Global Positioning System Goes Through Final Y2K Testing

"We are very confident these tests will show that the Global Positioning System will function properly into the year 2000 and beyond," said Mike Filler, command lead of Y2K testing for GPS at the Air Force Space Command, Peterson Air Force Base, Colo. DoD fielded and maintains the GPS, which can tell users their location anywhere in the world within a matter of feet.

The Year 2000 problem, nicknamed "Y2K" and "millennium bug," refers to a past computer industry practice of programming years with just two digits -- 1999 would be "99." The shorthand means some computer systems and equipment on Jan. 1, 2000, might read "00" as "1900." The error could generate more inaccurate data and even cause systems to shut down. Systems that won't handle the year change correctly must be fixed or replaced; those that will work correctly are called "Y2K-compliant."

Continued functioning of the GPS into the next millennium is critical to DoD's warfighting mission, Filler said. For example, the Navy and Air Force employ the system for sea and air navigation, while the Army and Marines use it to pinpoint positions during ground operations.

"We could not have done what we did in Desert Storm without GPS," Filler pointed out. "When we initially went into Kuwait, and then Iraq, we were essentially moving in featureless terrain. GPS was the feature that gave commanders the ability to maneuver effectively -- to know where all forces were at any given moment in time."

Although a DoD system, the GPS is used heavily by many major businesses and industries worldwide. Almost all transportation sectors use it, including the airline, rail, sea and trucking industries, as well as individuals, said Capt. Zannis Pappas, Space Command's GPS operations section chief.

"It's become very affordable and very easy to use," he added. "Anyone can buy a handheld receiver nowadays, and it's often used by people hiking, fishing, boating, camping or cross- country skiing. It's even becoming standard in some automobiles."

The system consists of three major segments, Pappas said. The first, referred to as the "space segment," is a constellation of 24 operational satellites that circle the earth. He said the system currently includes an additional three satellites, which gives the command the flexibility to take satellites off-line temporarily for routine maintenance or testing, such as the current Y2K tests.

The second component consists of monitor stations at Hawaii and Kwajalein Atoll in the Pacific, Ascension Island in the Atlantic, Diego Garcia in the Indian Ocean, and Colorado Springs, Colo.; ground antennas at Ascension, Diego Garcia, Cape Canaveral, Fla., and Kwajalein; and a master control station at Schriever [formerly Falcon] Air Force Base, Colo.

The monitor stations track all satellites and accumulate data. The Schriever control station processes data to determine satellite orbits and to update each satellite's navigation message. Updates are then transmitted to each satellite through the ground antennas.

The third segment is users, who receive the navigational and positioning information through a receiver.

Filler said two classes of GPS satellites successfully passed tests conducted in late April and early May. Tests on a third class are being conducted throughout July. The classes vary slightly in their technological sophistication and functions.

Y2K testing this month focuses on three key dates, Filler said. First, the test satellite's clock will be advanced to Jan. 1, 2000, to make sure the system doesn't read the year as 1900. It will also be tested to successfully read what Filler called "rollover dates" that occur in February 2000 -- because many computer systems weren't programmed to recognize 2000 as a leap year, the test ensures the satellites work properly between Feb. 28 and March 1.

Testing will also verify a non-Y2K-related phenomenon known as "end-of-week rollover." Filler said the GPS system counts in weeks. When fielded, the GPS satellites' clocks were set to count only up to 1,023 weeks -- about 20 years -- from January 1980. At midnight on Aug. 21 this year, the first 1,023 weeks end.

"From our perspective and the testing we've done, we don't anticipate any problems," Filler said. "What we expect is that the clocks will revert back to zero and then begin counting the weeks all over again. That would place the next rollover at April 6, 2019."

Although the rollover and Y2K are not expected to affect the satellites or ground control operations, Filler warned that GPS receivers may experience problems. The individual services are testing their receivers and upgrading and replacing them as needed. Personal GPS receivers also need to be checked.

"Most receivers made in the past five years should be OK, but it wouldn't hurt to check," Filler said.

The Federal Communications Commission and Department of Transportation are advising users of personal GPS receivers to contact the manufacturers to determine compliance. For manufacturer contact information, use the federal government's toll-free Y2K consumer hot line, 1-800-USA-4-Y2K, or visit the Consumer Information gateway at the Federal Trade Commission Web site at www.consumer.gov/y2k/index.html. The site has direct links to most manufacturers of consumer electronics.