NASA’s Juno will fly close to Jupiter’s icy moon Europa

This image of Jupiter’s moon Europa was taken by the JunoCam photographer aboard NASA’s Juno spacecraft on October 16, 2021, from a distance of about 51,000 miles (82,000 km). Credit: Image data: NASA/JPL-Caltech/SwRI/MSSS/Image processing by Andrea Luck

On Thursday, Sept. 29, at 2:36 a.m. PT (5:36 a.m. EDT), NASA’s Juno spacecraft will lie 222 miles (358 kilometers) from the ice-covered surface of Jupiter’s moon Europa. The solar-powered spacecraft is expected to obtain some of the highest-resolution images ever taken of parts of Europa’s surface, as well as gather valuable data on the Moon’s interior, surface composition and ionosphere, as well as its interaction with Jupiter’s magnetosphere.

Such information could benefit future missions, including the agency’s Europa Clipper spacecraft, which is scheduled to launch in 2024 to study the icy moon. “Europe is an interesting Jovian moon, it’s the focus of a future NASA mission,” said Juno principal investigator Scott Bolton of the Southwest Research Institute in San Antonio. “We are pleased to provide data that may assist the Europa Clipper team in mission planning, as well as provide new scientific insights into this icy world.”

With an equatorial diameter of 1,940 miles (3,100 km), Europa is about 90% the size of Earth’s moon. Scientists believe that a salty ocean lies beneath a crust of ice miles thick, raising questions about possible conditions capable of supporting life below Europa’s surface.

The close flyby It will adjust Juno’s trajectory, reducing the time it takes to orbit Jupiter from 43 to 38 days. It will be the closest NASA spacecraft to have come close to Europe since Galileo came within 218 miles (351 kilometers) on January 3, 2000. Additionally, this flyby marks the second encounter with a Galilean moon during the Juno extended mission. The mission explored Ganymede in June 2021 and plans to approach Io in 2023 and 2024.

Data collection will start an hour before closest approachwhen the spacecraft is 51,820 miles (83,397 kilometers) from Europe.

“The relative velocity between the spacecraft and the moon is going to be 14.7 miles per second (23.6 kilometers per second), so we’re screaming really fast,” said John Purdy, deputy mission manager for Juno at the Jet Propulsion Laboratory. “All steps have to go like clockwork to successfully get our planned data, because soon after the flyby is complete, the spacecraft needs to be re-orientated for our close approach to Jupiter, which happens only 7½ hours later.”

NASA's Juno will fly close to Jupiter's icy moon Europa

Juno’s extended mission includes flights to the moons Ganymede, Europa and Io. This graphic depicts the orbit of the Jupiter spacecraft—named “PJ” for perihelion, or the point of closest approach to the planet—from its primary mission in gray to 42 orbits of its extended mission in shades of blue and violet. Image Credit: NASA/JPL-Caltech/SwRI

The spacecraft’s full suite of instruments and sensors will be activated at the Europa encounter. Juno’s Active Particle Detector (JEDI) instrument and its medium-gain (X-band) radio antenna will collect data on the ionosphere in Europe. The wave experiments, the Jovian Auroral Distributions Experiment (JADE) and the magnetometer (MAG) will measure plasmas in the aftermath of the Moon while Juno explores Europa’s interaction with Jupiter’s magnetosphere.

MAG and Waves will also search for potential water plumes above Europa’s surface. “We have the right equipment to do the job, but picking up a shaft is going to take a lot of luck,” Bolton said. “We have to be in the right place at just the right time, but if we’re very lucky, that’s for sure.”

From inside and outside

Juno’s Microwave Radiometer (MWR) will delve into the crust of water ice in Europe, obtaining data on its composition and temperature. This is the first time such data has been collected to study the lunar cryosphere.

In addition, the mission expects to capture four visible-light images of the moon using the JunoCam (Public Sharing Camera) in flight. Juno’s science team will compare them to images from previous missions, looking for changes in Europa’s surface features that may have occurred over the past two decades. Visible light images will have an expected resolution of better than 0.6 miles (1 kilometer) per pixel.

Although Juno will be in Europa’s shadow when it is close to the moon, Jupiter’s atmosphere will reflect enough sunlight for Juno’s visible-light photographers to collect data. Designed to capture and search for star fields shining stars With known positions to help Juno get its directions, the mission’s stellar camera (called the Stellar Reference Unit) will capture a high-resolution black-and-white image of Europa’s surface. Meanwhile, the Jovian Infrared Auroral Mapper (JIRAM) will attempt to collect infrared images of its surface.

Juno’s close-up views and data from its MWR tool will report to Europa Clipper Expeditionwhich will perform nearly 50 flights after arriving in Europe in 2030. The Europa Clipper will collect data on the moon’s atmosphere, surface and interior — information that scientists will use to better understand Europa’s global subsurface ocean, the thickness of its ice crust, and plumes that might spew water subterranean to space.


An ultraviolet instrument plays a key role in NASA’s Europa Clipper mission


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