* Astronomy

NASA's Jupiter-Bound Juno Changes its Orbit

Navigators and mission controllers for NASA's Juno mission to Jupiter watched their computer screens as their spacecraft successfully performed its first deep-space manoeuvre. This first firing of Juno's main engine is one of two planned to refine the spacecraft's trajectory, setting the stage for a gravity assist from a flyby of Earth on Oct 9, 2013. Juno will arrive at Jupiter on July 4, 2016.
The deep-space manoeuvre began at 22:57 UT yesterday, when the Leros-1b main engine was fired for 29 minutes 39 seconds. Based on telemetry, the Juno project team believes the burn was accurate, changing the spacecraft's velocity by about 344 metres a second while consuming about 376 kilograms of fuel.
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Juno mission to Jupiter may get more science assignments

Juno's elliptical path calls for it to loop back around Earth next year to pick up a gravitational slingshot boost toward Jupiter.
The meetings at Marshall, which manages the NASA program that includes Juno, were to review the plan in terms of cost, staffing and schedule, NASA said. They were to make sure NASA and the Juno team were on the same page even though Juno is still a long way from Jupiter.
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Title: Jupiter's Moment of Inertia: A Possible Determination by JUNO
Authors: Ravit Helled, John D. Anderson, Gerald Schubert, David J. Stevenson

The moment of inertia of a giant planet reveals important information about the planet's internal density structure and this information is not identical to that contained in the gravitational moments. The forthcoming Juno mission to Jupiter might determine Jupiter's normalised moment of inertia NMoI=C/MR² by measuring Jupiter's pole precession and the Lense-Thirring acceleration of the spacecraft (C is the axial moment of inertia, and M and R are Jupiter's mass and mean radius, respectively). We investigate the possible range of NMoI values for Jupiter based on its measured gravitational field using a simple core/envelope model of the planet assuming that J_2 and J_4 are perfectly known and are equal to their measured values. The model suggests that for fixed values of J_2 and J_4 a range of NMOI values between 0.2629 and 0.2645 can be found. The Radau-Darwin relation gives a NMoI value that is larger than the model values by less than 1%. A low NMoI of ~ 0.236, inferred from a dynamical model (Ward & Canup, 2006, ApJ, 640, L91) is inconsistent with this range, but the range is model dependent. Although we conclude that the NMoI is tightly constrained by the gravity coefficients, a measurement of Jupiter's NMoI to a few tenths of percent by Juno could provide an important constraint on Jupiter's internal structure. We carry out a simplified assessment of the error involved in Juno's possible determination of Jupiter's NMoI.

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