Author: Anna Heiney

The gantry-like strongback is lowering away from the Falcon 9 rocket in anticipation of liftoff.

NASA, NOAA and SpaceX managers have completed their polls and declared Jason-3 “go” for launch, kicking off the final phase of the countdown, known as the terminal count. All systems are operating autonomously until liftoff. Weather remains “go.”

Launch is now only 10 minutes away.

SpaceX has polled its team of controllers and has reported “go” to begin terminal count.

NASA Launch Manager Tim Dunn just conducted a poll to verify his team is “go” for launch at 1:42:18 p.m. EST.

The countdown continues to progress smoothly toward liftoff of the SpaceX Falcon 9 rocket carrying the Jason-3 satellite. Launch remains scheduled for 10:42 a.m. PST / 1:42 p.m. EST at the start of a 30-second window of opportunity. The spacecraft is reported “green” and the Western Range is conducting a final check of its tracking systems.

Since the Jason-3 satellite needs to carry on the work of Jason-2 and Jason-1, it will fly at an altitude of about 1300 km on the same orbital track as its predecessors, making observations over the same location every 9.9 days.

Launch Weather Officer Lt. Joseph Round just briefed the launch team on weather conditions now and at launch time, and the forecast is unchanged. There is no chance of violating any  weather-related launch constraints; weather is “green,” or “go,” on all criteria. Although the launch pad remains socked in with coastal fog, this is not a concern for launch. Upper-level winds are “green” as well.

Fog rolls across Space Launch Complex 4 at Vandenberg Air Force Base in California, where the SpaceX Falcon 9 awaits launch. Photo credit: NASA Television

“Flying 1300 km high, at 6 km per second, while measuring sea surface heights to about 4 cm,
requires a pretty sophisticated set of instruments,” Spacecraft Mission Director Parag Vaze, Jason-3 project manager at the Jet Propulsion Laboratory, said Friday.

Jason-3’s primary instrument is the Poseidon-3B Altimeter, a radar altimeter that measures variations in the sea level across the world’s oceans with an accuracy as high as 1.3 inches (or 3.3 centimeters). Its goal: an accuracy as high as 1 inch (or 2.5 centimeters). For a full rundown on all the instrumentation on board, visit http://www.nesdis.noaa.gov/jason-3/press.html.

The Jason-3 satellite weighs about 1,100 pounds and is about the size of a minivan — 3.3 feet by 3.3 feet by 12.1 feet — once its solar panels are deployed.

About 154 seconds after launch, the main engine will cut off, followed by separation of the first stage about three seconds later.

The second-stage engine will  ignite after another eight seconds. Half a minute into the second-stage burn, the payload fairing will be jettisoned, having done its job of protecting the Jason-3 satellite during the first three minutes of flight. The first cutoff of the second-stage engine will take place nine minutes after liftoff. At this point the Jason-3 spacecraft and Falcon 9 second stage will have entered a 46-minute coast phase.

The second-stage engine will ignite for its second burn about 55 minutes after launch. Once Jason-3 has reached the desired orbit, the rocket will separate from the spacecraft about half a minute later, nearly 56 minutes after liftoff.