A - Overview
The Defense Support Program (DSP) early warning satellites contributed to a mission that was not originally intended for them -- interception of tactical ballistic missiles. But the analysis of the effects of Iraqi missile attacks, and the effectiveness of the DSP, are somewhat complicated by disparate data. "According to executives at Raytheon, the Patriot's builder, 50 Scuds were engaged and 49 intercepted.... a small number of Scud warheads came through --- no where near the majority... (about) 160 Patriots were fired, most of which self-destructed."(1) However, an official Army analysis, stated that "the system was used to engage only threatening Scuds within the missile footprint. Of the 47 Scuds against which it was fired, Patriot successfully intercepted 45. Throughout its entire period of employment in SWA the system demonstrated an overall operational readiness rate above 95 percent."(2)
B - Space Segment
The American Satellite Early Warning System (SEWS) consists of five Defense Support Program spacecraft.(3) 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.(4) 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.
|DSP SED 12||F- 6R||12/22/84|
|DSP SED 13||F- 5R||11/29/87|
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.(5) The November launch of DSP-I F-15 resulted in the removal of DSP-10 F-13 from operational status.
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.(6)
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,(7) will incorporate the upgraded sensors of the SEDS satellites, as well as improved resistance to laser attack.(8) The DSP-I satellites will also carry a laser communications package that will enable the satellites to relay warning information to each other.(9) 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.(10) 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 DSP system was "readjusted" to provide better coverage of the Middle East,(11) with two DSP satellites were maneuvered to provide optimal viewing of Scud launch areas.(12) The satellites rotate at 5 rpm, viewing launch areas at 12 second intervals. The use of two satellites provides stereo tracking data to calculate target impact areas. "The two DSP spacecraft observing the Persian Gulf/Indian Ocean area are older model DSPs equipped with the new telescope that is also being used on the two new Block-14 versions launched in 1989 and late 1990."(13)
C - Control Segment
The ground segment for the DSP includes a Simplified Processing Station, located at Kapaun Air Station, West Germany.(14) Operated by the 6th Detachment of the 1st Space Wing, the SPS became operational in late 1982. Although the SPS is located in Europe, data from the station is transmitted to Space Command headquarters in the United States for analysis and fusion with data from other sensors.
Data from the DSP is reported (erroneously) to be transmitted to Alice Springs, Australia, where it is evaluated to determine whether the signal is a false alarm.(15) According to Bruce Blair, a leading analyst of warning systems, after DSP detects a launch, "the satellite transmits the information to an Air Force Station in Alice Springs, Australia. Within about 45 seconds, analysts evaluate the information and decide whether to pass it on to North American Aerospace Defense Command (NORAD) in Colorado Springs, the only place where the final analysis can be made. By the time the rocket plume is identified at NORAD, it is about two minutes after the launch... It takes another minute or two before the information is relayed back to the Gulf."(16)
D - User Segment
A variety of alerting systems were implemented to transmit launch warnings from the DSP satellites. The American embassy in Baghdad received notification of Scud launches on 2 December via a telephone message from the State Department, as the launches were being conducted.(17) Launch warnings were transmitted to all Navy vessels in the theater from a central communications facility in Bahrain.(18)
By mid-January, Air Force Space Command had established data links with Patriot interceptor missile fire units to "provide the missile crews with near real-time information on the launch of Iraqi Scud missiles and the specific targets to which the missiles are heading."(19) According to one account, DSP operators "went on into the JCS (Joint Chiefs of Staff) and said 'we've figured out something we can do for (Patriot) if we do the following communications' upgrades... The results 'astounded the tactical people' and allowed warnings to be passed Israel and Saudi Arabia... 'In the past... you would have been feeding' data from the IR satellites to 'the warning system of North America, you would have been feeding the intelligence community and the national command authority.' But with the reoriented focus and new communications links, 'the lieutenant and the captain out there commanding a (Patriot) battery or whatever' had 'instant access' to a kind of information they had never seen."(20)
Thus, by the end of January Israel was receiving real-time intelligence on Scud launches.(21) "The infrared signature of the Iraqi boosters were detected by the United States early warning satellites, which simultaneously transmitted the launching warning to the Pentagon, which in turn relayed the warning instantly over a newly established and secure hotline, called Hammer Rick, to Tel Aviv..."(22)
