References of "Gérard, Jean-Claude"
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See detailThe Martian diffuse aurora: a model of ultraviolet and visible emissions
Gérard, Jean-Claude ULg; Soret, Lauriane ULg; Shematovich, V.I. et al

in Icarus (2017), 288

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar ... [more ▼]

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar activity on several occasions from the MAVEN spacecraft. We describe the results of Monte Carlo simulations of the production of several ultraviolet and violet auroral emissions for initial electron energies extending from 0.25 to 200 keV. These include the CO2+ ultraviolet doublet (UVD) at 288.3 and 289.6 nm and the Fox–Duffendack–Barker (FDB) bands, CO Cameron and Fourth Positive bands, OI 130.4 and 297.2 nm and CI 156.1 nm and 165.7 nm multiplets. We calculate the nadir and limb production rates of several of these emissions for a unit precipitated energy flux. Our results indicate that electrons in the range 50-200 keV produce maximum CO2+ UVD emission below 75 km, in agreement with the MAVEN observations. We calculate the efficiency of photon production per unit precipitated electron power. The strongest emissions are the CO2+ FDB, UVD and CO Cameron bands and the oxygen mission at 297.2 nm. The metastable a 3Π state which radiates the Cameron bands is deactivated by collisions below about 110 km. As a consequence, we show that the Cameron band emission is expected to peak at a higher altitude than the CO2+ UVD and FDB bands. Collisional quenching also causes the intensity ratio of the CO2+ UVD to CO Cameron bands to increase below ∼100 km in the energetic diffuse aurora. [less ▲]

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See detailGlobal Simulation of UV atmospheric Emissions
Gonzalez-Galindo; Lopez-Valverde; Forget et al

Poster (2017, January 19)

Detailed reference viewed: 11 (1 ULg)
See detailThree Types of Aurora observed by MAVEN/IUVS: Implications for Mars’ upper Atmosphere Energy Budget
Connour; Schneider; Jain et al

Poster (2017, January 17)

Detailed reference viewed: 21 (3 ULg)
See detailNO Nightglow studies status
Stiepen, Arnaud ULg; Jain; Deighan et al

Conference (2017, January 16)

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See detailMARTIAN ULTRAVIOLET AURORA: RESULTS OF MODEL SIMULATIONS
Gérard, Jean-Claude ULg; Soret, Lauriane ULg; