NASAのインスタグラム(nasa) - 10月21日 00時10分

Earth -- as seen by the Juno spacecraft flying by our home planet on October 9, 2013: In this image of Earth taken by JunoCam, you can see observations made during Juno’s Earth flyby gravity assist that was completed earlier this month. Several Juno science instruments made planned observations during the approach to Earth, including the Advanced Stellar Compass, JunoCam and Waves. These observations provided a useful opportunity to test the instruments during a close planetary encounter and ensure that they work as designed. The main goal of the flyby – to give the spacecraft the boost it needed in order to reach Jupiter – was accomplished successfully.

The Juno spacecraft was launched from Kennedy Space Center on August 5, 2011 toward Jupiter. Juno’s rocket, the Atlas 551, was only capable of giving Juno enough energy or speed to reach the asteroid belt, at which point the Sun’s gravity pulled Juno back toward the inner solar system. The Earth flyby gravity assist was planned as part of Juno’s trajectory to increase the spacecraft’s speed relative to the Sun so that it is sufficient to reach Jupiter. (The spacecraft’s speed relative to Earth remains constant.) Because of the flyby, Juno’s velocity relative to the Sun increases from 78,000 miles (126,000 kilometers) per hour to 87,000 miles (140,000 kilometers) per hour. Juno is moving much faster than satellites that orbit the Earth because Juno is orbiting the Sun, not Earth.

As of Oct. 17, Juno was approximately 4.4 million miles (7.1 million kilometers) from Earth. The one-way radio signal travel time between Earth and Juno is currently about 24 seconds. Juno has now traveled 1.01 billion miles (1.63 billion kilometers, or 10.9 AU) since launch. With the Earth flyby completed, Juno is now on course for arrival at Jupiter on July 4, 2016.

Image credit: NASA/JPL-Caltech/Malin Space Science Systems

#nasa #space #earth #juno #earthflyby #flyby #homeplanet #solarsystem #planets #jupiter #junocam

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