HWBRIEF
The Defense Support Program scanned the Earth from orbit for the heat of rocket launches. A new infrared constellation now carries the nuclear early warning mission.
For 55 years, a small fleet of infrared telescopes parked over the equator served as America's first eyes on a missile launch. Last month the last of them went dark, and the nuclear early-warning mission moved to a sharper constellation designed for a threat set the originals were never built to see.
The Defense Support Program ran continuously from November 1970 until September 2026. Its satellites were infrared telescopes in geosynchronous orbit, the belt where a satellite matches Earth's rotation and appears fixed over one point. They were built to detect the heat of a rocket plume rising from Soviet intercontinental ballistic missile fields.
The first block launched between 1970 and 1973 from what is now Cape Canaveral Space Force Station on a Titan IIIC rocket. Each satellite weighed about a metric ton and carried roughly 2,000 infrared detectors. Later DSPs grew to more than 6,000 detectors and around 2.5 tons. The final DSP launched in 2007; DSP-16 reached orbit in 1991 aboard space shuttle Atlantis, the only shuttle-launched DSP.
After the Cold War, the constellation took on new work. During the Gulf War, DSP satellites picked up Iraqi Scud launches, giving U.S. forces near-real-time warning of conventional strikes the 1970s architecture had never been asked to deliver.
US Space Force has now formally retired the constellation and is preparing the Next-Gen OPIR, or Overhead Persistent Infrared, program as its replacement. The mission is changing hands, not ending.