References of "Nichols, Jonathan"
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See detailOpen flux in Saturn's magnetosphere
Badman, Sarah; Jackman, Caitriuna; Nichols, Jonathan et al

in Icarus (2014), 231

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See detailCassini UVIS Saturn Auroral Images from the 2013 HST/Cassini Campaign
Pryor, Wayne; Jouchoux, Alain; Esposito, Larry et al

Conference (2013, October)

In 2013 coordinated observations of Saturn by the Cassini spacecraft and Hubble Space Telescope (HST) were obtained. During these observations the Cassini spacecraft provided a high-latitude view of ... [more ▼]

In 2013 coordinated observations of Saturn by the Cassini spacecraft and Hubble Space Telescope (HST) were obtained. During these observations the Cassini spacecraft provided a high-latitude view of Saturn's auroras. Intense auroras were observed by the Ultraviolet Imaging Spectrograph (UVIS) from close range (about 5 Saturn radii away). A 6-frame UVIS movie has been constructed from some of the observations from May 20- 21, 2013 showing the evolution of two bright auroral features. We report on the UVIS images, the corresponding spectra, and compare the UVIS data to HST images and data from other Cassini instruments. [less ▲]

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See detailCassini’s recent high inclination views of Saturn’s UV aurorae
Grodent, Denis ULg; Gustin, Jacques ULg; Radioti, Aikaterini ULg et al

Conference (2013, September)

On 22 May 2012, Cassini flew by Titan at a closest approach distance of 955 km. This T83 flyby significantly changed the inclination of the spacecraft’s orbit and marked the beginning of the XXM inclined ... [more ▼]

On 22 May 2012, Cassini flew by Titan at a closest approach distance of 955 km. This T83 flyby significantly changed the inclination of the spacecraft’s orbit and marked the beginning of the XXM inclined phase 1 which will last until March 16, 2015. During this 3-year period, the inclination of Cassini’s orbit reaches very high values, up to 62° in April 2013. This makes it possible to obtain exceptionally good views of Saturn’s poles to observe the auroral emissions in different wavelength ranges. In this presentation, we will summarize the auroral observations taken in the UV with the UVIS camera. We will focus on the morphology of the emission and pinpoint signatures that are attributed to various magnetospheric processes, such as dayside reconnection and auroral bifurcations, nightside reconnection, hot plasma injections. We will also take advantage of the view from nearly above the poles to describe the overall shape and size of the aurora, which are expected to respond to the solar wind conditions. This set of data is to be compared with the contemporaneous observations obtained from the different remote and in situ instruments onboard Cassini. It will also be completed by quasi- simultaneous UV observations of the northern aurorae caught by HST in April 2013 and may allow inter hemispheric comparisons. This information will be used to constrain the various processes at play in Saturn’s magnetosphere. [less ▲]

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See detailJupiter’s elusive bald patch
Grodent, Denis ULg; Bonfond, Bertrand ULg; Gustin, Jacques ULg et al

Conference (2013, July)

The detailed morphology of Jupiter’s UV auroral emissions is definitely very complex. To some extent, this complexity depicts the zoo of processes taking place inside, and sometimes, outside Jupiter’s ... [more ▼]

The detailed morphology of Jupiter’s UV auroral emissions is definitely very complex. To some extent, this complexity depicts the zoo of processes taking place inside, and sometimes, outside Jupiter’s enormous magnetosphere. One is naturally more inclined to focus on the bright emissions, but recent progresses in cosmology teach us that there is also important information in the darkness. In this present, preliminary study, we are exploring a dark region of Jupiter’s polar aurora -“Jupiter’s bald patch”- located poleward of the main emission (oval). It appears to be bordered by patchy features belonging to auroral regions often referred to as the swirl and flare regions. These regions contain the poleward most auroral features. Therefore, it is legitimate to ask whether this dark region, even closer to the pole, is actually the polar cap, implying some level of reconnection of Jupiter’s strong magnetic field with the interplanetary magnetic field. An ongoing HST campaign is providing stunning high temporal and spatial (and spectral) resolution time tagged images of Jupiter’s northern and southern aurora. They show that the bald patch is conspicuous on some images but much less obvious in others. They also suggest that it is not always completely devoid of emission, possibly alluding to a weak, intermittent, Dungey-like cycle. [less ▲]

