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Satellite Navigation Keeps Tanks Heading in Right Direction

February 28, 1991

WASHINGTON (AP) _ To keep from getting lost and to help avoid shooting friendly forces, American armored forces in the Persian Gulf have used an electronic gadget called the ″Slugger.″

The device, an electronic box about the size of a handheld scientific calculator, is designed to put troops in instant communications with a $768 million fleet of navigation satellites orbiting 11,000 miles overhead.

With the Slugger, any tank commander can learn immediately where he is, his speed and direction of travel, and how far it is to the next objective.

And, just as important, friendly tanks with the same equipment can be located and not attacked during the frenzy and fury of modern armored battles.

Operation Desert Storm was the first use of the Slugger and the nation’s fleet of Navstar Global Positioning Satellites in a massive, coordinated movement of tanks. And the Gulf War was the type of situation planners had in mind when the first Navstars were launched in 1978.

Army Maj. Ron Mazzia, a former tank company commander and executive officer of an armor battalion at Fort Knox, Ky., said the Slugger and its satellites have solved a lot of problems for American tankers who must maneuver across vast distances where there are no signs or roadways.

″When you’re moving across the desert at night with no moon, it is very dark. It’s like being inside a closet with the light off,″ he said. ″It can get very difficult to navigate.″

A tank commander using the Slugger can punch in a few instructions and the device will pick up signals from up to four of the 16 satellites in the Navstar constellation.

The signals give the precise time and the range to the satellites, and the Slugger, which is part computer and part communicator, converts the information to navigation data. It then displays an eight or 10 digit number on a screen. These numbers correspond to a specific grid, or square, on a map.

By matching Slugger’s numbers with those on the map, a tanker knows within 15 to 30 feet exactly where he is.

The Slugger can also tell how fast the tank is traveling, to within a few feet per second, and how far it must go to reach a specific location.

If the tanker is in communication with other tanks, aircraft or infantry units, they can exchange coded grid numbers and know the location of each other within a few feet.

″This can help prevent friendly fire losses,″ said Master Sgt. Ken Distler at the Fort Knox armor center. ″It helps us know with confidence the location of friendly forces who are out of sight.″

The same technique could work for airplanes flying overhead, though aircraft also have radar and other instruments that pick up the electronic or thermal signature of friendly tanks.

Mazzia said the Slugger also helps tank commanders keep in contact with resupply teams miles behind that lack the sophisticated night vision gear found on American tanks.

″Sometimes my unit supply team would stop and I would have to go find them,″ said Mazzia. ″I’d have to take up to 30 minutes just to locate my people.″

Now the Slugger solves that problem.

Mazzia said that in most operations, tankers are given several pages of maps with the navigation grid numbers. To coordinate the maneuvers, tank commanders mark their assigned routes on a clear plastic overlay. All the tank driver has to do is follow the markings on the overlay while checking progress using the Slugger.

The Navstars’ navigation magic is based on a set of the world’s most precise timepieces. Each of the satellites is equipped with four atomic clocks that are so accurate they will lose or gain only one second over 70,000 years.

Radio signals are beamed constantly from the satellites and the Slugger can lock on signals from four satellites at once. It takes the time and range information from the satellites and converts this information to navigation data for any of up to 45 map coordinates.

Each of the Navstars cost $48 million and there now are 16 in orbit. Eventually, the Air Force plans to launch a full fleet of 21, along with three orbiting spares.

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