Changes and additions:
- August 19: Posting initial release

Editor's Note: The launch window is roughly 10 minutes long. To maximize ascent performance, NASA targets the middle of the window. A final hold in the countdown at the T-minus nine-minute mark will be extended as required to hit the desired launch time.

EDT...........EVENT

Fri  08/21/09

10:30 PM......Call to stations
11:00 PM......Countdown begins

Sat  08/22/09

09:00 AM......Fuel cell reactant load preps
02:30 PM......MEC/SRB power up
03:00 PM......Clear crew module

03:00 PM......Begin 4-hour built-in hold
03:00 PM......Clear blast danger area
03:45 PM......Orbiter pyro-initiator controller test
03:55 PM......SRB PIC test
04:55 PM......Master events controller pre-flight BITE test
07:00 PM......Resume countdown

08:30 PM......Fuel cell oxygen loading begins
11:00 PM......Fuel cell oxygen load complete
11:00 PM......Fuel cell hydrogen loading begins

Sun  08/23/09

01:30 AM......Fuel cell hydrogen loading complete
02:30 AM......Pad open; ingress white room

03:00 AM......Begin 9-hour built-in hold
03:00 AM......Begin PRSD offload
03:00 AM......Crew module clean and vacuum
08:00 AM......PRSD offload complete
08:30 AM......OMBUU demate
12:00 PM......Countdown resumes

12:00 PM......Main engine preps; MECs 1 and 2 on
02:00 PM......FRCS Tyvek cover final inspection
06:30 PM......Deflate RSS dock seals
07:00 PM......Tile inspection
07:00 PM......TSM prepped for fueling

08:00 PM......Begin 13-hour 11-minute hold
09:30 PM......OIS communications check
10:20 PM......JSC flight control team on station
11:30 PM......Comm activation
11:45 PM......L-1 engineering briefing

Mon  08/24/09

12:00 AM......Crew weather briefing
01:00 AM......Flight crew equipment late stow
05:00 AM......RSS to park position
06:00 AM......Final TPS, debris inspection
07:00 AM......Ascent switch list
09:11 AM......Resume countdown

09:11 AM......ASP cockpit config
09:41 AM......Pad clear of non-essential personnel
09:31 AM......APU bite test
10:21 AM......Fuel cell activation
11:11 AM......Booster joint heater activation
11:41 AM......MEC pre-flight bite test
11:56 AM......Tanking weather update
12:41 PM......Final fueling preps; launch area clear
01:11 PM......Red crew assembled
01:56 PM......Fuel cell integrity checks complete

02:11 PM......Begin 2-hour built-in hold (T-minus 6 hours)
02:21 PM......Safe-and-arm PIC test
02:41 PM......Crew wakeup
03:11 PM......External tank ready for loading
03:34 PM......Mission management team tanking meeting
03:41 PM......Crew medical checks
04:11 PM......Resume countdown (T-minus 6 hours)

04:11 PM......LO2, LH2 transfer line chilldown
04:21 PM......Main propulsion system chill down
04:21 PM......LH2 slow fill
04:51 PM......LO2 slow fill
04:56 PM......Hydrogen ECO sensors go wet
05:01 PM......LO2 fast fill
05:04 PM......Crew medical checks
05:11 PM......LH2 fast fill
07:06 PM......LH2 topping
07:11 PM......LH2 replenish
07:11 PM......LO2 replenish

07:11 PM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
07:11 PM......Closeout crew to white room
07:11 PM......External tank in stable replenish mode
07:26 PM......Astronaut support personnel comm checks
07:51 PM......Crew photo op (recorded)
07:56 PM......Pre-ingress switch reconfig
08:30 PM......NASA TV coverage begins
09:14 PM......Final crew weather briefing
09:24 PM......Crew suit up begins
09:41 PM......Resume countdown (T-minus 3 hours)

09:46 PM......Crew departs O&C building
10:16 PM......Crew ingress
11:06 PM......Astronaut comm checks
11:31 PM......Hatch closure

Tue  08/25/09

12:01 AM......White room closeout

12:21 AM......Begin 10-minute built-in hold (T-minus 20m)
12:31 AM......NASA test director countdown briefing
12:31 AM......Resume countdown (T-minus 20m)

12:32 AM......Backup flight computer to OPS 1
12:36 AM......KSC area clear to launch

12:42 AM......Begin final built-in hold (T-minus 9m)
01:07 AM......NTD launch status verification
01:27:05 AM...Resume countdown (T-minus 9m)

01:28:35 AM...Orbiter access arm retraction
01:31:05 AM...Launch window opens
01:31:05 AM...Hydraulic power system (APU) start
01:31:10 AM...Terminate LO2 replenish
01:32:05 AM...Purge sequence 4 hydraulic test
01:32:05 AM...IMUs to inertial
01:32:10 AM...Aerosurface steering profile
01:32:35 AM...Main engine steering test
01:33:10 AM...LO2 tank pressurization
01:33:15 AM...GOX vent arm retraction
01:33:30 AM...Fuel cells to internal reactants
01:33:35 AM...Clear caution-and-warning memory
01:34:05 AM...Crew closes visors
01:34:08 AM...LH2 tank pressurization
01:35:15 AM...Orbiter to internal power
01:35:34 AM...Shuttle computers take control of countdown
01:35:44 AM...SRB steering test
01:35:58 AM...Main engine start (T-6.6 seconds)
01:36:05 AM...SRB ignition (LAUNCH)