Countdown Begins for Artemis II Wet Dress Rehearsal
Photo credit: NASA-Joel Kowsky
Kennedy Space Center, FL (January 31st, 2026) - NASA’s Space Launch System (SLS) rocket and Orion spacecraft are secured to the mobile launcher at Launch Pad 39B at NASA’s Kennedy Space Center in Florida as the agency moves into a critical prelaunch milestone for Artemis II.
The countdown for the Artemis II wet dress rehearsal officially began at 8:13 p.m. EST, marking L-48 hours, 40 minutes ahead of the opening of a simulated launch window scheduled for 9:00 p.m. Monday, Feb. 2. The test is expected to conclude at approximately 1:00 a.m. on Feb. 3.
The wet dress rehearsal is designed to fully exercise launch-day procedures and systems. Launch controllers at Kennedy Space Center, along with supporting teams at NASA Johnson Space Center in Houston and other NASA facilities, will execute a complete countdown sequence. This includes loading super-cold liquid oxygen (LOX) and liquid hydrogen (LH2) propellants into the SLS rocket, conducting a simulated launch countdown, practicing countdown holds and recycle procedures, and ultimately draining the propellant to rehearse scrub operations.
These steps are essential to confirming that hardware, software, and teams are fully prepared for launch day operations.
A 24/7 live video feed of the rocket at the pad continues online. NASA will also provide a dedicated tanking feed during propellant loading, along with real-time blog updates throughout the fueling day.
Understanding the Countdown
The countdown uses both “L-minus” and “T-minus” timing.
L-minus (L-) tracks the time remaining until liftoff in hours and minutes.
T-minus (T-) marks a precise sequence of automated and manual events leading to launch.
Planned pauses, known as holds, are built into the countdown to target a specific launch window and provide schedule flexibility. During holds, the T-clock stops, while L-time continues to advance.
During this rehearsal, teams will:
Pause at T-1 minute, 30 seconds for up to three minutes
Resume the count to T-33 seconds, then stop
Recycle the clock back to T-10 minutes
Conduct a second terminal count down to approximately T-33 seconds
This sequence simulates real-world launch conditions, including potential weather or technical constraints. At the conclusion of the test, propellants will be drained and engineers will review all data before establishing an official launch date.
While the Artemis II astronauts are not participating directly, crew-related milestones are integrated into the timeline. The Artemis closeout crew will rehearse procedures such as closing the Orion crew module and launch abort system hatches.
Countdown Timeline (All Times Approximate)
L-49 Hours, 15 Minutes and Counting
L-49H 15M: Launch team reports to stations; countdown begins
L-48H 40M: Countdown clock starts
L-47H 30M – L-38H 30M: Sound suppression water tank fill
L-48H 45M – L-39H 45M: LOX/LH2 system prep for vehicle loading
L-40H 30M – L-39H: ICPS powered up
L-39H 30M – L-38H 45M: Core stage powered up
L-38H 45M – L-34H 30M: RS-25 engine final preparations
L-34 Hours, 30 Minutes and Counting
L-33H 45M – L-33H 10M: ICPS powered down
L-32H 30M – L-28H 30M: Orion batteries charged to 100%
L-30H 30M – L-23H 30M: Core stage battery charging
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
L-14H 30M – L-13H: Non-essential personnel depart LC-39B
L-13H 15M – L-11H 05M: GN2 changeover and vehicle cavity inerting
L-12H 45M – L-11H 15M: Ground Launch Sequencer (GLS) activation
L-11 Hours, 40 Minutes and Counting
L-11H 35M – L-9H 20M: Built-in 2 hr 15 min hold
L-11H 40M – L-10H 30M: Weather and tanking briefing
L-10H 20M: Go/No-Go for tanking
L-10H 10M – L-9H 50M: Core stage LOX chilldown
L-10H 10M – L-9H 25M: Core stage LH2 chilldown
L-10H 20M – L-9H: Orion cold soak
L-10 Hours and Counting
L-9H 25M – L-9H: Core stage LH2 slow fill
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 10M – L-7H 25M: ICPS LH2 fast fill
L-7H 30M – Terminal Count: Core stage LH2 replenish
L-6 Hours and Counting
L-6H – L-5H 15M: ICPS LOX fast fill
L-5H 40M: Stage pad rescue / closeout crew assemble
L-4H 40M: Start 40-minute built-in hold
L-4H 30M – L-4H 20M: Crew module hatch closure
L-2H 40M – L-2H 20M: Launch Abort System hatch closure
L-1H 10M: Launch Director briefing
L-1H 45M – L-1H 40M: Closeout crew departs pad
L-40 Minutes and Holding
L-40M: Built-in 30-minute hold
T-10 Minutes and Counting
T-10M: GLS initiates terminal count
T-8M: Crew access arm retracts
T-6M: Core stage tank pressurization / Orion internal power
T-4M: Core stage APU start
T-1M 30S: Planned three-minute hold
T-33S: GLS sends go for automated launch sequencer / cutoff-recycle
During terminal count, teams retain multiple options to hold or recycle the clock depending on timing and launch window constraints. Any issue after handover to the automated launch sequencer on launch day would result in ending the attempt.
This wet dress rehearsal represents one of the final major tests before Artemis II carries astronauts around the Moon and back to Earth.