SpaceX is scheduled to launch 21 satellites for the Space Development Agency on a Falcon 9 rocket from Vandenberg Space Force Base early Monday morning.

The mission, designated Tranche 1 Transport Layer A (T1TL-A), marks the fourth launch of production satellites for the agency’s proliferated architecture. Liftoff from Space Launch Complex 4 East is set for 1:17 a.m. PDT (4:17 a.m. EDT / 0817 UTC), with a southerly trajectory planned.

The Falcon 9 first stage involved, booster B1103, will fly for the sixth time after previous missions including three Space Development Agency launches and three Starlink deployments. SpaceX aims to land the booster at Landing Zone 4 approximately 7.5 minutes after liftoff, which would represent the 37th landing at that site and the 668th successful booster recovery overall.

The satellites were built by Northrop Grumman and delivered to Vandenberg on September 28. They are part of a larger Transport Layer that will eventually include between 300 and 500 satellites operating in low Earth orbit at altitudes between 750 and 1,200 kilometers. Once fully deployed, the constellation is intended to provide coverage over 95 percent of the Earth’s surface with at least two satellites in view at any time.

The Transport Layer satellites will carry optical inter-satellite links designed to improve data transmission speed and reduce latency. According to the Space Development Agency, this capability will enable faster delivery of missile warning and tracking information to U.S. and allied forces.

The mission is managed under the National Security Space Launch Phase 2 contract awarded to SpaceX in August 2020. Previous Tranche 1 missions have been launched on September 10, 2025, October 15, 2025, and July 16, 2026, with satellite production handled by York Space Systems and Lockheed Martin on earlier flights.

Col. Ryan Hiserote, division chief for Assured Access to Space at Space Systems Command, previously stated that launch order would not be fixed. Following the T1TL-E launch in July, Space Force Portfolio Acquisition Executive GP Sandhoo described the constellation as a means to “neutralize any first-mover advantage” by delivering data to warfighters globally with near-instantaneous latency.

When complete, Tranche 1 will include 126 Transport Layer satellites, 28 Tracking Layer satellites, and four missile defense demonstration spacecraft. As of now, 63 satellites have been placed in orbit across three prior launches.

The launch will be webcast by Spaceflight Now, beginning approximately 30 minutes before liftoff.