Found in Space

The U.S. Army's 1st Infantry Division— known as the Big Red One— attacked Saddam Hussein's vaunted Republican Guard and a brigade of regular Iraqi troops Feb. 26, 1991, at 10 p.m., with no moon to shed light on the landscape of the Iraqi desert.

The Iraqi forces, some 8,000 men, were part of Saddam's strategic reserve, ordered to hold back the Allies so that the remaining Guard elements could withdraw from Kuwait. When they were 3,850 meters away, the U.S. Army's M-1 tanks registered the heat signatures of the Iraqi tanks on the M-1s' thermal-imaging sights. The U.S. gunners began to fire, filling the sky with balls of flame from exploding vehicles.

This was the division's second major battle in as many days, recalled Lt. Gen. Thomas Rhame, then the 1st Infantry's commander. This time the Iraqis were dug into defensive positions.

As one Iraqi lieutenant told Rhame, "No one goes into that desert and gets off the road because you get lost."

But the 1st Infantry had the technology needed to navigate across the desert. To get into position for the battle, the 1st Infantry, a group of 17,000 soldiers from Fort Riley, Kan., approached the Iraqis from the west, with more than 350 armored tanks, 150 Bradley Fighting Vehicles, 40 attack and utility helicopters, two 18-gun artillery battalions and nine Multiple Launch Rocket System launchers. They had to drive 50 miles north though rain and sandstorms that reduced visibility to nearly zero before they could wheel eastward with the 1st Infantry's sister divisions.

The 1st Infantry successfully made the trip because the group had mounted Magellan Systems Corp. Global Positioning System receivers inside some of its tanks and fighting vehicles and had rigged antennas outside. Each company of 14 tanks had one or two receivers, Rhame said. The remaining vehicles followed the leaders. "GPS saved our butt," Rhame said. "We couldn't see where we were going, but GPS took us right through it."

GPS receivers have displays that show the direction, in degrees of azimuth, left or right, that users follow to get to the coordinates that are keyed in. Altogether, the division had about 600 GPS receivers in operation during the ground war.

After six hours of battle, the 1st Infantry and its sister forces had destroyed the Iraqi troops and were headed east to cut off a major highway to Basra in Iraq. By daylight on Feb. 28, the 1st Infantry had traveled another 50 to 60 miles east and was sitting on the highway with 4,500 prisoners.

Moving large forces, such as the 1st Infantry, that far, that fast and with such precision is a major achievement that couldn't have been done without GPS, Rhame explained.

"I doubt very seriously we could have concluded that war in four days without GPS," Rhame said. GPS is "one of the major technology advances...in modern war."

Pinpoint Accuracy

For a technology that was so critical to U.S. military superiority, GPS is based on a relatively simple concept. A GPS receiver calculates its position by measuring its distance from three or more satellites and processing the data, a technique called triangulation. The U.S. military has 27 GPS satellites in orbit that provide worldwide coverage.

There are two GPS frequencies: one for military use and one for civilian and military use. The military signal is accurate in a 23- to 33-foot range, while the civilian signal, if not corrected, is accurate in a 231- to 330-foot range. DOD intentionally skews the civilian signal, a process called selective availability. Civilian accuracy can be improved to within 3 feet by using two receivers, one of whose coordinates is already known, in a technique known as differential GPS. More advanced techniques can improve GPS accuracy to less than half an inch.

Although it is lauded today, the military's GPS program had to fight for its survival. Air Force fighter pilots didn't want the technology because it cost too much, and they wanted more airplanes, recalled Xavier Kane, president of the GPS International Association and manager of a predecessor Air Force program in the late 1960s. And the Navy "was violently opposed to any satellite program for navigation except the one they had."

A potentially devastating blow was dealt in August 1973, when the infant program was turned down by the Defense System Acqui-sition Review Council because GPS did not sufficiently address the various military branches' needs, said Bradford Parkinson, the first director of the GPS Joint Program Office and now a Stanford University professor of aeronautics and astronautics.

The weekend following that "Black Thursday," the JPO staff put in "dawn-to-late-night" sessions in the Pentagon to restructure the program, Parkinson said. GPS was approved by the DSARC in December 1973.

As recently as 1982, the Air Force tried to cancel the program on the grounds that there were "too many black boxes on the airplane," Kane said. But that effort was headed off. Ironically, Air Force "indifference" proved a blessing to the program, Parkinson said. "It made life simpler.... We could just go off and build a system."

