Juno Mission Instruments and Objectives – A User-Friendly Overview

Juno Mission Instruments and Objectives – A User-Friendly Overview

Juno Mission Instruments and Objectives – A User-Friendly Overview

In the summer of 2016, NASA’s Juno spacecraft is going where no spacecraft has gone before. Up close and personal with our solar system’s juggernaut; Jupiter. Tasked with daunting mission goals, and some of the most lethal environments, the tiny craft is up to the challenge. This article will give a user-friendly, but detailed overview of the Juno mission instruments and objectives.

In this article we will look at:

Juno Mission Overview 

Jupiter, one of the five naked eye planets, has likely been observed for hundreds of years. As the biggest planet in our solar system, its first documented observations date back to the early 1600s with Galileo Galilei. Since then, Jupiter has served as one gigantic ball of mysteries and secrets.

In Roman mythology, Jupiter was the god of all gods. In order to conceal his mischievous behaviors, Jupiter shrouded himself in a cloak of clouds. It was only Jupiter’s wife, Juno that was able to peer through the clouds and observe her husband’s devious secrets.

Thus, NASA’s spacecraft baring the apropos name, Juno was launched in August 2011 to observe some of Jupiter’s deepest secrets. Like the mythological god’s wife, Juno will gaze through the planet’s clouds to collect a wealth of new information. The Advanced Juno mission instruments will allow the craft to carry out its observations.

Juno Mission Objectives

Credit: NASA

Understanding more about Jupiter is understanding more about our solar system’s evolution. Though several mysteries remain, astronomers know that the two are, in many ways, intertwined. Strapped to the nines with advanced mission instruments, Juno hopes to unravel some of these mysteries. The spacecraft’s mission goals will learn more about:

Jupiter’s Origins

Throughout the centuries, dozens of theories have emerged as to how Jupiter was formed. Currently, leading theories debate whether the gas giant has a solid or molten liquid core. Juno’s sophisticated measurements hope to determine the core’s mass and composition. In turn, this could help settle the formation debate and allow a single theory for how Jupiter was created.

Jupiter’s Interior

We now know that Jupiter is composed of predominantly hydrogen, with around 10% consisting of helium. Juno hopes to dive much deeper, beneath the planet’s clouds to understand more about its interior composition. Juno will do this by studying and mapping Jupiter’s gravitational and magnetic fields. A special suite of Juno mission instruments were built to obtain this information.

Jupiter’s Atmosphere

Juno will create accurate maps of Jupiter’s atmosphere at all latitudes of the planet. These maps will reveal the atmosphere’s varying composition, temperature, cloud opacity and dynamics.

Jupiter’s Magnetosphere

Ultimately, with its closest fly-by attempts, Juno will intensely explore Jupiter’s polar regions. Examinations will reveal three-dimensional structures of Jupiter’s complex magnetosphere and auroras. The most sensitive and advanced of the Juno mission instruments were equipped for this task. The instruments are so sacred that they are protected by a state-of-the-art titanium vault aboard the craft.

Juno Mission Instruments

To gather such complex information and operate within Jupiter’s hostile environment, Juno requires advanced tools. Built all over the world, the Juno mission instruments are custom-made to accomplish the mission’s lofty goals. At a glance, the nine Juno mission instruments are as follows:

Microwave Radiometer (MWR)

Juno’s Microwave Radiometer (MWR) is an instrument that can probe deep below Jupiter’s cloud tops. MWR will measure the atmosphere’s structure, chemical composition and movements. Collecting these measurements requires deep observation to full understand them. In fact, MWR will probe as deep as 340 miles below the planet’s visible outer clouds.

One of MWR’s primary goals is to determine the amount of water in Jupiter’s atmosphere. According to a Juno mission press release by NASA, “this information is the missing key to understanding Jupiter’s formation” (Jupiter Orbit Insertion Online Press Kit, NASA, 2016).

MWR will measure microwaves coming from inside of Jupiter. Even though Jupiter emits waves across several spectra, only microwaves can cut through the thick clouds. The depth from which waves escape Jupiter’s clouds depend on their specific frequencies. Therefore, Juno can intentionally measure certain wave frequencies in order to study specific atmospheric layers. It is the deepest layers that will reveal the atmospheric water content and thus, Jupiter’s formation.

Gravity Science Experiment

Juno’s Gravity Science Experiment uses telecom to monitor Jupiter’s internal dynamics. By studying the planet’s gravitational field, Juno can observe the movements of materials within Jupiter. Ultimately, this will allow us to determine what type of core Jupiter holds at its center.

Slight variations in Jupiter’s internal structure yield slight changes to the planet’s gravitational field. Due to these variations, Juno’s orbit is also ever so slightly affected. Finally, Juno’s slight orbital variations create slight variations in the spacecraft’s radio signal, which is constantly being received and monitored on Earth. These tiny frequency changes in the spacecraft’s signal to Earth are known as the Doppler Effect. This is the same effect that causes a police car’s siren to change its pitch up, or down when it moves towards you, or away from you.

This chain of small variations allows us to understand the gravitational changes occurring deep within Jupiter. And, thus, we are able to better understand more about its internal composition.

Magnetometer Experiment (MAG)

The Magnetometer Experiment (MAG) will allow Juno to three-dimensionally map Jupiter’s magnetic field. Understanding how the planet’s magnetic field is generated will return a wealth of understand about its internal composition.

Juno will perform short- and long-term observations of Juno’s internal dynamo activities. In this case, Dynamo is essentially how electrically-charged materials churn within Jupiter’s interior.

MAG also measures specific electrical currents, called Birkeland currents, that align themselves with the planet’s magnetic field. It is the Birkeland currents that help create Jupiter’s beautiful auroras on its poles.

