WASHINGTON — Europe’s first mission to Jupiter is ready to launch on the next to last flight of the Ariane 5 on April 13.

The Ariane 5 rocket, carrying the European Space Agency’s Jupiter Icy Moons Explorer, or JUICE, spacecraft rolled out to the pad at Kourou, French Guiana, on April 11. Liftoff is scheduled for 8:15 a.m. Eastern April 13 in an instantaneous launch window.

The launch will start a long journey for the six-ton spacecraft. It will perform several gravity-assist flybys of the Earth and Venus between August 2024 and January 2029 before arriving at Jupiter in mid-2031. Once at Jupiter, it will conduct 35 flybys of the large moons Europa, Ganymede and Callisto before going into orbit around Ganymede, the solar system’s largest moon.

“The main goal is to understand whether there are habitable environments among those icy moons,” said Olivier Witasse, JUICE project scientist at ESA, in an April 6 briefing. “We will characterize in particular the liquid water oceans which are inside the icy moons.”

JUICE will carry out those observations with a suite of 10 science instruments of which one, an ultraviolet imaging spectrograph, is provided by NASA. Several other instruments include contributions from NASA, the Japanese space agency JAXA and the Israel Space Agency.

JUICE will be joined by NASA’s Europa Clipper mission, scheduled to launch in October 2024 and arrive at Jupiter in 2030. That spacecraft will conduct dozens of flybys of Europa to study the potential for life on that icy moon.

It will be “very fantastic” to have both Europa Clipper and JUICE operating at the same time in the Jovian system, Witasse said. “The two missions are very complementary,” with the potential of joint observations. One example is planned flybys of Europa by the two spacecraft just four hours apart.

JUICE will focus more on Ganymede, entering orbit around the moon in late 2034 and remaining there through the end of the mission, currently planned for September 2035. That orbit will be at an altitude of 500 kilometers, but if there is sufficient fuel left on the spacecraft, he said the spacecraft could lower its orbit to 200 kilometers.

JUICE ultimately will crash onto the surface of Ganymede. “With the current knowledge of Ganymede, we can crash on the surface” without violating planetary protection guidelines to prevent harmful contamination. “We have shown that we cannot contaminate any subsurface ocean even if we crash on the surface.”

The launch is the sixth flight of the Ariane 5 to carry ESA science missions. The rocket has previously launched the XMM-Newton X-ray observatory, Rosetta comet mission, Herschel and Planck observatories, the BepiColombo mission to Mercury and, most recently, the James Webb Space Telescope, a NASA-led mission with European contributions.

Preparations for the JUICE launch have been similar to Ariane 5 missions with the exception of enhanced cleanliness requirements, according to Veronique Loisel, JUICE project director at Arianespace. That is similar to launches of imaging satellites, she said, but with additional contamination monitoring also used for the launch of JWST.

The launch is also the penultimate flight for the Ariane 5. The vehicle is scheduled to make its final launch in late June, carrying the Syracuse 4B military communications satellite for France and the Heinrich Hertz communications satellite for the German government.

“Is it routine? Never. Is it of special significance? Yes,” said Ruedeger Albat, head of the Ariane 5 program at ESA, of the final launches of the rocket. For those final launches there is a reinforced qualification monitoring and verification program, he said, but otherwise operations are kept as close to normal as possible.

He compared those final launches to an airline pilot’s final flight before retirement. “He will fly with much attention but stick as much as possible to nominal operations.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...