The countdown has entered a 40-minute hold at T-9 minutes. During the hold, a series of polls will be conducted to verify the readiness of managers and engineers at Kennedy Space Center and Mission Control in Houston to proceed with launch. Liftoff still is targeted for 14:56:28 CEST.

Courtesy of JSC PAO Kyle Herring, here is the sequence of events as the countdown resumes.

SPACE SHUTTLE COUNTDOWN – T-9 MINUTES TO MECO (Main Engine Cut-Off)

T Minus           EDT              EVENT
– 9:00              8:47:28 am    Countdown resumes at the T-9 minute mark
– 7:30              8:48:58 am    Orbiter Access Arm (OAA) retract
– 6:00              8:50:28 am    Verify Auxiliary Power Units (APU) ready to
start
– 5:00              8:51:28 am    Auxiliary Power Unit start
– 4:55              8:51:33 am    Liquid Oxygen replenish terminate
– 4:00              8:52:28 am    Purge Sequence 4 hydraulic test
– 4:00              8:52:28 am    Inertial Measurement Units to inertial
– 3:55              8:52:33 am    Flight Control Surface profile test
– 3:30              8:52:58 am    Main Engine profile test
– 2:55              8:53:33 am    LO2 tank pressurization
– 2:50              8:53:38 am    Gaseous Oxygen Vent Hood retraction
– 2:35              8:53:53 am    Fuel Cells to internal reactants
– 2:30              8:53:58 am    Clear caution and warning memory
– 2:00              8:54:28 am    Crew closes visors & initiates O2 flow
– 1:57              8:54:31 am    Liquid Hydrogen tank pressurization
– 1:40              8:54:48 am    Solid Rocket Booster joint heater
deactivation
–   :50              8:55:38 am    Endeavour to internal power
–   :31              8:55:57 am    Onboard computers take control of
countdown (T-31 sec)
–   :21              8:56:07 am    Solid Rocket Booster steering test
–   :46              8:55:42 am    Launch window opens
–   :09              8:56:19 am    KSC ground commanding removed by GLS (T-9
sec)
–   :06.6           8:56:21 am    Main Engine start (T-6.6 seconds)
0                 8:56:28 am    LAUNCH (ISS 220 miles up & SE of
Halifax, Nova Scotia)

+  5:00            9:01:28 am    Launch window closes (Flight Day 3
rendezvous)
+  8:23            9:04:51 am    Main Engine Cutoff (MECO) commanded
+  8:29            9:04 57 am    Zero thrust – orbit is 136 x 36 statute
miles
+ 15:00             9:11 am        APU/Hydraulic shutdown
+ 25:00             9:21 am        APU heater tank/fuel line/water sys 1A,
2A, 3A
cockpit switches to “auto”
+ 37:00             9:33 am        OMS 2 Burn – target 202.5 x 141.5 statute
miles (TGO 2:49)