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DARPA plans thousands-strong satellite constellation Space-BACN sandwich

Mmmm... BACN. Is there anything it can't do?

DARPA, the famously scattershot defence research agency of people's hearts, has turned its attention to recent announcements of planned and actual communications satellite constellation launches, asking: "Why can't these things all just talk to each other?"

The agency – which recently asked US defence contractors if they fancy building an ekranoplan, and launched a convoy-defence drone that sneezes other drones to death – is seeking to create a cheap new optical communications system that would allow newly launched satellites to exchange large quantities of data quickly, easily and securely, even if they are from different constellations.

The project, known as the Space-Based Adaptive Communications Node or Space-BACN – which believe it or not is officially pronounced "space bacon" – aims to link together future satellite constellations to provide a vast, thousands-strong aggregated communications network.

"There could be tens of thousands of small satellites launched into LEO over the next decade as the demand around the world for affordable space-based capabilities grows," said Greg Kuperman, Space-BACN program manager in DARPA's Strategic Technology Office.

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It intends to do this either by launching dedicated satellites equipped as Space-BACN network hubs, or by equipping future commercial and government satellites with this capability.

"Traditional government optical terminals for coherent space-based optical communications can cost hundreds of thousands to millions of dollars due to the many precision designed and manufactured components that are hand assembled by highly skilled experts in the field," said Kuperman.

"Commercial space companies, on the other hand, are developing ultra-optimized, single-mode coherent systems designed to achieve high-rate communications while lowering cost. These lower-cost systems, however, are not reconfigurable nor compatible with any other standard," he added.

DARPA is therefore asking for ideas that would create a standardised optical terminal that the agency hopes will eventually link future networks together, while conforming to what it calls its "100 cubed" requirements. This means the terminal should have a throughput of at least 100 gigabits per second, should consume less than 100 watts of power and should cost less than $100,000 in order to encourage uptake from present and future constellation builders.

In order to spur on the development of systems that would support Space-BACN, DARPA is also seeking proposals for what it sees as three vital technological components of the system.

The first is a low-cost optical aperture which can utilise all infra-red wavelengths in the C band and feed into an affordable single-mode fibre-optic line, allowing cheap, low-loss transmission capabilities. The second is a reconfigurable modem that can support different waveforms. The final piece would be a "cross-constellation command and control" system to automatically coordinate all of the different networks into one cohesive whole.

DARPA is also hoping that the low Earth orbit (LEO) arrangement that most of the new emerging constellations utilise will work in its favour as it seeks to establish Space-BACN as a new standard.

Most of the satellites in these low orbit networks are intended to be almost disposable, with lifespans of only three to five years. Therefore constellation owners will be constantly launching replacement vehicles, and this rapid turnover, "combined with the modularity of the Space-BACN terminal will facilitate rapid refresh cycles and insertions of new technology as it becomes available," the agency said of its hopes.

While all of these optical interoperability high jinks will undoubtedly lead to a nifty and highly useful network of government and commercial satellites that could be used for all manner of things, it must be remembered that when it isn't chasing imaginary butterflies and dancing to the tunes in its own head, DARPA is actually a defence research agency.

Space-BACN is ultimately intended as a way for the US military to make its comms networks less vulnerable by adding multiple redundancies in case individual satellites or even individual networks get knocked out by enemy action in future conflicts.

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The US Air Force has already conducted a joint operation with SpaceX in which its Starlink network was used during a live-fire exercise last year.

The vast number of LEO satellites currently planned means that there could be the capability to use Space-BACN to operate and coordinate forces down to the level of individual aircraft, drones or missiles.

The USA's potential enemies – China and Russia, for example – will undoubtedly be watching this situation with interest. Having seen the potential for a Space-BACN sandwich combining all of these networks, they will surely want to... ketchup. ®

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