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See detailBuilding galaxies, stars, planets and the ingredients for life between the stars. A scientific proposal for a European Ultraviolet-Visible Observatory (EUVO)
Gómez de Castro, Ana I.; Appourchaux, Thierry; Barstow, Martin et al

Report (2013)

The growth of luminous structures and the building blocks of life in the Universe began as primordial gas was processed in stars and mixed at galactic scales. The mechanisms responsible for this ... [more ▼]

The growth of luminous structures and the building blocks of life in the Universe began as primordial gas was processed in stars and mixed at galactic scales. The mechanisms responsible for this development are not well understood and have changed over the intervening 13 billion years. To follow the evolution of matter over cosmic time, it is necessary to study the strongest (resonance) transitions of the most abundant species in the Universe. Most of them are in the ultraviolet (UV; 950A-3000A) spectral range that is unobservable from the ground. A versatile space observatory with UV sensitivity a factor of 50-100 greater than existing facilities will revolutionize our understanding of the Universe. Habitable planets grow in protostellar discs under ultraviolet irradiation, a by-product of the star-disk interaction that drives the physical and chemical evolution of discs and young planetary systems. The electronic transitions of the most abundant molecules are pumped by the UV field, providing unique diagnostics of the planet-forming environment that cannot be accessed from the ground. Earth's atmosphere is in constant interaction with the interplanetary medium and the solar UV radiation field. A 50-100 times improvement in sensitivity would enable the observation of the key atmospheric ingredients of Earth-like exoplanets (carbon, oxygen, ozone), provide crucial input for models of biologically active worlds outside the solar system, and provide the phenomenological baseline to understand the Earth atmosphere in context. In this white paper, we outline the key science that such a facility would make possible and outline the instrumentation to be implemented. [less ▲]

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See detailUnraveling electron acceleration mechanisms in Ganymede's space environment through N-S conjugate imagery of Jupiter's aurora
Grodent, Denis ULg; Bonfond, Bertrand ULg; Gérard, Jean-Claude ULg et al

E-print/Working paper (2013)

There is strong scientific interest in Ganymede (Jupiter's third Galilean moon) and its surrounding environment, which stems from the likely presence of a liquid water ocean underneath its icy crust and ... [more ▼]

There is strong scientific interest in Ganymede (Jupiter's third Galilean moon) and its surrounding environment, which stems from the likely presence of a liquid water ocean underneath its icy crust and from its internally driven magnetic field. The interaction of the latter with Jupiter's magnetospheric plasma and its magnetic field gives rise to a unique situation in our solar system implying a mini-magnetosphere embedded within a giant-magnetosphere. This interaction generates Ganymede's ultraviolet auroral footprint in Jupiter's atmosphere. We propose to investigate the strong auroral connection between Jupiter and Ganymede and the variable characteristics of Ganymede's magnetosphere with an innovative approach, taking advantage of the large scale north-south asymmetries of Jupiter's magnetic field. The results obtained for Ganymede will be compared with the case of small injected hot plasma bubbles observed by the Galileo spacecraft and whose size and location are similar to those of Ganymede's magnetosphere. HST is currently the sole instrument capable of obtaining this information which pins down the proposed mechanisms linking the source and sink regions of auroral particles in the giant planets' magnetospheres. [less ▲]

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See detailJupiter system Ultraviolet Dynamics Explorer (JUDE), an instrument proposed for the ESA-JUICE mission
Grodent, Denis ULg; Bunce, Emma J.; Renotte, Etienne ULg et al

Report (2012)

In the proposal that follows we present a detailed concept for the science case, instrument requirements, technical design, calibration and operations, management structure, and financial plan for the ... [more ▼]

