Spaceflight Now

Liftoff of the first of 38 Vulcan missions for Amazon Leo at 12:40:30 a.m. EST (1740:30 UTC). The Centaur upper stage is going through its final few minutes of its first burn before going into a coast phase.

Watch live: youtube.com/watch?v=qcA9uM…

📸: @mdcainjr

Teams conducted another readiness check and polled 'go' for launch once again. Liftoff of the Vulcan Leo 1 mission is set for 12:40:30 p.m. EST (1740:30).

Watch live: youtube.com/watch?v=qcA9uM…

Centaur liquid oxygen is continuing topping, but is not 'go' from their position at this moment. Teams are assessing if they will be able to launch as they have nine minutes remaining in the window.

Watch live: youtube.com/watch?v=qcA9uM…

ULA is looking at a new T-0 liftoff of the Vulcan Leo 1 mission at 12:40:30 p.m. EST (1740:30 UTC). Teams ran into an oscillation issue with the liquid hydrogen pressure relief valve that caused a hold at T-20 seconds.

Watch live: youtube.com/watch?v=qcA9uM…

Hold called at T-20 seconds on the Vulcan Leo 1 mission.

Watch live: youtube.com/watch?v=qcA9uM…