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The Space Development Agency’s satellite constellation based in low Earth orbit is moving out of the demo phase and into operations.
The U.S. Space Force is months away from sending the first operational satellites for its signature proliferated constellation into low Earth orbit.
If all goes to plan, it will be a watershed moment for U.S. military acquisition and provide a trove of space-based capabilities to warfighters. First, it needs to be approved by the FAA.
- Space Development Agency is building more than 150 satellites under Tranche 1 contract
- Agency still needs FAA approval to use Link 16 over national airspace
The Space Development Agency’s (SDA) Proliferated Warfighter Space Architecture (PWSA) was conceived in 2019 as a vast, low-Earth-orbit-based constellation of sensors that perform seamless data communications, track hypersonic and cruise missiles, and provide enhanced battle management and alternative navigation services via layers of satellites that are replenished every half decade.
The agency is fielding the PWSA through a spiral acquisition model, recompeting two layers of transport and tracking assets over two-year tranches as new technology and capability needs come online.
In 2023 and early 2024, less than three years after contract awards were issued, the SDA launched 27 Tranche 0 satellites. Nineteen spacecraft make up the nascent Transport Layer, with 10 built by Lockheed Martin and nine by York Space Systems. The Tranche 0 Tracking Layer includes eight spacecraft, split between SpaceX and L3Harris Technologies. Those systems are being used to demonstrate Link 16 from space to ground and air systems and intersatellite laser communications.
The next tranche involves a sizable jump in satellite units, as the agency targets an operational constellation. Tranche 1 includes 156 space vehicles: 126 satellites for the transport layer, split among York Space Systems, Lockheed Martin and Northrop Grumman; and 30 satellites for the Tracking Layer, with Northrop Grumman building 14 and L3Harris contracted for 16 systems.
The SDA originally planned to launch the initial Tranche 1 spacecraft starting this fall, but production hiccups from Tier 3 suppliers pushed the timeline to year-end, SDA Director Derek Tournear says. He expects to procure 10 launches for Tranche 1 satellites under the National Security Space Launch contract—at a cadence of about one launch per month—and anticipates that the satellites will reach operational acceptance by the end of 2025.
For that to occur, the SDA must first receive approval from the FAA to deploy Link 16 from orbit over national airspace. The civil agency has yet to grant that approval, which has forced the SDA to conduct recent Link 16 tests over international waters and allied airspace in Australia.
The SDA is undergoing electromagnetic compatibility features certification via the Naval Information Warfare Systems Command (Navwar), Tournear says. Link 16 shares the same spectrum as certain GPS signals, and features are built into Link 16 radios that will automatically shut them down if they are suspected of interfering with navigation signals.
The FAA said in a statement that it is “collaborating with several federal agencies to understand the unique compatibility issues as we continue to work to ensure the safety of the national airspace system.”
The aviation regulator has indicated that it will grant a temporary frequency authorization that would allow the SDA to broadcast over national airspace, but only after Navwar has completed the certification tests, Tournear says. If the FAA does not issue a waiver by early 2025, Tranche 1 demonstrations will be affected, leading to delays in operational acceptance.
The SDA’s hardware deliveries have been hampered by supply chain hiccups for subcomponents like the optical communication terminals (OCT), which are key to connecting the PWSA’s Transport Layer. German OCT provider Mynaric, which supplies a number of SDA vendors, recently dismissed its CEO, Mustafa Veziroglu, as the company struggled to scale up production and to rein in development costs for its Condor Mk. 3 laser terminals.
The SDA is working to minimize these supply chain growing pains for future tranches, Tournear said Sept. 5 at the Defense News Conference in Washington. The agency was approved to begin Tranche 3 solicitations six months ahead of the original schedule, in part to give the supply chain more breathing room before launches for that tranche begin around 2028.
