Space Exploration —

ESA’s JUICE will voyage to Jupiter’s moons

ESA-only mission will escape gravity, NASA's budget woes.

ESA's JUICE will voyage to Jupiter's moons

The European Space Agency announced last week that it has chosen the Jupiter Icy moons Explorer, aka JUICE, as its next large science mission. JUICE was chosen over the New Gravitational wave Observatory (NGO) and the Advanced Telescope for High-Energy Astrophysics (ATHENA) by ESA's new Cosmic Vision 2015-2025 program.

JUICE will launch about ten years from now, and won't arrive at Jupiter until 2030. JUICE's solar-powered ion drive means the spacecraft will require more than 25 gravity assists. A stronger energy source could get it there faster, but as an ESA-only probe, JUICE doesn't currently have access to the roughly eight pounds of plutonium it would need to power its ion engine to Jupiter much more quickly. Both NASA and ESA are trying to solve the plutonium shortage for future spacecraft.

Upon arrival, JUICE will study Callisto first, imaging the moon's surface. It will fly on to Europa, making two passes, before orbiting at Ganymede, mapping its unique magnetosphere, imaging the moon's surface, and attempting to determine whether Ganymede has oceans underneath its water ice. Of all the moons in the Solar System, only Ganymede is known to have a magnetosphere, probably caused by convection within its iron core.

Until the spacecraft dies or its mission is cancelled, it will also study Jupiter's atmosphere, magnetosphere, and its interaction with the moons. The two unchosen spacecraft, NGO and ATHENA, are not gone forever. They'll be considered next year when ESA puts out another request for proposals.

The background of these three entrants in ESA's Cosmic Vision program is also of note:

In all three cases, NASA pulled out for funding reasons after years of planning and cooperation. They're not the only ones, either: the Terrestrial Planet Finder, W-FIRST, SIM and a host of other astrophysics and Mars missions (most recently ExoMars) have been cancelled or defunded. This is all to find funding for the James Webb Space Telescope. JWST is highly desirable to the science community, but when it finally launches sometime (hopefully) in 2018, its budgetary footprint on other science missions inside and outside the United States will have been large and deep.

That's not to say that JWST is setting a precedent. The Hubble Space Telescope, which has revolutionized astronomy, was also far more expensive than originally projected. Originally estimated to cost around $400 million, estimates for Hubble's costare now $5-7 billion, with a "b." The JWST has risen from an original estimated cost of $1.6B to $6.8B since funding was first allocated by Congress in 1997, a huge increase but nowhere near as spectacularly far off the original mark as Hubble.

The two spacecraft that weren't chosen, NGO and ATHENA, are not gone forever. They'll have another chance at funding next year when ESA puts out another request for proposals.

Further Reading

The ESA announcement.

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