For over 50 years the Pentagon has had early warning satellites in orbit aimed at spotting launches of ballistic missiles, especially the big intercontinental kind that can fly around the globe in less than 30 minutes and bring about nuclear Armageddon. Recently, these satellites have made news for their “secondary capabilities,” spotting the downing of Metrojet Flight 9268 and Malaysian Airlines Flight 17. These are the shadowy satellites that are capable of such amazing feats, and an idea of how they work.
In 1960, at the height of the Cold War and at the dawn of the space age, the first Missile Defense Alarm System (MiDAS) satellite was launched into low earth orbit. Six years later there was a constellation of nine of these satellites roaming the heavens, each scanning the Soviet Union for large infrared plumes, the tell-tale sign of a ballistic missile or rocket launch.
These fairly crude, low-earth orbit satellites, along with the radar-based Ballistic Missile Early Warning System, would be the basis for a Cold War ballistic missile surveillance system that would become ever more complex and capable as the years went by. If ballistic missile launches were detected and deemed a threat, the decision to retaliate would mean the National Command Authority making the call to do so within half an hour, an act that could bring an the end of humanity’s reign on Earth, permanently.
The first really reliable and full coverage space-based ballistic missile early warning capability came with the launch of the first Defense Support Program (DSP) satellite in 1970. These new satellites were much more capable than their MiDAS predecessors.
Early DSP satellite design was relatively straight forward, with the satellites’ spinning around their center axis while in geosynchronous orbit. This allows their telescopic infrared sensor to continuously sweep an area of the planet in a relatively brief amount of time, around six times in one minute. If something were detected, the information would immediately be data-linked to controllers on the ground at the 460th Space Wing located at Buckley AFB in in Colorado.
A total of 23 of these satellites have been launched over the program’s life, with constant upgrades made along the way. A DSP satellite was launched by the Space Shuttle on STS-44 in 1991, and the last one was launched by a Delta IV Heavy in 2007. Most famously, the Defense Support Program constellation of satellites were used to detect launches of SCUD missiles during Operation Desert Storm.
Although many DSP satellites are still in service today, the next generation of infrared ballistic missile early warning satellites has arrived and is called Space-Based Infrared System, or SBIRS (pronounced “sibbers”)for short. This vastly upgraded capability is based around two types of satellite payloads, the main geostationary orbit type has two-sensors instead of one, a scanner and a step-starer.
This dual sensor design gives SBIRS the ability to scan a wide area of the earth’s surface and stare at, or quickly flip between others areas in great detail, at the same time. This way, one sensor can view the globe persistently for launch detection, while the other can be tasked to more closely watch certain regions or even possibly to track missiles not just during launch, but after their rocket motors burn out and they are coasting in space or the extremes of the upper atmosphere. In doing so, the system can help differentiate the reentry vehicles/warheads from decoys or debris. This data can then be incorporated into the National Missile Defense sensor information “ecosystem”for tracking and targeting.