Mohawk Valley Astronomical Society

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Jumping Over Jupiter

by Perry Pezzolanella, MVAS

Jupiter is the largest of all the planets being ten times larger than Earth. Winds howl over 400 miles per hour with hurricanes raging for centuries. Lightning is so powerful that it could vaporize a city and radiation is so intense that it could kill a person or disable a spacecraft instantly. A world of such violence and extremes demands to be explored in detail.

A new mission, known as the Jupiter Polar Orbiter, is being designed to explore Jupiter. It is fittingly called Juno as she was the god-sister-wife of Jupiter and maintained a jealous vigil over her god-husband’s frivolous activities. When Jupiter had his tryst with Io, he spread a veil of clouds around the entire planet to conceal his activities. Juno was keen to this and used her special powers to penetrate the clouds and reveal the true nature of Jupiter. It may seem odd to have another mission to Jupiter so soon after the highly successful Galileo mission, but Galileo primarily explored the four largest moons: Io, Europa, Ganymede, and Callisto. It did not study Jupiter up close due to the intense radiation closer in and remained beyond the orbit of Io throughout most of the mission. The probe that Galileo released into Jupiter’s atmosphere survived for 75 minutes, but only sampled the upper levels and had the misfortune of falling through a dry slot; therefore, it did not sample the moisture-rich clouds. Many questions remained and new ones emerged. This dedicated orbiter will investigate Jupiter’s origin, interior structure, atmospheric composition and dynamics, and the polar magnetosphere.

Juno will be a spinning, solar powered spacecraft, which will be the first time that a spacecraft beyond the asteroid belt does not rely on thermo-nuclear generators for power. It will be put in polar orbit around Jupiter in order to perform detailed gravitational measurements to determine if there is a core of rock and ice, and how large it might be. The polar orbit will assure global coverage and complete views of the aurora. Juno will fly as close as 2700 miles above the cloud tops, which will keep it well below the dangerous radiation belt. It will explore the polar magnetosphere by mapping the magnetic fields and measure the number of charged particles interacting with the atmosphere that generate the dynamic aurora. Radio wave instruments will gather data to determine how the charged particles are accelerated in Jupiter’s magnetosphere. The instruments will be able to penetrate deep into Jupiter’s massive atmosphere, much deeper than the Galileo entry probe, to measure the internal convection far below the visible cloud tops. Juno will be able to detect the amount of water, ammonia, and methane deep in the atmosphere and may provide an answer as to why the Great Red Spot is reddish and why this super-hurricane has persisted since it was first seen nearly 400 years ago. Critical measurements will be made of the temperatures and wind velocities at different levels with hopes of discovering what drives the huge storms and powerful winds.

Juno will also carry an imager known as the JunoCam, which will be able to make high resolution photographs of the clouds and thunderstorms, and should be able to photograph the closer moons: Amalthea and Io. It will use three filters mounted directly on the detector to obtain the first close up color images of the poles. This camera will also be able to make movies of the swirling clouds and storms, which might lead to some of the most exciting discoveries of the mission. As part of a public engagement program, there are plans to invite students to work alongside the science team to capture the images and video once Juno is in orbit around Jupiter.

Juno is scheduled to launch during August 11-31, 2011 at a cost not to exceed $700 million. It will arrive at Jupiter on October 19, 2016 after a gravity assist from an Earth flyby on October 17-18, 2013. The goal will be to try to understand Jupiter’s origin and evolution. By better understanding Jupiter, we should be able to better understand the other gas giants: Saturn, Uranus, and Neptune, along with Jupiter’s role in the formation of the Solar System.