References of "Hubert, Benoît"
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See detailForbidden oxygen lines at various nucleocentric distances in comets
Decock, Alice ULg; Jehin, Emmanuel ULg; Rousselot, P. et al

in Astronomy and Astrophysics (2015), 573

Aims: We study the formation of the [OI] lines - that is, 5577.339 Å (the green line), 6300.304 Å and 6363.776 Å (the two red lines) - in the coma of comets and determine the parent species of the oxygen ... [more ▼]

Aims: We study the formation of the [OI] lines - that is, 5577.339 Å (the green line), 6300.304 Å and 6363.776 Å (the two red lines) - in the coma of comets and determine the parent species of the oxygen atoms using the ratio of the green-to-red-doublet emission intensity, I[SUB]5577[/SUB]/(I[SUB]6300[/SUB] + I[SUB]6364[/SUB]), (hereafter the G/R ratio) and the line velocity widths. <BR /> Methods: We acquired high-resolution spectroscopic observations at the ESO Very Large Telescope of comets C/2002 T7 (LINEAR), 73P-C/Schwassmann-Wachmann 3, 8P/Tuttle, and 103P/Hartley 2 when they were close to Earth (<0.6 au). Using the observed spectra, which have a high spatial resolution (<60 km/pixel), we determined the intensities and widths of the three [OI] lines. We spatially extracted the spectra to achieve the best possible resolution of about 1-2'', that is, nucleocentric projected distances of 100 to 400 km depending on the geocentric distance of the comet. We decontaminated the [OI] green line from C[SUB]2[/SUB] lines blends that we identified. <BR /> Results: The observed G/R ratio in all four comets varies as a function of nucleocentric projected distance (between ~0.25 to ~0.05 within 1000 km). This is mainly due to the collisional quenching of O([SUP]1[/SUP]S) and O([SUP]1[/SUP]D) by water molecules in the inner coma. The observed green emission line width is about 2.5 km s[SUP]-1[/SUP] and decreases as the distance from the nucleus increases, which can be explained by the varying contribution of CO[SUB]2[/SUB] to the O([SUP]1[/SUP]S) production in the innermost coma. The photodissociation of CO[SUB]2[/SUB] molecules seem to produce O([SUP]1[/SUP]S) closer to the nucleus, while the water molecule forms all the O([SUP]1[/SUP]S) and O([SUP]1[/SUP]D) atoms beyond 10[SUP]3[/SUP] km. Thus we conclude that the main parent species producing O([SUP]1[/SUP]S) and O([SUP]1[/SUP]D) in the inner coma is not always the same. The observations have been interpreted in the framework of the previously described coupled-chemistry-emission model, and the upper limits of the relative abundances of CO[SUB]2[/SUB] were derived from the observed G/R ratios. Measuring the [OI] lines might provide a new way to determine the CO[SUB]2[/SUB] relative abundance in comets. Based on observations made with ESO Telescope at the La Silla Paranal Observatory under programs ID 073.C-0525, 277.C-5016, 080.C-0615 and 086.C-0958.Tables 3 and 4 are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201424403/olm">http://www.aanda.org</A> [less ▲]

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See detailMonte Carlo Simulation of Metastable Oxygen Photochemistry in Cometary Atmospheres
Bisikalo, D. V.; Shematovich, V. I.; Gérard, Jean-Claude ULg et al

in The Astrophysical Journal (2015), 798

Cometary atmospheres are produced by the outgassing of material, mainly H[SUB]2[/SUB]O, CO, and CO[SUB]2[/SUB] from the nucleus of the comet under the energy input from the Sun. Subsequent photochemical ... [more ▼]

Cometary atmospheres are produced by the outgassing of material, mainly H[SUB]2[/SUB]O, CO, and CO[SUB]2[/SUB] from the nucleus of the comet under the energy input from the Sun. Subsequent photochemical processes lead to the production of other species generally absent from the nucleus, such as OH. Although all comets are different, they all have a highly rarefied atmosphere, which is an ideal environment for nonthermal photochemical processes to take place and influence the detailed state of the atmosphere. We develop a Monte Carlo model of the coma photochemistry. We compute the energy distribution functions (EDF) of the metastable O([SUP]1[/SUP]D) and O([SUP]1[/SUP]S) species and obtain the red (630 nm) and green (557.7 nm) spectral line shapes of the full coma, consistent with the computed EDFs and the expansion velocity. We show that both species have a severely non-Maxwellian EDF, that results in broad spectral lines and the suprathermal broadening dominates due to the expansion motion. We apply our model to the atmosphere of comet C/1996 B2 (Hyakutake) and 103P/Hartley 2. The computed width of the green line, expressed in terms of speed, is lower than that of the red line. This result is comparable to previous theoretical analyses, but in disagreement with observations. We explain that the spectral line shape does not only depend on the exothermicity of the photochemical production mechanisms, but also on thermalization, due to elastic collisions, reducing the width of the emission line coming from the O([SUP]1[/SUP]D) level, which has a longer lifetime. [less ▲]

