Advanced GPS Satellite set to Lift-off Tonight

United Launch Alliance will try again tonight to launch a Delta IV rocket with an advanced GPS satellite for the U.S. Air Force.

Tonight's launch window begins at 11PM EDT and lasts for 19 minutes. The current weather outlook forecasts a 70 percent chance of good weather in support of both fueling and launch operations here at Cape Canaveral Air Force Station.

This will be the fourth attempt in the past week to get Delta IV off the pad, following launch scrubs due to mechanical issues.

The latest scrub on Monday evening involved a countdown abort at T minus six seconds when the right hand solid rocket booster's nozzle steering vector control system relayed bad data to the control center.

The fifty-three foot long twin boosters on the Delta ignite at T-0 and burn the first 94 seconds of flight. Six seconds later they separate as the main stage RS-68 cryo-fueled engine burns for the next two and one-half minutes.

This evening's launch will mark the Delta program's golden anniversary of flight. This will be the twelfth Delta IV launch since it's first flight in 2002.

The mission's payload is the Global Positioning System 2F SV1 spacecraft for the Air Force. This enhanced tracking satellite is designed to operate for nearly twelve years as it soars high above earth in the GPS orbital plane of 11,000 miles high.

GPS 2F will assist the military with both aviation and land based support giving them two times better signal accuracy than the GPS 2R series. Schriever AFB's 50th Space Wing in Colorado will take over control of the new satellite following space craft separation.

The GPS 2F will separate from the Delta's smaller second stage at 2:33:03 am on Friday morning based on an on time launch from pad 37.