Juno In-Depth

This artist's rendering shows NASA's Juno spacecraft making one of its close passes over Jupiter. Image Credit: NASA/JPL-Caltech

This artist’s rendering shows NASA’s Juno spacecraft making one of its close passes over Jupiter. Image Credit: NASA/JPL-Caltech

One of the brightest objects in the night sky, Jupiter has enthralled humans since ancient times. Today, scientists believe that learning more about the planet may be the key to discovering our solar system’s origins and formation. They theorize that Jupiter didn’t always rest where it is now, but that it moved throughout the solar system in its youth, disrupting the formation of Mars, influencing the formation and location of the asteroid belt, and more.

The Juno mission is the latest in a long tradition of discovery at the gas giant. Scientists began to use space missions to unlock the planet’s secrets in the early 1970s when Juno’s earliest ancestors, Pioneer 10 and 11, launched. The pair of spacecraft reached the planet in late 1973 and early 1974. For the first time ever, scientists could obtain direct observations and close-up images of Jupiter, its moons and the mysterious Great Red Spot.

NASA’s Juno spacecraft, built by Lockheed Martin, successfully entered Jupiter’s orbit during a 35-minute engine burn on Monday, July 4. Confirmation that the burn had completed was received on Earth at 9:53 p.m. MDT (11:53 p.m. EDT). The spaceflight’s operations were controlled by a joint team at Lockheed Martin’s Mission Support Area near Denver and NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

During Juno’s approach, the planet’s gravity tugged at the spacecraft, accelerating it to speeds of over 250,000 kilometers per hour (150,000 mile per hour) relative to Earth – making it one of the fastest human-made objects ever. When Juno arrived at Jupiter, it slammed on the brakes, fired its main engine in reverse, and slowed down to enter Jupiter’s orbit.

NASA will fly the solar-powered spacecraft to within 2,900 miles (4,667 kilometers) of the cloud tops of Jupiter for a year-long mission to study our solar system’s largest planet.

In preparation for Juno’s arrival at Jupiter, astronomers used ESO’s Very Large Telescope to obtain spectacular new infrared images of Jupiter. They are part of a campaign to create high-resolution maps of the giant planet. These observations will inform the work to be undertaken by Juno over the coming months.

Juno is also using its own special camera, JunoCam, to capture high resolution views of Jupiter as the spacecraft approaches the giant planet. Now and throughout the mission, amateur astronomers are invited to submit images of Jupiter from their own telescopes. These views will be the basis for online discussions about which of Jupiter’s swirls, bands and spots JunoCam should image as it makes repeated, close passes over the planet. The ground-based views will be essential for identifying and tracking changes in the planet’s cloud features as Juno approaches. The public will act as a virtual imaging team, participating in key steps of the process, from identifying features of interest to sharing the finished images online.

JunoCam obtained its first image of Jupiter from orbit on July 10, 2016, at 10:30 a.m. PDT (1:30 p.m. EDT, 5:30 UTC), when the spacecraft was 2.7 million miles (4.3 million kilometers) from Jupiter on the outbound leg of its initial 53.5-day capture orbit.

Astronomers used the Hubble Space Telescope to study auroras on Jupiter using Hubble’s ultraviolet capabilities. As well as producing beautiful images, this program aims to determine how various components of Jupiter’s auroras respond to different conditions in the solar wind, a stream of charged particles ejected from the sun. While Hubble is observing and measuring the auroras on Jupiter, Juno is measuring the properties of the solar wind itself; a perfect collaboration between a telescope and a space probe.

On the evening of July 4, Juno performed a suspenseful orbit insertion maneuver, a 35-minute burn of its main engine, to slow the spacecraft by about 1,212 mph (542 meters per second) so it could be captured into the gas giant’s orbit.

During Juno’s orbit around Jupiter, its mission is to gather clues shrouded under Jupiter’s thick layers of clouds that reveal what the planet is made of on the inside, and to help answer some of the most fundamental questions about how planets form from swirling clouds of gas and dust.

The Juno spacecraft carries a payload of 29 sensors, which feed data to nine onboard instruments. Eight of these instruments (MAG, MWR, Gravity Science, Waves, JEDI, JADE, UVS, JIRAM) are considered the science payload. One instrument, JunoCam, is aboard to generate images for education and public outreach.

JEDI will measure charged particles accelerated to high energies within Jupiter’s magnetosphere, allowing researchers to study how their interaction with Jupiter’s atmosphere generates the most powerful aurora in the solar system. These detectors will provide data on particles with energies in the 30 to roughly 1,000 kiloelectron volt (keV) range.

A second particle instrument called the Jovian Auroral Distributions Experiment (JADE) will study lower energy (5- to 50-keV ions; 0.1- to 100-keV electrons) particles involved in the same processes

The magnetometers will map the planet’s magnetic field with extraordinary precision and observe its variations over time. This will be the first time scientists have mapped the magnetic field all around Jupiter and it will be the most complete map of its kind ever obtained about any planet with an active dynamo other than Earth. Each of the two vector magnetometers carries with it a pair of non-magnetic star cameras to determine its orientation in space.

The Waves instrument, which will measure radio and plasma waves in Jupiter’s magnetosphere. Data from the Waves investigation, presented as audio stream and color animation, indicated the spacecraft’s crossing of the bow shock just outside Jupiter’s magnetosphere on June 24 and the transit into the lower density of the Jovian magnetosphere on June 25.

Primary science observations are obtained within three hours of closest approach to Jupiter, although calibrations, occasional remote sensing and magnetospheric science observations are planned throughout the science orbits around Jupiter.

Juno will be forging into a treacherous environment with more radiation than any other place NASA has ever sent a spacecraft, except the sun. Mission engineers have protected the spacecraft from this harsh environment by enclosing the sensitive science instruments in a titanium fault.

Pressure at Jupiter’s core is millions of times that of Earth. Scientists expect Jupiter’s core to be more liquid than solid because of the pressure, but also expect it to be much denser than Earth’s core. At these enormous pressures, the hydrogen acts like an electrically , which is believed to be the source of the planet’s intense magnetic field. This powerful magnetic environment creates the brightest auroras in our solar system, as charged particles precipitate down into the planet’s atmosphere. Juno will directly sample the charged particles and magnetic fields near Jupiter’s poles for the first time, while simultaneously observing the auroras in ultraviolet light produced by the extraordinary amounts of energy crashing into the polar regions.

CU-Boulder Faculty and Students will play an important role in the mission. Three researchers from CU-Boulder’s Laboratory for Atmospheric and Space Physics (LASP) and five students, both undergraduates and graduate students, are part of the Juno mission. CU-Boulder Professor Fran Bagenal of LASP, who co-chairs the Juno Magnetospheric Working Group for NASA and is coordinating many of the science observations for the mission. Bagenal is particularly interested in Jupiter’s magnetosphere, the area of space around the planet that is controlled by its magnetic field.

Europe has provided some of the instrumentation for the mission and European scientists from Italy, France, Belgium, the UK and Denmark are part of the team of co-investigators that will help analyse data sent back by Juno. Amateur and professional scientists from across Europe are also involved in campaigns using ground- and space-based telescopes that will study Jupiter at a range of wavelengths to put Juno’s close-up observations into context.

Want something fun to do while you’re waiting for Juno to return results? Make a Juno Spacecraft Paper Model.

Using NASA’s Eyes on the Solar System and simulated data from the Juno flight team, you can also follow the journey of the Juno spacecraft in real-time.