A - Overview
Navigation satellites were one of the more pervasive and less visible space systems. The number of GPS receivers that they had available that could translate the encoded military signal was not nearly as many as needed. The military bought several thousand commercial receivers, and distributed them army and other ground units. To enhance the role of these systems, the Air Force stopped degrading the GPS signal, so that these commercial receivers could provide 16 meter accuracy. This has been particularly important, given the fact that many units are out in the desert where there are no landmarks, and nobody to stop and ask directions of, and as a result many units have had problems getting lost. So resupply convoys that are driving into the desert have at least on vehicle with one of these GPS receivers to keep them from getting lost. And the entire ground offensive was predicated on using GPS.
B - Space Segment
The long-running Transit navigation satellite program continued in operation in 1990, with a total of 12 operational and operable spare Transit satellites in orbit. Most of these spacecraft were launched over the past few years, but the total includes as Oscar 11 (TRANSAT), launched in 1977. Oscar 13, launched in 1967, failed in January 1989, after over 21 years of service in orbit(1).
The final three launches of these satellites occurred in 1988. Transit 23 and Transit 24 were launched on a Scout in April, and Transit 25 and Transit 26 were orbited in August. These two launches were the third and fourth flights of the Stacked Oscar On Scout (SOOS) launch program. And the more capable NOVA 2 was launched by a Scout on 16 June (somewhat confusingly, this launch was the third NOVA launch, NOVA three having been launched out of numerical sequence in October 1984. The Navy dropped plans for additional Transit launches that were originally scheduled for 1990, saving the Scout boosters for other missions.
The unexpectedly long life of many of these satellites has produced an embarrassment of riches, compounded by the impending introduction of the more capable Navstar Global Positioning System (GPS) into operational service in the early 1990's. Most military users of Transit, such as the Navy's ballistic missile submarines that were the original impetus for Transit, will soon shift to Navstar. However, the current Transit constellation will potentially remain in service to civilian users through the end of the century.
|Transit 19||Oscar 24||SOOS 1||8/03/85|
|Transit 20||Oscar 30||SOOS 1||8/03/85|
|Transit 21||Oscar 27||SOOS 2||9/16/87|
|Transit 22||Oscar 29||SOOS 2||9/16/87|
|Transit 23||SOOS 3||4/26/88|
|Transit 24||SOOS 3||4/26/88|
|Transit 25||Oscar 23||SOOS 4||8/25/88|
|Transit 26||Oscar 32||SOOS 4||8/25/88|
|Transit NOVA 1||5/15/81|
|Transit NOVA 2||6/16/88|
|Transit NOVA 3||10/12/84|
|Transit TIP-4||Oscar 11||TRANSAT||10/28/77|
Six Navstar navigation satellites, launched between 1980 and 1985, were in service at the outset of 1990. These satellites were used for the development and testing of Navstar receivers and user equipment. The total number of GPS satellites was originally planned to be 21 active plus 3 spares. This number was reduced to 18 active and 3 spares as a cost saving measure in the early 1980's,(2) but the number of active satellites was returned to 21 in 1987,(3) with this number planned for implementation by 1993.(4)
In the aftermath of the Challenger accident, the Air Force decided to remove the Navstars from the Shuttle manifest, and to launch them on an improved version of the proven Delta launch vehicle, known as the Delta II. A total of 20 of these rockets were ordered. With the launch of five new Navstar satellites in 1989, the Air Force began to implement the full complement of 21 active and 3 spare satellites will be required for the system can provide nearly continuous global coverage.(5) Although the first two satellites launched had been nicknamed Elvis (Presley) and Janis (Joplin), this practice ceased with the third and subsequent launches.(6)
|Navstar 1A- 5||2/09/80|
|Navstar 1A- 6||4/26/80|
|Navstar 1R- 9||6/13/84|
|Navstar 1A- 8||7/14/83|
|Navstar 2A-12||NDS 13||USA-35||2/14/89|
|Navstar 2A-13||NDS 14||USA-38||6/09/89|
|Navstar 2A-14||NDS 16||USA-42||8/18/89|
|Navstar 2A-15||NDS 17||USA-||10/21/89|
|Navstar 2A-16||NDS 18||USA-||12/11/89|
|Navstar 2A-17||NDS 19||USA-50||1/24/90|
|Navstar 2A-18||NDS 20||USA-53||3/26/90|
|Navstar 2A-19||NDS 15||USA-63||8/02/90|
|Navstar 2A-20||NDS 21||USA-64||10/01/90|
|Navstar 2A-21||NDS 26||USA-66||11/26/90|
The 16 GPS satellites in orbit provide between 19 and 20 hours of two-dimensional (latitude and longitude) coverage with three satellites in view, and 15 hours of three dimensional (including altitude) coverage with four satellites in view,(7) or by another estimate as much as 21 hours of three-dimensional coverage.(8)
The Navstar launched on 2 August, coincidentally with the Iraqi Invasion, was activated in a record 22 days, in contrast to the normal 30 day activation period.(9) And the other launches since August were placed into orbital locations intended to maximize coverage of the Mideast.(10) One ten-year old satellite, Navstar 6, was rendered inoperative by the failure of a reaction wheel on 11 December 1990, but was successfully reactivated on 16 January 1991.(11) This spacecraft remained in service through 6 March 1991, when it was permanently removed from service, reducing three dimensional coverage in the Middle East by about 45 minutes.(12)
The Coarse/Acquisition (C/A) code broadcast at 1575.42 MHz normally provides approximately 30 meter accuracy, while the precision Code (P-code) at the 1227.6 Y-Frequency provides 10 to 16 meter accuracy. Encryption of the C/A code under Selective Availability, which reduces C/A accuracy to 100 meters, began in mid-March 1990, and ceased on 10 August.(13) The P-code can also be encrypted, in a format referred to as Y-Code, which requires a KyK-13 decoder to decrypt.(14)
C - Control Segment
The Global Positioning System is controlled by the Air Force 2nd Space Wing at the Consolidated Space Operations Center (CSOC) at Falcon Air Force Station, CO.(15)
D - User Segment
The Army had a total of more than 5,000 GPS receivers in the theater at the outset of Operation Desert Storm.(16) These were distributed among the 36,000 vehicles and 600 aircraft of VII Corps, and the 23,000 vehicles and 1,000 aircraft of XVIII Corps.(17)
The GPS Joint Receiver Program, managed by Air Force Space Systems Division, was scheduled to enter full scale production in the Summer of 1990. Testing was generally successful on the larger five channel receivers on aircraft and attack helicopters. But operational testing of the smaller one-channel and two-channel receivers used by ground forces and transport helicopters demonstrated reliability problems. Rockwell Collins and Texas Instruments have delivered 3,100 units, including 1,200 single-channel manpacks.(18) Other sources suggest that total deliveries have amounted to 4,100 units.(19)
According the General Ronald Yates, commander of Air Force Systems Command,
immediately after the 2 August invasion, the GPS Program Office "made available approximately 900 hand-held demonstration units being tested DOD-wide... The Army and Marine Corps put such a top priority on GPS receivers that they recalled and redistributed all theirs within days. At the Army's request, the Joint Program Office has gone out for an emergency buy of 1,000 additional sets, 50 of which are scheduled to be delivered by the end of the month (September). The Air Force loaned all of its available receivers to the Army after the Iraqi invasion. Hundreds of receivers have already been deployed to the forces."(20) Assistant Commandant of the Marine Corps Lt. Gen. John Dailey noted that the Marines are using GPS receivers, "even though we are still learning how to use it."(21) Army forces using GPS included both the 82nd and 101st Airborne Divisions.(22)
Aircraft equipped with GPS receivers include the KC-135 tanker, B-52Gs flying conventional attack missions, as well as some F-16s.(23) However, a number of aircraft were not equipped with GPS, including the F/A-18, AV-8B, F-16B, FB-111, F-15E, and Ah-64A.(24)
Prior to the August invasion, the Army was using several hundred Trimpack Small Light-weight GPS Receivers (SLGR - Sluggers) in field demonstrations as part of a $4 million 1,012 unit contract. An addition buy of 1,000 of the $3,500 receivers was slated for completion by the end of 1990.(25) This $5.5 million dollar contract also included the cost of mounting and other hardware. A further 2,300 SLGRs were ordered in December, which brought the total buy to $17.5 million. These SLGRs were to include external antennas to be installed on M1A1 tanks to permit the receivers to function when the tank is sealed against chemical attack. An additional order for 4,100 units was placed on 30 January 1991, for $22.8 million. By early February, deliveries had totalled 3,000 receivers, with an additional 6,300 on order. Many of the SLGRs were mounted on light armored vehicles, HMMWV, supply trucks and helicopters.(26)
The US Army First Infantry Division was equipped with 500 hundred of the Magellan model 1000-M receivers by early December 1990, ordered under a $2 million contract.(27) In addition, 1,000 of these units were ordered after 30 November 1990 at a cost of $3.7 million, with 600 delivered by early February 1991, and the rest due by mid-March.(28) Other sources suggested that as many as 2,500 of these receivers had been delivered by early February.(29) Although some Trimble SLGRs were not slated for delivery until May, Magellan reportedly had excess receivers in stock at the outset of the ground war in late February.(30)
The three British Tornado GR.1 squadrons deployed to the Gulf were equipped with British C/A-code GPS receivers.(31) A small number of the Trimble SLGR receivers, equipped with HAVE QUICK anti-jamming devices, were also ordered by British forces.(32)
Without the encoding under Selective Availability, commercial receivers have a two-dimensional accuracy of about 25 meters, in contrast to the 100 meter accuracy when degraded by encryption. In addition to providing latitude and longitude coordinates, the commercial SLGRs provide Military Grid Reference System coordinates, facilitating coordination between Army and Air Force units.(33) According to Colonel Ronan Ellis, head of Army Space Command, "the conversion between these two grid reference systems is so difficult we have a hard time talking to each other. This little device is an almost immediate coordination device for locations between pilots and people on the ground simply because it talks in both coordinate systems."(34)
E - Operational Applications
The Saudi terrain has enhanced the utility of navigation aids such as GPS. The Army is using Navstar in conjunction with night-vision goggles, with "at least 50 percent of all training and most of its major movements under cover of darkness." Challenging local conditions have included shifting sands that can obliterate a road in a few days, difficulty in judging the distance to the local horizon, and the general absence of distinctive landmarks to assist in orienting crews. "Tank crews, infantrymen and pilots have spent hours lost in the desert."(35) According the General Ronald Yates, commander of Air Force Systems Command, "since Saudi Arabia is short on landmarks, these (GPS) receivers are especially valuable to ground units because they provide time, position and velocity."(36)
Army applications include "the ability to: (1) Find remote desert locations. (2) Synchronize rendezvous at precise time and locations. (3) Fire, if necessary, on targets with greater precision."(37) "Artillery commanders can draw on it to aim their guns. GPS can also be used to mark a path through a minefield. Instead of marking a field with flags that the enemy could also see, troops would give friendly units the GPS coordinates of the safe corridor."(38)
According to Colonel Ronan Ellis, head of Army Space Command, "there aren't enough (receivers) to satisfy all the requirements... whenever, convoys move to and from airfields; whenever units train out in the field; that whenever they resupply themselves, that these devices are being used. I would say that some units go down to battery, company, platoon."(39) Maj. Gen. Louis Del Rosso, Director of Army Space and Special Weapons, "Because of the nature of the terrain and the difficulty of navigation, hand-held (GPS receivers) have become very popular. Commanders have asked for all they can get their hands on... (Navigating the desert) is very, very difficult because it all looks the same... The results that are coming out of Operation Desert Shield will be more convincing than anything we've done so far. The commanders really love it. For example, take the development of equipment, such as howitzers for artillery. If you know (the location of) the howitzer or the launcher for a Multiple Launch Rocket System (MLRS), and you know where the target is, then you can compute the range and all the rest of the technical data and be fairly confident that you will have a first round hit. Right now, knowing where the howitzer or the launcher is, requires a (lengthy) survey. If you (install) on-board navigation equipment that can get its location from the GPS system... within less than a minute, sometimes 30 seconds, you can have the first round fire and then you can do it again."(40)
With the 1st Battalion, 320th Field Artillery, "Cyalume light sticks are used to mark the route for travel at night. They're dropped every 200 yards or so, making a trail across the desert... For most movements, the light sticks were not used. Instead, unit simply followed a compass azimuth, checking there location periodically with a global positioning system (GPS) receiver... GPS receivers were apportioned one per firing battery in the battalion, and were usually found on the passenger side of the lead vehicle. The combination of GPS and nigh vision goggles was impressive."(41)
