History of the Defense Support Program Satellites

Dwayne A. Day looks at the origins and evolution of the U.S. Defense Support Program Satellites, an early warning space constellation tasked with detecting missile launches.

STS-44 DSP deployment
NASA Johnson Space Center (NASA-JSC), Public domain, via Wikimedia Commons


One of the most important advantage of the system is that it allows the Americans to catch a Soviet Fractional Orbital Bombardment System (FOBS) attack in the early stages.

A FOBS attack could reduce the alert time provided by radar from 15 minutes to just five minutes. Satellites using infrared detection can spot the launch of any FOBS missile in the early phase of the attack.

For more information, hit the Source below

Source