The satellites that underpin American military power in space are, in significant ways, legacy systems designed for a threat environment that no longer exists. The GPS constellation began with satellites launched in the 1970s and 1980s, and while the oldest blocks have been replaced, the system architecture reflects an era when no adversary could threaten GPS satellites or jam their signals at scale. The Space Based Infrared System missile warning satellites, which detect ballistic missile launches from geosynchronous orbit, were designed before China and Russia had developed the electronic warfare capabilities they now deploy routinely. The Space Force is in the middle of a generational replacement of its satellite infrastructure — one of the largest and most consequential defense acquisition programs in the United States, and one that receives almost no public attention.
GPS III and GPS IIIF
The GPS III program is the current generation of GPS satellites, with the first launch in 2018 and ongoing production continuing through the mid-2020s. GPS III satellites offer three times the accuracy of the previous generation, eight times the anti-jam power, and a longer design life of 15 years. The increased anti-jam capability is the strategically significant upgrade: GPS III uses a new L1C civilian signal and a more powerful M-code military signal with a spot beam capability that can concentrate signal power over specific geographic regions to punch through jamming that would defeat older satellites.
Following GPS III, the GPS IIIF (Follow-On) program adds further capability upgrades including a new navigation technology satellite demonstration, improved on-orbit reprogrammability — the ability to update satellite software after launch — and compatibility with international GNSS signals from Europe's Galileo system and Japan's QZSS. The interoperability with allied systems is both a technical convenience and a strategic hedge: if GPS is jammed or degraded, allied GNSS signals provide backup positioning from independent constellations.
Next Generation Overhead Persistent Infrared
The current Space Based Infrared System (SBIRS) missile warning satellites were revolutionary when they launched but are approaching end of life and were designed before adversaries developed the ability to threaten geosynchronous satellites. The Next Generation Overhead Persistent Infrared program — Next Gen OPIR — is replacing SBIRS with a new architecture that is more survivable, more resilient, and capable of operating in a contested environment.
Critically, Next Gen OPIR includes not just geosynchronous satellites with wide-area missile launch detection but also satellites in polar orbits and potentially medium Earth orbit, providing coverage that is harder to blind or jam because the signals come from multiple orbital regimes. The distributed architecture means that even if an adversary could threaten some satellites in one orbit, the warning mission continues from others. This proliferated architecture — spreading capability across many satellites in multiple orbits rather than concentrating it in a few large, expensive geosynchronous platforms — is becoming the dominant design philosophy for military space systems.
Evolved Strategic SATCOM
Military satellite communications are similarly being restructured. The current Advanced Extremely High Frequency satellites provide nuclear-hardened communications for strategic command and control, but operate primarily from geosynchronous orbit where they are potentially vulnerable to co-orbital attack or jamming. The Evolved Strategic SATCOM program is developing the successor system with improved survivability and the ability to operate in multiple frequency bands and orbital regimes.
The shift toward proliferated low Earth orbit constellations for tactical communications — taking advantage of the cost reductions in small satellite manufacturing that commercial programs like Starlink have demonstrated — is also being evaluated for military purposes. The Space Development Agency, now integrated into the Space Force, is building the National Defense Space Architecture, a multi-layered constellation of hundreds of small satellites providing data transport, missile tracking, and communications from low Earth orbit. The first operational satellites have launched; the full constellation is planned for the late 2020s.
The hardening imperative
All of these programs share a common thread: they are designed for a threat environment that includes adversaries who can jam signals, blind sensors, physically threaten satellites, and conduct cyberattacks on ground systems. The Cold War-era satellites were built for a world where space was largely uncontested. Their replacements are being built for a world where space is, in the words of the Space Force's founding documents, a "warfighting domain."
The transition is expensive — GPS IIIF alone costs over $7 billion for the program — and slow, because satellite development timescales are measured in years and the threat environment evolves faster than acquisition cycles. Whether the replacement programs are keeping pace with the threats they are designed to address is a question that the Space Force's annual threat assessments answer guardedly, and that the classified versions of those assessments presumably answer with more candor.