The 24th Mechanized Infantry Division, in which every soldier is equipped with night-vision goggles, conducts two-thirds of its operations at night. The Division forces use GPS receivers "that seem to be installed on every other Hummer, the wide body successor to the World War II Jeep."(42)
One Army source noted that "'It's extremely hard to navigate in the desert. There are no trees and no road networks to tell you where you are.' This official said one important use of Navstar was in aiding US artillery. To aim artillery accurately, not only must the target be pinpointed, the location of the artillery must be known, he said. Navstar receivers with US artillery enable the artillery to aim accurately and quickly at an enemy target, destroying the enemy with the first blow. 'It's important to get first-round hits, if you don't want them firing back,' the Army official said. Navstar also played an important role in helping the Army's gas-guzzling M1A1 tanks rendezvous with their refueling trucks. Navstar receivers in the tanks and trucks -- which can suggest the proper direction to take to reach a given destination -- made the task simpler..."(43)
In the weeks before the ground war, GPS receivers were used to chart "the main supply route into Iraq for the western sector of the XVIII Airborne Corps."(44)
Air Force Applications
Aircraft equipped with Navstar include some F-16s, KC-135s and B-52s.(45) "B-52 bombers use it to time the release of their bombs from high altitude."(46) Navstar greatly reduces the risk of bomb targeting errors resulting from incompatible map coordinates. Missions planned using maps based on different ellipsoids or datums can introduce navigation error of hundreds of meters, which would produce similar inaccuracies in bomb delivery using non-visual techniques such as Continuously Computed Release Point (CCRP) or Visual Impact Point (VIP). Visual delivery modes such as Continuously Computed Impact Point or Dive Toss (DTOS) can avoid these errors, as can use of GPS on attack aircraft, although Block 40 F-16s are the only US attack aircraft currently so equipped.(47)
GPS receivers were also used for airspace management, reducing reliance on Identification-Friend-or-Foe (IFF) systems to avoid fratricide. The multiplicity of incompatible IFF systems in the Gulf complicated the task of aircraft identification, while GPS could keep aircraft on precisely plotted flight plans.(48) During January 1991, GPS receivers were installed on French Puma helicopters to enhance their search-and-rescue capabilities.(49)
Navy ships in the theater used GPS for minesweeping, rendezvous, and aircraft operations.(50) Navstar is central to the effectiveness of using Remotely Piloted Vehicles for fire spotting for battleship guns, since the system enables "both the ship and the RPV to know their exact positions on the Earth's surface. In simple trigonometry exercise, the altitude, heading and viewing angle of the RPV camera are combined by shipboard computers to produce the exact grid location of anything the camera sees. That location is then correlated with the ship's position."(51) Marine Corps personnel concluded that the smaller Pointer UAV "system needs to be equipped with a satellite based navigation system to cope with the featureless terrain."(52)
The first combat use of the Navy's Stand-off Land Attack Missile (SLAM), an air-launched version of the Harpoon cruise missile with a range in excess of 80 kilometers, succeeded in destroying an Iraqi hydroelectric facility in late January. The SLAM uses a GPS receiver to provide mid-course navigation updates.(53) This enables the missiles infrared seeker, derived from the Maverick, to be precisely oriented toward the target, when it is activated about one minute before impact, giving the missile a 16 meter CEP.(54)
F - Operational Limitations
Users of GPS normally face a number of operational limitations and constraints which were not relevant in the Gulf region.(55) Although concerns were expressed about the use of GPS in a conflict with the Soviet, given the vulnerability of the system to jamming, this was not a significant problem with the Iraqis. The accuracy of GPS can be significantly degraded by the motion of the receiving antenna caused by rough seas, but this was much less of a problem in the relatively calm waters of the Persian Gulf or Red Sea, compared with the stormy North Atlantic Ocean. And leafy trees in forests can cause cross reflections of the GPS signal than can cause errors of up to 700 meters, but the flat open terrain of the Saudi desert is an almost perfect operating environment, free of such sources of interference.
