The countdown for the Artemis II Wet Dress Rehearsal is underway at Kennedy Space Center. Yesterday at 8:13 PM ET, or L-48:40 hours, the simulated countdown began in preparation for a test launch window opening at 9 PM tomorrow, February 2nd.

Artemis II will not launch during this countdown, of course, as it is just a test countdown. The Artemis II crew will not be aboard during Orion the WDR.

Sometime around 1 AM ET Tuesday, or February 3rd, the WDR will conclude.

What Comes After The WDR

After the test cycle concludes, engineers and mission managers will review data gathered during the Wet Dress Rehearsal. This process may take a few days as each major system is reviewed. Since Artemis I, NASA has implemented changes to the liquid Hydrogen systems at LC-39B. That will be a particular area of concern, as H2 leaks bedeviled the Artemis I countdowns both in WDR and later on the night it launched.

After the Data Review, a Flight Readiness Review can be held, during which all aspects of the mission are reviewed: the SLS rocket, the Orion spacecraft, ground systems at the Cape, and the status of the recovery teams that would be first responders to a major anomaly, should one occur, and many others.

The FRR is last major review for the flight, and in it, the Artemis II management team will need to give the mission permission to proceed towards a launch. Only after that milestone is achieved will a launch date and time be announced by NASA.

The Wet Dress Rehearsal In Detail

L-49 Hours, 15 Minutes and Counting
Time	Activity
L-49H 15M	Launch team arrives on stations; countdown begins
L-48H 40M	Countdown clock begins
L-48H 45M – L-39H 45M	LOX/LH2 system preparations for vehicle loading
L-47H 30M – L-38H 30M	Fill water tank for sound suppression system
L-40H 30M – L-39H	Interim Cryogenic Propulsion Stage (ICPS) powered up
L-39H 30M – L-38H 45M	Core stage powered up
L-38H 45M – L-34H 30M	Final preparations of four RS-25 engines

L-34 Hours, 30 Minutes and Counting
Time	Activity
L-33H 45M – L-33H 10M	ICPS powered down
L-32H 30M – L-28H 30M	Charge Orion flight batteries to 100%
L-30H 30M – L-23H 30M	Charge core stage flight batteries
L-19H 30M – L-16H	Orion crew suit regulator leak checks
L-19H 15M – L-17H 45M	ICPS powered up for launch

L-15 Hours and Counting
Time	Activity
L-14H 30M – L-13H	All non-essential personnel leave Launch Complex 39B
L-13H 15M – L-11H 05M	Air-to-GN2 changeover and vehicle cavity inerting
L-12H 45M – L-11H 15M	Ground Launch Sequencer (GLS) activation

L-11 Hours, 40 Minutes and Counting
Time	Activity
L-11H 35M – L-9H 20M	Built-in hold: 2 hours, 15 minutes
L-11H 40M – L-10H 30M	Weather and tanking briefing
L-10H 20M	Go/No-Go decision to begin tanking
L-10H 20M – L-9H	Orion cold soak
L-10H 10M – L-9H 50M	Core stage LOX transfer line chilldown
L-10H 10M – L-9H 25M	Core stage LH2 chilldown

L-10 Hours and Counting
Time	Activity
L-9H 50M – L-9H 10M	Core stage LOX main propulsion system chilldown
L-9H 25M – L-9H	Core stage LH2 slow fill start
L-9H 20M	Resume T-Clock from T-8H 10M
L-9H 10M – L-8H 55M	Core stage LOX slow fill
L-9H – L-7H 40M	Core stage LH2 fast fill
L-8H 55M – L-6H 10M	Core stage LOX fast fill
L-8H 45M – L-8H 10M	ICPS LH2 chilldown
L-8H 10M – L-7H 25M	ICPS LH2 fast fill start
L-7H 45M – L-6H	ICPS LOX main propulsion system chilldown
L-7H 40M – L-7H 30M	Core stage LH2 topping
L-7H 30M – terminal	Core stage LH2 replenish
L-7H 25M – L-7H 05M	ICPS LH2 vent and relief test
L-7H 05M – L-6H 55M	ICPS LH2 tank topping start
L-6H 50M – terminal	ICPS LH2 replenish
L-6H 10M – L-5H 40M	Orion communications system activated (RF to Mission Control)
L-6H 10M – L-5H 40M	Core stage LOX topping

L-6 Hours and Counting
Time	Activity
L-6H – L-5H 15M	ICPS LOX fast fill
L-5H 40M – terminal	Core stage LOX replenish
L-5H 40M	Stage pad rescue; closeout crew assemble
L-5H 15M – L-5H	ICPS LOX vent and relief test
L-5H – L-4H 40M	ICPS LOX topping
L-4H 40M – terminal	ICPS LOX replenish; all stages replenish
L-4H 40M	Built-in hold: 40 minutes
L-4H 40M – L-4H 25M	Closeout crew to white room
L-4H 30M – L-4H 20M	Crew Module hatch preps and closure
L-4H 20M – L-3H 20M	Counterbalance mechanism hatch seal/press decay checks
L-3H 20M – L-2H 40M	Crew Module hatch service panel install/closeouts
L-2H 40M – L-2H 20M	Launch Abort System (LAS) hatch closure for flight
L-1H 45M – L-1H 40M	Closeout crew departs Launch Complex 39B
L-1H 10M	Launch Director brief – Flight vehicle/TPS scan results with CICE

L-40 Minutes and Holding
Time	Activity
L-40M	Built-in hold: 30 minutes

L-25 Minutes and Holding
Time	Activity
L-25M	Transition team to Orion-to-Earth comm loop following final NTD briefing
L-16M	Launch Director polls team for “Go” for launch

T-10 Minutes – Terminal Count
Time	Activity
T-10M	Ground Launch Sequencer (GLS) initiates terminal count
T-8M	Crew Access Arm retract
T-6M	GLS go for core stage tank pressurization; Orion set to internal power
T-5M 57S	Core stage LH2 terminate replenish
T-4M	GLS go for core stage APU start; APU starts; Core stage LOX terminate replenish
T-3M 30S	ICPS LOX terminate replenish
T-3M 10S	GLS go for purge sequence 4
T-2M 02S	ICPS switches to internal battery power
T-2M	Booster switches to internal battery power
T-1M 30S	Core stage switches to internal power; hold for 3-minute certification hold time verification
T-1M 20S	ICPS enters terminal countdown mode
T-50S	ICPS LH2 terminate replenish
T-33S	GLS sends “Go for Automated Launch Sequencer” command; GLS Cutoff/Recycle

Source: Countdown Begins for Artemis II Wet Dress Rehearsal, NASA, January 31, 2026.