NASA's Soil Moisture Active Passive (SMAP) observatory, which will produce the highest-resolution and most accurate maps of soil moisture ever obtained from space, is set to launch Thursday, Jan. 29, at 6:20 a.m. PST (9:20 a.m. EST) from Vandenberg Air Force Base in California. A United Launch Alliance Delta II rocket will carry SMAP into orbit. The launch window lasts three minutes.

Below is a list of milestones expected to occur during the mission's launch phase, if all goes as planned:

+ Prior to liftoff, and 0.2 seconds after the launch sequence has commenced, three solid motors ignite. They burn for 1 minute and 5 seconds, but are not jettisoned until 1 minute and 39 seconds into flight.

+ Main Engine Cutoff (MECO) occurs approximately 4 minutes and 22 seconds into flight, followed 6 seconds later by Stage I-II separation.

+ After the second stage ignites, 4 minutes and 55 seconds after liftoff, the launch vehicle nose cone splits open like a clamshell and falls away as planned.

+ Second-Stage Engine Cutoff (SECO-1) occurs about 10 minutes and 44 seconds after liftoff, and the spacecraft coasts in an intermediate orbit.

+ The second stage restarts 51 minutes and 38 seconds after liftoff, then cuts off again as planned.

+ At 56 minutes and 51 seconds after liftoff, SMAP separates from the rocket, beginning its own journey around Earth. Subsequent maneuvers over several weeks will place the observatory in its final target orbit of 426 miles above Earth (685 kilometers). The separation event will be monitored with a video camera attached to the second stage.

+ The second stage of the rocket, now separated from SMAP, moves to a lower orbit for deployment of three CubeSat missions: Firebird-II (consisting of two CubeSats), EXOCUBE and GRIFEX. A final burn will send the second stage into a safe reentry over the southern Pacific Ocean.

+ About a minute after separation, the SMAP spacecraft begins to deploy its three-panel solar array. It then looks for, and turns the array toward, the sun and starts a slow "rotisserie" roll to begin recharging its batteries and maintain proper system temperatures.

+ SMAP communicates with Earth, relaying its signal through NASA's Tracking and Data Relay Satellites and ground stations. This is expected to happen within minutes after the spacecraft separates from its rocket.

+ Once ground controllers have determined SMAP is healthy and stable, SMAP begins its commissioning phase, in which all systems and instruments are checked out and calibrated. These activities are planned to last no longer than 90 days after launch, after which science operations begin.

On launch day, NASA TV launch commentary coverage of the countdown begins at 4 a.m. PST (7 a.m. EST). For information on receiving NASA TV, go here.