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Warning - Overview

Early warning satellites carry infrared sensors that detect the heat from a rocket's engines. These satellites are used for monitoring missile launches to insure treaty compliance, as well as providing early warning of missile attack. They can also be used to locate the launch sites of missiles used in combat operations.

The American Satellite Early Warning System (SEWS) consists 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.(2) At the beginning of 1990 five DSP spacecraft were operational. DSP F-13 and DSP F-12, launched in 1982 and 1984 respectively, were on backup duty, and DSP F-6R launched in 1984, DSP F-5R, launched in 1987, and DSP-I 14, launched in 1989, were the primary operational spacecraft.(3) The second Improved DSP (DSP-I) was launched on Titan 4 on 12 November 1990. The DSP-I satellites, of which spacecraft 14 through 25 were on order in early 1989 with options for 26 through 28 under consideration,(4) will incorporate upgraded sensors and improved resistance to laser attack.(5) Two DSP satellites were used to track Iraqi Scud missile launches.(6) Although the system was slow to provide warning of initial Iraqi test launches in early December,(7) by the end of the year the system had been greatly improved.(8)

The elimination of the anti-missile mission requirement for Booster Surveillance and Tracking System (BSTS) in SDI led to a decision in 1990 to transfer budget authority for this program back to the Air Force,(9) which sought to justify continuation of the program, initially renamed the Advanced Warning System and subsequently termed the Follow-on Early Warning System (FEWS), on the basis of its improved early warning of missile attack, and enhanced intelligence collection and verification capabilities. The future of this project remains in doubt, since BSTS grew out of the Advanced Warning System which was rejected for deployment in 1983.(10) The greater sensitivity of the FEWS sensors could improve its ability to track third world missiles compared with the current capabilities of DSP early warning satellites.(11)

In the early 1960's the United States began launching a series of satellites known as Vela, dedicated to the detection of nuclear explosions on the Earth and in space. More recently, these dedicated satellites have been replaced by nuclear explosion detection sensors mounted on other spacecraft. The American Navstar navigation satellites, along with weather and early warning satellites, carry several types of sensors to detect the location and yield of nuclear explosions. This Integrated Operational Nuclear Detection System, or IONDS, will relay this information to widely dispersed mobile ground terminals, enabling battle managers to identify which targets were missed by defective missiles or warheads, and to assign further strikes.

On 8 August 1989, the Space Shuttle Orbiter Columbia deployed what appears to be the first of a new generation of MASINT satellites under the FOREST GREEN program. By early October amateur astronomers had noted that sunlight reflected from this spacecraft was flashing, as though the spacecraft were tumbling out of control.(12) But by mid-November the satellite was observed to have maneuvered to a higher orbit,(13) suggesting that the spacecraft was operational.

The expansion of treaty verification satellite programs has largely been the results of the efforts of Oklahoma Democratic Senator David Boren, Chair of the Senate Intelligence Committee. Under his proposal, as much as $5 billion was programmed(14) for a new system of satellites that would be deployed in the mid-1990's(15) or no later than the 1997-99 timeframe(16) to monitor Soviet laser testing.

The Space Based Wide Area Surveillance System (SB-WASS), with potential NATO(17) and Canadian(18) participation, would be used to track ships and aircraft on a global basis, although there is intense disagreement over the type of sensor that would be used. The Navy favors passive infrared sensors that would track the heat emitted by ships and aircraft, while the Air Force favors an active radar system, which it believes would have a superior all-weather capability(19). These technical preferences mark a reversal from earlier preferences. Navy interest in space-based radar extended from the Albatross studies of the early 1960's through the Clipper Bow effort of the late 1970's.(20) The Air Force and DARPA spent almost $500 million developing the Teal Ruby infrared system before deciding not to fly it.(21)

The choice is more than one of engineering convenience, since the infrared system could require as few as four satellites for continental air defense or 8 to 10 for global coverage,(22) while the radar system could require(23) anywhere from 8 to 24 massive spacecraft (weighing over 11,000 kilograms(24)), costing from $8 billion(25) up to $20 billion.(26) The Navy is interested primarily in a system to assist with fleet air defense, while the Air Force requirements also extend to strategic air defense, support of forces forward deployed in areas such as the Persian Gulf, as well as drug interdiction.(27) The Navy is seeking a system that will be responsive to tasking by fleet commanders, while the Air Force prefers a system that will be centrally directed by the U.S. Space Command.(28) The services also differ on how the space-based system would complement terrestrial systems, with the Air Force claiming that the space-based system could replace ground-based and airbased radars (such as AWACS),(29) and the Navy seeing the space-based system more as a complement to terrestrial systems.

