The Titan 2 rocket's pad at Vandenberg's Space Launch Complex-4 West. Photo: Justin Ray/Spaceflight Now

The Titan 2 rocket's 26-hour launch countdown begins this morning at Vandenberg Air Force Base for Wednesday's liftoff carrying a military weather satellite.

The Titan 2, a decommissioned Cold War Intercontinental Ballistic Missile modified by Lockheed Martin to launch satellites into space, is scheduled to lift off at 9:17 a.m. local time (1617 GMT; 12:17 p.m. EDT). A 10-minute launch window is available.

Officials gathered Monday to give approval for proceeding with the long-delayed mission to place the Defense Meteorological Satellite Program F16 spacecraft into polar-orbit.

"Everything is going fine," Tom Scanlan, Lockheed Martin's vice president of Titan programs, said in an interview Monday afternoon. "We just had the Launch Readiness Review with the Wing commander out here at Vandenberg. There are no issues being worked on the spacecraft, or on the booster or on the Range. So it looks like we are ready to launch."

The countdown is filled with final system checks and readying the launch pad for the liftoff. Unlike many rockets that are fueled during the countdown, the two-stage Titan 2 already has been loaded with its supply of storable propellants. Retraction of the mobile service tower from around the vehicle is expected to occur inside the final four hours of the count.

Wednesday's weather forecast is favorable for launching. Air Force meteorologists are predicting a 90 percent chance of meeting the launch weather rules with the only worry being gusty winds at the pad.

The launch time conditions are expected to include stratus clouds at 700 feet with 5/8ths sky coverage and tops at 1,100 feet, visibility of five nautical miles, northerly winds from 350 to 020 degrees at 5 to 10 knots, a temperature of 53 to 58 degrees F and fog in the area. Upper level winds will be from the west with a maximum of 65 knots around 45,000 feet.

The low clouds and fog could pose a problem for spectators along California's Central Coast trying to get a glimpse of the booster's ascent. Large crowds are expected to watch this launch since it will be the final Titan 2 rocket to fly. But Launch Weather Officer Lt. Breea Lemm reported Monday that the visibility shouldn't be greatly impacted.

"At the surface, weak on shore flow will enable a reestablishment of the marine layer, but this low-level stratus deck will be very thin and visibilities will not be significantly degraded."

"If we get fog, you hear a lot of rumble but you don't see much with respect to the launch. We hope it clears," said Scanlan. "We will keep our fingers crossed that everyone coming out to see it is going to be able to."

In any event, the fog isn't a constraint to launch.

"We will be able to launch through it," Scanlan said.

If the launch is delayed 24 hours, the forecast for Thursday calls for an 80 percent chance of acceptable weather conditions. Winds remain the only concern.

"Zonal flow remains aloft and in the lower levels expect a continuance of the marine layer," the launch weather officer reported. "Above the marine layer, a scattered layer of cirrus will be present at 30,000 to 32,000 feet. As the surface gradient tightens, expect surface winds to increase to 8-12 knots from the northwest. Upper level winds will increase slightly and continue from the west, reaching a maximum of 70 knots near 45,000 feet. Temperatures will remain in the upper 50's and low 60's, and no precipitation is expected."