U.S. still probing security satellite failure

By Andrea Shalal-Esa

WASHINGTON (Reuters) - Four months after the newest U.S. missile-warning satellite built by Northrop Grumman Corp failed in orbit, officials are still investigating what happened.

The classified Defense Support Program satellite known as DSP 23 was launched into geosynchronous orbit in November 2007 but stopped responding to commands in mid-September last year, as first reported by Reuters in November.

"There's not that much data available," one U.S. defense official said, describing the current investigation as sophisticated, long-distance detective work.

"You have to go back and recreate what might have been going on," said the official, who asked not to be named because he was not authorized to speak about the program. There may never be "great certitude" about what went wrong, he added.

Defense officials say possible causes for the failure range from defective parts or software problems, a natural phenomenon like a solar flare, or possibly, although unlikely, debris in space. An intentional attack was also possible, but very unlikely, they said.

Citing concerns about a toxic fuel tank, the U.S. government last February shot down a smaller classified satellite that failed due to software problems almost immediately after being launched into orbit in December 2006.

As a result of those software concerns, Lockheed Martin Corp was forced to rewrite code for its Space Based Infrared Satellites (SBIRS) that will succeed the DSP program.

It was not clear if similar software issues could be behind the latest satellite failure, but officials said that possibility was being closely investigated.

Northrop declined to comment on the September failure, referring questions to the U.S. Air Force, which owns and operates the satellite. Air Force officials declined to comment.

FUTURE VULNERABILITY?

The U.S. government has launched 23 of Northrop's DSP missile-warning satellites since 1970. Two failed to reach orbit and experts estimate that seven are still working, about twice the number needed to watch the entire Earth at once.

The September failure of the newest DSP satellite raises the possibility that the United States may have gaps in its ability to detect enemy missiles in the future, unless new satellites are launched soon, said analyst Loren Thompson.

"Everybody expects the oldest satellites to fail, but when you lose your newest satellite, you're taking years off the tail end of how long the constellation is going to be effective," said Thompson, of the private Lexington Institute.

The first two of Lockheed's SBIRS sensors are in orbit on board other satellites, but the first dedicated satellites are not due to be launched until 2010.

Lockheed's SBIRS program began in 1996 with the aim of launching the first satellites in 2004 at a cost of $4.2 billion. The program has been restructured several times and its price tag is now seen at well over $11 billion.