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DSP

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USA 159 Credit: Manufacturer Image

AKA: Defense Support Program;IMEWS;Integrated Missile Early Warning Satellites. Status: Operational 1970. First Launch: 1970-11-06. Last Launch: 2007-11-11. Number: 23 . Gross mass: 2,358 kg (5,198 lb). Height: 10.00 m (32.00 ft).

After forty years of service, they had grown from 900 kg to 2380 kg in mass, and gone from being capable of detecting ICBM launches to detecting and tracking tactical ballistic missiles, but followed the same operating principle and layout.

The Defense Support Program (DSP) constellation consisted of four spacecraft spaced around the earth in geosynchronous orbit plus one in-orbit spare that could be repositioned as needed. These spacecraft were initially designed to provide warning-at-launch of an intercontinental ballistic missile attack by the Soviet Union. This would provide additional minutes of warning compared to early warning radars, that could only detect missiles as they came 'over the horizon' and were easily disabled in the first stage of an attack. It also eliminated the advantage of the Soviet's fractional orbital bombing system R-36-O missiles, which placed warheads in orbit, allowing them to come 'under the radar' or from approach angles not covered by the early warning radars. It also provided warning of submarine-launched missiles, which could be launched from locations with inadequate radar coverage.

Such attacks never materialized, although the DSP's may have contributed to the Soviet decision to sharply limit R-36-O deployment to token levels. However the DSP's instead provided intelligence on nearly every medium- and long-range ballistic missile launch since being put in service, including the hundreds of Scud launches during the Iran-Iraq 'War of the Cities' in 1985-1986. They proved able to detect static tests of rocket engines on the earth's surface, as well as the exhaust plumes of military aircraft in afterburner. During America's long involvement with Iraq, they provided early warning of tactical ballistic missile launches against American or Allied targets, allowing shelter to be taken and Patriot missile defenses to be readied for the incoming missiles. When Chinese ballistic missile testing surged to a rate of one per week in 2006-2007, DSP was able to keep track of the activity.

Each satellite spent a month after launch in positioning, test, and systems initialization and calibration before being handed over to the USAF operational command. DSP's were controlled by the USAF from Falcon (later Schriever) AFB near Colorado Springs until 2007, when control transitioned to the new SBIRS Control Station in Aurora, Colorado.

The spacecraft were designed for a 3-5 year operational life, but this was extended to 10 to 15 years through careful fuel, power, and infrared temperature management techniques. The result was that by 2006 as many as 10 DSP's were still functioning, allowing two or three satellites to observe a single launch. This allowed for stereo views of launches and better plume characterization. The only DSP satellite to fail in service completely was DSP-19, which had a hydrazine propellant line rupture. But his spacecraft had endured extraordinary stresses during ascent aboard a malfunctioning IUS upper stage, which left it stranded in geosynchronous transfer orbit. Even this satellite proved useful. Since it transited the van Allen radiation belts twice daily, it allowed the USAF to assess the effect of an extreme radiation environment on DSP electronics.

As of 2007 it was planned that the new SBIRS satellite constellation would take over the prime missile warning function from DSP by the end of 2012. However the DSP's would be kept in service as back-ups and gap-fillers, with the belief that DSP-22 and -23 would remain in service until 2017-2022.

DSP satellites were built in a series of models of ever-increasing sophistication, weight, and capability:

