The Space Development Agency has awarded a combined $1.75 billion to L3Harris Technologies and Sierra Space Corporation to build 36 missile-tracking and missile-defense satellites, adding another layer to the Golden Dome for America missile-defense architecture.

Background

SDA has spent the past several years building the Proliferated Warfighter Space Architecture, a mesh of low-Earth-orbit satellites designed to detect and track missiles, including advanced hypersonic threats, and relay that data to warfighters through a common ground system. The agency builds the constellation in successive "tranches," each adding more spacecraft and more capable sensors while staying compatible with satellites already on orbit.

Golden Dome for America, the layered homeland missile-defense initiative, leans heavily on SDA's tracking satellites to spot missile launches and hand off custody to interceptors. The new award, designated Accelerated Missile Defense Tranche 3, or AMDT3, is built specifically to feed that architecture and to move faster than SDA's standard tranche timelines.

SDA already committed to a large slice of its Tranche 3 Tracking Layer in December, when it awarded contracts for 72 satellites to Lockheed Martin, Rocket Lab, Northrop Grumman and L3Harris. The July 13 award for 36 more spacecraft brings the Tranche 3 Tracking Layer total to 104 satellites, spread across five companies that now share responsibility for keeping the layer's sensor coverage and launch cadence on schedule.

The Accelerated Missile Defense Tranche 3 designation signals how SDA is treating this batch differently from the rest of Tranche 3. Rather than folding the 36 satellites into the same competition and schedule as the December awards, SDA ran AMDT3 as its own rapid-prototyping effort, aimed squarely at the tracking and defense needs Golden Dome for America has surfaced since the initiative was announced.

The Tracking Layer's job within the broader architecture is to give commanders continuous custody of missile threats from launch through intercept, using sensors distributed across a large number of satellites rather than concentrated on a handful of exquisite, expensive spacecraft. The four orbital planes split evenly between L3Harris and Sierra Space mirror how SDA has structured earlier tranches, spreading satellites across multiple planes to guarantee persistent coverage rather than relying on a single orbital track that leaves gaps as satellites pass out of view.

Key Details

L3Harris Technologies, based in Fort Wayne, Indiana, will receive approximately $955 million to build 18 satellites across two orbital planes. SDA describes these as missile-defense variants comparable to the agency's earlier Hypersonic and Ballistic Tracking Space Sensor, or HBTSS, demonstration satellites, which carry sensors tuned to track threats through the difficult midcourse and terminal phases of flight.

Sierra Space Corporation, based in Louisville, Colorado, will receive approximately $798 million to build the other 18 satellites, also across two orbital planes. SDA categorizes Sierra Space's spacecraft as missile-warning and missile-tracking variants, the sensor type SDA has flown in earlier tranches to give early indication of a launch before handing tracking duties to more specialized satellites.

Both awards are structured as fixed-price Other Transaction Authority agreements, the rapid-prototyping contract vehicle SDA has used across its tranches to move satellites from award to orbit faster than traditional acquisition allows. SDA expects both companies' satellites to be available by the end of 2028.

Every AMDT3 satellite is required to be interoperable with the spacecraft SDA has already fielded or awarded in Tranche 1, Tranche 2 and the rest of Tranche 3, all tied together through a common ground system. That interoperability requirement is central to how SDA has built the Proliferated Warfighter Space Architecture: rather than treating each tranche as a standalone constellation, the agency wants every new batch of satellites to plug into the same command-and-control infrastructure as the ones that came before it.

GP Sandhoo, the Space Force's Portfolio Acquisition Executive and SDA Director, is quoted in the agency's announcement discussing the awards, which SDA frames as a direct contribution to the Golden Dome for America initiative rather than a standalone tracking-layer buy.

What It Means for Contractors

The AMDT3 award confirms that SDA is willing to run parallel, accelerated buys on top of its standard tranche cadence when a priority initiative like Golden Dome demands it. Contractors who want a piece of that accelerated work should expect SDA to keep favoring firms with a demonstrated production line rather than newcomers, since the fixed-price OTA structure and the 2028 delivery target leave little room for schedule slip or unproven manufacturing processes.

L3Harris continues to compound its position across every SDA tranche, having already won Tracking Layer work in the December awards and now adding 18 more missile-defense satellites under AMDT3. That track record gives L3Harris a growing share of SDA's total spacecraft count and a strong argument for follow-on tranches as the agency continues to expand the Tracking Layer.

Sierra Space's award is notable because it hands the company a large, fixed-price national-security space production contract at a scale beyond its prior SDA work, a signal that SDA is still willing to bring in additional primes rather than consolidating the Tracking Layer among the four companies that split the December awards. Other space manufacturers pursuing SDA business should watch how Sierra Space executes on the 2028 timeline, since a clean delivery record would strengthen the case for opening future tranches to a broader industrial base rather than narrowing it.

The interoperability mandate embedded in the AMDT3 requirements is also a signal to subsystem and ground-segment vendors: SDA is not going to relax its common ground system requirement as Golden Dome adds urgency to the schedule, which means companies building sensors, buses or ground infrastructure for these contracts need to keep designing to the existing PWSA standard rather than proposing bespoke architectures, even under accelerated timelines.

More broadly, the award is another data point that Golden Dome for America is translating into real satellite production contracts rather than remaining a planning exercise. Contractors tracking the initiative should expect SDA to keep issuing additional Tracking Layer awards as the missile-defense architecture matures, with fixed-price OTAs remaining the preferred vehicle for companies that can show they can build and deliver on SDA's compressed schedules.

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