As I write, I am about to travel to Kourou, French Guiana, for the launch of the European Space Agency’s (ESA’s) Jupiter Icy Moons Explorer (JUICE) mission. I’m excited to have the chance to congratulate our ESA colleagues and JUICE team members in person and to wish JUICE a hearty bon voyage! But embarking on my somewhat convoluted trip to Kourou (via Paris!) has led me to thinking about how journeys, as well as destinations, are important in our business of planetary exploration.

All being well, JUICE will launch on its Ariane 5 from the Guiana Space Centre on April 13 and begin its eight-year journey to the Jupiter system [Update: After a one-day, weather-related delay, JUICE launched successfully on April 14.]. Eight years may sound long, but this journey will not be boring. JUICE will conduct several flybys, including those of Venus, Earth, and the first-ever Lunar-Earth gravity assist (LEGA) to help it on its way. The LEGA (a flyby of the Moon followed by one of Earth only a day and a half later) will save a substantial amount of propellant on the spacecraft.

JUICE will finally arrive at Jupiter in July 2031, where it will have a nominal science mission of four years. But even after it arrives at Jupiter, JUICE’s journeying will not be over. JUICE will first spend many months orbiting Jupiter itself, conducting several flybys of Europa, Ganymede, and Callisto. Then, in its final phase, JUICE will be the first spacecraft to orbit a moon in the outer solar system when it begins its orbital tour of Ganymede. Once all JUICE’s propellant has been consumed, the plan is for the spacecraft to be deorbited and to impact Ganymede at the end of 2035.

The significance of the JUICE mission, however, is obviously not just its journey. By observing Jupiter, Ganymede, Callisto, and Europa, in unprecedented detail, we hope to learn much more about the nature of the Jovian system — by characterizing Jupiter’s atmosphere, magnetic environment, ring system, and interactions with its satellites. Moreover, it is thought that Ganymede, Callisto, and Europa all bear oceans beneath their icy shells, so JUICE’s investigations will help investigate their potential habitability (both past and present).

To do this, JUICE is carrying a payload of 10 scientific instruments on its journey, built by teams at institutes from Europe, Japan, Israel, and the U.S. The payload includes Janus (an optical camera system), the Moons and Jupiter Imaging Spectrometer (MAJIS), the Sub-millimeter Wave Instrument (SWI), the Ganymede Laser Altimeter (GALA), the Gravity and Geophysics of Jupiter and Galilean Moons experiment (3GM), a magnetometer (J-MAG), and the Radio and Plasma Wave Investigation (RPWI). In particular, I’m extremely proud that NASA has contributed the UV imaging Spectrograph (UVS), led by Principal Investigator (PI) Randy Gladstone (SwRI), as well as enabling components for the Participle Environment Package (PEP). Development of the NASA-provided hardware for PEP, known as the Jovian Energetic Neutrals and Ions Sensor (JENI) and the Jovian Energetic Electron Sensor (JOEE), was led by PI Pontus Brandt (JHUAPL). Lastly, Co-PI Jeffrey Plaut (JPL) helped lead NASA/JPL’s contributions for the Radar for Ice Moon Exploration (RIME) instrument.

Of course, JUICE will not be exploring the Jovian system alone in the early 2030s. NASA’s own Europa Clipper mission is following hot on the heels of JUICE and is on track to launch in the fall of 2024. The Assembly, Test, Launch, and Operations (ATLO) phase of the mission is continuing a pace and eight of the nine scientific instruments have now been delivered to JPL for integration on the spacecraft. We expect the final instrument to be delivered this summer. You can follow along with Clipper’s progress in JPL’s High Bay 24/7 with the “Clipper Cam.”

The intricacies of launch vehicles and planetary dynamics mean that Europa Clipper will live up to its name and arrive at Jupiter in April 2030 — before JUICE, even though it will launch more than a year later. Clipper’s journey will include gravity assist flybys from Mars and then Earth. The spacecraft — equipped with its huge 30-meter-wide (100-foot-wide) solar panels — will orbit Jupiter and spend about three years conducting more than 40 close flybys of Europa.

Like JUICE, Europa Clipper will have a sophisticated science payload of 10 instruments. The Clipper instruments, however, are designed specifically to characterize Jupiter’s premier ocean world and investigate its habitability. The spacecraft’s cameras and spectrometers will provide high-resolution images and compositional maps of Europa’s surface and thin atmosphere. Data from the ice-penetrating radar, magnetometer, plasma sensors, and gravity investigation will give new insights into Europa’s ocean and deep interior. The thermal camera will help to pinpoint areas of warmer ice, shallow water bodies, and recent eruptions of water. Lastly, the dust analyzer and mass spectrometer will be used to study the chemistry of particles and gases in Europa’s immediate environment. In addition, because JUICE and Clipper will be in orbit around Jupiter contemporaneously, there will be some great opportunities for synergistic (two-point) measurements from many of the payloads.

Although missions to the outer reaches of our solar system come with long journeys and long waits for the science, they provide a great opportunity to train the next generation of leaders in planetary science missions. I’m happy to say that we are already working on plans for the future of the Europa Clipper Science team. Our goal is to create a Clipper extended mission science team that will be representative of our nation’s diversity. This effort will have several parts, including outreach, training, and opportunities for a broader set of institutions that have traditionally dominated planetary science. Our Here to Observe (H2O) undergraduate program is part of this broader plan. Europa Clipper played an important role in the success of H2O’s pilot, and I’m excited that we are now working to expand this program. The new Here to Observe (C.24) solicitation in ROSES-2023 is now open for proposals from non-R1 institutions for undergraduate students to observe PSD mission meetings/activities alongside mentors and peers — proposals can be submitted at any time! I can’t wait to see the journeys of students and early-career researchers as they grow with our long-lived missions.

For those with long memories, you might recall that the JUICE mission was selected in May 2012 after starting life as a reformulation of ESA’s component of the canceled joint NASA/ESA Europa Jupiter System Mission–Laplace, and that Europa Clipper was approved as our next flagship mission in 2015. Like many planetary missions, there have been long journeys for both JUICE and Clipper to get to the launch pad, but I know the collaborations and hard work from both teams will be worthwhile when they arrive at their destinations and undoubtedly transform our understanding of Jupiter and its icy worlds.

— Lori S. Glaze, Director, NASA’s Planetary Science Division, April 2023