• Phase I - the original model, for ICBM detection, was equipped with a 2000 pixel array. At the time they were often referred to as IMEWS (Integrated Missile Early Warning Satellites). Designed for launch by the Titan 3C, and used the booster's maneuverable Transtage to take the satellites to geostationary orbit. Mass of these models was 900 kg. The spacecraft was zero-momentum stabilized using a reaction wheel to counter the spacecraft spin. Body mounted cells and deployable panels generated 400 W. The payload included a 3.6 m Schmidt telescope with 2000 element infrared sensor, and separate nuclear detection sensors. The 15 month design life was vastly exceeded; instead reaching 7 to 12 years. The first four satellites launched were of this model, and made up the first DSP constellation.
• Phase II - these satellites had an extended 24-month design lifetime and a mass of 1040 kg. Power was increased to 680 W. Satellites 7 through 9 were of this model, and actual lifetime was seven to nine years. This was the second DSP constellation.
• Multi-Orbit Satellite/Performance Improvement satellites had a 36-month design life, and were designed to function in either geosynchronous or Molniya orbits (the latter to give coverage of submarine-launched-ballistic missile launches from the Arctic). They also had increased hardening against attack by blinding lasers, and improved detector arrays. Satellites 10 to 13 were of this model, with a mass of 1170 kg. Actual lifetime was 11 to 18 years. There were no acknowledged launch of this satellite types in the Molniya-type orbits; perhaps such launches were made covertly and were classified as communications or ELINT satellites by external observers. The four MOS/PIM satellites made up the third DSP constellation.
• Phase II Upgrade - Satellites 5 and 6, which were Phase II reserve satellites and had not been launched, were retrofitted for a 36-month design life, and equipped with the 6,000 detector array developed for the DSP-1 block 14 satellites, which provided enhanced capabilities for raid resolution and polar/global coverage. They were flown on missions 12 and 13, total mass 1670 kg. Perhaps these were rushed into service due to delays in development of the DSP-1.
• DSP-1 - Satellites 14 to 23 were significantly enlarged for a five-year design life, and increased survivability against countermeasures. They included the 6,000 pixel array, and were built in two series - Block 14 and Block 18. They had a launch mass of 2380 kg. Cost of the final satellite was $400 million.

All DSP's were equipped with dual radiation detectors designed to detect neutrons, gamma-, and x-rays produced by nuclear explosions in the atmosphere or space. These replaced the separate Vela satellites launched in the sixties. Beginning with DSP-23, these were supplemented by a 24-kg Space Atmosphere Burst Reporting System (SABRS), which would be used on the SBIRS-GEO satellites that would replace DSP.

It had been planned in the 1980's to equip the DSP's with a laser data cross-link produced by McDonnell-Douglas. This however was cancelled after its development cost ran vastly over budget.

Electric System: 1.30 average kW.

Photo Gallery

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USA 28 Credit: Manufacturer Image

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DSP 1 Credit: Manufacturer Image

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DSP 5 Credit: Manufacturer Image

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DSP 8 Credit: Manufacturer Image

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• IMEWS 1 - . Payload: DSP Phase 1 s/n 1 / OPS 5960. Mass: 900 kg (1,980 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1973-12-31 . USAF Sat Cat: 4630 . COSPAR: 1970-093A. Apogee: 36,128 km (22,448 mi). Perigee: 25,840 km (16,050 mi). Inclination: 16.40 deg. Period: 1,197.90 min.

  An Air Force Titan IIIC launched the 500th satellite to be placed in orbit successfully by a vehicle launched from Cape Canaveral. First generation geosynchronous ballistic missile launch detection satellite; placed in incorrect subsynchronous orbit. One account claimed that it exhausted its propellant before it could be put into operation, but a 2007service history chart showed that is was considered operational for three years, well beyond its planned life.

• IMEWS 2 - . Payload: DSP Phase 1 s/n 2 / OPS 3811. Mass: 900 kg (1,980 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1983-01-10 . USAF Sat Cat: 5204 . COSPAR: 1971-039A. Apogee: 36,527 km (22,696 mi). Perigee: 36,156 km (22,466 mi). Inclination: 10.50 deg. Period: 1,464.60 min.

  First generation geosynchronous ballistic missile launch detection satellite. First completely sucessful operational satellite, remained in service for nearly 12 years. Positioned over the Indian Ocean at 75 deg E in 1979-1982. As of 1983 May 11 located at 73.28W drifting at 7.684W degrees per day.

• IMEWS 3 - . Payload: DSP Phase 1 s/n 3 / OPS 1570. Mass: 900 kg (1,980 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1981-08-03 . USAF Sat Cat: 5851 . COSPAR: 1972-010A. Apogee: 35,962 km (22,345 mi). Perigee: 35,416 km (22,006 mi). Inclination: 0.20 deg. Period: 1,429.90 min. First generation geosynchronous ballistic missile launch detection satellite, remained in service for over nine years. Positioned over the Pacific Ocean at 165 deg E in 1979-1980. As of 2003 Mar 5 located at 74.63E drifting at 0.712W degrees per day..