E - Operational Applications
On December 2 Iraq launched three modified Scud missiles at 4:00 AM, 4:30 AM and 5:00 AM local time. The missiles were launched from the Basra area, and traveled 418 miles, impacting about 60 miles from the H-3 pumping station and military complex. The first missile was not detected until six minutes into its seven minute flight.(23) The satellites initially provided 90 to 120 seconds of warning time of Scud attack, out of a total of seven minutes from launch to impact. The process of launch evaluation required 120 seconds from initial launch detection to identification of impact area.(24)
During a visit by Defense Secretary Cheney on 21 December, the 354th Tactical Fighter Wing and the 101st Airborne Division were placed on a Condition Red NBC Alert, as a
result of DSP detection of an Israeli Chetz anti-missile interceptor test. The alert was in part a result of the failure of Israeli officials to notify the United States in advance of the launch,(25) although other sources suggested that some limited advance information had been provided.(26)
The problems with detecting the missile firings of 2 December had the effect of improving coordination between the US and Israel. By late December, a senior Israel official noted that "we were given almost everything we need to know at the time we needed to know it."(27) By late January, the DSP system was "identifying the likely target within 120 seconds of a Scud leaving its mobile launcher."(28) Others noted that "improved communications are enabling the DSP satellites to provide up to about 5 min. warning of a Scud warhead impact, compared with 90-120 sec. when the spacecraft first started observing the Iraqi Scuds in the current crisis... Missile warning officials said Iraqi President Saddam Hussein "blundered" when he launched two test Scuds before the war began. The tests enabled the US to ascertain the improvements needed to lengthen the DSP warning time of a Scud attack."(29)
F - Operational Limitations
The operational effectiveness of the DSP system is difficult to assess, given the variety of other systems that were operating in conjunction with it. Technical limitations of the satellite itself include limits on the accuracy of DSP prediction of Scud impact areas is limited by the short boost phase and relatively long interval between data points.(30)
At least two instances of operational shortcomings associated with the DSP can be identified. Ironically, these involve the first and final Iraqi missiles fired during the conflict.
Two Patriot batteries were shipped to Israel in early January, and four Patriot batteries were operational in Israel by 24 January (out of a total of as many as 12 that could have been deployed).(31) By 27 January, six Patriot batteries were deployed in Israel, jointly manned by Israeli and American troops.(32) Subsequently the total was increased to eight by the addition of batteries on loan from the Netherlands and Germany.(33) Each battery was able to defend an area with a radius of at least 3 kilometers around its location.(34)
Iraqi Hussein modified Scud missile launches on 2 December were not detected until about one minute before the first missile reached its target.(35) The Israeli government was reportedly concerned that this apparent failure of the American warning system would increase Israeli vulnerability to attack.(36) Several reasons were suggested for this failure, including the fact that system operators had not been expecting launches from the Basra region, resulting in delays in characterizing the launch, and that there were delays in this first test of the alerting system.(37) "Normally, the anticipated trajectories of hostile missiles are programmed into the sensors to alert US forces automatically to any incoming weapon. Some analysts suggest that the southern trajectories from Basra were programmed into the sensors, as were western trajectories from H-2 and H-3, but no westerly paths from Basra."(38)
On the first night of the air campaign, "American spy satellites were trained on Iraq to pick up Scud missile launches. At about 4 a.m. TACC (Tactical Air Command Center) screens lit up with a Scud alert... It was hours before anyone figured out what had caused the false alarm: the satellites had mistaken a flight of incoming B-52 bombers over Iraq for a barrage of Scud missiles."(39)
At least some of the false alarms of Scud attacks were due to the delay between the satellites detecting a launch and determining the target of the attack. On 11 February, following one Scud attack on Israel, "two hours later, the alarms sounded nationwide once again: Israelis were sent back to their safe rooms and ordered into their gas masks. But that was a false alarm. American satellites had detected a Scud launching, but this one was directed at Saudi Arabia..."(40)
The most significant failing occurred on 25 February, when the penultimate Iraqi missile fired during the war struck an American barracks at Khobar City, near Riyadh, killing 28 Americans and wounding 97 others. No air raid warning was given, nor were any Patriot interceptors fired at the incoming missile. Several explanations have been offered for this tragedy.
