Riding over three million pounds of thrust from its two solid-fueled booster rockets, a Titan 4B launcher tore through a cloud-filled sky Tuesday morning to heave a massive national security cargo into space.

The Titan 4 rocket is swallowed by a cloud deck moments after liftoff as seen from the Kennedy Space Center Complex 39 press site. Photo: Steven Young/Spaceflight Now

Blasting off from Cape Canaveral's Complex 40 at 12:29 a.m. EDT (0429 GMT) after a 77-minute delay to analyze a vehicle temperature reading, the $500 million Lockheed Martin vehicle promptly maneuvered itself on a 93.9-degree, due east heading for geosynchronous orbit.

Two minutes later, the Titan's liquid-fueled first stage engines lit as the solid motors burned out and fell away. Within nine minutes, the second stage had completed its job and released the Centaur upper stage with the clandestine payload on top.

The Centaur, making its last flight aboard a Titan rocket after three decades of service, was expected to perform three firings to propel the satellite cargo into the intended orbit.

After the first burn, a news blackout was imposed on the remaining launch events. The top-secret National Reconnaissance Office spacecraft was expected to arrive in the proper orbit nearly six hours after the launch began. But officials said the ultimate fate of the mission's success would be cloaked in secrecy.

The NRO, the government agency based in Chantilly, Virginia that is responsible for U.S. spy satellites, will operate the craft. It joins a vast network of intelligence-gathering spacecraft that eavesdrop on American adversaries, capture precision images of Earth and relay communications.

Government authorities will not reveal the identity or the purpose for the new satellite. But military watchers believe it is the third Advanced ORION -- a craft with a giant antenna designed to catch communication transmissions, telemetry and electronic signals from its perch in geostationary orbit 22,300 miles above the planet.

Space observers point out that two similar launches occurred in May 1995 and May 1998. Those flights of the Titan 4 also featured eastbound trajectories, liquid-fueled Centaur upper stages and the largest payload fairing made for the vehicle -- a nose cone 86-feet in length.

How the new satellite will be used in the war against terrorism isn't clear. The specific part of the globe to be covered by the craft is a secret.

But the overall U.S. spy satellite fleet has proven vital to the wars in Afghanistan and Iraq, Air Force General T. Michael Moseley wrote in a recent letter to U.S. News and World Report and released by the NRO.

"Operating over Afghanistan and Iraq, NRO and U.S. Air Force space systems provided coalition forces with a tremendous asymmetric intelligence advantage that allowed us to dominate the enemy quickly and completely in both fights. In the Iraqi campaign, I relied on NRO capabilities every day to conduct precise and effective strategic attack, counter-air and counter-land strikes against Saddam Hussein's regime. Moreover, NRO satellites were exceedingly capable supporting ground, naval, and special operations forces throughout the campaign.

"And I'm not alone in my assessment of the importance of these systems. As my boss, General Tommy Franks, noted in Congressional testimony on Afghanistan, 'the pieces of this operation which have been successful would not have been so without space-based assets. It's just very simply a fact.'"

Moseley, commander of U.S. Central Command's air component for Operation Enduring Freedom and Operation Iraqi Freedom, wrote the letter to the magazine in response to a scathing article published last month claiming that the NRO was failing to deliver intelligence.

Tuesday's launch was the first time in over five years that the NRO had lofted such a large satellite from the U.S. East Coast. The last successful launch was the suspected Advanced ORION mission in May 1998. Another Titan 4 launch in August of that year failed less than a minute after blastoff when the vehicle exploded, destroying what was believed to be a MERCURY-class eavesdropping craft designed to intercept government and military communications.

There are three Titan 4 rockets remaining to launch through 2005 and the NRO is the customer for two of them.

• Early 2004: An Air Force Defense Support Program missile-warning satellite is scheduled for liftoff from Cape Canaveral using a Titan 4 and Boeing-made Inertial Upper Stage on mission B-39.
  
  
• Fall 2004: The last Titan 4 launch from Florida will carry an NRO payload. This mission -- B-30 -- was transferred from Vandenberg Air Force Base in California where it was originally slated to launch.
  
  
• Early 2005: The Titan 4 era ends after 16 years with its 39th and final launch as another NRO cargo is put into orbit from Vandenberg on mission B-26.

The Titan program is also preparing for the last Titan 2 rocket launch presently on the books.

The Air Force's Defense Meteorological Satellite Program F16 weather spacecraft will ride the Titan 2 into polar orbit from Vandenberg in the coming weeks. A specific launch date is pending a review of Tuesday's Titan 4 launch to ensure there were no problems affecting common systems between the two rockets.

"Titan typically requires 14 days of separation between these two flights. However, the DMSP processing schedule dictates approximately 21 days of separation as they wait for the Titan 4 post-flight to give them the go ahead to fuel the satellite," the Air Force told Spaceflight Now.

Titan 2s were used by NASA's Gemini manned space program in the 1960s. The refurbished Intercontinental Ballistic Missiles also have completed a dozen successful launches of satellites since 1988.

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