One account noted that "an M-1 tank is sealed in battle to protect the soldiers inside from artillery, and biological and chemical weapons, and just as an automobile radio stops working inside a deep tunnel, the handheld Navstar receivers would not work inside the tanks. Thus the Army quickly had to retrofit the tanks with special antennas mounted atop the vehicles and linked to the Navstar receivers by a cable. 'That way, you won't have to open up the tank' to determine your position, says one army official."(56) According to another report, "... some military commanders say the satellite is sometimes difficult to pick up because of its position in the sky, particularly in the middle of the day."(57) And despite the combination of nigh-vision goggles and GPS, "the main convoy was unable to link up with the "A" battery commander, who had been scouting ahead for the next position. The latest in electronic and optical equipment is useful, but things still go wrong."(58)
Despite concerns that the loss of Navstar 6 could reduce the effectiveness of the system's operational support, the Air Force insisted that as of late January "we are providing the almost 24 hours per day of two dimensional coverage to the Middle East. The loss of Navstar 6 had virtually no effect on this coverage time."(59)
G - Alternative Systems
Other terrestrial navigation systems include the LORAN-C radio network, but it has a maximum range of about 1,500 kilometers, and a maximum accuracy of about 3/4 a kilometer.(60)
H - Iraqi Capabilities
One account noted that "the Iraqis are believed to have a few GPS units (GPS is widely used in the oil exploration industry), but have not integrated their use into their military the way the allies have."(61) This was illustrated on 6 August, when "by design or accident, two Iraqi tank columns had entered Saudi Arabia. Cheney gave King Fahd the photographs; they were the CIA's most convincing evidence that his nation was threatened. Middle Eastern officials have since persuasively argued that Hussein's soldiers entered Saudi Arabia by accident, but King Fahd didn't want to take any chances."(62)
Some observers suggested that Iraqi access to GPS, enhanced by the temporary termination of Selective Availability, enabled Iraq to make better use of its mobile Scud launchers. "Iraq is known to have purchased briefcase-size Global Positioning System receivers, giving them access to Navstar satellites... Using this constellation of electronic stars, the Iraqis can instantly compute the position of their deployed launchers (required before target data can be fed into the missiles), knocking valuable time off the old method that depends on traditional surveying techniques."(63) However, it is not clear how extensively this capability was used, since mobile missile launchers appeared to prefer to use pre-surveyed sites.(64)
I - Net Assessment
Navstar was probably one of the more successful military space applications in the Gulf War. Because of the unique operational environment, if ground forces had not had access to Navstar, the pace of operations would have been considerably slowed. One might venture that the American strategic maneuver to the west flank of the Iraqi forces would have been severely compromised in the absence of Navstar. Certainly the coordinated movement of thousands of vehicles across hundreds of kilometers of featureless terrain would have been much more difficult without Navstar.
According to Lt. Gen. John Woodmansee, former commander of the American Army V Corps in Germany, instances of casualties due to friendly fire could have been averted if GPS receivers had been more widely available, permitting dissemination of more precise information on the location of ground forces.(65)
1. Danchik, Robert, et al, "Navy Navigation System Status," Royal Institute of Navigation NAV-89 conference, London, 17-19 October 1989.
