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Juno Launch: Step-by-Step
Juno Launch: Step-by-Step
5 Aug 2011
(Source: Jet Propulsion Laboratory)

On Friday, Aug. 5, the launch window for NASA's Jupiter-bound Juno mission opens at 8:34 a.m. PDT (11:34 a.m. EDT) and extends through 9:43 a.m. PDT (12:43 p.m. EDT) at the Cape Canaveral Air Force Station in Florida. The satellite observatory is nestled inside the top of a United Launch Alliance Atlas V 551 rocket, the most powerful Atlas rocket in NASA's inventory.

The solar-powered Juno spacecraft will orbit Jupiter's poles 30 times to find out more about the gas giant's origins, structure, atmosphere and magnetosphere.

On launch day, Aug. 5, NASA TV commentary coverage of the countdown will begin at 6 a.m. PDT (9 a.m. EDT). The coverage will be webcast at .

Live countdown coverage on NASA's launch blog also begins at 6 a.m. PDT (9 a.m. EDT) at Coverage features real-time updates of countdown milestones, as well as streaming video clips highlighting launch preparations and liftoff. To access these features, and for more information on Juno, go to NASA's Juno website at, and to the mission site at .

The launch will also be online, with a live chat available, on Ustream TV, at . You can also follow the mission on Twitter at .

Here is a timeline of expected launch milestones:


Right after launch, the rocket will be airborne, carrying Juno up and over the Atlantic Ocean.
Solid rocket motors jettisoned -- occurs at about launch plus 106 seconds
The five solid rocket motors that have been providing some extra "get-up-and-go" for Juno's Atlas will complete their burn and be "stagger jettisoned." First, solids 1 and 2 separate from the rocket, followed 1.5 seconds later by solids 3, 4 and 5.

Fairing and stages separate -- occurs at about launch plus 4 minutes, 45 seconds

The Atlas's 68-footlong (21-meter-long) nose cone, or fairing, will separate and be jettisoned as planned, providing Juno and its Centaur upper stage with their first taste of exo-atmospheric existence. The Atlas V's 106.6 foot-long (33-meter-long) first-stage will have completed its tour of duty. The Centaur upper stage, which will provide the final kick for Juno, will begin the first of two scheduled burns.

Parking at 17,500 miles per hour -- occurs at about launch plus 10 minutes, 45 seconds

The Centaur upper stage will temporarily stop firing, as planned, and the rocket and Juno will begin a planned 30-minute coast phase, also known as a "parking orbit."

Centaur burns for Jupiter -- occurs at about launch plus 41 minutes, 33 seconds

The Atlas V's Centaur upper stage will begin a second burn. This approximately nine-minute-long burn will place Juno on its desired trajectory.

Spacecraft separates from Centaur -- occurs at about launch plus 56 minutes

The Juno spacecraft will separate from the Centaur upper stage of its Atlas V rocket. At this point, Jupiter will be five years and 1,740 million miles (2,800 million kilometers) away.


DC Agle 818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.

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Last Updated: 5 Aug 2011