According to a recent notice to industry posted on Sam.gov, SDA intends to release the first draft solicitations for Tranche 3 of the PWSA’s tracking and transport layers in early 2025. Those satellites — slated to begin launching in 2028 — are expected to provide advancements in capabilities from previous tranches, as well as feature new warfighting applications.

An SDA spokesperson confirmed that approximately 200 satellites will make up Tranche 3 of the PWSA. The constellation is being developed and fielded in batches or “tranches,” and it’s expected to eventually comprise hundreds of space vehicles in low-Earth orbit that carry critical technologies for data transport and missile defense missions.

The Tranche 3 transport layer is being divided into three separate variants — Upsilon, Sigma and Lambda — that each have slightly different capabilities, the same strategy SDA used to develop transport satellites for Tranche 2’s transport layer. The agency expects to issue up to two awards for each variant, according to the notice.

A draft solicitation for the Upsilon variant is slated be published in early 2025, and those for the Sigma and Lambda variants are to be released in the spring and summer of 2025, respectively. The final solicitation for the Upsilon and Sigma variants are anticipated to be released during the third quarter of fiscal 2025, followed by the final Lambda solicitation in the fourth quarter of FY ’25.

Because solicitations are still being finalized, the agency could not provide details as to what specific capabilities will be in each variant. However, the notice stated that Tranche 3 transport satellites will support “the advancement of the PWSA’s Tracking capabilities by adding capacity and robustness to the global mesh network.” 

SDA will also build out the PWSA’s ability to conduct position, navigation and timing (PNT) in Tranche 3, according to the notice. While transport satellites in the first and second batches are expected to deliver initial PNT capabilities, the third tranche will feature enhancements in time transfer and ranging technologies, the SDA spokesperson told DefenseScoop.

As for the Tranche 3 tracking layer, the agency plans to release a draft solicitation in the spring of 2025 and the final version in the summer, according to the notice. SDA previously published a request for information in July that sought industry feedback on its plans for the third tracking layer, which will include systems that are equipped with infrared sensors and able to provide warfighters with fire control-quality data.

At the same time, the notice indicated that SDA is considering development of a PWSA Enterprise Ground effort, although it didn’t provide specific details or timelines for when solicitations might be published.

The notice to industry for Tranche 3 came after the agency decided to adjust its acquisition strategy for the PWSA to allow more time for vendors to build their platforms. In September, SDA Director Derek Tournear said previous contracts required industry to have systems ready to launch within two-and-a-half years of the contract date, but the agency has since extended that to three years.

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The organization released a request for information posted to Sam.gov on Friday. In a related announcement, SDA said it’s looking for input on its upcoming Tranche 3, which will “accelerate the proliferation of missile defense capability to provide low-latency fire control-quality data.” The agency plans to purchase around 54 platforms — or potentially more — from one or more vendors.

The new RFI is the first one published for Tranche 3 of SDA’s Proliferated Warfighter Space Architecture (PWSA), a planned constellation of hundreds of satellites that carry communications, data transport, and missile warning and tracking capabilities. The agency’s systems stationed in low-Earth orbit (LEO) are intended to be part of a larger, multi-orbit proliferated space architecture of missile warning and tracking capabilities — one of the Space Force’s top budget priorities.

The Tranche 3 tracking satellites will be equipped with infrared sensors and be launched across six orbital planes, according to SDA. The agency is targeting a launch date of no later than April 2029 for the first plane, according to a release.

Responses to the RFI are due July 29, after which the agency plans to publish a final request for proposal.

Iterating off of the previous two tranches, Tranche 3 will provide fire control-quality data for warfighters. Fire control systems are able to create high-fidelity tracking information for incoming threats that includes the exact position and time accuracy needed for a missile defense system to send an interceptor to defeat targets.

The satellites in PWSA’s tracking layer are a separate effort from SDA’s experimental Fire-control On Orbit-support-to-the-war Fighter (FOO Fighter) program, which focuses on advancing next-generation fire-control capabilities for very specific threats.

In addition, the Tranche 3 tracking satellites will continue “to provide global, persistent indications, detection, warning, tracking, and identification of conventional and advanced missile threats, including hypersonic missile systems,” according to SDA. 

The first batch of 28 operational tracking satellites in Tranche 1 — built by Northrop Grumman and L3Harris — are scheduled to launch beginning in April 2025 and will offer “global mono coverage” for conventional missiles and hypersonic glide vehicles, an SDA fact sheet stated. 

Lockheed Martin, Sierra Space and L3Harris are contracted to develop satellites for Tranche 2, which will “complete near global stereo coverage” for missile warning and tracking missions while offering preliminary fire control capabilities, according to the fact sheet. The Tranche 2 satellites are scheduled to launch in 2027.

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SDA is currently developing a satellite constellation known as the Proliferated Warfighter Space Architecture (PWSA) that will be launched in batches known as tranches. With hundreds of satellites stationed in low-Earth orbit, the architecture aims to incrementally provide critical capabilities for the armed forces, such as satcom, missile warning and missile tracking. 

A significant effort for early tranches of the data transport layer focused on offering and proliferating the Link 16 tactical data link from space-based systems. Moving forward, SDA Director Derek Tournear said the agency is considering what other waveforms it wants to equip on Tranche 3.

“Transport is shifting from Link 16 … What we have with 126 Link 16 satellites in Tranche 1 and the 100 Link 16 satellites in Tranche 2 — we’ll have very good coverage for the Link 16 mission,” Tournear told reporters Wednesday during a media roundtable at the annual Space Symposium in Colorado Springs, Colorado. “The next big debate going on for transport is: what are the next tactical data links that we’re going to proliferate in Tranche 3?”

Link 16 is the only common tactical data link used across the United States’ military branches and the NATO alliance. SDA equipped its demonstration tranche of PWSA satellites with some Link 16 payloads and began demonstrating the first-ever space-to-ground transmissions of the data link in November 2023.

And while Tranche 3 is likely to include some Link 16 payloads to ensure overall resiliency of the capability, Tournear said a majority of the satellites will offer tactical satcom within the S-band — although which specific waveforms those could be are still up for debate.

The Beta variant of the Tranche 2 transport layer focused on providing tactical satcom via the S-band and Ultra High Frequency band down to very specific platforms, Tournear noted.

“What we do on Tranche 3 is being informed by what radios those platforms are actually planning on flying in that time frame,” he said. “Will it be a carbon copy of what they’re flying now that’s talking to the UHF S-band on our Tranche 2 Beta birds or will it be a different S-band wave form?”

As for the missile warning and tracking layer, Tournear said Tranche 3 will work toward getting the number of satellites necessary to detect and track high-speed missiles from space.

Across Tranche 1 and Tranche 2, SDA has contracted vendors for 82 satellites in its tracking layer. While the baseline plan for Tranche 3 has been around 54 satellites, the exact number of payloads will be determined as the department decides how much money to allocate to the program over the next couple of months.

A force design conducted by the Space Warfighting Analysis Center found that the Space Force would need around 135 tracking satellites in LEO for its missile warning and tracking mission, Tournear noted.

Right now, the agency is focused on getting to at least 100 tracking satellites in orbit to achieve the resiliency it needs, he added. The difference between that number and the overall goal of 135 is “assumptions in specific designs,” he said.

“It’s going to be continuing to build out off of Tranche 2 tracking and get towards that number of 100 satellites in the total LEO tracking constellation, adding in more of those missile defense satellites as we go to make sure that we have enough coverage for the missile defense mission by the 2030 time frame,” Tournear said.

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