����ֱ��

NASA has selected The ����ֱ�� University Applied Physics Laboratory (APL) in Laurel, Md., to build an innovative particle camera and instrument for flight aboard the JUpiter ICy moon Explorer (JUICE), a European Space Agency mission to be launched in 2022 to study the Jupiter system and three of its largest moons in unprecedented detail. APL is one of 15 scientific teams from Europe, Japan and the United States selected to develop the 11 experiments that will be conducted as part of the mission.

Under the direction of Pontus Brandt, the APL instruments — the Jupiter Energetic Neutrals and Ions (JENI) and the Jovian Energetic Electrons (JoEE) — will be flown as a part of the mission’s largest investigation, the Particle Environment Package (PEP). JENI advances a technique that APL has also used at Saturn and Earth, to image the otherwise invisible vast cloud of plasma and gas that surrounds Jupiter. The JoEE spectrometer will be used to understand the processes that make Jupiter the biggest particle accelerator in the solar system.

“Jupiter is a mini solar system once formed from a plasma and gas nebula by processes similar to those forming our own solar system,” explains Brandt. “If Jupiter’s ‘nebula’ were visible it would be the largest object in the night sky, much larger than the full moon. JENI’s unique images will provide movies of this huge, dynamic system like we’ve never seen before. JoEE’s superior measurement capabilities will be critical in resolving the mystery of how Jupiter’s surrounding plasma is heated to temperatures that make the solar corona appear lukewarm in comparison. Surprises are guaranteed.”

The spacecraft is scheduled to reach the Jupiter system in 2030 and conduct the first thorough exploration of that satellite system since NASA’s Galileo mission, which ran from 1989 to 2003. It follows the more focused study of aspects of Jupiter by NASA’s Juno mission, which will be operating at Jupiter in the 2016–2017 time frame. JUICE will orbit the planet for three years and travel past its moons, Callisto and Europa, multiple times, before orbiting Ganymede, a moon larger than Mercury.

Before JUICE arrives at Jupiter, JENI will collect images of the gas torus — or ring — that surrounds the planet, courtesy of Europa and the volcanically active moon Io. “It is a mystery how such a seemingly inert icy moon like Europa can produce such an enormous gas torus,” says APL’s Chris Paranicas, the deputy lead of JENI and JoEE. “JENI’s global images of how that gas is distributed and evolves in relation to Europa will remove a bottleneck in our understanding of its atmospheric release mechanisms.”

Twelve countries will work together to develop the six sophisticated instruments for the comprehensive PEP suite under the lead of Stas Barabash of the Swedish Institute of Space Physics in Kiruna. In addition to the JENI and JoEE investigations, PEP will investigate the three-dimensional structure of Jupiter’s stellar-like plasma disk; map how the intense plasma flow bombards the surfaces of the moons; and, for the first time, sample the moons’ tenuous atmospheres to understand how materials on and just below the surface are released.

“The Jovian system should really be viewed as our own solar system’s astrophysical object,” notes Barabash. “Its sheer size required us to take a novel approach by combining high-resolution in situ measurements, neutral gas mass spectroscopy and powerful global imaging.”

“The selection of JENI and JoEE is an exciting prospect for uncovering many mysteries of the enormous Jovian system, in particular by obtaining images similar to those provided by APL’s Ion and Neutral Camera of the MIMI investigation on the Cassini spacecraft now orbiting Saturn,” says APL’s Stamatios (Tom) Krimigis, who leads APL-designed particle experiments on Cassini as well as the Voyager mission. “We couldn’t do this at Jupiter with the Voyagers in the late ‘70s or with Galileo in the early ‘90s because we did not have the technology. It is gratifying to see a younger generation of scientists advancing the state of the art.”

For a simulated movie of what JENI may unravel at Jupiter, visit: . For more information about the JUICE mission, go online to .