The first explanation blamed "a breakdown in the US intelligence warning system..." meant that "the Iraqi missile was not immediately detected after being launched from southern Iraq. 'We didn't have the full warning time,' said one official... Normally, an array of US intelligence satellites, aircraft and ground-based equipment has been able to provide up to five minutes of warning. But in the attack Monday night, intelligence agencies learned of the incoming missile about two minutes before it approached Dahran... Officials said the missile launch was 'masked' by heavy cloud cover over southern Iraq, although they said that some detection equipment can penetrate overcast skies."(41) According to another American official, the satellites "picked up the launch, but it looked static, like it wasn't moving. We thought it was a ground fire," one of the oil well fires the Iraqis had started in Kuwait. "It was not until the Scud was descending over Saudi Arabia that both infrared satellites correctly analyzed the data and the Patriot defense systems were alerted."(42)
The second explanation noted that "The Scud apparently fragmented above the atmosphere, then tumbled downward. Its warhead blasted an eight-foot-wide crater into the center of the building... Brig. Gen. Richard I. Neal of the United States Command said. The Scud could not be tracked by the Patriot radar system, he said, because it had fragmented when it entered the atmosphere. 'The system we utilize to defeat this system has a known trajectory,' General Neal said. 'Our investigation looks like this missile broke apart in flight. On this particular missile is wasn't in the parameters of where it could be attacked."(43) According to Mike Elleman at Stanford University, when the missile reenters the atmosphere above 30 kilometers at about 2 kilometers per second, "'there is enough dynamic pressure to break up (the missile, causing)... it to tumble, and break up into three distinct sections: warhead, engine and fuel tanks."(44)
Another explanation was that the Patriot battery defending the area, which only had two minutes warning of the attack, was out of service at the time. According to Maj. Gen. James Baylor, commander of the 99th ARmy Reserve Command which was hit by the missile, "They could not have fired if they had wanted to. It was down for an upgrade of equipment... Its like a car engine that was down to get spark plugs in it." The general also suggested that Patriot would have been ineffective in any event, since the incoming missile was tumbling, generating an irregular trajectory that would have made it impossible for the Patriot computers to track the target.(45)
G - Alternative Systems
In addition to the DSP early warning satellites, at least three other missile launch detection systems were available. Signals intelligence could provide warning of impending launches. Radar systems for tracking missiles after launch would include the airborne AWACS radar and the FPS-79 radar at Diyarbakir in Turkey.
