WASHINGTON — The Space Force’s effort to develop a complex Space Data Network (SDN) of military and commercial satellites is beginning to move from concept to reality, in part due to its foundational role for enabling the Trump administration’s planned Golden Dome missile-defense shield.
The SDN, which is intended to speed getting sensor data to joint force shooters, has largely flown under the radar for military space watchers. However, it appears poised to emerge from the shadows: Pentagon Golden Dome czar Gen. Michael Guetlein said Tuesday in a rare public presentation at the McAleese Defense Programs Conference that the SDN is one of three service programs being put into place more quickly as part of Golden Dome’s recent $10 billion plus up.
Golden Dome, Guetlein has repeatedly explained, will succeed or fail based on whether data can be integrated and moved from missile warning/tracking sensors to interceptors in near-real time. The SDN will provide the communications pathways for doing that, as well as giving secure command and control to military leaders — meaning the network, as envisioned, will effectively be the backbone of one of the Pentagon’s most high-profile, and high-cost, efforts.
The Space Force has never published or fully outbriefed to industry its overarching Space Data Network Force Design, created by the Space Warfighting Analysis Center (SWAC) as a blueprint of the capabilities required to build the SDN and the budgetary investment needed over the next five or so years to develop them.
In part, according to sixservice and industry sources, this is because the Space Force and the Defense Department are still putting together a detailed implementation plan for that blueprint, including budgetary allocations. As a result, specific acquisition projects designed to substantiate the SDN force design remain somewhat murky.
“How this will be brought to fruition and into reality is a big question mark,” one former Pentagon SATCOM expert said.
“There is still a lot of open trade space … a lot of puzzle pieces to be put together,” one Space Force official told Breaking Defense.
In response to questions about what Defense Department satellite constellations are included in the SDN plan, a Space Force spokesperson said, “The SDN has a Backbone for moving data around the globe and also includes mission capabilities including MILSATCOM Broadband, Narrowband, and several Space Development Agency capabilities.”
However, “USSF Combat Forces Command will not disclose what systems will or will not be used as a part of the Space Data Network. Due to operational security, we are unable to discuss the speed or capabilities of these assets,” the spokesperson said.
The Space Development Agency referred Breaking Defense’s question about which of its capabilities were included in the SDN to the Space Force.
While officials are being circumspect in their comments, in recent months the service has begun to issue the first solicitations for some baseline elements for the SDN, industry sources said. Which means that the boost in funding from the Golden Dome coffers may be a step in taking the SDN from concept to reality.
Long Envisioned, But Never Substantiated
Practically since its inception, the Space Force has envisioned a multi-orbit, “hybrid” satellite communications (SATCOM) architecture comprising interlinked classified military and unclassified commercial communications satellites, missile warning/missile tracking satellites, and satellites providing position, navigation and timing data such as GPS. This network-of-networks would in essence become a space-based internet, sometimes referred to as “the outernet.”
The goal is to enable rapid and secure transmission of critical data to ground stations for dissemination to far-flung commanders, as well as directly to weapons platforms on the ground, in the air, at sea, in space and in cyberspace.
Implementing that vision has proven difficult, however, due to technological hurdles and programmatic stovepipes.
The SWAC, charged with crafting the Space Force’s desired future force structure over the next five to 15 years, took up the challenge of fleshing out the hybrid SATCOM concept in 2022, and finished a first force design in early 2023 — only to spend the last two years revamping and revising the framework and its components, and even the name,sources said.
“The Space Data Transport Force Design, now called the Space Data Network Force Design, established a hybrid architecture that integrates government-owned and commercial systems across multiple orbital layers to provide resilient and scalable data transport capabilities,” a Space Force spokesperson said. “Key features include orbit diversity to enhance resilience, multi-vendor interoperability to foster competition, and modular solutions to address diverse user needs.”
The force design also outlined “enabling capabilities” needed to ensure “seamless connectivity” among SDN’s various nodes, such as hybrid SATCOM terminals that can talk to both military and commercial satellites using a variety of frequency bands, and “Space Exchange Points” (sometimes called “translator satellites”) to intake and disseminate sensor data.
“By late 2024, the major SDN pieces had been assembled. They have continued to be refined since then,” the spokesperson added.
Changes in the SDN construct have been required in part due to the emergence of new technology and the Space Force’s effort, launched last May, to shift from bespoke military acquisition programs towards buying commercial services when possible, according to service and industry sources. Those changes, in turn, have driven the lack of clarity about what specific development projects and/or commercial acquisitions will be funded to provide the required enabling capabilities for SDN, these sources said — not to mention questions about which Space Force entities are in charge of program management and funding.
