First 'modernized' GPS satellite set for launch
BY JUSTIN RAY
Posted: February 8, 2005
An advanced Global Positioning System satellite built to transmit additional navigation signals to benefit military and civilian users around the world has arrived at Cape Canaveral Air Force Station to begin a three-month campaign leading to launch.
A Boeing Delta 2 rocket will haul the satellite into space during a launch tentatively targeted for May 20. The liftoff date could be moved up if an earlier slot can be negotiated on the Cape manifest.
"We're running ahead of schedule," Dave Podlesney, Lockheed Martin's GPS 2R program director, said in a telephone interview Tuesday.
The GPS constellation features 24 primary and several backup satellites flying in six orbital groupings 11,000 miles above Earth. The Air Force continues to launch new satellites as replacements to keep the critical navigation system in good health. Today, there are 30 functioning GPS satellites.
The GPS craft send continuous navigation signals that allow users virtually anywhere on the planet to find their position in latitude, longitude and altitude and determine time. The information is so accurate that time can be figured to less than a millionth of a second, speed within a fraction of a mile per hour and pinpoint location within a matter of feet.
The military's orbiting GPS constellation began to take shape in 1989. To replace the original satellites as they age, Lockheed Martin built 21 so-called "replenishment" satellites. Dubbed the "2R" series, this current generation of GPS spacecraft has seen 13 flown since 1997, although the first one was lost in a launch explosion. Now, the remaining 8 are being retrofitted with upgrades to provide additional capabilities once deployed in space.
Carrying the re-titled name GPS 2R-M, for Modernized, these upcoming satellites increase the power for existing signals and offer two new military signals as well as a second civilian signal.
The changes fit within the existing GPS 2R satellite design. The Modernized spacecraft, which will weigh 4,545 pounds at launch, only 60 pounds heavier than the earlier model, have a redesigned external antenna panel; and higher-power, more-efficient transmitters highlight the internal changes.
The navigation payload is built for Lockheed Martin by ITT Industries.
The improvements will provide greater accuracy, added resistance to interference and enhanced performance for all users, according to the Air Force. The advancements for the military will provide warfighters with a more robust jam-resistant signal and enable better targeting of GPS-guided weapons in hostile environments, while the new civilian signal removes ionospheric errors and improves accuracy, officials say.
Over the next three months at Cape Canaveral, technicians will conduct significant testing on the GPS 2R-M1 satellite to ensure it is ready for flight, including compatibility checks since this is the first craft of the new breed. The flight batteries will be installed, along with a solid-fueled kick motor that propels the satellite from the initial elliptical 11,000 by 100 mile orbit achieved during launch to reach the circular orbit of the GPS constellation.
As the launch nears, hydrazine fuel for the satellite's maneuvering thrusters will be pumped aboard. A larger solid-fueled motor that serves as the Delta rocket's third stage is brought into the processing hangar and the satellite will be mounted atop the booster in April.
The bottom two stages of the Delta 2 and nine strap-on solid motors will be assembled at the launch pad. The third stage and satellite duo are transported to pad for mating to the awaiting rocket about 10 days before liftoff.
The launch will mark the 53rd for a GPS satellite and the 42nd carried on a Delta 2 rocket.
Once circling the Earth, ground controllers will perform a multi-month test program to examine the new 2R-M satellite's performance and users' reception before proceeding with the next launch. If all goes well, the 2R-M2 satellite could lift off in October, with the next following behind in December or January.
Lockheed Martin has set aside several of the GPS 2R satellites that have not yet been upgraded in case a problem develops in space and the military needs to launch the proven design on short notice. The others are undergoing the overhaul process now.