NASA's Juno spacecraft continues to give us amazing views of Jupiter, now from its fourth perijove pass.

Juno at Jupiter
An artist's concept of NASA's Juno spacecraft at Jupiter.

Jupiter definitely bucked the Groundhog Day trend this past February 2nd by never giving us the same view twice.

NASA's Juno spacecraft completed its fourth perijove pass just 2,670 miles (4,300 kilometers) above the Jovian cloud tops on Thursday, February 2nd at 12:57 UT / 7:57 AM EST. Despite previous problems, all eight instruments were available for this close science pass, and we're already seeing some great images from this past weekend.

“(February 2nd) may be 'Groundhog Day' here on Earth, but it's never Groundhog Day when you are flying past Jupiter,” said Scott Bolton (Southwest Research Institute) in a recent press release. “With every close flyby we are finding something new.”

Welcome to Jovian Antarctica

Juno is currently in a long elliptical orbit around Jupiter, taking 53 days to complete one circuit. The most recent pass brought Juno over the planet's southern pole, giving us a look at the cloud-streaked region dappled with the white ovals of storms. As Junocam was delivering the eye candy, Juno's Jovian Infrared Auroral Mapper (JIRAM) was also collecting data. We've already heard the exotic hiss and crackle of Jovian auroras courtesy of Juno, with more radio hits to come.

Jupiter's south pole
Juno looks down on Jupiter's south pole from a range of 47,600 miles (76,000 kilometers). This image was taken on February 2, 2017.
NASA / MSSS / SwRI / JPL / Caltech

We've also already seen some tantalizing science from these first few flybys. For example, the extensive magnetic field around Jupiter seems to be larger and more powerful than previously thought. Also, the zones and belts seen along the Jovian cloud tops may extend deep into the planet's interior, although how deep they go is still unclear. Expect to see the first peer-reviewed papers using Juno data over the next few months, as Jupiter gives up some of the secrets of its deep interior.

NASA has also invited the public to play a role during each perijove pass, voting on features for JunoCam to target and image on each successive flyby.

“We are looking forward to people visiting our website and becoming part of the JunoCam imaging team,” says Candy Hansen (Planetary Science Institute) in a recent press release. “It's up to the public to determine the best locations in Jupiter's atmosphere for JunoCam to capture during this flyby.”

An outbreak of storms captured by JunoCam over the southern pole of Jupiter. This image was taken during the recent perijove pass on February 2nd.
NASA / JPL / Caltech

A Look at Io

Juno is the first mission in the outer solar system to be equipped with three school-bus-sized solar panels instead of a nuclear generator. So the spacecraft must carefully thread the radiation-riddled belts of Jupiter on each pass. Although this means Juno won't get any closeups of the Jovian moons, it might, after a fashion, make an interesting set of observations of Io.

Juno's solar panels
One of Juno's three large solar panels, extended during ground testing.
NASA / JPL / Caltech / Lockheed Martin

Hundreds of volcanoes on the innermost Galilean moon fling charged particles into Jupiter's magnetic field, generating a plasma torus that surrounds the planet like a giant inner tube, as well as a flux tube that connects the moon to the planet's poles. Researchers Paul Withers and Phillip Phipps (both at Boston University) have proposed using radio occultation events to study the flow and composition of these plasma structures: Juno would record radio waves as they pass through the plasma torus. Previous missions to Jupiter have never attempted such an observation, and successive passes will bring Juno ever deeper into the lethal radiation belts for a closer listen. It remains to be seen whether NASA will add this task to Juno's to-do list.

Jupiter's magnetosphere
This diagram shows the plasma torus and flux tube created by charged particles spewed from Io's volcanoes.
John Spencer / Wikipedia CC-BY-SA3.0

Juno: The Long Game

Launched atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida on August 5, 2011, Juno arrived in orbit around Jupiter last year on July 4, 2016. Juno will eventually settle into a shorter series of 14-day orbits, which have been delayed pending team evaluation. A final burn of the main engine was planned for October 19, 2016, but the main engine did not perform as expected and was shut down as a precautionary measure.

The next perijove pass is set for March 27th.

Ultimately, spacecraft disposal via destructive atmospheric entry into Jupiter will occur about a year from now in February 2018. Though its core instrument bus is contained in a protective titanium cage, Juno sustains cumulative radiation damage on each perijove pass. The discard maneuver occurring next year while engineers still have control over the spacecraft is necessary to avoid possible future contamination of Jupiter's moons.

Crescent Jupiter
A false-color image of Jupiter's polar haze from JunoCam, taken on Juno's December 16, 2016, close approach. The image was processed by amateur astronomer Gerald Eichstädt.
NASA / JPL / Caltech / Gerald Eichstädt

After next year, the next possible mission to Jupiter in the pipeline is NASA's proposed Europa flyby mission and the European Space Agency's Jupiter Icy Moons Explorer (JUICE), though neither mission will launch until 2022 at the earliest.

Enjoy our coming year at Jupiter, courtesy of NASA's Juno.




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