What justified GPS as an invaluable technology, however, was the Persian Gulf War. GPS was used to direct air strikes and guide attack helicopters as well as navigate tanks through the desert. In all, more than 9,000 commercial GPS receivers from vendors such as Magellan and Trimble Navigation Ltd. were used in the Gulf War.

GPS proved "an immeasurable tool" in a world without landmarks, recalled Sgt. Maj. Sam Nicholas, who served with the Central Command's 3rd Army Reserve Component Liaison Office— a job requiring "a good deal of movement."

At times, however, the cloud from the burning oil fields was so thick that it was impossible to get a fix on more than one or two satellites, he said.

Saving Scott O'Grady

Since the Gulf War, GPS has been used in every military conflict, most recently in the peacekeeping mission in Bosnia.

One well-reported incident was GPS' role in the rescue of Air Force Capt. Scott O'Grady, whose F-16 was shot down over Bosnia in June 1995. He evaded capture for six days and nights in enemy territory until he was rescued by a Marine Corps team.

O'Grady attributes his survival to his deep religious faith and to the dedication of the United States and Allied military forces trying to retrieve him. But technology played a role too in the form of a GPS receiver buttoned into the inside right pocket of his flight suit. It was one of the off-the-shelf models purchased by his squadron and issued to each pilot flying over Bosnia. He had received no formal training in the receiver's use; it was up to the pilot to read the instructions.

"To get rescued, I needed voice contact with friendly forces and my exact location to within a mile," he said. Using a map, he could only guess his position within five miles. GPS was valuable both for locating where he was and, having crashed in a heavily populated area, for navigating to places where he was less likely to be discovered by the enemy. "Every hiding spot I was in, before I got on the radio, I would take out the GPS and get a longitude and latitude readout," he said. "When the rescue forces finally heard me on the radio, I was able to tell them my exact location."

O'Grady taught himself how to operate the receiver at night by trial and error. He didn't want to turn on his flashlight to read the instruction card. He had to cup his hands over the luminescent readout so as not to be detected.

GPS still comes in handy for ground troops in Bosnia, a country whose hilly terrain and overcast winters make navigation difficult. Members of the U.S. 810th Military Police Company with the U.S. 2nd Armored Cavalry Regiment in Bosnia, for example, use GPS frequently as a location and navigation tool, said Staff Sgt. Maurice Jenkins.

GPS promises to revolutionize the U.S. arsenal as the technology is integrated into weapons systems— an effort Congress has mandated by 2000. Weapons such as the Joint Direct Attack Munition, an Air Force/ Navy program providing GPS strap-on kits for bombs, will change the paradigm from multiple airplanes per target to multiple targets per airplane, said Capt. Bert Johnston, the Navy's program manager for conventional strike weapons.

In one test, "we dropped four weapons directed to four targets from an airplane," Johnston said. Another test at China Lake, Calif., took place in a snowstorm, in which it was impossible for the staff at the target range to see the plane or the impact. The next day, a range technician found the bomb had struck "one yard or so from the target."

Directing Rescue Missions

Although GPS was developed for the military, civilian sales now dominate the market, with applications ranging from public service, to agriculture and surveying, to hiking and camping. Estimated worldwide sales in 1997 exceeded $3 billion, only $90 million of which was military. Handheld GPS receivers start at less than $100. Prices have been tumbling by as much as 30 percent a year, making receivers broadly accessible to consumers, said Charlie Trimble, president of Trimble Navigation.

St. Luke's Hospital in Superior, Wis., bought and distributed GPS receivers to emergency response units so they can call in medical helicopter service in the backwoods of Minnesota and Wisconsin, according to Gayle Mason, chief flight nurse. "Before, we had to spend a lot of time on the radio, figuring out where [the emergency response units] were," Mason said. But now the air ambulance can go "directly to the patient in a timely fashion."

The city of Phoenix uses GPS "to know where fire engines [are] when they [aren't] in the firehouse," according to Trimble. This setup once enabled an 83-second response to a 911 call, thereby saving the life of a child found at the bottom of a swimming pool. GPS also is used to locate ambulances in the San Francisco Bay area, Trimble said, saving two minutes on 911 response times. That's the "difference between life and death in many trauma situations," he said.

GPS technology also works at sea. A few years ago, Josh Hall, the skipper of a one-man yacht, was competing in an around-the-world race. But off the coast of Brazil, his craft started flooding below deck. Alerted by an emergency signal from Hall's GPS device, the British coast guard notified the nearest contestant— 84 miles away— who changed course and sailed to the rescue.

