DSP-4

The primary mission of the DSP satellite is to detect and report ICBM or SLBM raids against the U.S. and its allies. Secondary missions include space launch detection and nuclear detonation detection for international test ban treaties. Developed in response to the Soviet Union's first ICBM threat in the 1950s, DSP utilizes infrared sensors on orbiting satellites to detect rocket engine heat radiation, marking the inception of a space-based early warning system.