American and Israeli signals intelligence systems provided warning of missile attacks. It was reported that, apart from American intelligence, Israeli forces had "other ways of finding out about these things,"(46) which would probably consist of ground-based and air-based signals intelligence systems. As previously noted, signals intelligence systems provided warning of impending Iraqi missile launches. The missile launchers "have a radar, code named END TRAY by NATO, that it used to track a balloon sent into the upper atmosphere just before launch to help compute high altitude winds and increase accuracy of the missile. But Soviet doctrine calls for the radar to be turned on for only a short time, making in hard to detect. Also, although there are communications links to the surveyed sites, they are buried, so chances of picking up any emissions are minimal."(47) "... Iraq was using dummy missiles, complete with equipment that emitted electronic signals designed to fool attacking airplanes."(48)
The AWACS aircraft also appear to have provided notification of Scud launches. One account noted that fighters "are poised to attack Scud launchers as soon as AWACS flying radar platforms or other surveillance aircraft detect a launch... Once the missile is fired, the Iraqi technicians are almost certain to have betrayed their location to an AWACS...."(49) In one case, Col. David Cormak, a KC-135 aerial refueling tanker Wing commander, noted that "with state-of-the-art early warning aircraft systems... the Air Force knows a great deal about what the enemy is doing. When the Iraqis launched a pair of Scud missile in an apparent test-firing, Cormak added, his tankers 'knew it immediately".(50) Improved communications between the AWACS and fighter aircraft also helped in destroying more Scud mobile launchers. The AWACS aircraft can detect the missile shortly after launch, and analysis of the missile trajectory will indicate the location of the launch site.(51) This can be quickly processed by the Air Mission Control Center, which will modify the Air Tasking Order of strike aircraft in the vicinity, ordering them to attack the suspected missile launch site.(52) This new strategy, "in which warplanes attack the missile launchers within seconds of firing" was made possible by the continuous patrols over Iraqi airspace which began in early February, significantly improved the effectiveness of anti-Scud efforts.(53)
The E-3 Sentry Airborne Warning and Control System (AWACS) is one of the principal components of American air defense, air superiority, and air-to-ground operational planning. Connectivity to other combat elements is maintained through the Joint Tactical Information Distribution System (JTIDS).(54) Given the established ability of the AWACS to detect small targets such as light aircraft against a cluttered background, it would be expected that missiles such as the al-Hussein could also be detected. From an altitude of 10 kilometers, the AWACS could detect a missile at a similar altitude at ranges of in excess of 800 kilometers. Thus an AWACS on station over the Hail airfield in North-central Saudi Arabia (in practice the AWACS were probably stationed closer to the Iraqi border) would be able to detect al-Hussein missile launches from all Iraqi launch areas.
The Air Force FPS-79 UHF tracking radar at Diyarbakir/Pirinclik in Turkey is also capable of tracking Iraqi missiles during flight (the FPS-17 detection scanning radars have fixed antennae oriented toward the Soviet Union). The 10 meter diameter dish antenna system has a variable focus feed horn system which can provide a wide beam for target detection, and a narrow beam for tracking (other similar radars have scan rates in excess of 10o per second).(55) Operating at 432 MHz(56) this radar has a maximum detection range in excess of 4,300 kilometers.(57) Although the use of this radar was not mentioned during
|Target Altitude||Detection Range|
|50 km||800 km|
|100 km||1100 km|
|150 km||1350 km|
|200 km||1550 km|
|West Iraq||H-3||Jerusalem||400 km||125 km ?|
|West Iraq||Al Qaim||Haifa||800 km||180 km|
|South Iraq||Basra||Riyadh||600 km||150 km ?|
|South Iraq||Al-Amarah||Riyadh||800 km||180 km|
the war itself, one account of the Scud attack on the American barracks in Saudi Arabia noted the use of this radar, and noted that an American official stated that a "ground based radar in the region had detected the Scud launch and had tracked it all the way to impact."(58)
H - Iraqi Capabilities
Iraq had no capabilities similar to DSP, or the other systems used by the United States. However, Assistant Secretary of Defense for Public Affairs Pete Williams noted that "Saddam Hussein's people can presumably watch CNN, and when they launch a Scud, they can watch it come in." (59)
I - Net Assessment
According to one analysis, "the extent of the contribution by the Defense Support Program early warning satellites remains veiled, but US space assets clear helped the allies monitor Iraqi Scud missile activity and provide some warning of imminent missile attack. Whether DSP satellites are technically capable of being useful in future wars will be a subject of debate at the Pentagon and in Congress this year. Some military planners believe that an Advanced Warning System must be developed, despite its high cost, to replace DSPs, especially if futuristic defensive weapons are to use the satellites to trigger an interception. The argument over Advanced Warning Satellites versus upgraded DSPs has raged for several years, and the DSP contribution to the Persian Gulf war will be part of the debate this year."(60)
1. Safire, WIlliam, "The Great Scud-Patriot Mystery," The New York Times, 7 March 1991.
2. US Army, "Army Weapons Systems Performance in Southwest Asia," mimeo, 13 March 1991.
3. Ball, Desmond, A Base for Debate, (Allen & Unwin, London, 1987) is perhaps the most comprehensive discussion of the DSP system.
