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2021-10-01

DARPA’s ‘Space Layer’ to Interconnect LEO Constellations

Government and commercial small-satellite constellations continue to proliferate in low-earth orbit (LEO). Therefore, DARPA has unveiled a new effort to create an optical communications terminal to interconnect diverse constellations into a resilient “space layer” – an internet of small satellites.

Dubbed Space-Based Adaptive Communications Node (Space-BACN), the programme aims to create a low-cost, reconfigurable optical communications terminal that adapts to most optical inter-satellite link (OISL) standards. Space-BACN would allow seamless communication between various constellations that currently cannot talk to each other.

“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 programme manager in DARPA’s Strategic Technology Office. “The problem with this growth is that optical communications links are currently engineered to only connect satellites within a given constellation – they can’t dynamically adapt waveforms to communicate with satellites in other constellations. This lack of OISL standardisation results in a fragmented, stove-piped ‘Wild West’ space domain with new constellations that can’t interoperate, government satellites that can’t communicate between one another, and government satellites unable to take advantage of emerging commercial communications capabilities.”

Space-BACN envisions an adaptable communications terminal that could be reconfigured on-orbit to talk across different standards, presenting a leap in technology. The programme objectives are summarised as “100 Cubed”: 100 Gbps to support most optical standards, 100W or less to minimise power consumption, and under US$100K to make it affordable.

To achieve this, Space-BACN will focus on three key technical areas – first is a low-cost, optical aperture capable of coupling into single-mode fibre; second is a reconfigurable modem that can support multiple optical waveforms up to 100 Gbps, and the third is a novel cross-constellation command and control approach to automate interactions between government and commercial satellites. In addition to the technical challenges, a key driver for the programme is to lower cost and weight in order to facilitate ease of integration and use.

“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,” Kuperman said. “Commercial space companies, on the other hand, are developing ultra-optimised, 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.”

Since Space-BACN is focused on operating in LEO, it will be able to take advantage of advanced low-cost electronics that can reliably operate in lower radiation environments and more easily connect to the large number of other government and commercial LEO satellite constellations. Additionally, the shorter expected life span of LEO satellites – three to five years – combined with the modularity of the Space-BACN terminal will facilitate rapid refresh cycles and insertions of new technology as it becomes available.

Mosaic Warfare

Space-BACN also fits into the broader context of Mosaic Warfare, Joint All-Domain Command and Control (JADC2), and the future of warfare.

Dr Tim Grayson, director of DARPA’s Strategic Technology Office, said: “DARPA is fundamentally about technology, and our primary mission is developing these new technical capabilities. We are known for taking risks, and we are willing to do experimentation and some risk-taking with business models as well.

“We’re out there looking for the technologies that are going to change the nature of warfare and national security. So, in that regard, we want to invest in helping to develop what is the next capability.”

He described that DARPA is looking at creating an overall capability from a collection of individual elements. Therefore, it is looking at developing an integrated platform that includes a sensor, a weapon, and the means of communication, computing, and decision making to reach across the whole battlespace.

However, Grayson stressed, there is a risk of the inherent complexity of having everything tightly integrated onto one platform. This is where the concept of mosaic warfare comes in where instead of saying that all of these sensors, weapons and comms have to go together, the user can choose the best capability for that particular moment in time.

He added: “We’re looking at how we generate ad hoc interoperability at moments when we need it. And then ultimately, how do we help the human operators who have to work within these kinds of architectures manage the complexity that’s imposed upon them as an element of a mosaic architecture.”

Reference Text/Photo:

www.darpa.mil

www.defense.gov

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