In the late 1970s, a top-secret payload took to the skies, ushering in an era of missile detection that would last nearly four decades. These satellites, part of the Defense Support Program, were more than just celestial observers; they were the eyes of the Cold War, tasked with spotting any signs of nuclear launches.

The initial block of these satellites, launched from 1970 to 1973, carried 2,000 infrared detectors, essentially turning them into sensitive telescopes. Their mission was clear: to monitor the globe for missile launches, initially focusing on Soviet ICBMs. As the decades wore on, their capabilities expanded, with each satellite eventually boasting over 6,000 detectors and a hefty 2.5 tons in mass.

This program was integral to nuclear deterrence, providing crucial early warning of missile launches, but its usefulness extended beyond the cold war era. By the late 1990s, they were also used to detect conventional threats, such as Iraqi Scud missile launches. The final satellite, DSP-16, even hitched a ride on the space shuttle Atlantis in 1991. The Defense Support Program’s last flight in 2007 marked the end of an era in space-based missile surveillance.

With this program’s conclusion, the skies above the Earth will no longer be as meticulously monitored for missile launches. Will we be looking fewer stars, or more missiles, in the future?