NACOGDOCHES, Texas - As soon as NASA learned that debris from the space shuttle was raining down on this East Texas town, it quickly enlisted the academics at Stephen F. Austin University to precisely plot the location of every piece - data that will be collated with telemetry beamed from the doomed spacecraft to determine why it broke apart 39 miles above Texas on Saturday.

The university is the home of the Geographic Information Systems Laboratory, an institution adept at using satellite technology and advanced mapping techniques to pinpoint exactly where debris fell.

So, yesterday morning, just as the sun was rising, teams of students and staff members from Stephen F. Austin were on the road - with hand-held global positioning devices, yellow backpacks with dome-shaped receivers poking out and sack lunches so they could cover as much territory as possible.

"We have close to 1,000 places located over the last 72 hours," said W.L. Gardner Jr., project coordinator of the GIS lab.

'Missing link'

The goal is to map each spot and record a description of what has been found so that others can come along and take the items to Barksdale Air Force Base in Shreveport, La., where investigators for the National Aeronautics and Space Administration hope to reconstruct Columbia and find what shuttle program manager Ron Dittemore called "the missing link" that will unlock the mystery.

"If they don't have the position of all the pieces, they're not going to know how things blew off," said Sarah Williams, a GIS specialist at the Massachusetts Institute of Technology.

That's the long-term goal, but in the short term, officials think the work in Nacogdoches might help them see a pattern and lead them to find more of NASA's priority pieces, such as the flight computer or parts of the many experiments that were being conducted on board.

Pieces that linked together on the shuttle are likely to have come apart in close proximity to one another, or so the logic goes.

Investigators employed the same global positioning system, or GPS, after the Sept. 11 attacks in trying to recover debris after the World Trade Center collapsed into giant piles of rubble.

GPS is also used in more mundane ways. Cities use it to assist 911 dispatchers sending firefighters to a burning house - and to locate the nearest fire hydrant.

More and more automobiles are equipped with it, some to help drivers find their way to an unfamiliar destination without having to stop and ask for directions or trying to read a map over the steering wheel.

"Over the next couple of years, you'll be hearing about GPS ad nauseam," said Strite Potter, president of LinksPoint, a Connecticut-based firm that provided GPS data for the Fire Department of New York in the days after Sept. 11.

GPS can place an object at a precise latitude and longitude on the planet, with the help of 24 satellites orbiting the Earth. While the technology has been around in some form for more than 15 years, it has come into widespread use only over the past several years after former President Bill Clinton ordered the military to unscramble the necessary satellite signals.

For now, the students are concentrating their efforts in Nacogdoches County and in San Augustine County to the east. When they get more equipment, they will be able to cover more area. They talk with ease about the serious work they are doing, but when it comes to the grim reality that they could find human remains, they clam up, unwilling to talk about that.

They haven't slept much. Ever since they started this process early Saturday afternoon, they have been in the field from dawn until dusk and in the lab for hours more as the information is entered into a database.

When one of many callers asks Gardner whether she can drop anything by, he drawls back: "Tell her I need extra brain cells."

In his former career, Gardner was a paramedic in Galveston, Texas. He knows what someone responding to a disaster can face. He keeps an eye on these kids, to make sure they are coping. At times, when it's busy around here, it's easy to forget that they're not just cataloging metal and foam, they're tracking the results of a deadly accident.

More debris is being found every day. Some still seems to be falling.

"We have debris in the treetops," said Cathy Pulley, a graduate student in geography. "Now with the winds picking up, things are coming off trees and rooftops that we hadn't been able to find before."

100-mile path

On maps being produced in the lab - which looks like little more than a series of basic classrooms with computers lining the wall - a swath of rainbow colors is drawn along the 100-mile-long, 10-mile-wide path into Louisiana believed to contain the missing parts.

Students at Stephen F. Austin were skilled in GPS and mapping long before they were forced into action over the weekend. But until now, their biggest project was mapping every water pipe in this city of 30,000. Never before have they had such a beyond-the-books experience.

"This is real-world stuff," said Brett Williamson, a 22-year-old geography major. "It's not like stuff that's already out there that we GPS every day like the fire hydrants."

Tony Collett, another geography major, put on his orange vest yesterday and checked his equipment to make sure it was all in working order. He was about to head into the field for his fourth day of work. He was supposed to be in class but his professors gave him a pass, understanding the gravity of what he intended to do instead.

"It's been hectic," he said. "Everyone's got a piece in their back yard and we have to GPS everything from things the size of a paper clip to the size of this desk. A lot of stuff doesn't look like it belongs here. The makeup of the metal is visibly different than anything you'll see out there, especially in this town."

Seventeen years ago, when the space shuttle Challenger exploded over the Atlantic Ocean, GPS was not completely in place. In fact, the slowdown of the space program - the shuttle explosion was followed by the explosion of a Delta rocket carrying a weather satellite - in the months afterward delayed the implementation of GPS system. With no shuttles flying, and the most reliable rocket suddenly being checked for defects, new satellite launches were postponed.

Since then, Collett said, "society and science have advanced to the point where it can start leveraging the knowledge of where things are on the Earth."