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SpaceX launches Space Development Agency’s top secret Tranche 1 mission on Wednesday from California

September 10, 2025

On Wednesday, September 10 at 7:12 a.m. PT the Falcon 9 launched the Space Development Agency’s (SDA) first Tranche 1 mission to low-Earth orbit from Space Launch Complex 4 East (SLC-4E) at Vandenberg Space Force Base in California. Photos captured by Satnews unless otherwise accredited.

The SDA’s first spacecraft, Tranche 0, launched in 2023 and 2024 demonstrated capabilities such as laser communication between satellites, with the ground, and recently between a commercial partner’s satellite and an SDA terminal installed on an aircraft in flight.

The 21 satellites, built by York Space Systems, are the first, fully operational spacecraft for the constellation known as the Proliferated Warfighter Space Architecture (PWSA). It was formerly called the National Defense Space Architecture (NDSA), but the name was changed in 2023.

The launch is a new phase for SDA, which since 2019 has been planning a large constellation of government-owned missile tracking and data transport satellites in low Earth orbit.

21 satellites manufactured by York Space Systems for Space Development Agency’s upcoming Tranche 1 Transport Layer launch. Image: York Space Systems

The SDA said it was renamed “to more specifically reflect the agency’s mission to deliver needed space-based capabilities to the joint warfighter to support terrestrial missions through development, fielding, and operation of a proliferated low Earth orbit (pLEO) constellation of satellites.”

In 2019 the SDA was formed as an independent agency to safeguard the United States against hypersonic weapons. The agency also planned on offering a network of satellites and ground support systems that could unify the Department of Defense’s capabilities across a “resilient, threat-driven space surveillance and communications architecture,” according its establishing memorandum. It became a part of the U.S. Space Force in October 2022.

This was the sixth flight for the first stage booster supporting this mission, which previously launched five Starlink missions. Following stage separation, the first stage will land on the Of Course I Still Love You droneship, which will be stationed in the Pacific Ocean.

SpaceX ready for Space Development Agency’s top secret first Tranche 1 mission on Wednesday from California

TRANSPORT LAYER
SDA’s Transport Layer will provide assured, resilient, low-latency military data and communications connectivity worldwide to a full range of warfighter platforms.

SpaceX is targeting Wednesday, September 10 at 7:12 a.m. PT for a Falcon 9 launch of the Space Development Agency’s (SDA) first Tranche 1 mission to low-Earth orbit from Space Launch Complex 4 East (SLC-4E) at Vandenberg Space Force Base in California. If needed, a backup opportunity is available on Thursday, September 11 at 7:04 a.m. PT.

TRACKING LAYER
SDA’s Tracking Layer will provide global indications, warning, tracking, and targeting of advanced missile threats, including hypersonic missile systems.

This mission aims to deploy 21 satellites into low-Earth orbit to provide tactical data delivery, missile threat tracking, and support the warfighter’s terrestrial needs. 

A live webcast of this mission will begin about 10 minutes prior to liftoff, which you can watch here and on X @SpaceX. You can also watch the webcast on the new X TV app.

The space vehicles launched during this mission will serve a part of SDA’s Proliferated Warfighter Space Architecture, a new layered network of satellites in low-Earth orbit and supporting elements that will provide global military tactical communication and missile warning, indication, and tracking capabilities.

This will be the sixth flight for the first stage booster supporting this mission, which previously launched five Starlink missions. Following stage separation, the first stage will land on the Of Course I Still Love You droneship, which will be stationed in the Pacific Ocean.

There is the possibility that residents of Santa Barbara, San Luis Obispo, and Ventura counties may hear one or more sonic booms during the launch, but what residents experience will depend on weather and other conditions.

SpaceX to launch top secret Space Development Agency’s first Tranche 1 mission on Wednesday from California

SpaceX is targeting Wednesday, September 10 at 7:12 a.m. PT for a Falcon 9 launch of the Space Development Agency’s (SDA) first Tranche 1 mission to low-Earth orbit from Space Launch Complex 4 East (SLC-4E) at Vandenberg Space Force Base in California. If needed, a backup opportunity is available on Thursday, September 11 at 7:04 a.m. PT.

A live webcast of this mission will begin about 10 minutes prior to liftoff, which you can watch on X @SpaceX. You can also watch the webcast on the new X TV app.

This will be the sixth flight for the first stage booster supporting this mission, which previously launched five Starlink missions. Following stage separation, the first stage will land on the Of Course I Still Love You droneship, which will be stationed in the Pacific Ocean.

The space vehicles launched during this mission will serve a part of SDA’s Proliferated Warfighter Space Architecture, a new layered network of satellites in low-Earth orbit and supporting elements that will provide global military tactical communication and missile warning, indication, and tracking capabilities.

There is the possibility that residents of Santa Barbara, San Luis Obispo, and Ventura counties may hear one or more sonic booms during the launch, but what residents experience will depend on weather and other conditions.

Filed Under: Aircraft, Booster, Booster Recovery, Droneship, Droneship Landings, Hypersonic Weapon System, Low Earth Orbit (LEO), Military, PWSA, PWSA Transport Layer, Space Development Agency (SDA), SpaceX Falcon 9, Tranche 1, Warfighters, York Space Systems Tagged With: Featured

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