Due to concerns about engine, Juno to remain in elongated Jupiter orbit

Flyaway

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The Leros engine has commonalities with other engines that have called issues including MUOS 5 I believe.

“During a thorough review, we looked at multiple scenarios that would place Juno in a shorter-period orbit, but there was concern that another main engine burn could result in a less-than-desirable orbit,” said Rick Nybakken, Juno project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “The bottom line is a burn represented a risk to completion of Juno’s science objectives.”

Operating Juno beyond its designed lifetime comes with a price tag, too. The requested budget for Juno operations in fiscal year 2017 was $39.1 million, which was projected to fall to $14.5 million in 2018 as the mission came to a close. Now, if NASA must come up with an additional $100 to $150 million for an extended mission, those costs will almost certainly harm other missions in the agency’s science directorate.

https://arstechnica.com/science/2017/02/due-to-concerns-about-engine-juno-to-remain-in-elongated-jupiter-orbit/
 

Archibald

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How ironic ! Juno (notably its solar panels) was to be fried by Jupiter radiation belts, hence a short lived mission... fate has decided otherwise.
 

blackstar

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Archibald said:
How ironic ! Juno (notably its solar panels) was to be fried by Jupiter radiation belts, hence a short lived mission... fate has decided otherwise.

As I understand it, the maximum dose is encountered at closest approach. It will still have the same number of close approaches, but they will happen further apart because of the bigger orbit. Of course, a longer mission will cost more money.
 

Flyaway

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Juno in good health; decision point nears on mission's end or extension

https://www.nasaspaceflight.com/2018/02/juno-good-health-decision-point-missions-end-extension/
 

Flyaway

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Jupiter Abyss
NASA’s Juno spacecraft captured this view of an area within a Jovian jet stream showing a vortex that has an intensely dark center. Nearby, other features display bright, high altitude clouds that have puffed up into the sunlight.

The color-enhanced image was taken at 12:55 a.m. PDT (3:55 a.m. EDT) on May 29, 2019, as the spacecraft performed its 20th science flyby of Jupiter. At the time, Juno was about 9,200 miles (14,800 kilometers) from the planet's cloud tops, above approximately 52 degrees north latitude.
Citizen scientists Gerald Eichstädt and Seán Doran created and named this image using data from the spacecraft's JunoCam imager.

JunoCam's raw images are available for the public to peruse and process into image products at https://missionjuno.swri.edu/junocam/processing.

 

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'Shallow Lightning' and 'Mushballs' Reveal Ammonia to NASA's Juno Scientists

The spacecraft may have found where the colorless gas has been hiding on the solar system's biggest planetary inhabitant.

New results from NASA's Juno mission at Jupiter suggest our solar system's largest planet is home to what's called "shallow lightning." An unexpected form of electrical discharge, shallow lightning originates from clouds containing an ammonia-water solution, whereas lightning on Earth originates from water clouds.

Other new findings suggest the violent thunderstorms for which the gas giant is known may form slushy ammonia-rich hailstones Juno's science team calls "mushballs"; they theorize that mushballs essentially kidnap ammonia and water in the upper atmosphere and carry them into the depths of Jupiter's atmosphere.
 

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Possible Transient Luminous Events Observed in Jupiter's Upper Atmosphere

The Juno spacecraft has been in orbit around Jupiter since 2016. One of the instruments on this spacecraft is an ultraviolet spectrograph (UVS), which is primarily used to make ultraviolet images of Jupiter's auroras. During the first 4 years of the mission, the UVS has observed 11 transient bright flashes. These bright flashes look similar to lightning, but are located much higher in the atmosphere than the cloudy regions of Jupiter where lightning is generated. We suggest that these are observations of transient luminous events (TLEs) in Jupiter's upper atmosphere. In particular, we suggest that these are elves, sprites or sprite halos, three types of TLEs that produce spectacular flashes of light very high in the Earth's atmosphere in response to lightning strikes between clouds or between clouds and the ground. TLEs have previously only been observed on Earth, although theoretical and experimental work has predicted that they should also be present on other planets, including Jupiter. Comparing and contrasting TLE observations between Jupiter and Earth will improve our understanding of electrical activity in planetary atmospheres.

 

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Article looking at options for the Juno extended mission.


