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Defense Support Program

dsplogo.jpg - 19.8 KThe Defense Support Program (DSP) is a survivable and reliable satellite-borne system that uses infrared detectors to sense heat from missile plumes against the earth background, to detect and report in real-time missile launches, space launches and nuclear detonations. Typically, DSP satellites were launched into geosynchronous orbit on a Titan IV booster and inertial upper stage combination. However, one DSP satellite was launched using the space shuttle on mission STS-44 (Nov. 24, 1991). The final DSP satellite was launched on the new Evolved Expendable Launch Vehicle (EELV) Delta-4, Heavy, in Nov. 2007.

DOD initiated a new program late in 1963 to develop an improved infrared early warning system, which ultimately became the Defense Support Program. After an early phase known as Program 266, a contract for development of Program 949, the Defense Support Program (DSP), was awarded to TRW for the spacecraft on 6 March 1967 and to Aerojet for the infrared sensor on 1 March 1967. The new concept involved placing the satellites into orbits at geosynchronous altitude, where only three or four would be necessary for global surveillance. Like MIDAS, the satellites would employ telescopes and IR detectors, but the necessary scanning motion would be accomplished by rotating the entire satellite around its axis several times per minute. An evolving network of two, and later three, large ground stations in Australia, Europe, and the continental U.S. controlled the spacecraft and data.

The first DSP satellite was launched on 6 November 1970, using a Titan IIIC launch vehicle. A long series of increasingly larger, more sophisticated, and more reliable satellites followed, all of them except one launched on Titan III or Titan IV vehicles. By early 2003, twenty DSP satellites had been successfully launched. They provided a level of early warning that was, by then, indispensable for both military and civil defense. They also carried sensors that performed nuclear surveillance, a mission inherited from the Vela system. Although designed for strategic uses, DSP proved to be more versatile. During the Persian Gulf War, it provided early warning against tactical missiles as well. By 1997, SMC and Air Force Space Command had exploited that capability by adding central processing facilities and tactical ground stations to provide DSP tactical data to battlefield commanders more rapidly and efficiently.

DSP satellites have been the spaceborne segment of NORAD's Tactical Warning and Attack Assessment System since 1970. The satellites feed warning data, via communications links, to NORAD and US Space Command early warning centers within Cheyenne Mountain. These centers immediately forward data to various agencies and areas of operations around the world. Members of the Air Force Space Command 50th Space Wing's 1st Space Operations Squadron provide command and control support for the satellite.

Its effectiveness was proven during the Persian Gulf conflict, which took place from August 1990 through February 1991. During Desert Storm, DSP detected the launch of Iraqi Scud missiles and provided timely warning to civilian populations and coalition forces in Israel and Saudi Arabia.

Under contract to Air Force Materiel Command's Space and Missile Systems Center at Los Angeles AFB, CA, in support of the Air Force Program Executive Officer for Space, TRW in Redondo Beach, CA, built the satellites and integrates the sensor payload built by Aerojet Electronics Systems Division of Azusa, CA.

DSP repeatedly proven its reliability and potential for growth. DSP satellites exceeded their specified design life by some 30 percent through five upgrade programs. These upgrades allowed DSP to provide accurate, reliable data in the face of changing requirements -- greater numbers, smaller targets, advanced countermeasures -- with no interruption in service. Planned evolutionary growth has improved satellite capability, survivability and life expectancy without major redesign. On-station sensor reliability provided uninterrupted service well past their design lifetime.

The Satellite Early Warning System (SEWS) consisted of five Defense Support Program spacecraft.(1) Three of these provide frontline operational service, with two additional spacecraft available as backups should problems emerge with the primary satellites. The standard operating procedure is that primary reliance is placed on the three most recently launched satellites, with the two older satellites providing backup.(2) Because of the critical importance of this mission, a replacement satellite will normally be launched around the time that the oldest of the five spacecraft on-orbit nears the end of its operational life. This newly launched satellite will assume frontline duty, the eldest of the three frontline spacecraft will assume backup status, and the oldest satellite will be retired.

