Changes and additions:
- April 9: Posting initial release
- April 23: Updating throughout
- April 28: Updating for new May 11 launch date

Editor's Note: As of this writing, NASA flight planners are targeting launch 20 minutes after the opening of the Hubble launch window to improve ascent performance. A final 20-minute hold in the countdown at the T-minus nine-minute mark (timed from the opening of the window) will be extended as required to hit the desired launch time of 2:01 p.m. Updates will be posted as warranted.

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



Fri  05/08/09

03:30 PM......Call to stations
04:00 PM......Countdown begins

Sat  05/09/09

02:00 AM......Fuel cell reactant load preps
06:15 AM......MEC/SRB power up
06:45 AM......Clear crew module

08:00 AM......Begin 4-hour built-in hold
08:00 AM......Clear blast danger area
08:45 AM......Orbiter pyro-initiator controller test
08:55 AM......SRB PIC test
09:55 AM......Master events controller pre-flight BITE test
12:00 PM......Resume countdown

01:30 PM......Fuel cell oxygen loading begins
04:00 PM......Fuel cell oxygen load complete
04:00 PM......Fuel cell hydrogen loading begins
06:30 PM......Fuel cell hydrogen loading complete
07:30 PM......Pad open; ingress white room

08:00 PM......Begin 4-hour built-in hold
08:30 PM......OMBUU demate
11:00 PM......Crew module clean and vacuum complete
11:30 PM......Aft engine compartment purge

Sun  05/10/09

12:00 AM......Countdown resumes

12:00 AM......Main engine preps
12:00 AM......MECs 1 and 2 on; avionics system checkout
01:00 AM......SSME pneumatics checkout
01:30 AM......Deflate RSS dock seals; tile inspection
02:00 AM......Tile inspection
06:00 AM......TSM prepped for fueling

08:00 AM......Begin 13-hour 41-minute hold
09:00 AM......Debris inspection
09:30 AM......ASP crew module inspection
09:30 AM......OIS communications check
09:45 AM......JSC flight control team on station
11:30 AM......Comm activation
12:00 PM......Crew module voice checks
12:15 PM......Crew weather briefing
01:00 PM......Flight crew equipment late stow
05:00 PM......RSS to park position
06:00 PM......Final TPS, debris inspection
07:00 PM......Ascent switch list
09:41 PM......Resume countdown

09:41 PM......ASP cockpit config
09:41 PM......APU bite test
10:51 PM......Fuel cell activation
11:41 PM......Pad clear of non-essential personnel
11:41 PM......Booster joint heater activation
11:41 PM......MCC-H to launch comm

Mon  05/11/09

12:11 AM......MEC pre-flight bite test
12:26 AM......Tanking weather update
01:41 AM......Red crew assembled
01:56 AM......Final fueling preps; launch area clear
02:26 AM......Fuel cell integrity checks complete

02:41 AM......Begin 2-hour built-in hold (T-minus 6 hours)
02:51 AM......Safe-and-arm PIC test
03:41 AM......External tank ready for loading
04:06 AM......Mission management team tanking meeting
04:41 AM......Resume countdown (T-minus 6 hours)

04:41 AM......LO2, LH2 transfer line chilldown
04:51 AM......Main propulsion system chill down
04:51 AM......LH2 slow fill
05:21 AM......LO2 slow fill
05:26 AM......Hydrogen ECO sensors go wet
05:31 AM......LO2 fast fill
05:41 AM......LH2 fast fill
06:00 AM......Crew wakeup
06:56 AM......LH2 topping
07:41 AM......LH2 replenish
07:41 AM......LO2 replenish

07:41 AM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
07:41 AM......Closeout crew to white room
07:56 AM......Astronaut support personnel comm checks
08:30 AM......NASA TV coverage begins
08:41 AM......Pre-ingress switch reconfig
09:36 AM......Final crew weather briefing
09:46 AM......Crew suit up begins
09:56 AM......Crew departs O&C building
10:11 AM......Resume countdown (T-minus 3 hours)

10:26 AM......Crew ingress
11:21 AM......Astronaut comm checks
11:41 AM......Hatch closure
12:16 PM......White room closeout

12:51 PM......Begin 10-minute built-in hold (T-minus 20m)
12:53 PM......NASA test director countdown briefing
01:01 PM......Resume countdown (T-minus 20m)

01:02 PM......Backup flight computer to OPS 1
01:06 PM......KSC area clear to launch

01:12 PM......Begin final built-in hold (T-minus 9m)
01:32 PM......NTD launch status verification
01:41:49 PM...Launch window opens
01:52:49 PM...Resume countdown (T-minus 9m)

01:54:19 PM...Orbiter access arm retraction
01:56:49 PM...Hydraulic power system (APU) start
01:56:54 PM...Terminate LO2 replenish
01:57:49 PM...Purge sequence 4 hydraulic test
01:57:49 PM...IMUs to inertial
01:57:54 PM...Aerosurface profile
01:58:19 PM...Main engine steering test
01:58:54 PM...LO2 tank pressurization
01:59:14 PM...Fuel cells to internal reactants
01:59:19 PM...Clear caution-and-warning memory
01:59:49 PM...Crew closes visors
01:59:52 PM...LH2 tank pressurization
02:00:59 PM...SRB joint heater deactivation
02:01:18 PM...Shuttle GPCs take control of countdown
02:01:28 PM...SRB steering test
02:01:42 PM...Main engine start (T-6.6 seconds)
02:01:49 PM...SRB ignition (LAUNCH)