On a much smaller level, the Juno spacecraft itself creates miniature magnetic fields. To avoid this self-made magnetism from skewing data collection, MAG sits far from the rest of the instruments. Actually, Juno carries two MAG sensors for additional precaution. One sits 33 feet away from the main spacecraft, the other sits at 39 feet. Each sensor is mounted on a boom jutting out from Juno’s solar arrays (its wings).

Jovian Auroral Distributions Experiment (JADE)

Simply put, the Jovian Auroral Distributions Experiment (JADE) will determine what particles create Jupiter’s beautiful auroras. The series of four sensors will work to detect the electrons, hydrogen, helium, oxygen and sulfur ions in the areas around Jupiter.

During certain orbits, Juno will fly remarkably close to Jupiter; closer than any previous spacecraft. These close-approaches will allow for JADE to take exceptionally detailed observations of the polar auroras. The instrument will see detail as small as 30 miles. Given that Jupiter’s auroras span for thousands of miles, this level of detail is truly spectacular.

Jupiter Energetic-Particle Detector Instrument (JEDI)

The Jupiter Energetic-Particle Detector Instrument (JEDI) will study particles floating through space, and how they interact with Jupiter’s magnetic field. As these energetic particles reach the magnetic field, they often follow its path, and are guided to the planet’s poles. Next, they collide with the polar atmosphere and create massive, stunning auroras.

Working in concert with the spacecraft’s other instruments, JEDI will help further our understanding of how Jupiter’s auroras are created. JEDI will help to measure the different type of particles, how much energy they transport and how they react to transfer that energy into the Jovian atmosphere.

Jovian Infrared Auroral Mapper (JIRAM)

JIRAM is a combination of a camera and spectrometer. The instrument is able to study and map Jupiter’s auroras and atmospheric structure. To do so, it will probe as deep as 45 miles below the gas giant’s cloud tops.

Jupiter emits strong radiation in the radio and infrared spectra. However, only the radio waves are able to escape the thick atmospheric clouds. Therefore, JIRAM’s observation operate within the infrared spectrum to more or less, observe from within. Particularly, JIRAM will image auroras at the wavelength of hydrogen ions, which is the same wavelength that the planet’s methane absorbs light. What you are left with is a darkened background with a vivid and bright aurora in the foreground!

JIRAM will also measure the heat radiating from Jupiter. By doing this, it can determine the amount of water, and other elements in the planet’s atmosphere. Finally, measuring various specific wavelengths of heat and absorption in Jupiter can tell us a lot about the behavior and structure of its atmosphere, even beneath the thick cloud tops.

Ultraviolet Imaging Spectrograph (UVS)

The Ultraviolet Imaging Spectrograph (UVS), will visualize Jupiter’s auroras in the ultraviolet spectrum. This will allow us to further understand how they work and how particles interact with Jupiter.

UVS takes powerful ultraviolet images of the auroras. Working with the JADE and JEDI instruments, it helps to understand the full connection of the auroras, the particles and the magnetic field.


Juno’s Waves instrument measures radio and plasma waves in Jupiter’s magnetosphere. This allows us to learn about how Jupiter’s magnetic field, atmosphere and magnetosphere interact.

Jupiter has a gigantic sphere surrounding it, called the magnetosphere. Plasma gets trapped within this magnetic sphere and acts as an electrical circuit. This circuitry effect connects all regions of the magnetosphere together. Therefore, when activity in plasma happens in one region, it can be detected in a completely different region. Also, this electric activity within plasma causes waves.

Waves is a specific type of sensor that is able to detect these plasma waves. This allows Waves to monitor plasma activity within the entire gigantic magnetosphere of Jupiter from any location!


Finally, JunoCam, a visible-light camera has one primary goal: capture amazing photos of Jupiter. Though it is not one of the official Juno mission instruments, JunoCam’s visuals will help facilitate scientific understanding. But, what JunoCam lacks in scientific achievement, it makes up for in spades with visual brilliance!

The Juno spacecraft spins rather quickly, at twice per minute. This speed would cause motion-blurred imagery by a visual-light camera. So, JunoCam only captures sections of images at the same rate that the spacecraft is spinning. It then gathers the various sections, and compiles them together to create full images.

JunoCam was included on the spacecraft largely for “public engagement,” according to NASA. Members of the NASA amateur astronomy team will even allow for the public to help select photographic targets for JunoCam!

Unfortunately, Jupiter’s powerful radiation will damage JunoCam relatively quickly. The camera is only anticipated to last for around seven of the mission’s orbits. But, on the bright side, this is ample time to capture a myriad of staggering photos.

Juno Mission What’s Next?

For the Juno mission, the question of “what’s next” is answered in two parts. Juno herself will have a sad, but heroic ending. Once the spacecraft’s long and productive orbits are complete, NASA will intentionally crash her into Jupiter early in 2018.

For Juno:

But, this is a good thing! We, in science, now know that some of Earth’s most primitive microbes can survive in some of the hottest and coldest extremes. Meanwhile, Jupiter’s moon Europa remains one of the top candidates for hosting life outside of Earth. Therefore, NASA is taking no risk in potentially contaminating the promising moon, and crashing Juno to rid any chances!

For Us:

While our human ending is nowhere as tragic as Juno’s, we’ve got our work cut out for us! Although the JunoCam will return breathtaking images to us, even within the upcoming weeks, the rest of the data is not as simple. The complex instruments on Juno require complex deciphering. NASA, along with many other teams, will scour this data diligently for the next 2-3 years!

However, taking years to scan data is a good thing when you consider the outcome. The potential information gathered will result in mankind better understanding how our solar system came to be. We will also learn more about our mysterious largest planet and what its role was in this creation. That is entirely worth the wait.

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