Space Force plans to invest billions in sprawling Space Data Network in FY27

The Space Force’s budget request for fiscal 2027 includes billions of dollars in funding for the Space Data Network (SDN), which could turn the service’s plan to create a complex web of military and commercial data relay satellites into reality.

The SDN is envisioned as a multi-orbit, hybrid satellite communications architecture comprising both military-owned and commercial systems built by different vendors. Once fully operational, the SDN will serve as a single, unified network that allows the Pentagon to securely move data via multiple pathways to ground stations and weapons platforms.

While the project’s development has largely happened behind closed doors, SDN’s mission is aligned with a number of ongoing initiatives at the Defense Department. Given the architecture’s ability to rapidly transfer data across domains, the SDN is likely to be a linchpin for the Combined Joint All-Domain Command and Control (CJADC) effort. 

President Donald Trump’s Golden Dome architecture will also require secure comms pathways between missile warning/tracking sensors and interceptors. The SDN is one of three programs that will benefit from a recent $10 billion plus-up to the missile defense shield’s budget, Golden Dome czar Gen. Michael Guetlein said in March.

A Space Force spokesperson told DefenseScoop that the SDN is being billed as a “family of systems” comprising multiple Space Force capabilities.

That includes the “backbone” architecture, a “space link” mission enclave and the Transport Layer of data relay satellites developed by the Space Development Agency. Other service-specific and commercial platforms will be integrated into the SDN as well, the spokesperson added.

Funding for the SDN is scattered among various programs in the Space Force’s FY27 budget — including both research-and-development and procurement dollars in both the base budget and reconciliation funding requests.

Notably, budget documents indicate that several components were initiated in fiscal 2026 because they contributed to Golden Dome. 

“The SDN Family of Systems provide robust, resilient, high-capacity, low-latency communications and tactical data links for the Joint Force,” the Space Force spokesperson said. “These systems serve three primary missions: space data transport, tactical communications and broadband satellite communications (SATCOM).”

One of the foundational elements of the SDN is known as the Space Data Network – Backbone. The existing architecture serves as the core communications layer by facilitating backhaul connections across the Defense Department’s entire network.

According to the Space Force’s budget request, the service is prioritizing building out the SDN Backbone over fielding new Transport Layer satellites under the Space Development Agency’s Proliferated Warfighter Space Architecture (PWSA).

The Space Force is asking for $1.5 billion in FY27 to conduct research and development for the SDN – Backbone — all of which hinges on Congress passing another reconciliation package.

The program is divided into two lines of effort, budget documents show. The first will accelerate fielding of a proliferated low-Earth orbit (pLEO) mesh constellation and ground architecture, while the second provides money to bring additional vendors into the program.

Along with funds for continued RDT&E, the Space Force is also requesting $1.6 billion in procurement for the SDN – Backbone under an effort called Proliferated Low Earth Orbit SATCOM, according to Maj. Gen. Frank Verdugo, Air Force deputy assistant secretary for budget.

“We have $1.6 billion in reconciliation funding and have been investing in that procurement account for Proliferated Low Earth Orbit SATCOM,” Verdugo told reporters April 21 during a briefing on the Department of the Air Force’s FY27 budget request. “The Space Data Network – Backbone — previously MILNET — is a resilient, joint network architecture providing high-capacity and low-latency data transport.”

MILNET refers to a classified program run by both the Space Force and the National Reconnaissance Office to field a massive SATCOM constellation in low-Earth orbit using SpaceX’s Starshield terminals. The effort was first revealed in 2025 as a government-owned, contractor-operated constellation comprising over 480 satellites. 

Initial reports indicated that MILNET was being considered as a replacement capability for future tranches of the SDA’s Transport Layer, which is part of the agency’s PWSA constellation.

The move appeared to be final in fiscal 2026 when the Space Force zeroed out funding for the Tranche 3 transport birds before SDA could award development contracts. However, Congress later reinstated $500 million to continue Tranche 3’s development.

A chief concern among lawmakers was that supplanting SDA’s transport satellites with MILNET would create over-dependence on SpaceX, the program’s sole vendor. Space Force officials later asserted that it planned to eventually bring multiple contractors into the program.

Plans to cancel the Tranche 3 transport layer appear to be in motion once again, as the Space Force’s budget request for FY27 did not include any funding for the program. A service official told DefenseScoop during the April 21 briefing that the requirements for Tranche 3 transport are now being rolled into the larger SDN architecture.

The Space Force spokesperson said that the Transport Layer will be integrated into the SDN to provide tactical communications — connecting individual deployed systems with satellites on orbit. The agency’s Tranche 1 and Tranche 2 satellites were allocated a combined $817 million of RDT&E funds in the Space Force’s FY27 budget request, they said.  

“As an enclave within the Space Data Network (SDN), the PWSA Transport Layer, is an integrated component within the warfighting architecture,” budget documents stated. “PWSA’s integration with the SDN will improve the resiliency and survivability of network connectivity between the PWSA and our warfighters.”

SDA will also develop auxiliary and “sub-constellations” alongside the Transport Layer to provide additional capabilities, including missile warning and SATCOM, according to the documents.

Furthermore, the Space Force is also requesting $1.4 billion in FY27 base funding for another SDN component referred to as the Space Link constellation. The service’s budget justification notes the money will go towards creating a new “mission enclave” — a separate comms environment inside the larger SDN architecture.

The Space Link constellation will also enable the communications requirements for space-based interceptors under Golden Dome, according to the documents.

“In coordination with Army, Air Force, [U.S. Northern Command] and [U.S. Space Command], this funding will support the adoption of a commercially derived Radio Frequency (RF) payload and prototypes for integration onto multiple planes of space vehicles, and launch of the space vehicles,” budget documents stated.