Toughest Battle Ahead

Despite its successes, GPS may now be facing its biggest threat. At a November meeting of the World Radio Communication Conference, which allocates spectrum, supporters of the International Maritime Satellite Organization tried to take a portion of GPS bandwidth for mobile satellite services. This attempted "incursion" into the civilian portion of the GPS spectrum, if successful, could have serious consequences for users, said Scott Pace, a policy analyst for Rand Corp. and a conference observer. It could affect the acquisition time, availability, integrity and reliability of the signal.

Although GPS advocates were able to gather support at the conference, they were only successful in deferring a decision until the next meeting in 1999. What the United States needs to do now, one consultant said, is to put together a "deal" to build support for GPS worldwide. This should include turning off selective availability, adding a second civil frequency and guaranteeing continued free access to the signals. "Most people see GPS as a utility," he said. "They don't realize how weak it is.''

-- Adams is a free-lance writer based in Alexandria, Va.

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GPS Components

Satellites: At least 24 GPS satellites orbit the Earth every 12 hours and transmit continuous navigational signals. Manufacturers are Rockwell, Lockheed Martin Corp. and Boeing Information Services.

Ground Control: The master operational control system is at Falcon Air Force Base, Colo.

Receivers: As many as 120 U.S. companies make GPS receivers and related equipment. The top players are Trimble Navigation Ltd., Magellan Systems Corp., Motorola Corp., Rockwell and Honeywell Inc.

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The Future of the GPS Program

BY CHARLOTTE ADAMS

The future of the $20 billion Global Positioning System, as envisioned by the Joint Program Office's (JPO) GPS Modernization effort, includes enhancements to make GPS more robust and useful.

Increasing signal power in combat theaters, for example, would make signals easier to acquire and harder to jam. Changing the coding structure would make signals harder to spoof and easier to lock onto, said Air Force Col. Jim Armor, the JPO program director at Los Angeles Air Force Base, Calif. While JPO regards a second civil frequency—- something civil agencies and commercial users want for greater accuracy—- as an ideal, it is also examining options for reusing the existing frequencies. A major program review is scheduled for the fall.

When future GPS satellites migrate to the new Evolved Expendable Launch Vehicle, JPO would also be able to offer almost 800 watts of power on the satellite—- a vast increase from the original specification. But no final decisions have yet been made on what to do with the extra power and payload capacity.

It is also important to increase the constellation size, said Kirk Lewis, the leader of a special Independent Review Team assigned by the Pentagon to evaluate the options for protecting and improving the system. Besides increasing signal power, Lewis wants to see as many as 30 satellites—- up from the standard 24-satellite constellation size—- in order to reduce vulnerability to jamming.

Lewis' chief concern at the moment is the Inmarsat threat. "What GPS may look like in the future depends on how well we can protect the L1 and L2 [frequencies] in the short run," he said. The review team wants to convince the American people that now is the time to make a commitment to go from a "weak" to a "strong" system. Lewis thinks $750 million over and above current spending levels would be enough to get a strong modernization program rolling.

Other JPO programs include the Defense Advanced GPS Receiver, which is expected to be awarded in the next two years, and a new-generation Miniaturized Airborne GPS Receiver. The latter will take an open-systems approach to reduce the cost of integrating and upgrading GPS gear.

The Defense Advanced Research Projects Agency also is developing advanced navigation technologies and miniaturizing GPS user equipment. The agency's GPS Guidance Package program, for example, which integrates fiber-optic inertial guidance with GPS, aims at a unit 7 pounds in weight and 100 cubic inches in volume, according to Air Force Lt. Col. Beth Kaspar, the program manager. This amounts to a fourteenfold reduction in volume and an almost sevenfold reduction in weight, compared with Inertial Navigation System/GPS equipment that Navy aircraft now use. Brassboard units, which are pre-prototype INS/GPS units, have been successfully tested on F-18s and Army fire support vehicles.

DARPA also is working on smaller, more accurate clocks for GPS receivers, allowing faster startup and signal acquisition/reacquisition in a jamming environment. One contractor, Culver City, Calif.-based Q-Tech, is expected to introduce clocks for handheld units next year that will provide up to three orders of magnitude greater accuracy than today's receivers while requiring the same power levels.

Further into the future, the agency is looking at putting pseudolytes—- which are satellite surrogates—- on tactical unmanned aerial vehicles to broadcast GPS signals locally. Low-power (less than 1 watt), low-cost (less than $1,200 per unit), man-portable INS/GPS units for infantry and weapons system operations are also in the works.