US Military Ends Missile Launch Detection Program

The Defense Support Program has ended. For more than half a century, it was one of the quiet pillars of American nuclear deterrence, and now it's officially over. The US Space Force confirmed last month that the final two surviving Defense Support Program satellites were retired after an on-orbit maneuvering exercise in early September, closing a chapter that began with a top-secret launch from Cape Canaveral in November 1970. And that's it.

Two Satellites Raise Their Orbits One Last Time

Independent orbital tracking showed the two satellites raised their orbits by a few hundred kilometers following the exercise, a move typically associated with disposal into graveyard orbits above geostationary space. The Space Force statement confirmed this marked the program's official retirement. It's over. That ending closed a continuous watch stretching across the Cold War, the Gulf War, and decades beyond, a span so long that the officers who first stood it up could never have imagined it would outlast the Berlin Wall, the Soviet Union, and so much else they're now gone. And they don't make watches like that anymore.

"The DSP constellation was foundational to the defense of our nation," said US Space Force Col. Brandon Davenport, Mission Delta 4 Commander. "These last two satellites were the culminating end to over a half century of space-based early warning. The DSP constellation ensured deterrence during the Cold War and protected our deployed warfighters from the Gulf War until their retirement last month."

That is a remarkable run. It began when space-based infrared observation was still experimental and satellite manufacturing mostly produced bespoke spacecraft rather than production lines.

How a Secret Payload Became a Sentinel Network

It starts with a rocket. A Titan IIIC lifted off from Space Launch Complex 40 at what was then Cape Canaveral Air Force Station in late 1970, and the military would later disclose that its top-secret payload was a Defense Support Program satellite. The first block of these spacecraft, launched from 1970 to 1973, weighed roughly 1 metric ton and carried about 2,000 infrared detectors apiece. So they're telescopes. Highly sensitive ones, each placed into geosynchronous orbit to watch the globe for the heat signature of a missile launch.

Initially built to identify Soviet ICBMs, the satellites became vital to nuclear deterrence. Later, they proved useful in conventional warfare as well, including detecting Iraqi Scud missile launches. Over time the military expanded the constellation, improving reliability and adding capability. Each satellite eventually carried more than 6,000 infrared detectors and weighed about 2.5 tons.

Satellites in the Defense Support Program kept flying into space until 2007. One of them, DSP-16, launched aboard the space shuttle Atlantis in 1991. The fleet's launch history spanned a range of rockets, from various Titan vehicles to the Delta IV Heavy and even NASA's shuttle.

A Launch Pad That Outlived Its Rockets

Much has changed around the program since that first launch. The Titan IIIC bowed out in 1982 after dozens of flights. Various Titans kept launching from Space Launch Complex 40 until 2005, when the US Air Force turned the pad over to a small, largely unknown startup called SpaceX, a competitive process hotly opposed by United Launch Alliance. Cape Canaveral is now a Space Force station.

The rockets changed, the pad changed hands, and the launch site got a new name. The mission stayed the same. At least a handful of these satellites flew as silent sentinels for more than 55 years, right up until last month.

The Replacements Already in Orbit

The United States isn't flying blind. It's not without the Defense Support Program. In 2011, the military began launching a new generation of infrared satellites known as the Space Based Infrared System, and those spacecraft carry better sensors, which generally allows them to detect dimmer events and provide longer warning times. They're better. So we've got longer warning times.

The military's been busy. More recently, they've been developing Next-Generation Overhead Persistent Infrared satellites, which is a long and complicated name for hardware that's meant to do a very serious job. The first one could launch soon. It's coming within the next 12 months, if everything holds. And it's set to ride a Vulcan rocket, so we've got a timeline and a vehicle, and now we just wait to see if they're both ready.

So the retirement is less an ending than a handoff. The Defense Support Program that started as a secret experiment and grew into a global watch network has passed its duties to newer hardware with sharper eyes and faster warnings.

• First Defense Support Program satellites launched: 1970 to 1973, about 1 metric ton each with roughly 2,000 infrared detectors.
• Later satellites: more than 6,000 infrared detectors and about 2.5 tons.
• Final launches: continued until 2007, including DSP-16 on Atlantis in 1991.
• Replacement systems: Space Based Infrared System from 2011, and Next-Generation Overhead Persistent Infrared satellites expected to begin launching within a year.

The ending is quiet. For the engineers and operators who spent entire careers tending to this constellation, who tracked every pass and logged every anomaly across decades of silent service, that quiet ending is fitting. The satellites never made headlines while they worked. They don't need them now. They simply watched, waited, and raised their orbits one final time.