The Defense Support Program is a program of the U.S. Space Force that operates the reconnaissance satellites which form the principal component of the Satellite Early Warning System currently used by the United States. DSP satellites, which are operated by the 460th Space Wing, detect missile or spacecraft launches and nuclear explosions using sensors that detect the infrared emissions from these intense sources of heat. During Desert Storm, for example, DSP was able to detect the launches of Iraqi Scud missiles and provide timely warnings to civilians and military forces in Israel and Saudi Arabia. The satellites are in geosynchronous orbits, and are equipped with infrared sensors operating through a wide-angle Schmidt camera. The entire satellite spins so that the linear sensor array in the focal plane scans over the earth six times every minute. Typically, DSP satellites were launched on Titan IVB boosters with Inertial Upper Stages. However, at least one DSP satellite was launched using the Space Shuttle, the known example being Atlantis on mission STS-44. The last known DSP satellite was launched in 2007 aboard the first operational flight of the Delta IV Heavy rocket, as the Titan IV had been retired in 2005. All 23 satellites were built by the prime contractor Northrop Grumman Aerospace Systems, formerly TRW, in Redondo Beach, California. The 460th Space Wing, with headquarters at Buckley Air Force Base, Colorado, has units, primarily the 2d Space Warning Squadron, that operate DSP satellites and report warning information, via communications links, to the NORAD and USSTRATCOMearly warning centers within the Cheyenne Mountain Complex, Colorado. These centers immediately forward data to various agencies and areas of operations around the world. Air Force Space Command's SBIRS Wing at the Space and Missile Systems Center, Los Angeles AFB, California is responsible for development and acquisition of the satellites.
History
The Defense Support Program replaced the 1960s space-based infrared Missile Defense Alarm System. The first successful launch of MiDAS was 24 May 1960 and there were twelve launches before the DSP program replaced it in 1966. The first launch of a DSP satellite was on 6 November 1970 and since then it has become the mainstay of the United States ballistic missile early warning system. For the last 40 years they have provided an uninterrupted space-based early warning capability. The original DSP satellite weighed 2,000 pounds and had 400 watts of power, 2,000 detectors and a design life of 1.25 years. Throughout the life of the program, the satellite design has undergone numerous improvements to enhance reliability and capability. The weight grew to 5,250 pounds, the power to 1,275 watts, the number of detectors increased threefold to 6,000 and the design life has been increased to a goal of five years. The numerous improvement projects have enabled DSP to provide accurate, reliable data in the face of evolving missile threats. On-station sensor reliability has provided uninterrupted service well past their design lifetime. Recent technological improvements in sensor design include above-the-horizon capability and improved resolution. Increased on-board signal-processing capability improves clutter rejection. Enhanced reliability and survivability improvements were also incorporated. The 23rd, and last DSP satellite was scheduled to be launched on 1 April 2007, aboard a Delta IV Heavy rocket, but the launch was postponed until mid-August 2007 after two structural cracks were found in the metal launch table at pad 37B, caused by a fuel leak during testing. Further delays forced the launch back to 11 November 2007, when the satellite launched at 01:50:00 UTC. This satellite died in space sometime during 2008, for reasons unknown. It is now adrift in geosynchronous orbit and remains a potential hazard to other craft. The Department of Defense sent a MiTEx spacecraft to inspect DSP 23 sometime in 2008. Another DSP satellite was lost in 1999, after its Inertial Upper Stage failed following launch from a Titan IV booster. DSP satellites will be replaced by the Space-Based Infrared System satellites. The project was originally to have had 25 satellites, but the last two have been canceled, mainly due to SBIRS. There were five major improvement programs on the 13 satellites:
Block 3: Multi-Orbit Satellite Performance Improvement Modification, 1979–1984, four satellites
Block 4: Phase II Upgrade, 1984–1987, two satellites
Block 5: DSP-I, 1989
More recently, there has been some effort put into using DSPs' infrared sensors as part of an early warning system for natural disasters like volcanic eruptions and forest fires.
Limitations
The DSP constellation may have offered an excellent vantage point for an early warning system against state-centric threats such as missiles, but military analysts warn its ability to collect intelligence on non-state actors is severely limited.
General characteristics
Primary mission: Strategic and tactical missile launch detection
