There will be one more built-in hold at T-4 minutes, and launch management will take that opportunity to verify the Delta II rocket, JPSS-1 spacecraft and all other necessary assets are ready for launch. The countdown will resume at 1:43 a.m. At 1:47 a.m., the Delta II rocket’s main engine and six of its nine solid rocket motors will ignite, and JPSS-1 will be on its way into polar orbit.
Watch for a chain of events starting at about 4 minutes, 20 seconds after liftoff: the main engine will cut off (MECO), the first and second stages will separate, the rocket’s second-stage engine will start its first burn, then the payload fairing will separate and fall away. The entire sequence takes less than 20 seconds.
The second-stage engine cuts off (SECO 1) about 10-and-a-half minutes into the flight, starting a coast phase lasting approximately 40 minutes. At the end of the coast phase, the engine ignites again for a short burn — less than half a minute — with JPSS-1 spacecraft separation expected 57 minutes after liftoff. An additional quick engine burn then will be followed by deployment of the CubeSats.