At the beginning of 1990 five DSP spacecraft were operational. DSP F-13, launched in 1982 respectively, and DSP F-12 launched in 1984, were on backup status. DSP F-6R, launched in 1984, DSP F-5R, launched in 1987, and DSP-I F-14, launched in 1989, were the primary operational spacecraft.(3) The November launch of DSP-I F-15 resulted in the removal of DSP-10 F-13 from operational status.

Developments in the DSP have enabled it to provide accurate, reliable data in the face of tougher requirements such as greater numbers of targets, smaller targets and advanced countermeasures. Through five upgrade programs, DSP satellites have exceeded their design lives by some 30 percent.

DSP

The original DSP weighed 2,100 pounds, had 400 watts of power, 2,000 detectors and a design life of three years.

DSP

In the 1970's, the satellite was upgraded to meet new mission requirements. As a result, the weight grew to 3,960 pounds, the power to 680 watts, the number of detectors increased by threefold to 6,000, and the design life was three years with a goal of five years.

Adding a reaction wheel removed unwanted orbit momentum from DSP vehicles. The wheel can be made to turn rapidly by command from ground stations. Its spinning motion then acts as a negative force on the satellite's movements. This "zero momentum" approach permits spacecraft orbit control with minimum fuel expenditure. As a result, reaction wheels have been added to other systems including Defense Meteorological Satellite Program, Navstar Global Positioning System and Defense Satellite Communication System satellites.

DSP-SEDS

As their designation indicates, F-5R and F-6R are both refurbished spacecraft that were originally manufactured in the mid-1970's, but placed in storage because of the unexpectedly long operational life of the DSP series. In the early 1980's these two spacecraft were refurbished under the Sensor Evolutionary Development Program (SEDS), which greatly improved the sensitivity of their sensors.(4)

The major elements of the Sensor Evolutionary Development (SED) sensor are: IR Telescope Subsystem (IR); Star Sensor Subsystem (SS); Status Monitor Subsystem (SMS); Signal Electronics Subsystems (SES); Thermal Control Subsystem (TCS); and Advanced Radec I (ARI). Detection of IR sources is accomplished with the telescope and Photo-Electric Cell (PEC) array portions of the IR telescope Subsystem. The PEC detector array, mounted in the telescope center line to coincide with the image surface of the telescope optics, scans the Earth's surface through rotation of the satellite. As a detector passes across an IR source it will develop an electronic signal. the many signals are relayed to processing units where they are grouped and sent to the ground for mission usage.

DSP-I (Improved)

dsp_sts_s.jpg - 45.6 K Today's DSP satellite weighs 5,200 pounds, requires 1250 watts of power, and is approximately 33 feet long, 14 feet in diameter, Recent technological improvements in sensor design includes above-the-horizon capability for full hemispheric coverage and improved resolution. Increased on-board signal-processing capability improves clutter rejection enhancing reliability and survivability.

The DSP-I (Improved) satellites, of which spacecraft 14 through 25 were on order in early 1989 with options for 26 through 28 under consideration,(5) will incorporate the upgraded sensors of the SEDS satellites, as well as improved resistance to laser attack.(6) The DSP-I satellites will also carry a laser communications package that will enable the satellites to relay warning information to each other.(7) This will greatly reduce the vulnerability of this system to attacks on its ground stations, since all the satellites will be able to communicate with any of the system's ground stations. However, the June 1989 DSP-I (F-14) did not incorporate this laser communication systems, due to technical problems.(8) Instead, DSP F-14 carried an experimental sensor package for the Strategic Defense Initiative Organization to assess the utility of ultraviolet sensors for tracking missiles.

The sensor and the spacecraft, which together comprise the satellite, are placed in geosynchronous-equatorial orbit so that the telescope is pointed toward the earth and rotated at six revolutions per minute. To provide a scanning motion for the infrared (IR) sensor, the satellite is spun about its Earth-pointing axis. The axis of the satellite's rotation is normal to the earth's surface. A prime requirement of the spacecraft is to provide attitude control to maintain the pointing direction accurately. Satellite-spin momentum is reduced to a nominal value of zero by introducing an equal and opposite momentum achieved through operation of a Reaction Wheel. The resulting "zero momentum" satellite is attitude controlled by gas thrusters.