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See detailThe EChO science case
Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul et al

in ArXiv e-prints (2015), 1502

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general ... [more ▼]

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has been designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large and diverse planet sample within its four-year mission lifetime. EChO can target the atmospheres of super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300K-3000K) of F to M-type host stars. Over the next ten years, several new ground- and space-based transit surveys will come on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on finding bright, nearby systems. The current rapid rate of discovery would allow the target list to be further optimised in the years prior to EChO's launch and enable the atmospheric characterisation of hundreds of planets. Placing the satellite at L2 provides a cold and stable thermal environment, as well as a large field of regard to allow efficient time-critical observation of targets randomly distributed over the sky. A 1m class telescope is sufficiently large to achieve the necessary spectro-photometric precision. The spectral coverage (0.5-11 micron, goal 16 micron) and SNR to be achieved by EChO, thanks to its high stability and dedicated design, would enable a very accurate measurement of the atmospheric composition and structure of hundreds of exoplanets. [less ▲]

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See detailMagnetic Reconnection During Major Magnetospheric Storms
Hubert, Benoît ULg; Milan, S.E.; Cowley, S.W.H.

Poster (2014, December)

We combine imaging of the proton aurora from the SI12-IMAGE instrument with ionospheric convection measurement from the SuperDARN radar network to analyze the cycle of magnetic flux opening and closure of ... [more ▼]

We combine imaging of the proton aurora from the SI12-IMAGE instrument with ionospheric convection measurement from the SuperDARN radar network to analyze the cycle of magnetic flux opening and closure of the Earth magnetosphere. Interaction between the solar wind and the Earth geomagnetic environment causes a reconfiguration of the magnetic field that connects the interplanetary magnetic field (IMF) to the geomagnetic field. This reconnection process produces open magnetic field lines (i.e. field lines of the magnetosphere that close through the interplanetary medium) that are dragged to the magnetotail by the solar wind flow, where they eventually reconnect again, back to a closed topology. The SI12 imaging of the Doppler-shifted Lyman-α emission of the proton aurora is used to estimate the location of the boundary separating open and closed field lines at ionospheric altitude. We then estimate the open magnetic flux of the Earth magnetosphere, encircled by this boundary. The rate of reconnection causing a variation of the open magnetic flux can be expressed as a voltage in application of Faraday’s law. This voltage is measured along the open/closed field line boundary determined from the imaging data. The electric field associated with the voltage has two origins: motion of the boundary and the ionospheric field. We use the ionospheric electric field deduced from ionospheric convection measurement from the SuperDARN to estimate the reconnection voltage at the magnetopause (flux opening) and in the magnetotail (flux closure) accounting for the motion of the open/closed field line boundary determined from the SI12 images. The method is applied during several (strong) geomagnetic storms. These intervals are characterized by large values of open flux and reconnection rates, as a result of coupling between the solar wind and the geomagnetic environment. We present these results in terms of a magnetospheric mode that develops under strong coupling with the solar wind, a condition known to be prone to the development of sawtooth events, characterized by overloading of the magnetosphere with open magnetic flux. [less ▲]

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See detailMagnetospheric modes and magnetic reconnection.
Hubert, Benoît ULg; Milan, S.E.; Cowley, S.W.H.

