space-BACN) may one day allow satellites owned by different governments, U.S. government departments and agencies and the private sector to communicate with one another. If successful, the capability will vastly expand worldwide communications capabilities by allowing efficient and effective satellite communications pathways.

Currently, satellites within various constellations only communicate amongst themselves, Greg Kuperman, the Space-BACN program manager at the Defense Advanced Research Projects Agency (DARPA), explained. So, for example, Space Development Agency (SDA) satellites only communicate with other SDA systems. “Right now, all of the systems going up have a single protocol, a single language they can talk. So, SpaceX can only talk to SpaceX, SDA can only talk to SDA, Amazon can only talk to Amazon, NASA can only talk to NASA.”

With Space-BACN in place, NASA and SDA satellites could communicate with SpaceX and Amazon systems if all parties agree. “The purpose is to create a multiprotocol, reconfigurable optical communications terminal to enable space-to-space communications between government and commercial satellites as well as government-to-government satellites, and hopefully one day, commercial to commercial,” Kuperman said.

The system would enable greater communications flexibility and efficiency than is currently available. The most favorable communications path might change quickly for warfighters or everyday users. It might be through a SpaceX constellation now and 10 minutes later through SDA satellites and then NASA systems. “What I want to be able to do is to change the language that I can talk effectively on the fly so that as my mission needs change, as the services change, as the availability changes, I can change who I talk to,” Kuperman said. “I’m not locked into talking to only one particular provider, one particular network or one particular mechanism.”

The initial focus likely will be on communications among U.S. government constellations and possibly industry as well. “DARPA is a U.S. military organization, so I initially anticipate, like, the Space Development Agency wants to talk to a NASA satellite that maybe wants to talk to whatever other constellation might be going up there, and also to enable having those satellites talk to commercial entities,” Kuperman stated.

Eventually, U.S. military or intelligence agency satellites could communicate with those from allied countries if the governments agree. “There’s nothing, in theory, that should stop it from talking to a European Space Agency or something else. It’s more a matter of policy than it is of capability,” Kuperman said. “I don’t want to be saying it will because that is not for me to decide, but from a technological standpoint, it is intended to allow anyone who has a Space-BACN terminal to talk to anyone else that terminal is allowed to talk to.”

Kuperman didn’t compare Space-BACN to the universal translators of "Star Trek" fame during an interview with SIGNAL Magazine, but it’s an easy comparison to make. “Space-BACN is meant to be a low-cost, easy-to-use optical communications terminal that can effectively talk whatever you’re talking, so think of it as multilingual. It can talk different languages. If you talk German, it can talk German. If you talk English, it can talk English.”

Initially, he suggested, Space-BACN would act as a gateway between satellite constellations. “But then in the future, as new satellites go up and constellations refresh, they could all natively use Space-BACN, and there would be no longer a need for gateways whatsoever. They would all just be able to talk between one another using the Space-BACN optical communications terminal as their native pathway.”

Satellite languages are defined by the pulsating action or light waves of their respective lasers. They use two communication modes: incoherent and coherent. With incoherent modes, it’s all about laser intensity, and the phase of the wave is not important. With coherent modes, the phase is critical. Both options have their pros and cons.

“In an incoherent mode, I’m looking at the intensity of the light. Basically, think of it as on-off. Is the light on, or is the light off? The light will be effectively pulsating,” Kuperman explained. “That allows you to have simpler constructions, which has been the bulk of what you see today but also limits the maximum data rate that you can talk.”

Coherent communication, on the other hand, is based on the timing of the light wave. “Coherent communications means that I now need to be able to look at where the signal is with respect to phase. If you can imagine a sine wave or a cosine, it has up and down. All you’re going to be changing with that up and down is the respect to time,” Kuperman elaborated. “That allows me now to have a lot more information that I can push through the waveform, but it requires a lot more sophisticated processing to be able to pick up the differences in the up/down portion of your wave.”

The program includes three technical areas: a low-cost, highly capable modular telescope capable of transmission and reception of light; reconfigurable processing; and across-constellation command and control. All three technical areas present major challenges.

“Think of the thousands of satellites that are launching into low-Earth orbit right now. Imagine two optical telescopes that need to rotate, point and connect across thousands of miles of space while these satellites are moving at high speed in different directions, and imagine that each of them is talking a different language, and I’m basically turning a knob to say what language I am going to be using so that I can then talk to them,” Kuperman said.

Driving down the cost while increasing capabilities will be one of the bigger challenges. “We are able to have different types of optical terminals on NASA systems, for example, but they’re very expensive. We need to be able to have these mass produced in quantity at very low cost, and that’s going to be an exceptionally high challenge,” Kuperman offered.

The goal is to produce terminals at roughly $100,000 each, but because of the desired dramatic increase in capability, it’s hard to quantify how much cheaper that would be over current, less capable systems, which can cost hundreds of thousands of dollars. Other goals include building a system that requires only 100 watts of power and communicates with any waveform at rates up to 100 gigabits per second. “Those three things combined should make it lower cost, lower power and more capable than anything you can go and get today, which should enable its proliferation,” Kuperman stated.

DARPA kicked off the program with an informal phase zero, which ended in the summer and required participants to design the architecture. They then selected 11 teams to move forward for the formal program. By the program’s end, agency officials hope to partner with one or more military, government or commercial organizations to transition the technology from the laboratory. Kuperman reports that both classified and unclassified agencies have shown interest, and so have commercial companies.