Sierra Space Advances Missile Tracking Satellite Design for SDA Tranche 2

Sierra Space has successfully passed the Critical Design Review (CDR) for its missile tracking satellites under the U.S. Space Development Agency’s (SDA) Tranche 2 Tracking Layer program. This milestone confirms that the company’s satellite architecture is technically mature and ready to move into production—supporting a key component of the Department of Defense’s proliferated low Earth orbit (pLEO) missile warning and tracking constellation.

Missile Warning from Orbit: The SDA’s Tracking Layer Vision

The SDA’s Tracking Layer is a cornerstone of the U.S. Department of Defense’s effort to create a resilient and responsive space-based missile warning system. Unlike legacy systems such as SBIRS (Space-Based Infrared System), which rely on a small number of high-value geosynchronous satellites, the SDA model is built on a proliferated constellation of smaller spacecraft in low Earth orbit (LEO). This approach enhances survivability against anti-satellite threats and provides persistent global coverage with reduced latency.

Tranche 2 represents the third iteration of this effort and includes plans for at least 54 satellites equipped with wide field-of-view infrared sensors capable of detecting and tracking hypersonic glide vehicles (HGVs), ballistic missiles, and other advanced threats. These platforms will feed real-time data into Joint All-Domain Command and Control (JADC2) networks via optical inter-satellite links and tactical datalinks.

Sierra Space’s Role in Tranche 2

In August 2023, Sierra Space was awarded a $740 million contract by the SDA to deliver 18 infrared sensing satellites as part of Tranche 2 Tracking Layer Beta. The company is one of three prime contractors selected alongside Lockheed Martin (18 satellites) and L3Harris Technologies (18 satellites). The total constellation will form a globally distributed mesh network capable of persistent missile detection and precision tracking.

Sierra Space’s solution integrates advanced overhead persistent infrared (OPIR) sensors with high-speed optical crosslinks on a modular satellite bus platform. While specific sensor specs remain classified or proprietary, it is known that these systems are designed to detect dim targets against complex backgrounds—such as maneuvering HGVs flying below traditional radar horizons or within cluttered atmospheric layers.

Critical Design Review Passed: What It Means

The successful completion of CDR marks a pivotal engineering checkpoint where all major subsystems—power management, thermal control, communications payloads, propulsion modules, sensor integration—are validated against mission requirements. According to Sierra Space officials and corroborated by SDA statements, this milestone confirms that their satellite design meets performance thresholds necessary for full-scale production.

“Achieving CDR demonstrates our readiness to build at speed,” said Tom Vice, CEO of Sierra Space. “We are now positioned to deliver next-generation national security space assets that can detect emerging threats like hypersonic missiles.”

This progress aligns with SDA timelines aiming for initial launches in late FY2025 or early FY2026. The CDR also enables long-lead procurement activities such as radiation-hardened components and cryogenic sensor assemblies—a critical step given global supply chain constraints in aerospace electronics.

Industrial Base Implications & Production Strategy

Sierra Space plans to leverage its large-scale production facilities in Colorado—including its new “Spacecraft Factory” near Louisville—to manufacture these platforms at scale. The facility features automated assembly lines tailored for pLEO smallsat constellations—a model inspired by commercial space practices but adapted for defense-grade reliability standards.

• Modular Bus: Designed for rapid integration across multiple mission types including ISR and comms relays
• Sensor Payload: Co-developed with undisclosed partners; optimized for wide-area surveillance in MWIR/LWIR bands
• Crosslink Capability: Compatible with SDA optical link standards; supports mesh networking across orbital planes
• Cyber Hardening: Includes onboard encryption modules compliant with NSA Type-1 standards

This industrial approach reflects broader DoD efforts to adopt commercial space manufacturing efficiencies while maintaining mission assurance through rigorous MIL-STD testing protocols.

The Strategic Context: Countering Hypersonic Threats

The urgency behind programs like Tranche 2 stems from growing concerns over adversary advances in hypersonic weapons technology—particularly from China’s DF-ZF glide vehicle and Russia’s Avangard system. These systems can maneuver unpredictably at Mach 5+ speeds within the upper atmosphere, evading traditional radar coverage arcs.

The only viable detection method involves persistent infrared sensing from LEO orbits where parallax effects enable better angle-of-arrival estimation compared to GEO platforms alone. By deploying dozens of overlapping sensors across multiple orbital planes (~1000 km altitude), the SDA aims to achieve “birth-to-death” tracking capability—from launch plume detection through midcourse maneuvering phases—all feeding into fire control-quality data streams usable by ground-based interceptors or airborne shooters.

SDA’s Broader Architecture Integration Plans

The Tracking Layer is just one pillar within the SDA’s broader National Defense Space Architecture (NDSA), which also includes Transport Layer nodes (for data relay), Custody Layer assets (for target custody/ID), Navigation Augmentation segments (for GPS-denied ops), and Battle Management layers supporting JADC2 fusion centers.

Sierra Space’s contribution will integrate directly into this mesh network via optical terminals adhering to OISL interoperability standards defined by SDA—including compatibility with Link-16 gateways on terrestrial forces or airborne platforms like E-7 Wedgetail or F-35 Block IV aircraft.

Next Steps Toward Launch Readiness

Following CDR clearance, Sierra Space moves into final integration testing phases including environmental qualification campaigns—vibration tables simulating launch loads; thermal vacuum chambers replicating orbital conditions; EMI/EMC tests ensuring no interference between payload subsystems.

If timelines hold steady—and barring procurement delays—the first batch of Sierra-built Tranche 2 Beta satellites could be manifested on Falcon 9 rideshare missions starting Q4 FY2025 under National Security Space Launch Phase 3 contracts managed by USSF/SSC.

A Competitive Landscape Emerges

Sierra faces stiff competition not only from Lockheed Martin and L3Harris but also from startups like Rocket Lab—which recently won an SDA contract under T1TL—and established players like Northrop Grumman eyeing future tranches beyond T3/T4. The maturation of OPIR payload miniaturization and AI-enabled onboard processing may further disrupt traditional defense satellite hierarchies over the next decade.