The basics functions of the spacecraft are to: provide a spin-controlled, stable, Earth pointing vehicle for the mission data sensing and processing equipment; furnish the on-board functions required to position, control, and maintain the satellite in its proper Earth orbit; furnish, condition, and control the electrical power for all satellite requirements; provide secure downlink capabilities to transmit mission data, State-of-Health (SOH), and other relevant information to the ground for final processing; and provide a secure uplink command receiving, processing, and distribution capability for both spacecraft and sensor ground-generated commands. The spacecraft consists of the following principal systems: structure; Communication and Command and Mission Data Message; Electrical Power and Distribution; Propulsion; Attitude Control; and Thermal.

The sensor's purpose is to detect, locate, and identify targets of interest that are intense sources of IR radiation. The Defense Support Program geosynchronous satellites & other spacecraft provided continuous warning of launches & explosions during the Operation Iraqi Freedom campaign in early 2003.

  • 26 missile launches detected
  • 186 high-explosive events
  • 1,493 "static IR events"

While securing the DSP-23/Delta IV launch vehicle after the Wet Dress rehearsal held on 28 February 2007, two structural cracks were observed in the metallic Launch Table. The cracks appeared on the bottom of the launch table's starboard and center bays; roughly underneath the liquid oxygen servicing equipment for the starboard and center booster cores. There was no damage to the heavy launch vehicle.

A combined ULA and Air Force investigation team, supported by the Aerospace Corporation, determined that a liquid oxygen leak inside the launch table most likely led to the fracturing of the low carbon construction steel plates from cryogenic temperatures. The origin of the leak appears to be from the vacuum jacketed liquid oxygen propellant lines inside the launch table, which are used to fill the booster tanks. These lines were replaced in 2006 with a new design with a longer predicted service life. Replacement of the liquid oxygen lines required de-erection of the launch vehicle for access considerations.

The United States Air Force's Defense Support Program Flight 14 exceeded 20 years of on-orbit operations in 2009. DSP Flight 14 was launched on June 14, 1989 on a Titan IV launch vehicle. Northrop Grumman developed and launched DSP Flight 14 under contract to the United States Air Force's Space and Missiles Systems Center. DSP Flight 14 was still operational after 20 years on orbit because of the focus on reliability in design and production coupled with careful on-board fuel conservation and health and safety management since it was launched.

Air Force Space Command's Space and Missile Systems Center and the 460th Space Wing confirmed that Command and Control of the Space-Based Infrared Systems and Defense Support Program satellites and payloads was transferred from their legacy ground system to the new Block 10 ground system. AFSPC approved cutover of C2 for DSP and SBIRS constellations 18 March 2016 from the legacy sites at Buckley AFB, Colorado, Schriever AFB, Colorado, and Boulder, Colorado to one consolidated site at the Mission Control Station at Buckley AFB, Colorado, and its backup mission control station at Schriever AFB. Cutover was successfully completed 21 March 2016.

References

1. Ball, Desmond, A Base for Debate, (Allen & Unwin, London, 1987) is perhaps the most comprehensive discussion of the DSP system.

2. Kenden, A., "Military Maneuvers in Synchronous Orbit," Journal of the British Interplanetary Society, February 1983, V. 36, pp. 88-91.

3. "Advanced Missile Warning Satellite Evolved From Smaller Spacecraft," Aviation Week & Space Technology, 20 January 1989, page 45.

4. Cushman, J., "AF Seeks Invulnerable Warning Satellites," Defense Week, 16 January 1984, pp 1, 10-14.

5. "Air Force to Decide by End of Month on DSP Acquisition Method," Aerospace Daily, 5 October 1989, page 30-31.

6. Covault, Craig, "New Missile Warning Satellite to be Launched on First Titan 4," Aviation Week & Space Technology, 20 January 1989, page 34-40. (This article is an excellent review of the history an status of this program).

7. Cushman, J., "AF Seeks Invulnerable Warning Satellites," Defense Week, 16 January 1984, pp 12.

8. Goodman, Adam, "Problems Plague McDonnell Douglas Laser," St. Louis Post Dispatch, 13 August 1989, page 1 (an extremely thorough treatment of this problem).

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