In the proposal that follows we present a detailed concept for the science case, instrument requirements, technical design, calibration and operations, management structure, and financial plan for the Jupiter system Ultraviolet Dynamics Experiment (JUDE), which will provide an outstanding solution to the UV instrumentation requirements for the JUICE mission. The JUDE instrument will represent a novel technical capability in UV instrumentation for planetary science, and will deliver the first true UV imaging capability beyond Earth orbit. The JUDE instrument design consists of two separate channels – the imaging channel (ImaC) and the spectrograph channel (SpeC), neither of which has any moving parts. This simple combination of two autonomous channels allows a true image and a spectrum at FUV wavelengths to be obtained simultaneously, allowing science goals to be realised which are not possible with a traditional scanning-slit imaging-spectrograph design The international consortium assembled to build the JUDE instrument is formed of two institutes from two European countries, and one from the United States. Prof. Denis Grodent (Université de Liège, Belgium) will act as the PI for the entire instrument team and the ULg/CSL team will provide a substantial hardware contribution to the instrument in the form of the optics, coatings, and Data Processing Unit (DPU). Dr Emma Bunce (University of Leicester, UK) will act as Co-PI for the instrument and the UoL team will supply the Micro-Channel Plate (MCP) detectors and read-out electronics. Prof. John Clarke (Co-I) of Boston University, USA will provide the grating element for the spectral channel of the instrument, in addition to instrument calibration activities. The science Co-Is are gathered from multiple institutes/nations including Belgium, UK, Germany, Italy, and the United States (see Part 1 for the full team list). Collectively, the team have decades of expertise in the areas of outer planet magnetospheres, planetary auroral and atmospheric emissions and surface UV observations from multiple platforms including Cassini UVIS, Juno UVS, Hubble Space Telescope, and numerous terrestrial missions. The team also have roles on non-UV instruments which will maximise the interpretation of the JUDE data. The two instrument channels are built on proven and robust technology with much flight heritage (e.g. Juno, Cassini, BepiColombo, IMAGE, ROSAT, Chandra, Voyager, Freja, DE-1, Swift). More specifically, the optics and focal plane detector proposed for the JUDE instrument are widely based on previous designs by CSL, at the ULg and UoL, for the FUV Spectro-Imager on the NASA IMAGE spacecraft, the UV Spectrograph on the NASA Juno mission to Jupiter, and the ROSAT Wide Field Camera. The data return from the instrument will greatly benefit the European and international science communities in planetary and terrestrial sciences, and the knowledge obtained will be generally applicable to broader astrophysics disciplines (e.g. extrasolar planetary physics). In answering the UV science objectives for the JUICE mission the JUDE instrument will clearly address the ESA Cosmic Vision Themes 1: What are the conditions for planet formation and the emergence of life? and 2: How does the Solar System work? The JUDE images (in particular) provide a clear path towards a high-level related programme of education and public outreach which the JUDE team are well equipped and keen to exploit. The JUDE instrument will contribute to all of the UV-related science objectives of JUICE, plus additional science objectives not listed in the Science Requirements Matrix. - At Ganymede and other moons (Europa and Callisto) JUDE will contribute directly to breakthroughs in the following scientific areas: 1) the characterisation of local environment, specifically through the first investigation of the morphology and variation of Ganymede’s aurora. A clear understanding of the auroral and atmospheric emissions at Ganymede will provide vital information on their formation mechanisms and will contribute to studies of the interaction of the Ganymede magnetosphere with Jupiter’s magnetosphere; 2) the first detailed observations of the satellites’ atmospheric (exosphere/ionosphere) composition and structure through measurements of their atmospheric emission and absorption spectra during multiple stellar occultation opportunities; and 3) the study of the satellites surface composition using surface reflectance measurements. The measurements at UV wavelengths are essential because they allow the study of the relationship between the satellites’ surface weathering, their atmospheres and the external environment which is mainly affected by the surrounding Jovian magnetosphere. By carefully studying processes at the surface and in the satellites’ atmospheres together, JUDE will provide the information required to distinguish between two classes of compositional heterogeneities at the satellites’ surfaces: 1) heterogeneities that arise from interaction with the external environment; 2) heterogeneities that arise from dynamical interaction with the subsurface. - With respect to Jupiter, JUDE will: 1) provide “state of the art” measurements of the Jovian atmospheric dynamics and transport through high temporal and spatial resolution auroral imaging; 