The Atlas V rocket is on internal power. Liftoff is now only two minutes away.
Only four minutes left in the countdown! Launch is coming up at 10:44 p.m.
The MMS spacecraft is confirmed on internal power.
Lebo and United Space Alliance also are “go” to pick up the count at the T-4 minute mark. The hold will be released at 10:40 p.m.
The MMS spacecraft is switching from ground to internal power.
Baez has polled his team members and confirmed all are ready to move into the terminal countdown at the end of the T-4 minute hold.
When the countdown clock ticks down to zero, the Atlas V’s first-stage engine and two solid rocket boosters will ignite, together generating about one and a half million pounds of thrust at sea level. The vehicle will go supersonic shortly before it flies through the area of maximum dynamic pressure, or “max Q,” about a minute and two seconds into the flight. The boosters burn out and jettison approximately two minutes after liftoff.
Just past the four-minute mark, several key events happen one after another in about 20 seconds: the Atlas booster engine cuts off, the Atlas and Centaur separate, the Centaur’s engine ignites, and the payload fairing is jettisoned. The Centaur engine will burn until 13-and-a-half minutes into flight. At that point, it performs its first cutoff, beginning a 59-minute coast phase.
Launch is scheduled for 10:44 p.m.
Tonight’s launch weather forecast has improved to 90 percent “go.”
“All LCCs are ‘go’ and expected to remain ‘go,’ ” 45th Weather Squadron Officer Clay Flinn reported, referring to a set of rules known as Launch Commit Criteria (LCC).
Countdown clocks have paused for 30 minutes, the final built-in hold of the night. Coming up, NASA Launch Manager Omar Baez and ULA Launch Conductor Doug Lebo will both check in with their teams one more time to make sure the Atlas V, MMS and Eastern Range are ready to proceed.
The countdown will enter a 30-minute hold at the T-4 minute mark at 10:10 p.m. During the hold, managers will conduct a final “go-no go” poll for launch.