• IMEWS 4 - . Payload: DSP Phase 1 s/n 4 / OPS 6157. Mass: 900 kg (1,980 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1980-11-01 . USAF Sat Cat: 6691 . COSPAR: 1973-040A. Apogee: 35,786 km (22,236 mi). Perigee: 35,777 km (22,230 mi). Inclination: 0.30 deg. Period: 1,435.90 min.

  First generation geosynchronous ballistic missile launch detection satellite, remained in service for over seven years. Positioned in geosynchronous orbit over the Indian Ocean at 75E in 1973; over the Americas at 105 deg W in 1979-1980. As of 1983 Jan 3 located at 73.21W drifting at 1.648W degrees per day.

• Simplified Processing Station for the Defense Support Program - . Spacecraft: DSP. IBM was awarded a contract to develop a Simplified Processing Station for the Defense Support Program. Target price of the contract was $23.3 million..

• Aeronutronic Ford Corporation was awarded a $7.25 million contract to modify the satellite tracking sets at the DSP ground stations. - . Spacecraft: DSP. Aeronutronic Ford Corporation was awarded a $7.25 million contract to modify the satellite tracking sets at the DSP ground stations..

• IMEWS 5 - . Payload: DSP Phase 2 s/n 7 / OPS 3165. Mass: 1,040 kg (2,290 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1987-12-31 . USAF Sat Cat: 8482 . COSPAR: 1975-118A. Apogee: 35,785 km (22,235 mi). Perigee: 35,671 km (22,164 mi). Inclination: 3.00 deg. Period: 1,436.00 min. Second generation geosynchronous ballistic missile launch detection satellite, remained in service for over twelve years. As of 1982 Dec 16 located at 34.61E drifting at 0.823E degrees per day..

• IMEWS 6 - . Payload: DSP Phase 2 s/n 8 / OPS 2112. Mass: 1,040 kg (2,290 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1984-07-01 . USAF Sat Cat: 8916 . COSPAR: 1976-059A. Apogee: 35,860 km (22,280 mi). Perigee: 35,620 km (22,130 mi). Inclination: 0.50 deg. Period: 1,433.30 min.

  Second generation geosynchronous ballistic missile launch detection satellite, remained in service for over eight years. Positioned over the Atlantic Ocean from 1976 to 1981: at 35 deg W in 1976-1977; at 65 deg W in 1977-1979; and 35 deg W in 1979-1980; and 65 deg W in 1980-1981. Then moved over the Pacific Ocean at 125 deg W, then 140 deg W in 1981-1982; then over the Indian Ocean at 75 deg E in 1982-1984.

• System 6.1 software for the Defense Support Program (DSP) Ground Data System - . Spacecraft: DSP. System 6.1 software for the Defense Support Program (DSP) Ground Data System was turned over to the Aerospace Defense Command..

• DSP Sensor Evolutionary Development - . Spacecraft: DSP. The Preliminary Design Review for the DSP Sensor Evolutionary Development (SED) Program was held..

• IMEWS 7 - . Payload: DSP Phase 2 s/n 9 / OPS 3151. Mass: 1,040 kg (2,290 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1984-01-01 . USAF Sat Cat: 9803 . COSPAR: 1977-007A. Apogee: 35,860 km (22,280 mi). Perigee: 35,620 km (22,130 mi). Inclination: 0.50 deg. Period: 1,433.30 min. Second generation geosynchronous ballistic missile launch detection satellite, remained in service for nearly seven years. Positioned in geosynchronous orbit over the Pacific Ocean at 135 deg W in 1977-1979; over the Indian Ocean 70 deg E in 1979-1984..

• Improved sensor for Defense Support Program satellites. - . Spacecraft: DSP. Aerojet ElectroSystems Company was awarded a contract to complete the design of an improved sensor for the Defense Support Program satellites. The sensor would be incorporated into satellite 14..

• Simplified Processing Station for DSP satellites. - . Spacecraft: DSP. SAMSO awarded IBM a $4.9 million contract to provide the Simplified Processing Station with the capability to receive health and status data as well as mission data from the DSP satellites..