However, their are serious questions concerning the ability of the SB-WASS to track stealth targets, as well as concerns about the vulnerability of these low-flying satellites to Soviet ASAT attack,(30) and approval of development of this system has been deferred to 1990, with a first test flight anticipated around 1995.

By 2013 the Department had made very significant improvements in Overhead Persistent Infrared, or OPIR. And the newest Air Force satellite, satellite Space-Based Infrared Systems, SBIRS, doing amazing work in what is highly needed in the area of missile warning, missile defense, battle space awareness, and technical intelligence. The Air Force was doing a good job on the scanning sensor. The staring sensor, which has much better fidelity, really hadn't fully been wrung out yet, because the USAF had been so focused on getting the scanning sensor calibrated and certified.


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

5. 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).

6. Covault, Craig, "USAF Missile Warning Satellites Providing 90-Sec. Scud Attack Alert," Aviation Week & Space Technology, 21 January 1990, page 60-61.

7. Toth, Robert, "Iraqi Missile Test Had US Thinking War Had Started," Los Angeles Times, 21 December 1990, page A1, A11.

8. Diehl, Jackson, "Jordon's Troop Shifts Raise Questions in Israel," The Washington Post, 2 january 1991, page A17, A23.

9. Lawler, Andrew, "Pentagon Revamping BSTS; Project Moving to Air Force," Space News, 14 May 1990, page 1, 20.

10. General Accounting Office, "DOD Acquisition: Case Study of the Air Force Advanced Warning System," GAO/NSIAD-86-45S-14, 31 July 1986.

11. "BSTS is in a 'Time of Peril': Hard," SDI Monitor, 6 July 1990, page 150.

12. "Secret CIA Satellite Launched by Shuttle Columbia Observed 'Tumbling' By Astronomers in 7 Countries," Aviation Week & Space Technology, 9 October 1989, page 35.

13. "Secret DoD Shuttle Payload Boosted to Higher Orbit," Aerospace Daily, 8 December 1989, page 393.

14. "A Secret Laser Hunter," Newsweek, 3 october 1988, page 7.

15. "CIA Chief Warns Congress Not to Cut Recon Satellites," Aerospace Daily, 30 November 1989, page 323.

16. Foley, Theresa, "Monitoring Soviet Space Weapons Adds to Demand for U.S. Intelligence," Aviation Week & Space Technology, 27 February 1989, page 22-23.

17. "DOD Considering 27 New NATO Programs for Nunn Funds Over Two Years," Inside the Pentagon, 25 August 1989, page 13-14.

18. Lowman, Ron, "Canada, U.S. Work to Hone Space-Based Radar Objectives," Defense News, 20 November 1989, page 21.

19. "Piotrowski Says CINCs Prefer Space-Based Radar to Nay Infrared Surveillance," Electronic Combat Report, 29 September 1989, page 1.

20. Robinson, Bill, "Space Based Radar," Air Force Industry Briefing, 1 March 1989.

21. Smith, Bruce, "TEAL RUBY Spacecraft to Be Put in Storage at Norton AFB," Aviation Week & Space Technology, 8 January 1990, page 22-23.

22. Lynch, David, "Space Surveillance Effort in Limbo," Defense Week, 25 september 1989, page 13.

23. U.S. Air Force Scientific Advisory Board, "Summer study on Space Based Radar," September 1987.

24. Lynch, David, "Space Surveillance Effort in Limbo," Defense Week, 25 september 1989, page 13.

25. "Piotrowski Says CINCs Prefer Space-Based Radar to Nay Infrared Surveillance," Electronic Combat Report, 29 September 1989, page 1.

26. Hasley, Donna, "JCS Bid to Define Space Surveillance Mission May Resolve USAF, Navy Fight," Inside the Pentagon, 10 March 1989, page 1, 10.

27. "Drug Wars Turning to Star Wars," Space News, 9 October 1989, page 2.

28. "Airborne, Space Radars Top ADI Needs," Military Space, 22 May 1989, page 5-6.

29. Canan, James, "The Big Hole in NORAD," Air Force Magazine, October 1989, pages 54-59.

30. "Senate Armed Services Committee Report," Inside the Pentagon, 27 July 1989, page 8.

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Page last modified: 10-04-2016 20:51:03 ZULU