4. Kenden, A., "Military Maneuvers in Synchronous Orbit," Journal of the British Interplanetary Society, February 1983, V. 36, pp. 88-91.
5. "Advanced Missile Warning Satellite Evolved From Smaller Spacecraft," Aviation Week & Space Technology, 20 January 1989, page 45.
6. Cushman, J., "AF Seeks Invulnerable Warning Satellites," Defense Week, 16 January 1984, pp 1, 10-14.
7. "Air Force to Decide by End of Month on DSP Acquisition Method," Aerospace Daily, 5 October 1989, page 30-31.
8. 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).
9. Cushman, J., "AF Seeks Invulnerable Warning Satellites," Defense Week, 16 January 1984, pp 12.
10. Goodman, Adam, "Problems Plague McDonnell Douglas Laser," St. Louis Post Dispatch, 13 August 1989, page 1 (an extremely thorough treatment of this problem).
11. "Space Support," Military Space, 24 September 1990, page 8.
12. Covault, Craig, "USAF Missile Warning Satellites Provide 90-Sec. Scud Attack Alert," Aviation Week & Space Technology, 21 January 1991, page 60-61.
13. Covault, Craig, "Recon Satellites Lead Allied Intelligence Effort," Aviation Week & Space Technology, 4 February 1991, page 25-26.
14. Desmond Ball, A Base for Debate, (Allen & Unwin, Sydney, 1987), pp 58-62.
15. Covault, Craig, "USAF Missile Warning Satellites Provide 90-Sec. Scud Attack Alert," Aviation Week & Space Technology, 21 January 1991, page 60-61.
16. Carey, Peter, "The Eyes in the Sky Keeping Watch on Iraq," Business Week, 4 February 1991, page 41.
17. Tyler, Patrick, "Embassy Deputy in Iraq, Unschooled as Diplomat, Plays the Top US Role," The New York Times, 18 December 1990.
18. Lamb, David, "Iraq Launches 3rd Missile - but Not at Allied Forces," Los Angeles Times, 29 December 1990, page 15.
19. "Scud Warning," Aviation Week & Space Technology, 28 January 1991, page 19.
20. "Space Success in Gulf War Seen Making Case for ASAT," Aerospace Daily, 15 March 1991, page 441-442.
21. "Israel Will Need IFF Codes for Retaliatory Strike," Defense Daily, 4 February 1991, page 174.
22. Tyler, Patrick, "US Tells of Retaliation Plan the Israelis Abandoned," The New York Times, 7 March 1991, page A1, A10.
23. Gertz, Bill, "US Detects Iraqi Missiles at Last Minute," The Washington Times, 10 December 1990, page A8.
24. Covault, Craig, "USAF Missile Warning Satellites Provide 90-Sec. Scud Attack Alert," Aviation Week & Space Technology, 21 January 1991, page 60-61.
25. Gellman, Barton, "Gulf Crisis Nearing Moment of Truth, Cheney Tells Troops," The Washington Post, 22 December 1990, page A12.
26. Scmitt, Eric, "Talks Unlikely, War Closer, Cheney Tells Troops in Gulf," The New York Times, 22 December 1990.
27. Diehl, Jackson, "Jordan's Troop Shifts Raise Questions in Israel," The Washington Post, 2 January 1991, page A17, A21.
28. "Iraqi Missile Movements Shrouded by Darkness," Flight International, 30 January 1991, page 7.
29. "Scud Warning," Aviation Week & Space Technology, 28 January 1991, page 19.
30. Covault, Craig, "USAF Missile Warning Satellites Provide 90-Sec. Scud Attack Alert," Aviation Week & Space Technology, 21 January 1991, page 60-61.
