Defense Support Program

History

The Defense Support Program succeeded the space-based infrared Missile Defense Alarm System (MIDAS), which had its first successful launch on 24 May 1960 with MIDAS-2. Twelve MIDAS launches occurred before DSP replaced it in 1970. The first DSP launch, designated IMEWS-1 (Integrated Missile Early Warning Satellite), took place on 6 November 1970, benefiting from funds released by the cancellation of the Manned Orbiting Laboratory. Since then, DSP has provided uninterrupted space-based early warning for 45 years.

The original satellite weighed 2,000 pounds (900 kg), produced 400 watts of power, carried 2000 detectors, and had a design life of 1.25 years. Over the program's life, satellite design underwent numerous improvements: weight grew to 5,250 pounds (2380 kg), power to 1275 watts, detectors increased threefold to 6000, and design life was extended to a goal of ten years. Improvements included above-the-horizon capability, improved resolution, enhanced on-board signal-processing for clutter rejection, and increased reliability and survivability.

The 23rd and final DSP satellite, DSP-23, was scheduled for launch on 1 April 2007 aboard a Delta IV Heavy rocket but was postponed after structural cracks were found in the metal launch table at pad 37B caused by a fuel leak during testing. Further delays moved the launch to 11 November 2007 at 01:50:00 UTC. DSP-23 died in space sometime during 2008 for unknown reasons and now drifts in geosynchronous orbit as a potential hazard. The Department of Defense sent a MiTEx spacecraft to inspect DSP-23 in 2008.

Another satellite, DSP-19, was lost in 1999 after its Inertial Upper Stage failed following launch from a Titan 4B booster; the two IUS stages failed to separate completely, leaving the satellite out of control in a useless orbit. The project originally planned 25 satellites, but the last two were canceled mainly due to SBIRS. DSP satellites have been replaced by the Space-Based Infrared System (SBIRS) satellites. There were five major improvement programs across the 23 satellites: Block 1 (Phase I, 1970–1975, five satellites), Block 2 (Phase II, 1976–1987, seven satellites), Block 3 (Multi-Orbit Satellite Performance Improvement Modification, 1989–1991, three satellites), Block 4 (Phase II Upgrade, 1994–1997, two satellites), and Block 5 (DSP-Improved, 1999–2007, six satellites).

More recently, effort has been put into using DSPs' infrared sensors as part of an early warning system for natural disasters like volcanic eruptions and forest fires. DSP satellites were operated by the Air Force 460th Space Wing until 2020, when it was replaced by the Space Force Mission Delta 4.