2. Clarke, Christopher, "...and a Star to Steer By," Defense Electronics, June 1989, page 57-64.
3. Klass, Philip, "Defense Dept. Will Seek Funds to Expand Navstar Constellation," Aviation Week & Space Technology, 5 October 1987, page 30-31.
4. "Magnavox Prepares for GPS Buildup," Military Space, 25 September 1989, page 3-5.
5. Kolcum, Edward, "First USAF/McDonnell Douglas Delta 2 Launch Begins New Military Space Era," Aviation Week & Space Technology, 20 February 1989, page 18-19.
6. "News and Comment," Air Force Magazine, October 1989, page 29.
7. "Sluggers Pinch Hit for Army GPS," Military Space, 24 September 1990, page 1, 8.
8. "Newsmaker Forum: Brig. Gen. Garry Schnelzer," Space News, 17 December 1990, page 22.
9. "Navstar Turned on in Record Time," Space News3 September 1990, page 2.
10. "Newsmaker Forum: Brig. Gen. Garry Schnelzer," Space News, 17 December 1990, page 22.
11. Kiernan, Vincent, "War Tests Satellites Prowess," Space News, 21 January 1991, page 1, 36.
12. Kiernan, Vincent, "Controllers Deactivate Ailing Navstar Satellite," Space News, 11 March 1991, page 4, 21.
13. Kiernan, Vincent, "Air Force Alters GPS Signals to Aid Troops," Space News, 24 September 1990, page 1, 35.
14. Klass, Philip, "Inmarsat Decision Pushes GPS to Forefront of Civ Nav-Sat Field," Aviation Week & Space Technology, 14 January 1991, page 34-35.
15. Kiernan, Vincent, "Loss of GPS Craft Deals Setback to Troops in Gulf," Space News, 7 January 1991, page 3, 20.
16. Kiernan, Vincent, "Loss of GPS Craft Deals Setback to Troops in Gulf," Space News, 7 January 1991, page 3, 20.
17. Atkinson, Rick, "Outflanking Iraq: Go West, Go Deep," The Washington Post, 18 March 1991, page A1, A14.
18. "Sluggers Pinch Hit for Army GPS," Military Space, 24 September 1990, page 1, 8.
19. McMillan, Sue, "Pentagon Stops Scrambling Codes From Satellites," Colorado Springs Gazette-Telegraph, 21 September 1990, page 3.
20. "Desert Shield Prompts Acceleration of AMRAAM, SFW Testing," Aerospace Daily, 19 September 1990, page 457.
21. Baker, Caleb, "Desert to Double as Test Range," Defense News, 3 September 1990, page 1.
22. "DoD Quickly Buys Commercial GPS Terminals for Desert Shield," Aerospace Daily, 27 August 1990, page 331.
23. "DoD Quickly Buys Commercial GPS Terminals for Desert Shield," Aerospace Daily, 27 August 1990, page 331.
24. "Collins Wins Miniature GPS Receiver Job," Military Aerospace & Electronics, February 1991, page 14.
25. "Sluggers Pinch Hit for Army GPS," Military Space, 24 September 1990, page 1, 8.
26. Henderson, Breck, "Ground Forces Rely on GPS To Navigate Desert Terrain," Aviation Week & Space Technology, 11 February 1991, page 77.
27. "Land Mobile," Mobile Satellite Reports, 14 December 1990, page 6.
28. "Collins Wins Miniature GPS Receiver Job," Military Aerospace & Electronics, February 1991, page 14.
29. Henderson, Breck, "Ground Forces Rely on GPS To Navigate Desert Terrain," Aviation Week & Space Technology, 11 February 1991, page 77.
30. Anderson, Jack, "Navigating the Desert in Armor," The Washington Post, 7 March 1991, page 13.
31. Barrie, Douglas, "Tornados in Gulf to Use Global Positioning System Receivers," Flight International, 16 January 1991, page 10.
32. Hyde, James, "Services Accelerate Programs to Benefit Troops in Middle East," Armed Forces Journal International, October 1990, page 18-19.
33. "Army Space Command Demo Efforts Go Operational in Desert Shield," Aerospace Daily, 20 November 1990, page 305-306.