Moving Parts: Backbone, Tactical Comms And Network Orchestration
That said, service and industry sources explained that the SDN will need capabilities to allow three primary technical functions: backhaul communications, fronthaul communications and network orchestration.
Up to now, the Space Force has been largely focused on developing a backbone constellation to provide backhaul communications — that is, the ability to move massive amounts of data to and from various satellite networks with low lag times.
As one telecommunications industry exec put it, the backbone constellation will be a “a big router, rather a bunch of big routers [i.e. satellites], carrying a lot of traffic.”
The idea is that the backbone “will connect between satellite constellations in space,” Todd Harrison, senior fellow at the American Enterprise Institute, said. “So a missile warning satellite can connect to this backbone, as could a comms satellite with a Link16 payload or an imagery satellite.
“And I think that backbone is probably MILNET,” he added.
MILNET is the name of a classified Space Force effort that involves communications payloads hosted on the constellation stationed in low Earth orbit (LEO) SpaceX is providing to the National Reconnaissance Office for its proliferated-LEO imagery architecture. The Department of the Air Force, which oversees Space Force acquisition, since last June has been weighing whether to substitute MILNET for the Space Development Agency’s Transport Layer of data relay birds in LEO.
A decision on how to proceed is expected to be spelled out in the upcoming fiscal 2027 budget. However, in recent months Space Force officials have been hinting that both programs are likely to go forward as pieces of the SDN.
In fact, several Space Force and industry sources said the term MILNET is no longer en vogue — with one calling it “the program formerly known as MILNET” in reference to the late pop singer Prince. One reason for the terminology shift is that the service wants to emphasize that it is working to engage multiple vendors, not just SpaceX, in building out the infrastructure for backhaul communications — perhaps with an eye to concerns raised by some members of Congress about granting a sole source contract to the company.
In response to a question from Breaking Defense about the SDN force design’s impact on that decision, a Space Force spokesperson said that the force design “serves as the guiding vector for the USSF resource allocation in the FY27 budget, though other factors were also involved.”
One way the decision about the fate of the two LEO SATCOM efforts could go, according to service and industry sources, is that MILNET becomes the de facto SDN backbone, while the Transport Layer constellation’s purpose is narrowed down to providing “tactical” or “fronthaul” communications.
Fronthaul communications refers to the links from a deployed terminal (e.g., on a ship, airplane, or Army radio) and a satellite. For example, SDA already has proven the ability of the Transport Layer satellites to push targeting data through Link 16, which is widely used by US and allied forces.
Other Space Force SATCOM networks also provide this type of communications, such as the Mobile User Objective System (MUOS) network for narrowband communications in the ultra-high frequency band — a capability most used by the US Navy, but also by multiple aircraft and soldiers on the ground.
Finally, the third part of the SDN is the “Mission Operations Center,” which will provide “network orchestration” via hardware such as antennas and terminals as well as software. The service on Jan. 23 issued a request for information about how such a center could be created and/or what commercial services might be available to support it.
Network orchestration enables autonomous shifting of data among the various satellite constellations in various orbits and down to the multiple ground stations supporting them — allowing data to “hop” from one constellation to another in the event of a slowdown in transmission due to bandwidth congestion or adversary jamming.
“That Mission Operations Center is very critical, and we are well aligned with its pivotal role in the space data network,” said Rajeev Gopal, vice president for Advanced Systems at Hughes. He noted that his company is already connecting diverse commercial networks with communications satellites in geosynchronous and low earth orbits utilizing smart orchestration under policy-based management.
“So that technically has been done in the commercial domain. Now the challenge is to do it securely across military and commercial networks,” he told Breaking Defense in an email.
Interested vendors had a deadline of Feb. 27 to respond to the RFI.
The Air Force Research Laboratory (AFRL) also is funding startups to potentially provide artificial intelligence capabilities to support the SDN’s network orchestration.
California-based Aalyria was tapped by AFRL’s Rapid Architecture Prototyping and Integration Development unit to support its Space Data Network Experimentation program via an award through the lab’s Space Technology Advanced Research Fast-tracking Innovative Software and Hardware (STAR-FISH), initiative to demonstrate its AI-enabled network orchestration concept, the firm announced on Jan. 22.
“Aalyria will evaluate how its Spacetime AI-enabled orchestration software can integrate diverse satellite systems, ground infrastructure, and communications links into a seamless, resilient network for defense operations,” the release said.
