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DARPA Space-BACN developing space optical communications terminal to link commercial constellations for militarys

The falling costs of space launch and the increasing capabilities of small satellites have enabled the emergence of radically new space architectures—proliferated constellations made up of dozens, hundreds, or even thousands of satellites in low orbits.


Several commercial companies plan to establish space internet constellations consisting of hundreds to thousands of satellites, each to create global internet services. Starlink and its competitors, such as OneWeb, Telesat and Amazon’s Project Kuiper, have embraced a new approach to satellite internet. Rather than placing a couple big satellites in geosynchronous orbit, these companies want to place thousands of broadband satellites in low Earth orbit. These satellites are only a few hundred miles above the Earth so they can cut down delays to around 20 milliseconds, which is hardly noticeable from a user’s perspective.


By 2027, SpaceX plans to have as many as 12,000 Starlink satellites in orbit beaming high-speed internet to tens of millions of customers around the planet.  In addition to Starlink, OneWeb and Telesat have both announced their intention to create LEO broadband constellations with 650 and 292 satellites, Backed by Virgin Group, OneWeb is building a new global knowledge infrastructure accessible to everyone, particularly in rural areas in just 10 years, according to Greg Wyler, the founder of the company. Iridium company recently completing a two-year upgrade of its global communications network, replacing all of its satellites and upgrading the supporting ground infrastructure. Iridium’s satellite constellation now consists of 66 operational space vehicles and nine on-orbit spares.


The U.S.  DOD  plan  to draw from a deepening well of commercially available satellite communications (SATCOM) technology to enhance military internet tactical networking for warfighters on the ground, in the air, and at sea. The idea is to capitalize on commercial communications satellite constellations under development to reduce military SATCOM costs, as well as enhance reliability and data throughput.


New constellations that are in different stages of acquisition are procuring single-waveform cross-link communication systems that meet their mission’s or business objective’s particular needs to interconnect their own constellation. These single-waveform systems are only capable of talking to other systems that support that particular waveform, almost exclusively consist of custom-made components, and have little to no reconfigurability.


While most waveforms operate within the same wavelength band, they differ in wavelengths, polarization, clock rate, spatial acquisition sequence, modulation format, framing, and error correction coding. As each constellation acquires its own proprietary communications links, satellite communications (SATCOM) becomes severely fragmented with only isolated islands of connectivity.


Space-BACN aims to overcome today’s lack of on-orbit interoperability among current and future space communications.

Intersatellite links are links between satellites. Intersatellite links (ISL) can be considered as particular beams of multi-beam satellites; the beams, in this case, are directed not towards the earth but towards other satellites. For bidirectional communication between satellites, two beams are necessary—one for transmission and one for the reception.  There is yet no standardization of communications or optical intersatellite links in this domain, researchers point out.


Instead, the Space-BACN program seeks to create a reconfigurable space-to-space optical communications terminal that can connect heterogeneous constellations that operate on different optical intersatellite link specifications that otherwise would not be able to communicate with one another.


The Defense Advanced Research Projects Agency (DARPA) is developing a space-based communication node with the goal to create a reconfigurable, multi-protocol intersatellite optical communications terminal that is low size, weight, power, and cost (SWaP-C), easy to integrate, and will have the ability to connect heterogeneous constellations that operate on different optical intersatellite link (OISL) specifications that otherwise would not be able to communicate.

Space-BACN seeks to develop an intersatellite optical communications terminal that is low size, weight, power, and cost (SWaP-C); easy to integrate; and operate on platforms in low Earth orbit (LEO). The project involves space-based communications, optical intersatellite links, reconfigurable modems, modular components, and space command and control.


The Space-BACN program aims to revolutionize the way space-based communications work by developing low-cost, high-speed reconfigurable optical datalinks to connect various low-earth orbit (LEO) constellations…and we’re looking for the best minds out there to help us make this a reality.



The core of Space-BACN is a reconfigurable, multi-protocol low SWaP-C optical communications terminal that can support most current and future single wavelength waveforms in space up to 100 Gbps, uses less than 100 W of power, costs less than $100k (in production), and can be easily integrated into most satellites. From a networking perspective, the terminal is a physical and link layer device (layer 1 & 2 of the Open Systems Interconnection (OSI) stack). Such a terminal could be reconfigured on-orbit to talk across different standards, presenting a revolutionary leap in technology from the current state-of-the-art.


The Space-BACN program consists of three technical areas — two of which are part of this solicitation: A modular, low SWaP-C optical aperture to separate the front end of the optical intersatellite link from the signal processing via single-mode fiber; and a reconfigurable modem able to support several optical waveforms as fast as 100 gigabits per second on one wavelength.


Technical Area 1 (TA1): A modular, low SWaP-C optical aperture that will separate the front end of the OISL from the signal processing via single mode fiber (SMF). The optical aperture will include an overall terminal controller, responsible for pointing, acquisition, and tracking (PAT) functions, and terminal command and telemetry, as well as transmit (TX) optical amplification and optional receive (RX) low-noise optical amplification.


To achieve the coherent processing needed for flexible high-rate optical communications, an optical aperture must couple light into an SMF. Key challenges include focusing and stabilizing light over highly-variable thermal, shock, and vibration environments; operating on any pair of TX and RX wavelengths within the specified optical bandwidth; and accommodating any of multiple PAT sequences.


Traditional diffraction-limited optical apertures for space are highly engineered, tuned, and hardened, which results in them being incredibly expensive and only producible in small quantities. To reduce cost, Space-BACN aims to simplify the design and automate assembly and tuning of the optical components. The TA1 subsystem may consist of one or more distinct components. Ease of integration is valued, but multi-component implementations are acceptable if there are performance and/or SWAP-C benefits.


Technical Area Two (TA2): A reconfigurable modem that can support multiple optical waveforms up to 100 Gbps on a single wavelength. To date, highly reconfigurable communications systems have only been demonstrated in the radio frequency (RF) domain where bandwidths and data rates are an order of magnitude lower than the optical regime. Recent advances in optical communications and digital signal processing technologies have made a 100 Gbps reconfigurable space terminal within reach. In the fiber datacom/telecom world, the convergence to volume-manufacturable integrated photonic circuits has resulted in ubiquitous, low SWaP-C, high data rate transceivers.


Space-BACN will leverage advanced integrated technologies such as analog-to-digital/digital-to-analog converters capable of sampling at 50+ GSps, narrow linewidth tunable lasers, optical in-phase and quadrature (IQ) modulators, and equalizers. The reconfigurable modem is envisioned to support multiple waveforms within the limits of sampling rate, where a specific single-wavelength waveform includes the details of symbol amplitude and phase, modulation, framing, and forward error correction. The focus is on current and near-future industry-supported waveforms; development of custom waveforms specific to this effort is excluded.



The agency has made awards in the first two of the three-month-long “Phase 0” design, Kuperman told Breaking Defense in an email. For both of these Technical Areas, Phase 0 awards each totaled $300,000 over 15 weeks, the DARPA solicitation noted.


Kuperman said the firms winning Phase 0 contracts for this “front end” of the optical terminal system are: CACI, Honeywell, L3 Technologies (L3 Harris), MBRYONICS, Mynaric, SA Photonics and Boeing.




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