With war raging half-a-world away, a routine but crucial rocket launch from Florida next week will deploy a fresh tactical navigation satellite into the U.S. military's Global Positioning System -- the orbiting network that ground, air and sea forces rely upon for guidance.

A Boeing Delta 2 rocket will launch the GPS 2R-9 satellite. Photo: Jeff Wolfe/Johnson Controls

A Boeing Delta 2 rocket is scheduled for blastoff at 4:54 p.m. EST (2154 GMT) Monday from Cape Canaveral's pad 17A. The day's available launch window extends 15 minutes.

The NAVSTAR Global Positioning System Block 2R-9 spacecraft will ride the three-stage rocket into an approximate transfer orbit with a high point of 11,000 nautical miles, low point of 100 miles and inclination of 39.0 degrees.

The Lockheed Martin-built satellite will circularize its orbit and join the GPS constellation to fill a slot being vacated by an aging spacecraft. The Air Force says the new GPS 2R-9 satellite -- also known as SVN-45 -- will be maneuvered into the network's Plane D, Slot 3. It is expected to enter service within a month of launch.

The GPS 2-5 is currently in that position. Also known as SVN-17, the craft was launched in December 1989. Despite its advanced age, the satellite remains operational. Controllers plan to shift it toward the D1 slot, making it a "close pair" with the GPS 2A-11 satellite that was launched in July 1991, program officials said.

"Since satellites can be moved within an orbital plane but not between planes, the GPS replenishment strategy considers the relative strength of the six GPS orbital planes. The Constellation Sustainment Assessment Team determined that the D-plane carried the greatest overall need," the Air Force's Space and Missile Systems Center told Spaceflight Now.

"(GPS 2-5) is over 13 years old and has been operating on three of four reaction wheels since December 2000. A satellite requires three reaction wheels to maintain attitude control and to perform the GPS missions. Except for some risk associated with the three remaining reaction wheels, (GPS 2-5) is in relatively good condition."

An artist's concept of a GPS Block 2R satellite orbiting Earth. Photo: Lockheed Martin

The GPS network features 24 primary satellites split into six orbital planes with four spacecraft in each. Some planes also have additional satellites to enhance coverage and serve as backups. Today, the orbiting system has 27 craft that are considered healthy, the Air Force said.

GPS satellites operate 11,000 miles above Earth at an inclination of 55 degrees to either side of the equator, providing precision location, speed and timing information to military forces and civilian users anywhere in the world.

"We use GPS for other space-based systems to locate targets, and we use them to guide our weapons. We can also keep track of supplies, and we use them for logistics operations," said Col. Steven Fox, director of the Army Space Program Office.

Monday's mission -- valued at roughly $100 million -- will be the second of three regularly scheduled GPS replacement launches planned in 2003. The most recent occurred on January 29. The Air Force is targeting July 24 for the deployment of GPS 2R-10.

This launch comes at a time when U.S. and coalition forces are depending on the Pentagon's armada of orbiting satellites in the fight to liberate Iraq. Beyond GPS, the U.S. military operates weather, communications, missile-warning and various reconnaissance satellites. Many of those birds were launched from the Florida spaceport.

The 45th Space Wing emblem. Credit: Air Force

"Control of the battlefield begins here," said Brig. Gen. Greg Pavlovich, the 45th Space Wing commander at Cape Canaveral.

"Everyone is seeing how critical GPS is to fighting wars. You simply can't fight wars without space. Every operational GPS satellite in space today was launched from the Cape. That is how critically important the Space Coast is to national defense and to protecting America's freedom," Pavlovich continued.

A Defense Satellite Communications System craft was successfully launched earlier this month aboard a Boeing Delta 4 rocket. A Milstar communications satellite is scheduled for liftoff aboard a Titan 4 on April 6.

"There is very important work to be done here on the Cape to support our people fighting the war and we are leaning forward and will accomplish our mission."

America's other primary launch site -- Vandenberg Air Force Base in California -- is gearing up for a pair of national security space missions in June. A Lockheed Martin Atlas 2AS rocket will haul a classified spy satellite cargo into orbit, while a new weather observatory is scheduled to be deployed atop a refurbished Titan 2 missile.