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FLIGHT DAY:  Countdown • 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12

STS-133 Launch Countdown Milestones and Times

(All times are Eastern)

Launch-3 Days (Monday, Feb. 21)
  • Prepare for the start of the STS-133 launch countdown
  • Perform the call to stations (2:30 p.m.)
  • Countdown begins at the T-43 hour mark (3 p.m.)
  • Begin final vehicle and facility closeouts for launch
  • Check out backup flight systems
Launch-2 Days (Tuesday, Feb. 22)
  • Configure avionics systems for launch
  • Review flight software stored in mass memory units and display systems
  • Verify backup flight system software in Discovery’s general purpose computer
  • Activate and test navigational systems (4 a.m.)
  • Complete preparations to load power reactant storage and distribution system (6 a.m.)
  • Flight Crew Equipment early stow and flight deck preliminary inspections complete (7 a.m.)

    Enter 4-hour built-in hold at T-27 hours (7 a.m.)

  • Clear launch pad of all nonessential personnel
  • Perform test of the vehicle's pyrotechnic initiator controllers and range safety system

    Resume countdown (11 a.m.)

  • Begin operations to load cryogenic reactants into Discovery’s fuel cell storage tanks (11 a.m.)

  • Enter 8-hour built-in hold at T-19 hours (7 p.m.)

  • Demate orbiter mid-body umbilical unit (11:30 p.m.)
Launch-1 Days (Wednesday, Feb. 23)
  • Resume orbiter and ground support equipment closeouts

    Resume countdown (3 a.m.)

  • Main engine avionics, pneumatics and controller checkout (3 a.m.)
  • External Tank feedline inspection/camera cleaning
  • Flight Crew Equipment stowage
  • Begin removal of pad ground support equipment

    Enter built-in 13 hours, 25 minute hold at T-11 hours (11 a.m.)

  • Activate the orbiter's communications systems
  • Lower engine support platforms, retract access platforms
  • External Tank Inspections
  • Rotating Service Structure begins move away from Discovery to the park position (8 p.m.)
  • Perform ascent switch list
  • Complete Flight Crew Systems time critical stowage (middeck payloads)
  • Fuel cell flow-through purge complete
Launch Day (Thursday, Feb. 24)
    Resume countdown at T-11 hours (12:25 a.m.)

  • Activate the orbiter's fuel cells (1:35 a.m.)
  • Clear the pad of all nonessential personnel (2:25 a.m.)
  • Switch Discovery's purge air to gaseous nitrogen (2:25 a.m.)
  • Complete final walkdowns

    Enter 2-hour built-in hold at the T-6 hour mark (5:25 a.m.)

  • Clear pad of all personnel (5:35 a.m.)
  • Complete tanking preparations
  • Launch team verifies no violations of launch commit criteria prior to cryogenic loading of the external tank

    Resume countdown (7:25 a.m.)

  • Chill down propellant transfer lines (7:25 a.m.)
  • Begin loading the external fuel tank with about 500,000 gallons of cryogenic propellants (about 7:35 a.m.)

    Enter 2-hour, 30-minute built-in hold at T-3 hours (10:25 a.m.)

  • Perform inertial measurement unit preflight calibration
  • Align Merritt Island Launch Area tracking antennas
  • Complete filling the external tank with its flight load of liquid hydrogen and liquid oxygen propellants (about 10:25 a.m.)
  • Final Inspection Team and Closeout Crew proceeds to launch pad

    Resume countdown at T-3 hours (12:55 p.m.)

  • Perform open loop test with Eastern Range
  • Crew departs Operations and Checkout (O&C) Building for the pad (1 p.m.)
  • Complete closeout preparations in the White Room
  • Check cockpit switch configurations
  • Begin Eastern Range final network open loop command checks
  • Flight crew begins entry into the orbiter (1:30 p.m.)
  • Astronauts perform air-to-ground voice checks with Launch and Mission Control
  • Begin to close Discovery’s crew hatch (2:35 p.m.)
  • Perform hatch seal and cabin leak checks
  • Complete White Room closeout
  • Closeout crew moves to fallback area
  • Primary ascent guidance data is transferred to the backup flight system

    Enter 10-minute hold at T-20 minutes (3:35 p.m.)

    NASA test director conducts final launch team briefings

    Resume countdown at T-20 minutes (3:45 p.m.)

  • Transition the orbiter's onboard computers to launch configuration
  • Start fuel cell thermal conditioning
  • Close orbiter cabin vent valves
  • Transition backup flight system to launch configuration

    Enter estimated 45-minute hold at T-9 minutes (5:56 p.m.)

  • Final launch window determination
  • Launch director, Mission Management Team and NASA test director conduct final polls for "go/no go" to launch

    Resume countdown at T-9 minutes (about 4:41 p.m.)

  • Start automatic ground launch sequencer (T-9 minutes)
  • Retract orbiter crew access arm (T-7:30)
  • Start APU recorders (T-6:15)
  • Start auxiliary power units (T-5)
  • Terminate liquid oxygen replenish (T-4:55)
  • Start orbiter aerosurface profile test (T-3:55)
  • Start main engine gimbal profile test (T-3:30)
  • Pressurize liquid oxygen tank (T-2:55)
  • Begin retracting the gaseous oxygen vent arm (T-2:50)
  • Fuel cells to internal reactants (T-2:35)
  • Pressurize liquid hydrogen tank (T-1:57)
  • Deactivate bi-pod heaters (T-1:52)
  • Deactivate solid rocket booster joint heaters (T-0:50 seconds)
  • Orbiter transfers from ground to internal power (T-0:50 seconds)
  • Ground launch sequencer go for auto sequence start (T-0:31 seconds)
  • Booster gimbal profile (T-0:21 seconds)
  • Ignition of three space shuttle main engines (T-6.6 seconds)
  • Booster ignition and liftoff (T-0)

    Preferred launch time: 4:50:24 p.m.

Flight Day Archive:  Countdown • 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12

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