The Defense Support Program (DSP) satellite, moments before launch from the cargo bay of Space Shuttle Atlantis. DSP is designed to sense the heat plumes from missile launches against Earth's background and to detect nuclear detonations. To this end, it has an infrared detector comprising 6,000 elements (shiny tube closest to camera). DSP has a design life of 5 years in geostationary orbit. Various DSP satellites have been launched since the early 1970s, and have provided the space-based segment of the USA's early warning network. This latest DSP satellite was deployed on 24 November 1991, the first day of Mission STS-44. Atlantis returned to Earth on 1 December 1991.