U.S. Advises Nations Building Satellite Navigation Systems To Be Patient

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  Space News Business

U.S. Advises Nations Building Satellite Navigation Systems To Be Patient

By PETER B. de SELDING
Space News Staff Writer
posted: 27 February 2008
03:01 pm ET





MUNICH, Germany —


U.S. GPS managers attending the Munich Satellite Navigation Summit had advice for their Russian, European and Chinese counterparts, who are all planning GPS-similar global constellations: Be patient.



“The first GPS satellite was launched 30 years ago, in February 1978,” said Richard W. McKinney, director of the European Space Liaison at the Office of the Under Secretary of the U.S. Air Force, which runs the GPS system.

“It was the first of 11 developmental satellites launched before the system was operational,” McKinney said Feb. 19. “The first operational satellite was launched in February 1989, with full operational capability starting in 1995 – six years after the first operational satellites. It has taken us a long while to get where we are.”

Where GPS is now is the largest operational fleet ever: 30 functioning spacecraft, with a 31st whose atomic clock remains operational 17 years after launch but has been taken out of the operational rotation.

Seventeen of the 30 operational satellites are the newer Block 2R and 2RM spacecraft, said Air Force Lt. Col. Harold Martin of the U.S. Space Command. Martin said three more GPS 2RM launches are scheduled for 2008, with the first Block 2F spacecraft scheduled for the spring of 2009.



The newer satellites have higher-performance atomic clocks and provide better positioning and timing accuracy, Martin said.



An upgraded GPS ground network means Air Force controllers have fewer moments when they are not in contact with all the satellites to assure the spacecraft are functioning correctly.

The ground-network upgrade, called the Architecture Evolution Plan and completed in September, features a new backup control station and additional monitoring facilities. Martin said all GPS satellites are now visible to GPS controllers 100 percent of the time, rather than 96 percent of the time, as was the case before the upgrade.

A contractor for the first eight GPS 3 satellites is expected to be selected in April after a long competition between Boeing- and Lockheed Martin-led teams.



These satellites are expected to be substantially larger than their predecessors. Boeing is offering a modified version of its BSS 702 satellite platform, with Lockheed Martin proposing a modified A2100 frame.

Martin said the substantial weight and size gain for GPS 3 is almost all due to higher specifications for positioning, navigation and timing (PNT) services and not because of GPS’s other, little-mentioned all-military missions.

“The vast majority is related to PNT,” Martin said. “The need for increased power means bigger solar arrays, and a bigger satellite overall.”

In addition to being able to assure signal reception in an environment of intentional or unintentional interference, the higher power on the GPS 3 satellites will be used to provide high-intensity spot beam coverage of selected areas for at least the later versions of the Block C generation.

The satellites




also will be fitted with a capability to permit autonomous operations for up to six months.

As has been the case with previous GPS generations, GPS 3 will add capability with each succeeding block. Block B is expected to feature more intersatellite communications capability. Block C is likely to have an integrity-monitoring function to provide error notifications to users, as well as the spot-beam feature.



Don DeGryse, vice president of navigation systems at Lockheed Martin, said the eight Block B satellites are expected to be ordered three years after Block A, with 16 Block C spacecraft ordered two years after that.

Michael A. Rizzo, director of navigation systems at Boeing, cautioned Europe’s Galileo managers that their current plans to deliver two Galileo satellites per month at peak production “will be a real challenge.” Twenty-six Galileo satellites are scheduled to be delivered and launched between 2011 and 2013.