At the prelaunch news conference Tuesday, the twin moon-bound GRAIL spacecraft and the United Launch Alliance Delta II rocket that will send them on their mission were reported ready to fly, with the late-summer Florida weather presenting the only question for launch day.
Launch Weather Officer Joel Tumbiolo reported that a stationary front that will be parked over the state and plume of tropical moisture will produce anvil clouds and local showers that give the launch team a 40 percent chance of acceptable weather at liftoff time on Thursday. The same conditions will continue on Friday, with an improving weather picture going into the weekend.
Earlier in the day, the final Launch Readiness Review was conducted and the rocket and spacecraft were given a "go" for launch from Cape Canaveral Air Force Station's Space Launch Complex 17B in Florida. There are two instantaneous launch windows at 8:37:06 a.m. and 9:16:12 a.m. EDT.