Poster (2014, November)

We combine imaging of the proton aurora from the SI12-IMAGE instrument with measurement of the ionospheric convection from the SuperDARN radar network to analyze the cycle of magnetic flux opening and ... [more ▼]

We combine imaging of the proton aurora from the SI12-IMAGE instrument with measurement of the ionospheric convection from the SuperDARN radar network to analyze the cycle of magnetic flux opening and closure of the Earth magnetosphere. Interaction between the solar wind and the Earth geomagnetic environment causes a reconfiguration of the magnetic field that connects the interplanetary magnetic field (IMF) to the geomagnetic field. This reconnection process produces open magnetic field lines (i.e. field lines of the magnetosphere that close through the interplanetary medium) that are dragged to the magnetotail by the solar wind flow, where they eventually reconnect again, back to a closed topology. The SI12 imaging of the Doppler-shifted Lyman-α emission of the proton aurora is used to estimate the location of the boundary separating open and closed field lines at ionospheric altitude. We then estimate the open magnetic flux of the Earth magnetosphere, encircled by this boundary. The rate of reconnection causing a variation of the open magnetic flux can be expressed as a voltage in application of Faraday’s law. This voltage is measured along the open/closed field line boundary determined from the imaging data. The electric field associated with the voltage has two origins: motion of the boundary and the ionospheric field. We use the ionospheric electric field deduced from ionospheric convection measurement from the SuperDARN to estimate the reconnection voltage at the magnetopause (flux opening) and in the magnetotail (flux closure) accounting for the motion of the open/closed field line boundary determined from the SI12 images. The method is applied during substorms, steady geomagnetic convection intervals, sawtooth events and geomagnetic storms. These different intervals are characterized by different values of open flux and reconnection rates, as a result of different coupling between the solar wind and the geomagnetic environment. We interpret these differences as different dynamic modes of the magnetospheric system. Shock-induced flux closure events are also presented, as an exceptional situation that differs from the modes presented above. [less ▲]

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See detailDiurnal thermosphere scale height from MEX/SPICAM grazing limb data
Stiepen, Arnaud ULg; Gérard, Jean-Claude ULg; Bougher, S et al

Conference (2014, July 01)

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See detailIonization Fraction in the Thermosphere of the Exoplanet HD 209458b
Ionov, D. E.; Bisikalo, D. V.; Shematovich, V. I. et al

in Solar System Research (2014), 48

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See detailNonthermal O(1S) and O(1D) populations in cometary atmospheres
Hubert, Benoît ULg; Bisikalo, D.V.; Shematovich, V.I. et al

Conference (2013, December)

Recent developments in the field of cometary science have motivated many studies dealing with the nucleus composition and mineralogy, and also with the photochemistry of the coma. In particular, ground ... [more ▼]

Recent developments in the field of cometary science have motivated many studies dealing with the nucleus composition and mineralogy, and also with the photochemistry of the coma. In particular, ground based observations have shown that the visible oxygen emissions at 557.7 and 630 nm, both belonging to the Rosetta-VIRTIS-M passband, present different line profiles, pointing to specific photochemical processes. In this work, we present a Monte Carlo simulation of the O(1D) and O(1S) photochemistry including photodissociation of H2O, CO2 and CO, quenching, collisional thermalization and radiative decay. The model solves Boltzmann's integro differential equation including sources and sinks, as well as a prescribed expansion velocity of the coma. The energy distribution functions (EDF's) of O(1S) and O(1D) are computed at cometocentric distances ranging between 10 and 5000 km. We find that the EDF's of both O(1D) and O(1S) are strongly nonthermal, up to a degree that sharply varies with cometocentric distance, as thermalization is less efficient when the density of the dominant species is reduced. It follows that the Doppler profile of the visible radiations emitted by both species is non-gaussian in a frame of reference moving with the expanding coma. The nonthermal volume emission rate is then integrated along a set of chosen line of sights, accounting for the explicit Doppler profiles derived from the EDF's as well as the expansion motion, and the Doppler profile of the full coma is computed. It appears that most of the line width is due to the expansion motion, although the detailed line shape remains sensitive to the nonthermal nature of the EDF's. Our computation can then be compared with the line profiles observed from the ground with the UVES spectrograph mounted on the ESO-VLT. [less ▲]

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See detailAnomalous OI-989 Å intensity profile: solving an old mystery.
Hubert, Benoît ULg; Gérard, Jean-Claude ULg; Shematovich, Valery I. et al

Poster (2012, December 06)

Sounding rocket measurements conducted in 1988 under high solar activity conditions had revealed that the intensity of the thermospheric OI emission at 989 Å presents an anomalous vertical profile ... [more ▼]