Meanwhile, work is moving ahead for the SDA’s Tranche 2 satellites. That represents yet another leap in unit numbers—264 space vehicles in total, of which 210 are dedicated to the Transport Layer—with added capabilities and upgrades, fielded on the same two-year turnaround with launches to begin in 2026.
The vendors for the Tranche 2 Transport Layer are: Lockheed Martin, with 36 satellites, Northrop Grumman (74), Rocket Lab (18), York Space Systems (72) and Tyvak (10). The tracking layer vendors are Lockheed Martin, L3Harris and Sierra Space, building 18 satellites each. Most companies are in the process of reaching design review milestones.
Under Tranche 2, the SDA separated the hardware contracts into multiple variants for the first time and welcomed new vendors Tyvak, Rocket Lab and Sierra Space. Tyvak’s parent company, Terran Orbital, provides the bus for Lockheed Martin’s transport and tracking layer spacecraft.
The SDA also will launch eight satellites built by Millennium Space Systems under the Fire-control On Orbit-support-to-the-war Fighter (FOO Fighter) program, taking flight alongside the Tranche 2 spacecraft. These systems will provide an operational demonstration of fire control capabilities—separate from but complementary to the Tracking Layer spacecraft—with launch expected by early fiscal 2027.
With Tranche 1 satellites approaching delivery and Tranche 2 system designs underway, the SDA soon will release solicitations for Tranche 3, including about 140 satellites for the transport layer and 54 Tracking Layer satellites, to begin launching in 2028. The SDA wants to release the first Tranche 3-related solicitation for ground systems by the end of 2024, with spacecraft requests for proposals coming out early next year.
By 2028, the initial Tranche 1 satellites are to start decommissioning, and the new spacecraft will replenish the PWSA, primarily on the Transport Layer. “That means you have to maintain that Link 16 constellation and then add additional capabilities,” Tournear says.
Tranche 3 systems will include advanced phased-arrays that allow the PWSA to service more users at once, primarily those using S-band signals, he says. On the Tracking Layer, Tranche 3 systems also will replenish decommissioning satellites while beginning to layer in a global missile defense capability.
The PWSA has stayed fairly true to the design envisioned in 2019 by the SDA’s first director, Fred Kennedy, who previously led DARPA’s Tactical Technology Office, Tournear says. The agency identified the data communications backbone enabled by the transport layer and beyond-line-of-sight targeting and tracking as the quickest and most efficient capabilities for the warfighter, he adds. Other capabilities—notably navigation, battle management and custody—are being incorporated into the next tranches.
For navigation, the SDA is adding situational awareness sensors to all transport satellites to detect jamming or spoofing on the ground, Tournear says. The agency also is embedding a position, navigation and timing (PNT) signal over its Link 16, Ka-band and optical communication channels to offer alternate PNT to users in a GPS-denied environment. That capability is being incorporated on a small scale on Tranche 1 satellites and will be part of Tranche 2’s baseline satellites.
The battle management element is enabled by standalone processors on the transport satellites that will then operate “as a federated cloud computing system in space,” Tournear says. SAIC is building the Battle Management Command, Control and Communications application factory, and the company reached the minimum viable product milestone in June, says Andy Sullivan, company vice president of strategic space.
The SDA wants to have several applications processed by and approved to move through the application factory before the Tranche 1 satellites are launched and ready to begin on-orbit testing, Sullivan adds.
The original SDA vision included an independent constellation of remote-sensing spacecraft performing the custody mission, but that was soon deferred in favor of partnerships with other agencies and commercial partners already building such systems. Recently, the SDA has identified several niche missions for the Defense Department that would use an agency-derived custody layer, and the FOO Fighter satellites will help demonstrate those capabilities before new birds are added into future tranches, he says.
The agency recently chose to rename what was originally called the “support cell” of the PWSA to the ground and launch cell, to better reflect its mission of supporting satellite operations. The original plan also included a deterrence element in the constellation, but that mission will now be performed by other Space Force and Defense Department offices, Tournear says.
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