NASA’s Juno Spacecraft Images Big Dipper

NASA’s Jupiter-bound Juno spacecraft tested its JunoCam instrument on one of the icons of the night sky – the Big Dipper. Image credit: NASA/JPL-Caltech/SWRI/MSSS

In England it is known as the “Plough,” in Germany the “Great Cart,” and in Malaysia the “Seven Ploughs.” Since humanity first turned its eyes skyward, the seven northern hemisphere stars that compose the “Big Dipper” have been a welcome and familiar introduction to the heavens.

“I can recall as a kid making an imaginary line from the two stars that make up the right side of the Big Dipper’s bowl and extending it upward to find the North Star,” said Scott Bolton, principal investigator of NASA’s Juno mission to Jupiter from the Southwest Research Institute in San Antonio. “Now, the Big Dipper is helping me make sure the camera aboard Juno is ready to do its job.”

Launched on Aug. 5, 2011, the solar-powered Juno spacecraft is 279 days and 380 million miles (612 million kilometers) into its five-year, 1,905-million-mile (3,065-million-kilometer) journey to Jupiter.  Once there, the spacecraft will orbit the planet’s poles 33 times and use its nine instruments to image and probe beneath the gas giant’s obscuring cloud cover to learn more about Jupiter’s origins, structure, atmosphere and magnetosphere, and look for a potential solid planetary core. 


Juno Mission to Jupiter (Artist’s Concept)

One of those instruments, JunoCam, is tasked with taking closeups of the gas giant’s atmosphere. But, with four-and-a-half years to go before photons of light from Jupiter first fill its CCD (charge-coupled device), and a desire to certify the camera in flight, Juno’s mission planners took a page from their childhood and on March 21, aimed their camera at a familiar celestial landmark.

“I don’t know if it’s the first space-based image of the Big Dipper but, as it was taken when we were well beyond Mars orbit, it’s probably from the farthest out,” said Bolton. “But much more important than that is the simple fact that JunoCam, like the rest of this mission, works as advertised and is ready for its day in the sun – around Jupiter.”

The JunoCam test image of the Big Dipper is online at: .
Juno’s name comes from Greek and Roman mythology. The god Jupiter drew a veil of clouds around himself to hide his mischief, and his wife, the goddess Juno, was able to peer through the clouds and reveal Jupiter’s true nature….
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Jupiter’s Moment of Inertia: A Possible Determination by JUNO

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 normalized moment of inertia NMoI=C/MR^2 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.

Juno probe heads for Jupiter from Cape Canaveral

The Atlas 5 rocket launched from Cape Canaveral Air Force Station after a brief delay caused by a helium leak

A $1.1bn (£0.7bn) unmanned Nasa space mission has launched from Florida on a journey to the planet Jupiter.

The Juno spacecraft will cruise beyond Mars to put itself in orbit around the gas giant in 2016.

It is the first solar-powered mission to venture this far from the Sun.

The mission launched atop an Atlas 5 rocket from the Cape Canaveral Air Force Station on Friday at 12:25 local time (16:25 GMT; 17:25 BST), after a brief delay caused by a helium leak.

There were concerns with the helium charging system on the rocket’s Centaur upper stage, but a small leak on the “ground side” of the rocket was found to be the culprit.

“Today, with the launch of the Juno spacecraft, Nasa began a journey to yet another new frontier,” said the agency’s administrator Charles Bolden.

“The future of exploration includes cutting-edge science like this to help us better understand our Solar System and an ever-increasing array of challenging destinations.”

Pushing boundaries

At Jupiter, where the intensity of sunlight is only 1/25th of that at Earth, space missions would normally resort to a plutonium battery.

But Juno will instead travel with three wings coated with 18,000 solar cells.

“As a solar-panelled mission, we have to keep those solar panels facing the Sun and we never go into Jupiter’s shadow,” the mission’s chief scientist Scott Bolton told BBC News.

“Those are things we can do and still accomplish our science; it doesn’t hurt us. But it would have been easier if we could have pointed just any way we wanted. We’ve had to develop [a strategy], and in fact we’ve advanced solar cell technology in doing so.”

Juno’s mission is to probe the secrets of the Solar System by explaining the origin and evolution of its biggest planet.

The spacecraft’s remote sensing instruments will look down into the giant through the many layers and measure their composition, temperature, motion and other properties.

This should yield some remarkable new insights into the coloured bands that wrap around the planet, and a new perspective on the famous Great Red Spot – the colossal storm that has raged on Jupiter for hundreds of years.

Scientists also want to measure the abundance of water in the atmosphere – an indicator of how much oxygen was present in Jupiter’s region of the Solar System when it formed.

The probe will also try to settle old arguments over whether the planet hosts a rocky core or whether its gases go all the way down to the centre in an ever more compressed state.

And it will look for the deep swirling sea of liquid metallic hydrogen that many suspect is the driver behind Jupiter’s strong magnetic field.

Juno is the second in Nasa’s so called New Frontiers class missions. The first, New Horizons, was launched towards dwarf planet Pluto in 2006 and should arrive at its target in 2015.