Sounding rocket measurements conducted in 1988 under high solar activity conditions had revealed that the intensity of the thermospheric OI emission at 989 Å presents an anomalous vertical profile. Observation presents an intensity much higher than what can be expected compared with theoretical results including the photochemical sources of excited oxygen and the radiative transfer of the photons of the OI-989 sextuplet especially above the exobase. Attempts were conducted to clarify the discrepancy by including the non-thermal O(3P) population that appears around the exobase and higher, and that can scatter Doppler-shifted photons of the line profile farther from the rest wavelength. All attempts based on detail modeling of the photochemical processes and radiative transfer revealed unable to account for the discrepancy. Recently the FUV and EUV solar flux has been obtained at very high spectral resolution with the SOHO-SUMER instrument, revealing a significant solar oxygen emission at 989 Å, i.e. a source of photons that had never been accounted for before. In this study, we compute the radiative transfer of the OI-989 Å multiplet including the photochemical sources of excited oxygen, the scattering of incident solar photons and the effect of non-thermal atoms. We find a good agreement with the previous sounding rocket observation, solving the old mystery. We also compare the model simulations with the observations of the STP-78 satellite to better determine the relative importance of the various parameters at work in the radiative transfer of the OI-989 Å multiplet. [less ▲]

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See detailKuaFu: exploring the Sun-Earth connection
Milan, Steve; Dunlop, Malcolm; Fazakerley, Andrew et al

in Astronomy and Geophysics (2012), 53

Steve Milan and the KuaFu team explain why this space mission will provide space weather data that will help to understand and mitigate the risks it poses to our increasingly technological society.

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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 detailCassini-UVIS observation of dayglow FUV emissions of carbon in the thermosphere of Venus
Hubert, Benoît ULg; Gérard, Jean-Claude ULg; Gustin, Jacques ULg et al

in Icarus (2012), 220

We analyze FUV spatially-resolved dayglow spectra obtained at 0.37 nm resolution by the UVIS instrument during the Cassini flyby of Venus. The intensities of the ultraviolet multiplets of carbon at 126.1 ... [more ▼]

We analyze FUV spatially-resolved dayglow spectra obtained at 0.37 nm resolution by the UVIS instrument during the Cassini flyby of Venus. The intensities of the ultraviolet multiplets of carbon at 126.1, 156.1 and 165.7 nm are determined using a least squares fit technique applied to all dayglow spectra recorded by UVIS along the Cassini track. These intensities are compared with the results of a full radiative transfer model of these emissions, that includes the known photochemical sources of photons and resonant scattering of sunlight. The carbon density profile of the Venus thermosphere has never been directly measured and is taken from a model. We find a serious disagreement between these observations and modeling that can be accounted for by applying a scaling factor to the carbon column. This needed scaling factor is found to increase monotonically with solar zenith angle, suggesting a possible photochemical origin to the disagreement, possibly involving the photochemistry of molecular oxygen to which the carbon density is highly sensitive. [less ▲]

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See detailMeasurements of the helium 584 Å airglow during the Cassini flyby of Venus
Gérard, Jean-Claude ULg; Gustin, Jacques ULg; Hubert, Benoît ULg et al

in Planetary and Space Science (2011), 59

The helium resonance line at 584 Å has been observed with the UltraViolet Imaging Spectrograph (UVIS) Extreme Ultraviolet channel during the flyby of Venus by Cassini at a period of high solar activity ... [more ▼]

The helium resonance line at 584 Å has been observed with the UltraViolet Imaging Spectrograph (UVIS) Extreme Ultraviolet channel during the flyby of Venus by Cassini at a period of high solar activity. The brightness was measured along the disk from the morning terminator up to the bright limb near local noon. The mean disk intensity was ˜320 R, reaching ˜700 R at the bright limb. These values are slightly higher than those determined from previous observations. The sensitivity of the 584 Å intensity to the helium abundance is analyzed using recent cross-sections and solar irradiance measurements at 584 Å. The intensity distribution along the UVIS footprint on the disk is best reproduced using the EUVAC solar flux model and the helium density distribution from the VTS3 empirical model. It corresponds to a helium density of 8×10[SUP]6[/SUP] cm[SUP]-3[/SUP] at the level of where the CO[SUB]2[/SUB] is 2×10[SUP]10[/SUP] cm[SUP]-3[/SUP]. [less ▲]

