1. |
- Fletcher, Leigh N., et al.
(författare)
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Jupiter Science Enabled by ESA's Jupiter Icy Moons Explorer
- 2023
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Ingår i: Space Science Reviews. - : Springer Nature. - 0038-6308 .- 1572-9672. ; 219:7
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Forskningsöversikt (refereegranskat)abstract
- ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible imaging (340-1080 nm), visible/near-infrared spectroscopy (0.49-5.56 & mu;m), and sub-millimetre sounding (near 530-625 GHz and 1067-1275 GHz). This is coupled to radio, stellar, and solar occultation opportunities to explore the atmosphere at high vertical resolution; and radio and plasma wave measurements of electric discharges in the Jovian atmosphere and auroras. Cross-disciplinary scientific investigations enable JUICE to explore coupling processes in giant planet atmospheres, to show how the atmosphere is connected to (i) the deep circulation and composition of the hydrogen-dominated interior; and (ii) to the currents and charged particle environments of the external magnetosphere. JUICE will provide a comprehensive characterisation of the atmosphere and auroras of this archetypal giant planet.
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2. |
- Mi, Yongcui, 1986-, et al.
(författare)
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Beam shaping with a deformable mirror for gap bridging in autogenous laser butt welding
- 2023
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Ingår i: Optics and Lasers in Engineering. - 0143-8166. ; 169
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Tidskriftsartikel (refereegranskat)abstract
- In autogenous laser butt welding the variability of the joint gap can cause problems in terms of weld seam quality. A suitable strategy to alleviate this is to dynamically shape the laser beam instead of a circular-shaped beam with typical Gaussian or top hat distributions. Currently available systems cannot reach sufficient performance due to both the real time control system for the shape variation and the limited laser power currently manageable. In the present work, the possibility of bridging the joint gap during welding using a deformable mirror to elongate the focused laser beam from circular to transversal elliptical shape was investigated. The effect of the beam shaping on the geometry of the weld pool and of the weld cross sections was analysed, for different values of the gap in comparison with a circular Gaussian beam. It was demonstrated that the adoption of a transversal elliptical laser beam makes the welding process more stable, especially for large gaps (i.e. larger than the circular beam radius). Thanks to the beam shaping, the extension of the fused zone (in terms of the cross section area, height and width) resulted to be less sensitive to the gap's dimension; in addition, the extension of the heat affected zone and the presence of undercuts were evidently reduced.
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- Rotundi, Alessandra, et al.
(författare)
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Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun
- 2015
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 347:6220
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Tidskriftsartikel (refereegranskat)abstract
- Critical measurements for understanding accretion and the dust/gas ratio in the solar nebula, where planets were forming 4.5 billion years ago, are being obtained by the GIADA (Grain Impact Analyser and Dust Accumulator) experiment on the European Space Agency's Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between 3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) detected 35 outflowing grains of mass 10(-10) to 10(-7) kilograms, and 48 grains of mass 10(-5) to 10(-2) kilograms, respectively. Combined with gas data from the MIRO (Microwave Instrument for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio of 4 +/- 2 averaged over the sunlit nucleus surface. A cloud of larger grains also encircles the nucleus in bound orbits from the previous perihelion. The largest orbiting clumps are meter-sized, confirming the dust/gas ratio of 3 inferred at perihelion from models of dust comae and trails.
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4. |
- Van Hoolst, Tim, et al.
(författare)
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Geophysical Characterization of the Interiors of Ganymede, Callisto and Europa by ESA's JUpiter ICy moons Explorer
- 2024
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Ingår i: Space Science Reviews. - : Springer. - 0038-6308 .- 1572-9672. ; 220:5
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Forskningsöversikt (refereegranskat)abstract
- The JUpiter ICy moons Explorer (JUICE) of ESA was launched on 14 April 2023 and will arrive at Jupiter and its moons in July 2031. In this review article, we describe how JUICE will investigate the interior of the three icy Galilean moons, Ganymede, Callisto and Europa, during its Jupiter orbital tour and the final orbital phase around Ganymede. Detailed geophysical observations about the interior of the moons can only be performed from close distances to the moons, and best estimates of signatures of the interior, such as an induced magnetic field, tides and rotation variations, and radar reflections, will be obtained during flybys of the moons with altitudes of about 1000 km or less and during the Ganymede orbital phase at an average altitude of 490 km. The 9-month long orbital phase around Ganymede, the first of its kind around another moon than our Moon, will allow an unprecedented and detailed insight into the moon's interior, from the central regions where a magnetic field is generated to the internal ocean and outer ice shell. Multiple flybys of Callisto will clarify the differences in evolution compared to Ganymede and will provide key constraints on the origin and evolution of the Jupiter system. JUICE will visit Europa only during two close flybys and the geophysical investigations will focus on selected areas of the ice shell. A prime goal of JUICE is the characterisation of the ice shell and ocean of the Galilean moons, and we here specifically emphasise the synergistic aspects of the different geophysical investigations, showing how different instruments will work together to probe the hydrosphere. We also describe how synergies between JUICE instruments will contribute to the assessment of the deep interior of the moons, their internal differentiation, dynamics and evolution. In situ measurements and remote sensing observations will support the geophysical instruments to achieve these goals, but will also, together with subsurface radar sounding, provide information about tectonics, potential plumes, and the composition of the surface, which will help understanding the composition of the interior, the structure of the ice shell, and exchange processes between ocean, ice and surface. Accurate tracking of the JUICE spacecraft all along the mission will strongly improve our knowledge of the changing orbital motions of the moons and will provide additional insight into the dissipative processes in the Jupiter system. Finally, we present an overview of how the geophysical investigations will be performed and describe the operational synergies and challenges.
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