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Defense Support Program

-- History --

The Defense Support Program (DSP) is an early warning satellite system operated by Air Force Space Command (AFSPC) and developed by the Air Force's Space and Missile Systems Center. DSP provides 24 hour, worldwide surveillance for missile warning and nuclear burst detection and serves as the space segment of the U.S. Integrated Tactical Warning & Attack Assessment System.

The DSP program was a follow-on to the Missile Defense Alarm System (MIDAS) and Vela Programs. MIDAS was started in 1960 and proved the operational concept of space based infrared detectors and other technologies by 1963. The Vela program was developed in 1963 to monitor nuclear test ban treaty compliance. Both programs were consolidated into the Defense Support Program, and the first operational DSP satellite was launched on 6 November 1970. Since then, the program has undergone several upgrades and a total of 18 successful launches.

The original DSP satellite configuration, Phase I, was used on flights one through four and were launched into geostationary orbit on a Titan IIIC between 1970-1973. These satellites weighed approximately 2000 pounds and used Short Wavelength Infrared (SWIR), Lead Sulfide detectors to provide below the horizon (BTH) missile warning coverage. The design life of Phase I satellites was 1.25 years.

After the fourth satellite, the system was upgraded to allow for longer lifetimes and increased capability. This configuration, known as Phase II, weighed approximately 2300 pounds and had a two year design life. Phase II satellites were used for flights five through seven and launched between 1975-1977 on a Titan IIIC.

Flights eight through 11 were launched between 1979-1984 and contained further performance improvements to the Phase II configuration. Responding to additional Soviet threats, these satellites were capable of operating in geostationary or highly elliptical orbits and contained additional electronics packages. Designated as the Multi-Orbit Satellite/ Performance Improvement (MOS/PIM) configuration, these satellites weighed approximately 2600 pounds, had a design life of three years and were launched on Titan IIIC and 34D boosters.

During the original Phase II production, two satellites were put into storage because the on-orbit spacecrafts were operating longer than expected and the MOS/PIM satellites were already being developed. These two satellites were brought out of storage in the early 1980s and retrofitted with a new primary sensor that allowed for above the horizon (ATH) SWIR coverage and increased polar resolution. This configuration, used on Flights 12 and 13 and known as the Phase II Upgrade, also contained a Medium Wavelength Infrared detector for added capability against shorter range missiles. These satellites weighed 3700 pounds, had a design life of three years and were launched on the Titan 34D.

In 1989, the system was improved again. Flights 14 through 18 were modified to provide higher resolution and greater sensitivity in both short and medium wavebands. These satellites weighed approximately 5300 pounds, measured more than 28 feet in height and 13 feet in diameter and were launched on the Titan IV booster, with the exception of DSP Satellite 16 which was launched on the Space Shuttle Atlantis. This satellite configuration was designated DSP-1 and has a design life of five years.

The DSP system has proven itself many times throughout its 26 year operational life time. Originally designed to detect long range ballistic missiles, DSP proved its capability with theater class missiles by detecting and tracking Iraqi Scuds during the Desert Storm conflict. This DSP data enabled theater commanders to protect civilian population centers and coalition forces in Israel and Saudi Arabia.

In 1995, DSP was augmented again with the Attack and Launch Early Reporting to Theater (ALERT) capability and again in 1997 with the Joint Tactical Ground Station (JTAGS). These systems provide vastly improved capabilities to process satellite warning data and distribute it to battlefield commanders in minimum time through efficient communication links.

-- Concept of Operation --

The DSP system consists of several satellites in geostationary orbit, an Overseas Ground Station (OGS) in Australia, a European Ground Station (EGS), a CONUS Ground Station (CGS) and Mobile Ground Terminals (MGTs). Each satellite has the capability to view nearly an entire hemisphere of the earth and can detect missile launches from any location within its field of view. The satellites use a spinning motion to sweep its infrared detector arrays across the earth's surface to detect the hot missile plumes of boosting missiles. The data collected during these sweeps is relayed down to one of the three Air Force ground stations or MGTs around the world and then communicated to the National Command Authority or to commanders in the field. Data can also be received at the contractor's operations center. Alternately, U.S. and Allied forces deployed overseas can receive data directly from orbiting DSP satellites using the JTAGS system.

-- Schedule --

DSP Flight 18 lifted off from Launch Complex 40 at Cape Canaveral on 23 February 1997. There are five more satellites in the series that are scheduled to be launched between 1997 and 2003. The new SBIRS architecture will enter service during this time with improved capabilities to ensure there won't be any gap in our nation's early warning capability into the next century.

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