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See detailEUV spectroscopy of the Venus dayglow with UVIS on Cassini
Gérard, Jean-Claude ULg; Hubert, Benoît ULg; Gustin, Jacques ULg et al

in Icarus: International Journal of Solar System Studies (2011), 211

We analyze EUV spatially-resolved dayglow spectra obtained at 0.37 nm resolution by the UVIS instrument during the Cassini flyby of Venus on 24 June 1999, a period of high solar activity level. Emissions ... [more ▼]

We analyze EUV spatially-resolved dayglow spectra obtained at 0.37 nm resolution by the UVIS instrument during the Cassini flyby of Venus on 24 June 1999, a period of high solar activity level. Emissions from OI, OII, NI, CI and CII and CO have been identified and their disc average intensity has been determined. They are generally somewhat brighter than those determined from the observations made with the HUT spectrograph at a lower activity level, We present the brightness distribution along the foot track of the UVIS slit of the OII 83.4 nm, OI 98.9 nm, Lyman-ß + OI 102.5 nm and NI 120.0 nm multiplets, and the CO C-X and B-X Hopfield-Birge bands. We make a detailed comparison of the intensities of the 834 nm, 989 nm, 120.0 nm multiplets and CO B-X band measured along the slit foot track on the disc with those predicted by an airglow model previously used to analyze Venus and Mars ultraviolet spectra. This model includes the treatment of multiple scattering for the optically thick OI, OII and NI multiplets. It is found that the observed intensity of the OII emission at 83.4 nm is higher than predicted by the model. An increase of the O[SUP]+[/SUP] ion density relative to the densities usually measured by Pioneer Venus brings the observations and the modeled values into better agreement. The calculated intensity variation of the CO B-X emission along the track of the UVIS slit is in fair agreement with the observations. The intensity of the OI 98.9 nm emission is well predicted by the model if resonance scattering of solar radiation by O atoms is included as a source. The calculated brightness of the NI 120 nm multiplet is larger than observed by a factor of ˜2-3 if photons from all sources encounter multiple scattering. The discrepancy reduces to 30-80% if the photon electron impact and photodissociation of N[SUB]2[/SUB] sources of N([SUP]4[/SUP]S) atoms are considered as optically thin. Overall, we find that the O, N[SUB]2[/SUB] and CO densities from the empirical VTS3 model provide satisfactory agreement between the calculated and the observed EUV airglow emissions. [less ▲]

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See detailA superposed epoch investigation of the relation between magnetospheric solar wind driving and substorm dynamics with geosynchronous particle injection signatures
Boakes, P. D.; Milan, S. E.; Abel, G. A. et al

in Journal of Geophysical Research. Space Physics (2011), 116

We report a superposed epoch analysis of the hemispheric open magnetic flux, maximum nightside auroral intensity, geomagnetic activity, and solar wind and interplanetary magnetic field conditions around ... [more ▼]

We report a superposed epoch analysis of the hemispheric open magnetic flux, maximum nightside auroral intensity, geomagnetic activity, and solar wind and interplanetary magnetic field conditions around the time of substorm onset for three distinct categories of substorms defined by their energetic particle injection signatures. Substorms identified from global auroral imagery are classified into one of three categories based on their energetic particle injection signatures as seen at geosynchronous orbit by the Los Alamos National Laboratory spacecraft. Category 1 events are associated with a “classic” substorm injection, category 2 events show varied activity (i.e., energetic enhancements not following the evolution expected for classic substorms), and category 3 events show no apparent injection activity. The superposed epoch analysis reveals that the three distinct particle injection categories exhibit distinct differences in the level and continuity of magnetospheric driving by the solar wind, such that category 1 events can be described as classic substorm events, category 2 as continuously driven events, and category 3 as weak events. The results of this study suggest that the level and continuity of the dayside solar wind driving of the magnetosphere during substorms have a direct impact on the injection of energetic particles to geosynchronous orbit at substorm onset. These results could have considerable value in empirical predictions of the space weather environment. [less ▲]

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See detailComparison of magnetotail magnetic flux estimates based on global auroral images and simultaneous solar wind—magnetotail measurements
Shukhtina, M. A.; Sergeev, V. A.; Dejong, A. D. et al

in Journal of Atmospheric & Solar-Terrestrial Physics (2010), 72

We compared simultaneous magnetotail magnetic flux F estimates, (1) based on in situ spacecraft measurements in the tail and solar wind (F[SUB]T[/SUB]) with (2) the polar cap magnetic flux, estimated from ... [more ▼]