34. "Army Space Command Demo Efforts Go Operational in Desert Shield," Aerospace Daily, 20 November 1990, page 305-306.
35. Moore, Molly, "US Training, Tactics Shift With Desert Sand," The Washington Post, 25 November 1990, page 1, A25.
36. "Desert Shield Prompts Acceleration of AMRAAM, SFW Testing," Aerospace Daily, 19 September 1990, page 457.
37. "Collins Wins Miniature GPS Receiver Job," Military Aerospace & Electronics, February 1991, page 14.
38. Burgess, John, "Satellites' Gaze Provides New Look at War," The Washington Post, 19 February 1991, page A13.
39. "Army Space Command Demo Efforts Go Operational in Desert Shield," Aerospace Daily, 20 November 1990, page 305-306.
40. Kiernan, Vincent, "Newsmaker Forum: Maj. Gen. Louis Del Rosso," Space News, 7 January 1991, page 22.
41. Evans, David, "Desert Shield: From the Gulf," US Naval Institute Proceedings, January 1990, page 77-80.
42. Sloyan, Patrick, "US Girds for Night Battles," Long Island Newsday, 15 October 1990, page 4.
43. Kiernan, Vincent, "Satellites Play Key Role in Swift Gulf Victory," Space News, 4 March 1991, page 1, 20.
44. Tharp, Mike, et al ,"Countless Unsung Heroes," US News & World Report, 18 March 1991, page 39-49.
45. "Space Supports Mideast Buildup," Military Space, 27 August 1990, page 1-2.
46. Burgess, John, "Satellites' Gaze Provides New Look at War," The Washington Post, 19 February 1991, page A13.
47. Bina, David, "Measure With an Ax and Fly With a Micrometer," Air Land Bulletin, 31 December 1990, page 13-14.
48. Barrie, Douglas, "Tornados in Gulf to Use Global Positioning System Receivers," Flight International, 16 January 1991, page 10.
49. "French Search, Rescue Units Aided by GPS Receivers," Aviation Week & Space Technology, 25 February 1991, page 44.
50. "DoD Quickly Buys Commercial GPS Terminals for Desert Shield," Aerospace Daily, 27 August 1990, page 331.
51. Frantz, Douglas, "Big Guns Find Targets Thanks to Little Drones," Los Angeles Times, 11 February 1991, page A1, A7.
52. Baker, Caleb, "Gulf War Takes Toll on Pioneer UAVs," Defence News, 18 March 1991, page 20, 30.
53. "With Testing Incomplete, SLAM Scores Military Success," Defense Daily, 23 January 1991, page 105.
54. "SLAM Makes Combat Debut," Jane's Defense Weekly, 2 February 1991, page 137.
55. "Collins Wins Miniature GPS Receiver Job," Military Aerospace & Electronics, February 1991, page 14.
56. Kiernan, Vincent, "Guidance From Above in the Gulf War," Science, 1 March 1991, page 1012-1014.
57. Moore, Molly, "US Training, Tactics Shift With Desert Sand," The Washington Post, 25 November 1990, page 1, A25.
58. Evans, David, "Desert Shield: From the Gulf," US Naval Institute Proceedings, January 1990, page 77-80.
59. Dickman, Robert, "What Setback," Space News, 4 February 1991, page 14.
60. Pollack, Andrew, "War Spurs Navigation by Satellite," The New York Times, 6 February 1991, page D1, D7.
61. Burgess, John, "Satellites' Gaze Provides New Look at War," The Washington Post, 19 February 1991, page A13.
62. Perry, Mark, "The Secret Plot to Out Saddam Hussein," Regardie's, November 1990, page 43-56.
63. Boldrick, Michael, "The Message of the Scuds," The Wall Street Journal, 7 February 1991.
64. Kennedy, Michael, "Air Patrols Making Scud Launches a Risky Business," The Philadelphia Inquirer, 4 February 1991, page 6-A.
65. "Space Eye in the Back of Your Head," Space News, 18
February 1991, page 2.