Juno space probe reaches milestone in first lap around Jupiter

NASA's most ambitious Jupiter probe yet has reached 'apojove,' the turning point in Juno's first orbit around the gas giant.

Ringo H.W. Chiu/AP/File
Scott Bolton (l.) and Rick Nybakken, in a post-orbit insertion briefing at NASA's Jet Propulsion Laboratory on July 4 in Pasadena, Calif. On July 31, Juno reached 'apojove,' its furthest distance away from Jupiter during the first of its two elliptical 'capture orbits,' before it will settle into its 14-day data-gathering orbits in October.

Juno has already gone further into Jupiter's orbit than any space probe before it, and the satellite is now heading into the second half of its first full orbit around the solar system's largest planet.

When Juno arrived at Jupiter on July 4, it began the first of two 53-day "capture orbits." Having now reached "apojove," the furthest point from Jupiter during this long, elliptical orbit, Juno will now move closer and closer to the gas giant until it reaches "perijove," its closest approach, on Aug. 27. 

Juno's first lap of Jupiter represents the final step before the probe can settle into its scientific mission, collecting new data on the planet's surface and climate that astronomers believe will shed light on the solar system's formation. 

After the probe completes its first two orbits, it can start on its primary mission goals – locate the gas giant's core, if any, and search for water in Jupiter's atmosphere. The "precious" data Juno gathers, NASA scientists have said, will help them better understand how the gas giants formed, as The Christian Science Monitor's Jason Thomson wrote in June:

Like its namesake, Juno the spacecraft will peer beneath the thick clouds of the solar system’s largest planet to uncover secrets of Jupiter's formation and current conditions....

Jupiter is composed largely of hydrogen and helium, just like the sun, leading scientists to suppose that it, too, was born in the early days of our solar system, capturing material left over from the birth of our star. Because of the planet’s enormous mass, it may have retained its original composition, unlike Earth, providing an opportunity to peer into the past. 

With both the five-year trek from Earth to Jupiter and the risky, radiation-laden Jupiter-orbit insertion behind it, Juno has entered the final preparation phase. In October, after completing the two capture orbits, Juno will fire its engine to shorten its orbital period down to 14 days and begin its science mission.

"We're in an excellent state of health, with the spacecraft and all the instruments fully checked out and ready for our first up-close look at Jupiter," said Rick Nybakken, the project manager for Juno at NASA's Jet Propulsion Laboratory in Pasadena, Calif., in a press release last week.

During Juno's information-gathering skim through Jupiter's gassy atmosphere on Aug. 27, its cameras will turn on to catch the mission's first high-resolution images, the Monitor reported previously. Although Juno's primary goal in probing Jupiter's gassy envelope is scientific, the steady stream of photos beamed back to Earth will also help the public engage with the $1.1 billion project.  

Although this first capture orbit will return plenty of data and images, Juno will begin gathering steady data in October, the start of its official mission to study the planet's dense radiation output and magnetic fields before making a final dive into Jupiter's atmosphere in February 2018.

"For five years we've been focused on getting to Jupiter. Now we're there, and we're concentrating on beginning dozens of flybys of Jupiter to get the science we're after," said Scott Bolton, the primary investigator for Juno at San Antonio's Southwest Research Institute, in a NASA statement.

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