Announcement of extended missions for Juno & InSight.

 

Flyaway

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October 28, 2021
RELEASE 21-140
NASA’s Juno: Science Results Offer First 3D View of Jupiter Atmosphere

This illustration combines an image of Jupiter from the JunoCam instrument aboard NASA’s Juno spacecraft with a composite image of Earth to depict the size and depth of Jupiter’s Great Red Spot.

Credits: JunoCam Image data: NASA/JPL-Caltech/SwRI/MSSS; JunoCam Image processing by Kevin M. Gill (CC BY); Earth Image: NASA

New findings from NASA’s Juno probe orbiting Jupiter provide a fuller picture of how the planet’s distinctive and colorful atmospheric features offer clues about the unseen processes below its clouds. The results highlight the inner workings of the belts and zones of clouds encircling Jupiter, as well as its polar cyclones and even the Great Red Spot.

Researchers published several papers on Juno’s atmospheric discoveries today in the journal Science and the Journal of Geophysical Research: Planets. Additional papers appeared in two recent issues of Geophysical Research Letters.

“These new observations from Juno open up a treasure chest of new information about Jupiter’s enigmatic observable features,” said Lori Glaze, director of NASA’s Planetary Science Division at the agency’s headquarters in Washington. “Each paper sheds light on different aspects of the planet’s atmospheric processes – a wonderful example of how our internationally-diverse science teams strengthen understanding of our solar system.”

Juno entered Jupiter’s orbit in 2016. During each of the spacecraft’s 37 passes of the planet to date, a specialized suite of instruments has peered below its turbulent cloud deck.

“Previously, Juno surprised us with hints that phenomena in Jupiter’s atmosphere went deeper than expected,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio and lead author of the Journal Science paper on the depth of Jupiter’s vortices. “Now, we’re starting to put all these individual pieces together and getting our first real understanding of how Jupiter’s beautiful and violent atmosphere works – in 3D.”

Juno’s microwave radiometer (MWR) allows mission scientists to peer beneath Jupiter’s cloud tops and probe the structure of its numerous vortex storms. The most famous of these storms is the iconic anticyclone known as the Great Red Spot. Wider than Earth, this crimson vortex has intrigued scientists since its discovery almost two centuries ago.

The new results show that the cyclones are warmer on top, with lower atmospheric densities, while they are colder at the bottom, with higher densities. Anticyclones, which rotate in the opposite direction, are colder at the top but warmer at the bottom.

The findings also indicate these storms are far taller than expected, with some extending 60 miles (100 kilometers) below the cloud tops and others, including the Great Red Spot, extending over 200 miles (350 kilometers). This surprise discovery demonstrates that the vortices cover regions beyond those where water condenses and clouds form, below the depth where sunlight warms the atmosphere.

The height and size of the Great Red Spot means the concentration of atmospheric mass within the storm potentially could be detectable by instruments studying Jupiter’s gravity field. Two close Juno flybys over Jupiter’s most famous spot provided the opportunity to search for the storm’s gravity signature and complement the MWR results on its depth.

With Juno traveling low over Jupiter’s cloud deck at about 130,000 mph (209,000 kph) Juno scientists were able to measure velocity changes as small 0.01 millimeter per second using a NASA’s Deep Space Network tracking antenna, from a distance of more than 400 million miles (650 million kilometers). This enabled the team to constrain the depth of the Great Red Spot to about 300 miles (500 kilometers) below the cloud tops.

“The precision required to get the Great Red Spot’s gravity during the July 2019 flyby is staggering,” said Marzia Parisi, a Juno scientist from NASA’s Jet Propulsion Laboratory in Southern California and lead author of a paper in the Journal Science on gravity overflights of the Great Red Spot. “Being able to complement MWR’s finding on the depth gives us great confidence that future gravity experiments at Jupiter will yield equally intriguing results.”

Belts and Zones

In addition to cyclones and anticyclones, Jupiter is known for its distinctive belts and zones – white and reddish bands of clouds that wrap around the planet. Strong east-west winds moving in opposite directions separate the bands. Juno previously discovered that these winds, or jet streams, reach depths of about 2,000 miles (roughly 3,200 kilometers). Researchers are still trying to solve the mystery of how the jet streams form. Data collected by Juno’s MWR during multiple passes reveal one possible clue: that the atmosphere’s ammonia gas travels up and down in remarkable alignment with the observed jet streams.