2) allow a new understanding of the Jovian magnetosphere as a fast rotator through interpretation of the Jovian aurora as direct evidence for the 3D magnetosphere dynamics – a view which is continuously available in the planet’s upper atmosphere (independent of the spacecraft location within the magnetosphere); 3) investigate the magnetosphere as a giant accelerator through observations of the field-aligned current systems responsible for acceleration of electrons (and production of aurora); 4) discover the plasma sources and sinks of the moons through auroral imaging of the moon footprints in Jupiter’s atmosphere as a witness of the electromagnetic interactions taking place; 5) obtain new information on Jupiter’s atmospheric structure and composition through multiple stellar occultation opportunities. In addition, JUDE will make remote observations of the Io torus emissions and will provide the first in situ observation of the variability of the torus, over the lifetime of the mission, providing important information about the internal activity of the moon. JUDE offers a unique opportunity to obtain the first concurrent datasets of the different coupled elements of the Jupiter system: Io's atmosphere, aurora, the plasma torus, the Jovian plasma sheet and the Jovian aurora. The JUDE imaging and spectral channels are both designed to capture FUV lines from sulphur ions in the Io plasma torus. Finally, JUDE’s remote sensing capability offers an exciting opportunity to discover the Europa “plume” activity that may be present, through limb observations during flybys and from more distant observing locations. The Ganymede-focused and moon related science objectives will be addressed in the Ganymede orbit phase and during the multiple moon flybys, whilst the Jupiter science will be predominantly achieved during the Jupiter Equatorial Phases and during the high-inclination phase. The JUDE UV imager and spectrograph will produce discovery level science at Ganymede and the first true 2D UV images from Jupiter orbit. The exceptional JUICE trajectory affords many opportunities for breakthrough science discoveries in accordance with the SciRD; in addition to those, it provides unprecedented opportunities to directly witness the electromagnetic connection between Ganymede and Jupiter by making the first simultaneous UV observations of the respective atmospheres within the JUDE field-of-view. This is possible as a direct consequence of the JUDE true imaging capability. To successfully meet the science requirements outlined above, the JUDE ImaC has a spatial resolution of 20 arcsec over a circular field-of-view with 6˚ diameter, which allows a 100 km spatial resolution on Jupiter from Ganymede orbital distances (and 20 m resolution on Ganymede from 200 km, for example). JUDE’s ImaC mirrors and detector window will be covered with multilayer coatings which efficiently select a narrow bandpass from 130 to 143 nm, to allow measurements of the faint Oxygen lines at 130.4 nm and 135.6 nm in Ganymede’s (and other moon’s) atmosphere. This bandpass also allows observations of the SIV lines (between 140.5 and 142.4 nm) emitted within the Io plasma torus and in Io’s atmosphere. The bright Jovian emissions will also be suppressed within this bandpass which will necessarily limit the count rate to an acceptable level. The Ly-α line at 122 nm will be largely excluded as will the reflected sunlight longward of 150 nm. The sensitivity of the ImaC is 50 Rayleigh (at 3-sigma). The SpeC has a spectral resolution of 0.5 nm in order to meet the requirements of the SciRD, and has a field-of-view which is a 6˚ x 0.1˚ slit co-aligned with, and centred on, the ImaC circular field-of-view. The lower wavelength of the SpeC bandpass is set to ~110 nm in order to include the bright Ly-α line (useful to study the H corona) in a region of reduced transmission. The upper wavelength limit, ~195 nm, is such that transmission is slowly decreasing in the 180-195 nm spectral region, allowing measurements of the moon’s albedos beyond 165 nm, as well as the detection of compounds such as CO2, SO2, O2, O3, H2CO3 and H2O2 by comparing JUDE reflectance spectra to those obtained in laboratory studies. FUV emission lines from S and O are also observable within the bandpass and B-type stars emitting within this waveband will allow occultation experiments to be performed, to determine the composition and structure of the moon’s atmospheres and the detection of a possible Europa plume. The same is true for the Jovian atmosphere for which attenuation by H2 and hydrocarbons allows determination of the atmospheric structure. The sensitivity of the SpeC is 10 R/nm (at 3-sigma). The JUDE instrument channels: ImaC and the co-aligned SpeC, are both operating within the 110–195 nm range. Each channel has independent optics and detector elements, providing a level of redundancy such that loss of either imager or spectrograph does not constitute an entire loss of science. In contrast to more conventional (e.g. scanning or pushbroom) imaging spectrographs, JUDE can provide high time resolution (<1 second) high throughput images over a wide field of view (6° diameter) with no time variation across the field – a capability which is critical in gaining a better understanding of the complex dynamical processes