Cold War Satellites Finally Retire After 50+ Years

In late 1970, a top-secret US military satellite known as the Defense Support Program (DSP) was launched into geosynchronous orbit. This marked the beginning of a critical early warning system designed to detect nuclear missile launches. For over five decades, these satellites served as silent sentinels, evolving from experimental infrared observation platforms to essential components of national defense.

The initial DSP satellites, weighing about 1 metric ton, were equipped with thousands of infrared detectors to monitor the globe for ICBMs. Over time, the satellites were upgraded, increasing their mass to 2.5 tons and their detector count to over 6,000. These systems proved vital not only for nuclear deterrence during the Cold War but also for tracking conventional threats, such as Iraqi Scud missile launches.

Last month, the final two DSP satellites, believed to be DSP-20 and DSP-22, executed an on-orbit maneuvering exercise, raising their orbits to graveyard positions and officially retiring the program. This concludes over 55 years of continuous space-based early warning. The US Space Force confirmed the retirement, highlighting the constellation's foundational role in defense and deterrence.

The retirement of the DSP constellation is being addressed by two replacement programs. The Space Based Infrared System (SBIRS), which began launching in 2011, offers enhanced sensors for dimmer event detection and longer warning times. Additionally, the Next-Generation Overhead Persistent Infrared (Next-Gen OPIR) satellites are under development, with the first expected to launch on a Vulcan rocket within the next year.