“By following the ammonia, we found circulation cells in both the north and south hemispheres that are similar in nature to ‘Ferrel cells,’ which control much of our climate here on Earth”, said Keren Duer, a graduate student from the Weizmann Institute of Science in Israel and lead author of the Journal Science paper on Ferrel-like cells on Jupiter. “While Earth has one Ferrel cell per hemisphere, Jupiter has eight – each at least 30 times larger.”

Juno’s MWR data also shows that the belts and zones undergo a transition around 40 miles (65 kilometers) beneath Jupiter’s water clouds. At shallow depths, Jupiter’s belts are brighter in microwave light than the neighboring zones. But at deeper levels, below the water clouds, the opposite is true – which reveals a similarity to our oceans.

“We are calling this level the ‘Jovicline’ in analogy to a transitional layer seen in Earth’s oceans, known as the thermocline – where seawater transitions sharply from being relative warm to relative cold,” said Leigh Fletcher, a Juno participating scientist from the University of Leicester in the United Kingdom and lead author of the paper in the Journal of Geophysical Research: Planets highlighting Juno’s microwave observations of Jupiter's temperate belts and zones.

Polar Cyclones

Juno previously discovered polygonal arrangements of giant cyclonic storms at both of Jupiter’s poles – eight arranged in an octagonal pattern in the north and five arranged in a pentagonal pattern in the south. Now, five years later, mission scientists using observations by the spacecraft’s Jovian Infrared Auroral Mapper (JIRAM) have determined these atmospheric phenomena are extremely resilient, remaining in the same location.

“Jupiter’s cyclones affect each other’s motion, causing them to oscillate about an equilibrium position,” said Alessandro Mura, a Juno co-investigator at the National Institute for Astrophysics in Rome and lead author of a recent paper in Geophysical Research Letters on oscillations and stability in Jupiter’s polar cyclones. “The behavior of these slow oscillations suggests that they have deep roots.”

JIRAM data also indicates that, like hurricanes on Earth, these cyclones want to move poleward, but cyclones located at the center of each pole push them back. This balance explains where the cyclones reside and the different numbers at each pole.

More About the Mission

JPL, a division of Caltech in Pasadena, California, manages the Juno mission. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington. Lockheed Martin Space in Denver built and operates the spacecraft.

Follow the mission on Facebook and Twitter, and get more information about Juno online at:

 

Flyaway

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Revelations on Jupiter's formation, evolution and interior: Challenges from Juno results

Abstract
The Juno mission has revolutionized and challenged our understanding of Jupiter. As Juno transitioned into its extended mission, we review the major findings of Jupiter's internal structure relevant to understanding Jupiter's formation and evolution. Results from Juno's investigation of Jupiter's interior structure imply that the planet has compositional gradients and is accordingly non-adiabatic, with a complex internal structure. These new results imply that current models of Jupiter's formation and evolution require a revision. In this paper, we discuss potential formation and evolution paths that can lead to an internal structure model consistent with Juno data, and the constraints they provide. We note that standard core accretion formation models, including the heavy-element enrichment during planetary growth is consistent with an interior that is inhomogeneous with composition gradients in its deep interior. However, such formation models typically predict that this region, which could be interpreted as a primordial dilute core, is confined to ∼10% of Jupiter's total mass. In contrast, structure models that fit Juno data imply that this region contains 30% of the mass or more. One way to explain the origin of this extended region is by invoking a relatively long (~2 Myrs) formation phase where the growing planet accretes gas and planetesimals delaying the runaway gas accretion. This is not the same as the delay that appears in standard giant planet formation models because it involves additional accretion of solids in that period. However, both the possible new picture and the old picture are compatible with the formation scenario recently proposed to explain the separation of two meteoritic populations in the solar system. Alternatively, Jupiter's fuzzy core could be a result of a giant impact or convection post-formation. These novel scenarios require somewhat special and specific conditions. Clarity on the plausibility of such conditions could come from future high-resolution observations of planet-forming regions around other stars, from the observed and modeled architectures of extrasolar systems with giant planets, and future Juno data obtained during its extended mission.

 
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