The Space Development Agency spent Monday writing checks. On July 13, 2026, the Pentagon office responsible for building a mesh of low-Earth-orbit missile-tracking satellites awarded a combined $1.75 billion to two contractors — L3Harris and Sierra Space — to build 36 more spacecraft for the Tracking Layer of the Proliferated Warfighter Space Architecture. The satellites are destined for Tranche 3 of that architecture, a segment SDA has branded the Accelerated Missile Defense Tranche 3, or AMDT3, and they're explicitly framed as part of the broader Golden Dome missile-defense push.

L3Harris, based in Fort Wayne, Indiana, picked up roughly $955 million to build 18 satellites in a missile-defense variant. Sierra Space, headquartered in Louisville, Colorado, will build the other 18 in a missile-warning/tracking variant, for $798 million. Add it up and you get $1.75 billion for 36 spacecraft, spread across four orbital planes. SDA says the satellites are expected to be available for launch by the end of 2028.

What exactly did SDA buy?

Two variants of the same basic mission: watching for missiles from space. The Tracking Layer is the part of the Proliferated Warfighter Space Architecture built specifically to detect and follow ballistic and hypersonic threats from birth to impact, feeding that data down to interceptors and command centers. Splitting the order between a "missile-defense" variant and a "missile-warning/tracking" variant reflects the layered nature of the job — some satellites are tuned to support fire-control-quality tracking precise enough to cue an interceptor, while others are built more for the broader early-warning mission of spotting a launch and characterizing its trajectory.

GP Sandhoo, SDA's Portfolio Acquisition Executive for Missile Warning and Tracking, framed the awards around speed, saying the goal is to accelerate deployment of the Tracking Layer rather than let it move at the pace of a traditional satellite program. That urgency is baked into the "Accelerated" in AMDT3's name, and it lines up with the wider Golden Dome effort, which has leaned on SDA's tranche-based approach — buy in batches, launch fast, iterate — instead of the exquisite, decade-long satellite programs the Pentagon is better known for.

The bigger number behind the number

Monday's 36 satellites don't stand alone. According to Air & Space Forces Magazine's reporting, this award brings the combined Tranche 3 total to 104 vehicles once you fold in contracts issued the previous December. That's a meaningful data point: it means SDA has now committed to building well over 100 tracking and defense satellites under Tranche 3 alone, on top of whatever came before in Tranches 0, 1, and 2.

L3Harris CEO Chris Kubasik put a number on his company's slice of that pipeline, telling reporters the company now has "more than 70 missile tracking and defense satellites on order" — a figure that spans this award and prior contracts, and underscores how central L3Harris has become to SDA's tracking constellation.

There's also a legislative thread running through this. The Senate Armed Services Committee has directed SDA to field at least 45 satellites equipped with HBTSS — Hypersonic and Ballistic Tracking Space Sensor payloads — within Tranche 3. HBTSS is the sensor technology purpose-built for spotting hypersonic glide vehicles, which fly lower and maneuver more than traditional ballistic missiles, making them harder for older radar and satellite systems to track continuously. Monday's award doesn't specify how many of the 36 new satellites carry HBTSS payloads, but it moves SDA closer to whatever floor Congress has set.

Two contractors, two approaches

Splitting the buy between L3Harris and Sierra Space fits a pattern SDA has followed across earlier tranches: award parallel contracts to multiple manufacturers rather than lock the constellation into a single vendor's bus and sensor design. It hedges against a single company's manufacturing hiccup delaying the whole tranche, and it keeps competitive pressure on pricing for the next round of awards. L3Harris has a long track record in missile-warning payloads and space sensors, built up over previous SDA tranches and legacy missile-warning satellite work. Sierra Space is a newer entrant to this specific niche but has been expanding its national-security space portfolio alongside its better-known commercial space ambitions.

Why It Matters

Golden Dome is the Trump administration's answer to a strategic problem that has been building for years: adversaries, particularly China and Russia, are fielding hypersonic and maneuverable missile systems that traditional ground-based radar and existing satellite constellations struggle to track continuously from launch to impact. A space-based tracking layer solves the geometry problem — satellites in low Earth orbit can maintain a persistent, overlapping view of a threat's full flight path in a way that fixed ground radar, limited by the horizon, cannot.

The scale matters as much as the technology. A single satellite, however capable, is a single point of failure and a single target. Proliferating dozens of relatively low-cost satellites across multiple orbital planes — the model SDA has pursued since Tranche 0 — makes the constellation more resilient to both technical failure and, more pointedly, to anti-satellite attack. That's a deliberate departure from the small-number, exquisite-satellite approach that defined missile-warning architecture for decades.

The pace is the other story. A 2028 launch target for satellites awarded in mid-2026 is aggressive by any defense-acquisition standard, and it reflects the "accelerated" branding SDA has attached to this tranche. Whether L3Harris and Sierra Space can deliver 36 satellites — with sensors sensitive enough to track hypersonic threats — on that timeline, without the schedule slips that have plagued past space programs, will be the real test of whether Golden Dome's tracking layer can move at the speed its name promises.

Sources