Changes and additions:
- Jan. 3: Posting initial release
- Jan. 31: Updating timeline

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.

EST...........EVENT

Thu  02/04/10

01:30 AM......Call to stations
02:00 AM......Countdown begins
02:00 AM......BFC test, vehicle closeouts

06:00 PM......Begin four-hour built-in hold
06:45 PM......SSV PIC resistance test
10:00 PM......Resume countdown (T-27 hours)

10:00 PM......Begin PRSD load

Fri  02/05/10

06:00 AM......PRSD load complete
06:00 AM......PRSD off load

06:00 AM......Begin nine-hour built-in hold
11:00 AM......OMBUU securing
03:00 PM......Resume countdown (T-19 hours)

03:00 PM......Main engine preps
11:00 PM......Begin 13-hour 14-minute built-in hold

Sat  02/06/10

02:34 AM......Comm activation
04:04 AM......Flight crew equipment late stow
08:00 AM......RSS retraction
10:04 AM......Ascent switch list
12:14 PM......Resume countdown
12:34 PM......Pad clear of non-essential personnel
12:34 PM......APU bite test
01:24 PM......Fuel cell activation
02:14 PM......Booster joint heater activation
02:44 PM......MEC pre-flight bite test
02:59 PM......Tanking weather update
03:44 PM......Final fueling preps; launch area clear
04:14 PM......Red crew assembled
04:59 PM......Fuel cell integrity checks complete

05:14 PM......Begin 2-hour built-in hold (T-minus 6 hours)
05:24 PM......Safe-and-arm PIC test
06:14 PM......External tank ready for loading
06:37 PM......Mission management team tanking meeting
07:14 PM......Resume countdown (T-minus 6 hours)

07:14 PM......LO2, LH2 transfer line chilldown
07:24 PM......Main propulsion system chill down
07:24 PM......LH2 slow fill
07:54 PM......LO2 slow fill
07:59 PM......Hydrogen ECO sensors go wet
08:04 PM......LO2 fast fill
08:07 PM......Crew medical checks
08:14 PM......LH2 fast fill
10:09 PM......LH2 topping
10:14 PM......LH2 replenish
10:14 PM......LO2 replenish

10:14 PM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
10:14 PM......Closeout crew to white room
10:14 PM......External tank in stable replenish mode
10:29 PM......Astronaut support personnel comm checks
10:59 PM......Pre-ingress switch reconfig

Sun  02/07/10

12:14 AM......Final crew weather briefing
12:19 AM......Crew suit up begins
12:44 AM......Resume countdown (T-minus 3 hours)

12:59 AM......Crew departs O&C building
01:19 AM......Crew ingress
02:09 AM......Astronaut comm checks
02:34 AM......Hatch closure
03:04 AM......White room closeout

03:24 AM......Begin 10-minute built-in hold (T-minus 20m)
03:34 AM......NASA test director countdown briefing
03:34 AM......Resume countdown (T-minus 20m)

03:35 AM......Backup flight computer to OPS 1
03:39 AM......KSC area clear to launch

03:45 AM......Begin final built-in hold (T-minus 9m)
04:15:47 AM...NTD launch status verification
04:30:47 AM...Resume countdown (T-minus 9m)

04:34:47 AM...Orbiter access arm retraction
04:34:47 AM...Launch window opens
04:34:47 AM...Hydraulic power system (APU) start
04:34:52 AM...Terminate LO2 replenish
04:35:47 AM...Purge sequence 4 hydraulic test
04:35:47 AM...IMUs to inertial
04:35:52 AM...Aerosurface profile
04:36:17 AM...Main engine steering test
04:36:52 AM...LO2 tank pressurization
04:37:12 AM...Fuel cells to internal reactants
04:37:17 AM...Clear caution-and-warning memory
04:37:47 AM...Crew closes visors
04:37:50 AM...LH2 tank pressurization
04:38:57 AM...SRB joint heater deactivation
04:39:16 AM...Shuttle GPCs take control of countdown
04:39:26 AM...SRB steering test
04:39:40 AM...Main engine start (T-6.6 seconds)
04:39:47 AM...SRB ignition (LAUNCH)