New data on radiation show missions to Jupiter’s moon Europa are possible

Scientists from NASA’s Juno mission have developed the primary full 3D radiation map of the Jupiter system, together with characterizing the depth of the high-energy particles close to the orbit of the icy moon Europa, and the way the radiation atmosphere is sculpted by the smaller Jovian moons orbiting close to Jupiter’s rings.

The work depends on information collected by Juno’s star digicam Superior Stellar Compass (ASC) designed and constructed by Technical College of Denmark, and Stellar Reference Unit (SRU), which was constructed by Leonardo, S.p.A. in Florence, Italy. The 2 datasets complement each other, serving to Juno scientists characterize the radiation atmosphere at completely different energies.

Each ASC and SRU are low-light cameras designed to help within the challenges of deep-space navigation. Most of these devices are on virtually all interplanetary and Earth-orbiting spacecraft. To get them to function as radiation detectors, the Juno science crew had to have a look at the cameras in an entire new gentle.

“On Juno we attempt to innovate new methods to make use of our sensors to find out about nature and have used lots of our science devices in methods they weren’t designed for,” stated Scott Bolton, Juno principal investigator from the Southwest Analysis Institute in San Antonio.

“That is the primary detailed radiation map of the area at these larger energies, which is a serious step in understanding how Jupiter’s radiation atmosphere works. That we have been in a position to create the primary detailed map of the area is an enormous deal, as a result of we do not carry an instrument designed to search for radiation. The map will assist in planning observations for the following era of missions to the Jovian system,” says Bolton.

Counting fireflies

Juno’s ASC star digicam photos of stars to find out the spacecraft’s orientation in space, which is important to the success of the spacecraft’s MAG experiment. However the 4 star cameras—situated on Juno’s magnetometer increase—have additionally proved to be beneficial detectors of high-energy particle fluxes in Jupiter’s magnetosphere. They report “laborious radiation”—ionizing radiation of high-penetrating energy that impacts a spacecraft with ample power to go via the ASC star digicam’s shielding.

“Each quarter-second the ASC takes a picture of the celebrities,” stated Juno scientist John Leif Jørgensen, professor on the Technical College of Denmark.

“Very energetic electrons that penetrate its shielding depart a telltale signature in our photos that appears just like the path of a firefly. The instrument is programmed to depend the variety of these fireflies, giving us an correct calculation of the quantity of radiation,” says Jørgensen.

Due to Juno’s ever-changing orbit, the spacecraft has traversed virtually all areas of space close to Jupiter.

ASC information from the star digicam recommend that there’s extra very excessive power radiation relative to decrease power radiation close to the moon Europa’s orbit than beforehand thought. The info additionally confirms that the quantity of excessive power electrons current on the aspect of Europa dealing with into its orbital path of movement is bigger than the moon’s slipstream.

This is because of the truth that many of the electrons in Jupiter’s magnetosphere overtake Europa from behind because of Jupiter and its magnetic discipline rotation, however the very excessive power electrons drift backwards, virtually like fish swimming upstream, they usually slam into Europa’s main aspect.

The radiation information from the Jupiter system shouldn’t be the primary unplanned scientific contribution ASC has made to the mission. Even earlier than arriving at Jupiter, ASC information was used to measure the interplanetary dust impacting Juno. And the imager even found a beforehand uncharted comet utilizing the identical dust detection method—distinguishing small bits of the spacecraft ejected by microscopic dust impacting Juno at very excessive velocity.

The outcomes from the Juno mission are within the closing spherical of peer assessment and might be printed within the journal Geophysical Analysis Letters.

Mud rings

Just like the ASC the SRU has been utilized as a radiation detector and a low gentle imager.

Information from Juno’s SRU and ASC point out that, like Europa, the small “shepherd moons” that orbit inside or near the sting of Jupiter’s rings (and assist to carry their form) additionally seem to work together with Jupiter’s radiation environment. When the spacecraft flies on magnetic field lines related to ring moons or dense dust, the radiation depend on each ASC and SRU dropped precipitously. The SRU can be accumulating uncommon low gentle photos of the rings from Juno’s distinctive vantage level.

“There’s nonetheless numerous thriller about how Jupiter’s rings have been shaped, and only a few photos have been collected by prior spacecraft,” stated Heidi Becker, lead co-investigator for the SRU and a scientist at NASA’s Jet Propulsion Laboratory, which manages the mission.

“Generally we’re fortunate and one of many small shepherd moons might be captured within the shot. These photos permit us to be taught extra exactly the place the ring moons are presently situated and see the distribution of dust relative to its distance from Jupiter.”