|The twin solid rocket boosters are ignited and space shuttle Columbia launches from pad 39A at Kennedy Space Center, Florida, beginning the 108th shuttle mission.
|Start roll maneuver
|Columbia beings a programmed roll maneuver to achieve a northeasterly track from KSC, heading toward a 28.5 degree inclination to the equator.
|The shuttle completes the programmed roll maneuver and is now positioned heads down, wings level.
|Start throttle down
|The three liquid-fueled main engines are throttled down to 72 percent rated thrust to ease the vehicle's flight through the dense lower atmosphere.
|Columbia's main engines begin throttling back up. The engines' thrust level will be taken to 104.5 percent.
|The shuttle passes through the area of maximum aerodynamic pressure that is experienced during its climb to orbit.
|Having consumed all their propellant, the solid rocket boosters are jettisoned from the attachment points on the external fuel tank. The boosters parachute into the Atlantic Ocean for recovery and reuse.
|Columbia is now too far downrange and traveling too fast to make an emergency Return-to-Launch-Site abort landing at Kennedy Space Center. A problem after this point during flight requiring an abort would lead to a Trans-Atlantic Abort Landing, Abort-to-Orbit or Abort-Once-Around.
|Rolls to heads up
|A programmed maneuver rolls Columbia to a heads up position, placing the shuttle atop the external tank. This is done to improve communications between the shuttle and NASA's orbiting Tracking and Data Relay Satellite System.
|Columbia's three main engines are shut down. The external fuel tank is jettisoned moments later. An upcoming firing of the OMS engines will boost the shuttle from its current sub-orbital trajectory to a safe altitude as the chase begins to rendezvous with the Hubble Space Telescope.