taking place in the Jovian magnetosphere. The primary optic in each channel is a multilayer-coated mirror operating at normal incidence, with flight heritage in the form of the scan mirror in the Ultraviolet Spectrograph (UVS) now en-route to Jupiter onboard JUNO. The imaging channel uses a secondary mirror to of a similar type to focus the image onto the focal plane detector, while in the spectrograph channel, the secondary is a spherical, holographic grating. The spectrograph design is simple, with heritage in airglow spectrographs flown on terrestrial UV missions, and the Imaging UV Spectrograph for MAVEN. The grating element is produced by Jobin-Yvon, who have produced diffraction gratings for major missions including SOHO and HST. Each channel includes an identical microchannel plate (MCP) detector with the robust, radiation-tolerant performance required for a mission in the formidable environment of Jupiter. Such detectors are well proven, having flown on many missions including ROSAT (UoL heritage). They have also operated in the vicinity of Jupiter, in the focal plane of the UV spectrograph onboard the Voyager probes. The detector readout is a new type of capacitive division image charge readout (C-DIR; invented by Dr Jon Lapington) which offers, simultaneously, high spatial resolution and high count rate performance. Adaptive signal processing capabilities allow JUDE to accommodate the very wide dynamic range expected, from observations of Jupiter’s auroral ovals which emit with intensities of mega Rayleighs, to the weak (few tens of Rayleigh) emissions found at Ganymede. The readout structure is simple and robust, and has already been demonstrated in laboratory trials, while the electronics chain has its heritage in particle physics detectors, and has therefore been designed with radiation tolerance as a primary consideration. Pre-launch and in-flight calibrations will be implemented to assure that the JUDE data are suitable for quantitative scientific analysis. The proposed JUDE configuration successfully meets the scientific objectives of the JUICE mission. Our decision to implement an imaging channel instead of covering the MUV waveband increases the whole mission’s scientific output while remaining compliant with the MPDD. Due to its high-temporal resolution read-out system, JUDE is capable of producing volumes of data that are incompatible with the limited telemetry allocated to the UV instrument, even after a modest compression factor is applied. We therefore have proposed a mode of operation (the JUDE reference mode) which takes 1 minute snapshots over an observation opportunity (for example during a flyby sequence). Using this reference mode, and taking the maximum count rate estimates for the various targets, we find that the JUDE data volume is compliant with the tight allocation for the UV instrumentation of 40 GBytes/year The JUDE design presented in this proposal is above the mass allocation. We believe that all components of our design are necessary to reach the scientific goals of JUICE mission and that any major changes (such as the descope of a channel) will be at the considerable expense of the expected science return. However, further optimisation will be performed during the Phase A to bring JUDE into the allocated mass envelope while compromising its scientific return only slightly. We propose an efficient management structure with clearly delineated responsibilities. The Principal Investigator, Prof. Denis Grodent (Be) will take on the responsibilities as specified in the JUICE payload Announcement of Opportunity, supported closely by the Co-PI Dr Emma Bunce (UK) and by the team of Co-Investigators. The contribution of each country is represented by lead Co-Investigators: Prof. John Clarke (Boston University), Dr. Candy Hansen (PSI), and Dr Xianzhe Jia (University of Michigan), and Dr Nigel Bannister (UK) as CoI and Instrument Scientist (see Figure 1 below). The philosophy has been to assign well-defined tasks to each institute with an overall project manager to coordinate the efforts. The Consortium Project Manager (Etienne Renotte, CSL) will execute the managerial tasks relevant to the instrument development. The Product and Quality Assurance management will be implemented by all hardware contributors. Each consortium institute has a local project manager for their respective work packages, reporting to the Consortium Project Manager. The outreach potential of JUDE’s instantaneous wide field images is enormous. The potential PhD students of 2030 who we hope to educate and inspire with JUDE images and spectra are currently 3 years old; their supervisors are in secondary school. The team regards the educational aspects of the instrument and data as particularly important, and we plan a comprehensive JUDE/JUICE programme of outreach to schools and to the public, as part of the project and one which will be initiated upon selection. The national funding agency of Belgium serves as the Lead Funding Agency (LFA) for the JUDE instrument. The letters of endorsement from Belgium and United Kingdom are included in this proposal. Although the agencies endorse their respective national contributions, funding will be secured after the selection of the instrument proposal, according to the usual procedure. [less ▲]