We compared simultaneous magnetotail magnetic flux F estimates, (1) based on in situ spacecraft measurements in the tail and solar wind (F[SUB]T[/SUB]) with (2) the polar cap magnetic flux, estimated from global auroral images (using proton-induced or electron-induced emissions, F[SUB]p[/SUB] or F[SUB]e[/SUB], respectively). Simultaneous F[SUB]p[/SUB] and F[SUB]e[/SUB] estimates gave the correlation coefficient CC=0.74, indicating that these measures are not absolutely precise. Regression analysis of F[SUB]T[/SUB] versus F[SUB]e[/SUB] and F[SUB]p[/SUB] gave CC values 0.73 and 0.50, correspondingly. F[SUB]T[/SUB] values, containing closed magnetic flux, are systematically higher than F[SUB]p[/SUB] and F[SUB]e[/SUB] by 20-30%. Motivated by diverse results, published by different groups, we reanalyzed the F dependence on the dayside merging electric field E[SUB]m[/SUB] for different dynamical states. The linear regression F(E[SUB]m[/SUB]) for substorm onsets shows a large slope ˜0.07-0.12GWb/(mV/m) for all F[SUB]p[/SUB], F[SUB]e[/SUB] and F[SUB]T[/SUB], confirming the loading-unloading substorm scheme. For SMC intervals this slope is only 0.03 GWb/(mV/m). [less ▲]

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See detailA superposed epoch analysis of auroral evolution during substorms: Local time of onset region
Milan, S. E.; Grocott, A.; Hubert, Benoît ULg

in Journal of Geophysical Research. Space Physics (2010), 115

Previous workers have shown that the magnetic local time (MLT) of substorm onset depends on the prevailing east-west component of the interplanetary magnetic field (IMF). To investigate the influence of ... [more ▼]

Previous workers have shown that the magnetic local time (MLT) of substorm onset depends on the prevailing east-west component of the interplanetary magnetic field (IMF). To investigate the influence of the onset MLT on the subsequent auroral response we perform a superposed epoch analysis of the auroral evolution during approximately 2000 substorms using observations from the FUV instrument on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft. We subdivide the substorms by onset latitude and onset local time before determining average auroral images before and after substorm onset, for both electron and proton aurorae. We find that during the growth phase there is preexisting auroral emission in the MLT sector of the subsequent onset. After onset the auroral bulge expands eastward and westward, but remains centered on the onset sector. Approximately 30 min after onset, during the substorm recovery phase, the peaks in electron and proton auroral emission move into the postnoon and prenoon sectors, respectively, reflecting the “average” auroral precipitation patterns determined by previous studies. Superposed epoch analysis of the interplanetary magnetic field for the substorms under study suggests that the B[SUB]Y[/SUB] component of the IMF must be biased toward positive or negative values for up to a day prior to onset for the onset MLT to be influenced. [less ▲]

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See detailAn evaluation of the contributions of the distant and near-Earth neutral lines to magnetotail reconnection rates and magnetic flux closure
Milan, Steve; Boakes, Peter; Imber, Suzanne et al

Conference (2010, May 01)

The expanding-contracting polar cap paradigm relates the dayside and nightside rates of magnetic reconnection to changes in the size of the ionospheric polar cap, the amount of magnetic flux in the ... [more ▼]

The expanding-contracting polar cap paradigm relates the dayside and nightside rates of magnetic reconnection to changes in the size of the ionospheric polar cap, the amount of magnetic flux in the magnetotail lobes, and the excitation of ionospheric and magnetospheric plasma convection. Expansions of the polar cap are the consequence of dayside reconnection, the merging of interplanetary magnetic flux with the terrestrial dipole to increase the proportion of the dipole that is open. Contractions of the polar cap are caused by magnetic reconnection in the magnetotail at a distant neutral (or X-) line (DXL) and near-Earth neutral line (NEXL), the latter especially during substorms, to reduce the open flux in the magnetosphere. There is debate surrounding the proportion of flux closure provided by the DXL and NEXL, and hence whether substorms dominate the nightside contribution to ionospheric and magnetospheric convection. This study utilizes a 7-day interval of auroral observations from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite and convection measurements by the Super Dual Auroral Radar Network (SuperDARN) to quantify the nightside rates of reconnection during substorm and non-substorm periods and hence investigate DXL and NEXL flux closure. [less ▲]

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