T-11 hours and counting

Activate the orbiter's fuel cells

Clear the blast danger area of all nonessential personnel

Switch the orbiter's purge air to gaseous nitrogen

T-6 hours and holding

Mission Management Team and launch director receive weather update

Launch team verifies no violations of launch commit criteria before loading the external tank with propellants

Clear pad of all personnel

Chill-down of propellant transfer linesBegin loading the external tank with about 500,000 gallons of cryogenic propellants

T-6 hours and counting

Finish filling the external tank with its flight load of liquid hydrogen and liquid oxygen propellants

T-3 hours and holding

This built-in hold typically lasts two-and-a-half hours.

External tank loading enters stable replenish

Perform inertial measurement unit preflight calibration

Align Merritt Island Launch Area (MILA) tracking antennas

Final Inspection Team proceeds to the launch pad to conduct a detailed analysis of the vehicle as the team walks up and down the entire launch tower

Closeout Crew proceeds to the launch pad to configure the crew module for countdown and launch and assist the astronauts with entry into the orbiter

Televised weather briefingFlight crew weather briefing

Astronaut Support Person enters crew module and begins comm checks

T-3 hours and counting

Crew departs for the launch pad and, upon arriving at the pad, begins entry into the orbiter via the White Room

Complete close-out preparations in the launch pad's White Room

Check cockpit switch configurations

Astronauts perform air-to-ground voice checks with Launch Control (Kennedy Space Center) and Mission Control (Johnson Space Center)

Close the orbiter's crew hatch and check for leaks

Complete White Room close-out

Close-out crew retreats to fallback area