• IMEWS 10 - . Payload: DSP MOS/PIM s/n 11 / OPS 7484. Mass: 1,170 kg (2,570 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1984-06-01 . USAF Sat Cat: 11397 . COSPAR: 1979-053A. Apogee: 35,854 km (22,278 mi). Perigee: 35,712 km (22,190 mi). Inclination: 1.80 deg. Period: 1,435.90 min.

  First Multi-Orbit Satellite / Performance Improvement ballistic missile launch detection satellite, remained in service for nearly six years. Positioned in geosynchronous orbit over the Pacific Ocean at 135 deg W in 1979-1982; 85 deg W in 1982-1984; 135 deg W in 1984; 125 deg W in 1985..

• Contract to upgrade the Ground Communications Network for the DSP program. - . Spacecraft: DSP.

  Technology Development Corporation, a minority small business, was awarded a contract to upgrade the Ground Communications Network for the DSP program. The basic contract was valued at $5,251 million, and it carried options valued at $8,555 million. This was the largest contract ever awarded under the federal government's Disadvantaged Business Program.

• IMEWS 11 - . Payload: DSP MOS/PIM s/n 10 / OPS 7350. Mass: 1,170 kg (2,570 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1992-01-01 . USAF Sat Cat: 12339 . COSPAR: 1981-025A. Apogee: 35,527 km (22,075 mi). Perigee: 35,463 km (22,035 mi). Inclination: 2.00 deg. Period: 1,421.20 min.

  Multi-Orbit Satellite / Performance Improvement ballistic missile launch detection satellite, remained in service for nearly eleven years. Positioned in geosynchronous orbit over the Pacific Ocean at 69 deg W in 1981-1982; 135 deg W in 1982-1984; 75 deg E in 1984-1985. As of 2003 Mar 6 located at 40.27E drifting at 0.598E degrees per day.

• IMEWS 13 - . Payload: DSP MOS/PIM s/n 13 / OPS 8701. Mass: 1,170 kg (2,570 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1998-12-31 . USAF Sat Cat: 13086 . COSPAR: 1982-019A. Apogee: 35,598 km (22,119 mi). Perigee: 35,520 km (22,070 mi). Inclination: 2.00 deg. Period: 1,424.40 min.

  Multi-Orbit Satellite / Performance Improvement ballistic missile launch detection satellite, remained in service for over sixteen years. Positioned in geosynchronous orbit over the Pacific Ocean at 68 deg W in 1982; 35 deg W in 1983-1988; 165 deg W in 1988-1989; 35 deg W in 1989-1991.

• DSP - . Payload: DSP MOS/PIM s/n 12 / OPS 7641. Mass: 1,170 kg (2,570 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 2002-12-31 . USAF Sat Cat: 14930 . COSPAR: 1984-037A. Apogee: 35,530 km (22,070 mi). Perigee: 35,530 km (22,070 mi). Inclination: 1.30 deg. Period: 1,423.00 min.

  Multi-Orbit Satellite / Performance Improvement ballistic missile launch detection satellite, remained in service for nearly eighteen years. Positioned in geosynchronous orbit at 135 deg W in 1984-1985; 65 deg E in 1985-1988; as of 31 December 1990 at 99.16 deg W drifting at 0.050 deg W per day.

• USA 7 - . Payload: DSP Phase 2 Upgrade s/n 6R. Mass: 1,670 kg (3,680 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1994-12-31 . USAF Sat Cat: 15453 . COSPAR: 1984-129A. Apogee: 35,915 km (22,316 mi). Perigee: 35,619 km (22,132 mi). Inclination: 3.40 deg. Period: 1,445.80 min.

  Reserve Phase 2 DSP ballistic missile launch detection satellite fitted with Block 14 sensors, remained in service for nearly eighteen years. Observed Scud launches during Gulf War. Positioned in geosynchronous orbit at 155 deg W in 1985-1988; 65 deg E in 1988-1991; 145 deg E in 1991-1992; 105 deg E in 1992-1993; 5 deg E in 1993-1994.

• USA 28 - . Payload: DSP Phase 2 Upgrade s/n 5R. Mass: 1,670 kg (3,680 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 1987-12-31 . USAF Sat Cat: 18583 . COSPAR: 1987-097A. Apogee: 35,558 km (22,094 mi). Perigee: 35,514 km (22,067 mi). Inclination: 2.90 deg. Period: 1,423.30 min.