31. Diehl, Jackson, "Scud Missile Attack on Israel Kills 1, Injures Dozens," The Washington Post, 26 January 1991, page A13, A16.
32. Claiborne, William, "Patriots Launched to Meet New Scud Attack Over Israel," The Washington Post, 27 January 1991, page A22.
33. "Israelis Push USA for More Patriots," Flight International, 13 March 1991, page 13.
34. "Missile Fired at Israel," The New York Times, 1 February 1991, page A11.
35. Gertz, Bill, "US Detects iraqi Missiles at Last Minute," Washington Times, 10 December 1990, page 8.
36. Diehl, Jackson, "Israel Shuns First Strike Against Iraq," The Washington Post, 27 December 1990, page A1, A20.
37. "Satellite-based Alerting Network Aided in Destruction of Scud," Aerospace Daily, 21 January 1991, page 106-107.
38. Toth, Robert, "Iraqi Missile Test Had US Thinking War Had Started," The Los Angeles Times, 21 December 1990, page A1, A11.
39. Mathews, Tom, et al,"The Secret History of the War," Newsweek, 18 March 1991, page 28-39
40. "32nd Scud Fired At Israel," The New York Times, 12 February 1991, page A13.
41. Gertz, Bill, "US Eyes Failed to Detect Missile," The Washington Times, 27 February 1991, page B3.
42. Royce, Knut, "Why Killer Scud Wasn't Intercepted," Newsday, 28 February 1991, page 16.
43. Lorch, Donatella, "Twisted Hulk of Warehouse Tells a Grim Story of Death," The New York Times, 27 February 1991, page A18.
44. Baker, Caleb, "Scud Upgrades Flaws, Patriot Limitations Allow Barracks Strike," Defense News, 11 March 1991, page 3, 23.
45. Nussbaum, Paul, "Patriot Battery Unusable, General Says," Philadelphia Inquirer, 28 February 1991, page 6.
46. Diehl, Jackson, "Israel Shuns First Strike Against Iraq," The Washington Post, 27 December 1990, page A1, A20.
47. "Scud Launch Procedures May Hold Key to Defeat of Mobile Missiles," Aerospace Daily, 28 January 1991, page 149-150.
48. Richter, Paul, "Foe Skilled at Trickery, Decoys Show," Los Angeles Times, 24 January 1991, page A1, A18.
49. Cody, Edward, "Command of the Skies Eases High-Tech Hunt for Scud Launchers," The Washington Post, 4 February 1991, page A13.
50. Gugliotta, Guy, "Gas on the Go for Hungry Warthogs," The Washington Post, 25 December 1990, page A44.
51. Kennedy, Michael, "Air Patrols Making Scud Launches a Risky Business," The Philadelphia Inquirer, 4 February 1991, page 6-A.
52. "Communications Speed-Up Seen Aiding Anti-Scud Campaign," Aerospace Daily, 11 February 1991, page 240.
53. Kennedy, Michael, "New Strategy May Bring End to Scud Threat," Los Angeles Times, 4 February 1991, page A1, A14.
54. "JTIDS Airborne Terminals Demonstrate Operating Problems," Defense Electronics, January 1985, page 23.
55. Thomas, Paul, "Space Traffic Surveillance," Space/Aeronautics, November 1967, page 75-86.
56. DeVere, G.T., "The NORAD Space Network," Spaceflight, July/August 1985, page 306-309.
57. Jackson, P., "Space Surveillance Satellite Catalog Maintenance," AIAA/NASA/DOD Orbital Debris Conference, Baltimore, MD, 16-19 April 1990, AIAA Paper 90-1339.
58. Royce, Knut, "Why Killer Scud Wasn't Intercepted," Newsday, 28 February 1991, page 16.
59. "The JDW Interview," Jane's Defense Weekly, 2 February 1991, page 160.
60. "Lessons Learned Above the Gulf," Space News, 4 March 1991,