The United States has layers of sensors that can spot, track and identify ballistic missile launches like the Russian IRBM fired over Ukraine on Thursday — a Cold War system that has been refined over decades into an unwavering global network.

Six Lockheed Martin and Northrop Grumman satellites, known as SBIRS, for Space-Based Infrared Systems, sit in geostationary orbit around the earth hunting for launch signatures, according to the US Space Force, which operates them.

They – and a network of smaller satellites in lower orbits – use a variety of sensors to detect the firing of a ballistic missile anywhere on the planet within seconds, from small, unsophisticated weapons such as scuds to intercontinental ballistic missiles (ICBMs). ), said William Alberque, visiting fellow at the Henry L. Stimson Center.

“The things you can do with video, plus IR, plus synthetic aperture radars, plus ground-based radars … all these things come together,” Alberque said. “Processing all this data at very high speed means we have the ability to know more about what’s being launched than ever before.”

Rocket engines, for example, produce different exhaust gases at different temperatures depending on the fuel and other design factors. These “signatures” can quickly identify a missile.

Ground sensors include massive solid-state early warning radars in the United States, Canada, and the United Kingdom. Together with the satellites, the system can determine the missile’s type, launch angle, azimuth, apogee, speed, size and landing point, among other things.

In addition to the Space Force, many other US government organizations are involved, including the National Geospatial Intelligence Agency, the US Strategic Command, and the Missile Defense Agency. Regional military commands may also be involved.

Some launch notifications can be automated, such as smaller, short-range weapons that pose no threat to the US or its allies. More serious alerts for longer-range weapons or a direct threat require human analysis and decision-making.

In the case of Russia’s strike on Ukraine near the city of Dnipro, there was no concern about a nuclear strike, as there were no signs of moving warheads, training other forces, or involvement of the 12th Chief Directorate of the Russian Ministry of Defense. , which controls its nuclear weapons, Alberque said.

“That would be a huge signature for potential use,” he said, referring to nuclear weapons.

Early warning systems as a concept emerged in the 1950s, at first to identify bomber formations and later expanded to detect missiles. The first systems used enormous ground-based radars to search for missiles rising over the horizon and were linked to defensive systems that often included nuclear-tipped interceptors.

The Space Force is in the middle of a nearly $15 billion program for more advanced early warning satellites called Next Generation Overhead Persistent Infrared. The system will include geostationary satellites, the first of which is scheduled for delivery in 2025, and polar orbiting satellites scheduled for launch in 2028.