  Reserve DSP ballistic missile launch detection satellite fitted with Block 14 sensors, remained in service for only five years.. Observed Scud launches during Gulf War. Positioned in geosynchronous orbit at 35 deg W in 1988-1989; 10 deg E in 1989-1992; 35 deg W in 1992-1993; 105 deg E in 1993; 165 deg W in 1999.

• USA 39 - . Payload: DSP-1 Block 14 F14. Mass: 2,360 kg (5,200 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. USAF Sat Cat: 20066 . COSPAR: 1989-046A. Apogee: 35,614 km (22,129 mi). Perigee: 35,699 km (22,182 mi). Inclination: 3.10 deg. Period: 1,421.80 min.

  First DSP-1 Block 14 ballistic missile launch detection satellite; first Titan 4 launch. Positioned in geosynchronous orbit at 165 deg W in 1990-1994; 145 deg W in 1999; 166 deg W in 2000.. Still in service as of March 2007. As of 2007 Feb 5 located at 145.23W drifting at 0.014W degrees per day.

• USA 65 - . Payload: DSP-1 Block 14 F15. Mass: 2,360 kg (5,200 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. Completed Operations Date: 2006-01-01 . USAF Sat Cat: 20929 . COSPAR: 1990-095A. Apogee: 35,699 km (22,182 mi). Perigee: 35,614 km (22,129 mi). Inclination: 3.10 deg. Period: 1,421.80 min. DSP-1 Block 14 ballistic missile launch detection satellite. Positioned in geosynchronous orbit at 105 deg E in 1991; 70 deg E in 1991-1992; 5 deg E in 1992-1993; 35 deg W in 1993; 38 deg W in 1999-2004. Believed to have been taken out of service in 2006..

• USA 75 - . Payload: DSP-1 Block 14 F16. Mass: 2,360 kg (5,200 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. USAF Sat Cat: 21805 . COSPAR: 1991-080B. Apogee: 35,787 km (22,236 mi). Perigee: 35,795 km (22,241 mi). Inclination: 2.50 deg. Period: 1,421.90 min.

  DSP-1 Block 14 ballistic missile launch detection satellite, deployed from shuttle STS-44 on 25 November 1991. Only DSP launched from the shuttle before the Challenger disaster moved the payload to the Titan 4. Positioned in geosynchronous orbit at 130 deg W in 1992; 70 deg E in 1992; 8 deg E in 1999; 40 deg W in 2000. Still in service as of March 2007.

• USA 107 - . Payload: DSP-1 Block 14 F17. Mass: 2,360 kg (5,200 lb). Nation: USA. Agency: USAF. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. USAF Sat Cat: 23435 . COSPAR: 1994-084A. Apogee: 35,790 km (22,230 mi). Perigee: 35,780 km (22,230 mi). Inclination: 0.00 deg. Period: 1,436.10 min. DSP-1 Block 14 ballistic missile launch detection satellite. Positioned in geosynchronous orbit at 103 deg E in 1999. Still in service as of March 2007..

• USA 130 - . Payload: DSP-1 Block 18 F18. Mass: 2,380 kg (5,240 lb). Nation: USA. Agency: USAF. Manufacturer: TRW. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. USAF Sat Cat: 24737 . COSPAR: 1997-008A. Apogee: 35,790 km (22,230 mi). Perigee: 35,780 km (22,230 mi). Inclination: 0.00 deg. DSP-1 Block 14 ballistic missile launch detection satellite. Positioned in geosynchronous orbit at 70 deg E in 1999. Still in service as of March 2007..

• USA 142 - . Payload: DSP-1 Block 18 F19. Mass: 2,380 kg (5,240 lb). Nation: USA. Agency: USAF. Manufacturer: TRW. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. USAF Sat Cat: 25669 . COSPAR: 1999-017A. Apogee: 35,800 km (22,200 mi). Perigee: 720 km (440 mi). Inclination: 28.00 deg.

