Just when you thought it was safe to go back in the water . . .

Discovery of a power anomaly in signal generator of the first GPS Block IIF space vehicle (SV) has thrown a new wrinkle into the long-delayed follow-on generation of spacecraft.

In reviewing test data from the final phase of SV1 thermal vacuum test, [government and Boeing mission assurance teams] identified a new concern that a component in the L2 transmitter may not have sufficient design margin to operate at its highest required power throughout the satellite lifetime.

Designed and manufactured by the Boeing Company, the IIF satellites carry a navigation payload with high-power amplifiers built — like the payloads on all versions of the GPS satellites to date — by the ITT Corporation in Clifton, New Jersey.

“Boeing has identified multiple options for addressing the concern and is working parallel solutions to deliver redesigned transmitters this summer,” said the GPS Wing spokesman.

Launch of the first IIF had been expected in October. Now the GPS Wing predicts that launch only as “late 2009.”

“Second launch will be scheduled based on constellation sustainment needs,” said the Wing spokesman, “but is not projected for sooner than six months after the first launch.”

Current status of the IIFs? SV1 is awaiting Final Integrated System Test; SV2 is in Initial Integrated System Test.

Meanwhile, the U.S. Air Force is in a race against the clock to get the new L5 signal on the air by August 26, 2009, in order to meet an International Telecommunications Union (ITU) deadline for securing a preferential L5 frequency allocation for GPS operations.

The first and perhaps only opportunity to meet the deadline: a modernized GPS Block IIR-M satellite — IIR-20(M) — with an experimental L5 signal demostration payload scheduled for a March 24 launch.

And if problems should arise with the IIR(20)-M satellite or launch? “Originally, the U.S. planned to meet the deadline with the first IIF satellite,” said the spokesman. “The IIR-20 demo payload was developed as the back-up plan.”

Should the IIR(20)-M’s L5 signal not get on the air, it could deprive GPS of unconditional use of the frequency.  Failure to get the L5 signal on the air by the ITU deadline would give priority to whichever GNSS system begins broadcasting on that frequency first — effectively placing the burden of proof on latter-day GNSS providers that their signals wouldn’t interfere with signals of the first system.

Europe’s Galileo faced a similar situation with its signal allocations following a disastrous electrical malfunction with its first Galileo In-Orbit Validation Element (GIOVE) satellite at a production facility in Italy. That led the European Space Agency (ESA) to contract for a stripped-down satellite (GIOVE-A), which could be built and launched quickly in order to meet the program’s ITU deadline.

More information:

http://www.insidegnss.com/node/1387