BY JUSTIN RAY August 17, 2000 -- Follow the countdown and launch of a U.S. Air Force Titan 4B rocket with a classified payload for the National Reconnaissance Office. Reload this page for the very latest on the mission live from Vandenberg Air Force Base, Calif.				Snapshots The Titan 4B rocket sits poised for liftoff Thursday. Top Photo: Justin Ray/Spaceflight Now. Liftoff occurred on-time at 4:45 p.m. local time. Bottom Photo: Airman 1st Class Amanda Edwards Flight data file Vehicle: Titan 4B (B-28) Payload: Classified NRO cargo Launch date: August 17, 2000 Launch time: 2345 GMT (7:45 p.m. EDT) Launch site: SLC-4E, Vandenberg AFB, Calif. Pre-launch briefing Launch preview - Read our story for a complete preview of the Titan 4 launch. Launch timeline - Chart with times and descriptions of events to occur during the launch. Titan 4B - Description of America's most powerful unmanned rocket. Video vault A video produced by the U.S. Air Force shows the Titan 4B rocket launching on Aug. 17 through ground and aerial cameras.   PLAY (335k, 48sec QuickTime file) USAF video of Titan 4B rocket's first stage igniting and spent solid-fuel boosters separating to fall into the Pacific.   PLAY (158k, 26sec QuickTime file) The U.S. Air Force Titan 4B rocket lifts off from Vandenberg Air Force Base in California with a classified spacecraft for the National Reconnaissance Office.   PLAY (376k, 22sec QuickTime file) Tracking cameras follow the Titan 4B rocket as it heads away from Vandenberg Air Force Base.   PLAY (416k, 1min 09sec QuickTime file) An infrared tracking camera atop the Santa Ynez peak sees the Titan 4B rocket's first stage ignite and the twin solid rocket booster separate.   PLAY (193k, 31sec QuickTime file) What is believed to be a Lacrosse radar imaging spy satellite is seen in a Lockheed Martin clean room in 1998. This could be the same craft being launched.   PLAY (157k, 19sec QuickTime file) From our history archives is the October 1997 launch of a Titan 4 rocket with the third Lacrosse radar imaging satellite for the NRO.   PLAY (214k, 24sec QuickTime file) Look back into our history file and watch a U.S. Air Force Titan 4 rocket lift off in daylight from Vandenberg Air Force Base in California.   PLAY (201k, 22sec QuickTime file) Download QuickTime 4 software to view this file.