  The Titan 4B placed the IUS upper stages and DSP-1 Block 14 ballistic missile launch detection satellite. payload into a 188 km x 718 km x 28.6 deg parking orbit. The first stage of the IUS burned at 18:14 GMT and put the second stage and payload into a geosynchronous transfer orbit. The IUS second stage fired at 23:34 GMT in order to place the spacecraft in geosynchronous orbit. However, at least one connector remained attached between the stages, and the second stage motor nozzle did not extend properly. When the stage fired, the vehicle tumbled wildly during the burn. Separation of the DSP was achieved. Although it could not perform its primary mission, it did provide a good test case in that the effects of radiation on its systems could be monitored as they underwent twice-daily passages of the Van Allen Radiation Belts. However after some weeks the hydrazine propellant aboard the satellite vented into space due to a broken fuel line. It was believed this had been induced by the wild ride aboard the IUS-2 stage.

• USA 149 - . Payload: DSP-1 Block 18 F20. Mass: 2,380 kg (5,240 lb). Nation: USA. Agency: USAF. Manufacturer: TRW. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. USAF Sat Cat: 26356 . COSPAR: 2000-024A. Apogee: 35,790 km (22,230 mi). Perigee: 35,780 km (22,230 mi). Inclination: 0.00 deg.

  DSP-1 Block 14 ballistic missile launch detection satellite. Delivered by the two-stage IUS-22 solid rocket into geostationary orbit. Fullfilled mission of DSP 19 launched in 1999 into the wrong orbit when its IUS stage failed. Still in service as of March 2007. As of 2005 Apr 2 located at 8.05E drifting at 0.166E degrees per day.

• USA 159 - . Payload: DSP-1 Block 18 F21. Mass: 2,380 kg (5,240 lb). Nation: USA. Agency: USAF. Manufacturer: TRW. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. USAF Sat Cat: 26880 . COSPAR: 2001-033A. Apogee: 35,780 km (22,230 mi). Perigee: 35,780 km (22,230 mi). Inclination: 2.90 deg. Period: 1,435.76 min.

  Launch postponed from February, then delayed from July 27. USA 159 was a US Air Force Defense Support Program infrared missile early warning satellite was placed by the Titan core into a 328 x 663 km x 28.7 deg parking orbit. The Boeing IUS-16 upper stage then fired its first solid motor to enter geostationary transfer orbit. The second IUS solid motor fired at around 14:00 GMT placing DSP Flight 21 in near-geosynchronous orbit. Still in service as of March 2007.

• USA 176 - . Payload: DSP-1 Block 18 F22. Mass: 2,380 kg (5,240 lb). Nation: USA. Agency: NSA. Manufacturer: TRW. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. USAF Sat Cat: 28158 . COSPAR: 2004-004A. Apogee: 36,105 km (22,434 mi). Perigee: 35,852 km (22,277 mi). Inclination: 0.68 deg. Period: 1,445.94 min.

  DSP-1 Block 14 ballistic missile launch detection satellite. Last flight of the IUS upper stage. Launch delayed from November 4, 2003, and January 17, 2003. Planned IMEX piggyback payload cancelled. Still in service as of March 2007, expected to remain operational until 2017-2022. As of 2004 Feb 15 located at 96.66W drifting at 2.464W degrees per day.

• USA 197 - . Payload: DSP-1 Block 18 F23. Mass: 2,270 kg (5,000 lb). Nation: USA. Agency: NSA. Manufacturer: TRW. Class: Surveillance. Type: Early warning satellite. Spacecraft: DSP. USAF Sat Cat: 32287 . COSPAR: 2007-054A. Apogee: 36,325 km (22,571 mi). Perigee: 35,800 km (22,200 mi). Inclination: 0.00 deg. Period: 1,436.00 min.

  Final DSP launch. The series was to be replaced by SBIRS, which was in the middle of a troubled development program. The Delta 4H performed well after problems on its first launch. The RL10-powered upper stage made three burns before releasing the early-warning satellite in its final geosynchronous orbit. Total cost of the flight was $700 million, with the DSP worth $400 million. The DSP carried a special 25 kg supplementary payload designed to detect extremely small nuclear tests in space. The payload was required by a secret White House/National Security Council directive to detect any attempted covert nuclear tests by Iran or North Korea.