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See detailJUDE: A Far-UV Imager for JUICE
Grodent, Denis ULg; Bunce, Emma; Bannister, Nigel et al

Poster (2011, August 31)

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See detailObservational evidence of a localized magnetic anomaly near Jupiter’s North Pole
Grodent, Denis ULg; Bonfond, Bertrand ULg; Gérard, Jean-Claude ULg et al

Conference (2008, April 18)

We have analyzed more than 1000 HST/ACS images of Jupiter’s ultraviolet auroral emission in the northern hemisphere. A systematic planet center finding algorithm made it possible to infer reliable and ... [more ▼]

We have analyzed more than 1000 HST/ACS images of Jupiter’s ultraviolet auroral emission in the northern hemisphere. A systematic planet center finding algorithm made it possible to infer reliable and consistent jovicentric location of the auroral footprints of Io, Europa and Ganymede. These footprints form reference contours which provide an absolute magnetic mapping from the ionosphere of Jupiter to the equatorial plane, independent of any magnetic field model. So far, the VIP4 magnetic field model is the most accurate in terms of fitting the auroral emissions. However, it cannot reproduce the distorted shape of the satellites UV footpaths in the “kink region” in the northern ionosphere between S3 longitudes 80 ̊-150 ̊. We show that the model is significantly improved by decreasing the VIP4 surface magnetic field in the kink region and by adding a localized dipolar perturbation field beneath the surface. [less ▲]

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See detailAuroral evidence of a localized magnetic anomaly in Jupiter's northern hemisphere
Grodent, Denis ULg; Bonfond, Bertrand ULg; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research (2008), 113(A9),

We analyze more than 1000 HST/Advanced Camera for Survey images of the ultraviolet auroral emissions appearing in the northern hemisphere of Jupiter. The auroral footprints of Io, Europa, and Ganymede ... [more ▼]

We analyze more than 1000 HST/Advanced Camera for Survey images of the ultraviolet auroral emissions appearing in the northern hemisphere of Jupiter. The auroral footprints of Io, Europa, and Ganymede form individual footpaths, which are fitted with three reference contours. The satellite footprints provide a convenient mapping between the northern Jovian ionosphere and the equatorial plane in the middle magnetosphere, independent of any magnetic field model. The VIP4 magnetic field model is in relatively good agreement with the observed footprint of Io. However, in the auroral kink sector, between the 80 degrees and 150 degrees System III meridians, the model significantly departs from the observation. One possible way to improve the agreement between the VIP4 model and the observed footprints is to include a magnetic anomaly. We suggest that this anomaly is characterized by a weakening of the surface magnetic field in the kink sector and by an added localized tilted dipole field. This dipole rotates with the planet at a depth of 0.245 R-J below the surface, and its magnitude is set to similar to 1% of Jupiter's dipole moment. The anomaly has a very limited influence on the magnetic field intensity in the equatorial plane between the orbits of Io and Ganymede. However, it is sufficient to bend the field lines near the high-latitude atmosphere and to reproduce the observed satellite ultraviolet footpaths. JUNO's in situ measurements will determine the structure of Jupiter's magnetic field in detail to expand on these results. [less ▲]

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