Defense Support Program
The U.S. Air Force Space Command-operated Defense Support Program (DSP) satellites form the principal component of the United States Satellite Early Warning System (SEWS). In their 22,300 mi (35,900 km) geosynchronous orbits, they use non-imaging infrared sensors to detect the infrared light emitted from the intense sources of heat caused by missile or spacecraft launch booster plumes. They are occasionally also known as Integrated Missile Early Warning System (IMEWS) satellites.
The satellites are equipped with infrared sensors operating through a wide-angle Schmidt telescope. The entire satellite spins so that the focal plane scans over the earth. Over several scans a stationary heat source such as a forest fire or volcanic eruption may be discriminated by ground software from a rapidly moving one.
Typically, DSP satellites are launched on a Titan IVB booster and Inertial Upper Stage (IUS) combination. However, one DSP satellite was launched using the space shuttle on mission STS-44 (November 24, 1991). The last one (flight 23) is slated to be launched on the new Delta 4 Heavy.
The 460th Space Wing, with headquarters at Buckley Air Force Base, Colo., has units that operate DSP satellites and report warning information, via communications links, to the North American Aerospace Defense Command and U.S. Strategic Command early warning centers within Cheyenne Mountain, located near Colorado Springs, Colorado. These centers immediately forward data to various agencies and areas of operations around the world. Air Force Materiel Command's SBIRS Program office 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 (MiDAS). The first successful launch of MiDAS was May 24, 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 30-odd years they have provided an uninterrupted space-based early warning capability. The original DSP satellite weighed 2,000 pounds (900 kg) 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 (2,380 kg), the power to 1,275 watts, the number of detectors increased three-fold 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 is scheduled to be launched in early 2007, after which DSP satellites will be replaced by the Space-Based Infrared System (SBIRS) satellites. The project was originally to have had a life of 25 satellites, but the last two have been cancelled, mainly due to SBIRS.
There were five major improvement programs prior to the current block:
- Block 1: Phase I, 1970-1973, 4 satellites
- Block 2: Phase II, 1975-1977, 3 satellites
- Block 3: Multi-Orbit Satellite Performance Improvement Modification (MOS/PIM), 1979-1984, 4 satellites
- Block 4: Phase II Upgrade, 1984-1987, 2 satellites
- Block 5: DSP-I (DSP-Improved), 1989
The satellites' effectiveness was demonstrated during Desert Storm, when DSP detected the launch of Iraqi Scud missiles and provided warning to civilian populations and coalition forces in Israel and Saudi Arabia.
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.
General characteristics
- Primary mission: Strategic and tactical missile launch detection
- Contractor team: Northrop Grumman, formerly TRW (for satellite bus) and Aerojet Electronics Systems (for IR sensor)
- Weight: 5,250 lb (2,380 kg)
- Orbit altitude: 22,000 miles (35,900 km)
- Power plant: Solar arrays generate 1,485 watts
- Height: 32.8 ft (10 m) on orbit; 28 ft (8.5 m) at launch
- Diameter: 22 ft (6.7 m) on orbit; 13.7 ft (4.2 m) at launch
- Date first deployed: 1970
- Latest Satellite Block: Sats 18-23
- Unit Cost: $400 million
Source:
Some of the information in this article is taken from the Fact Sheet published by Air Force Space Command, Public Affairs Office; 150 Vandenburg St., Suite 1105; Peterson AFB, CO, April 2004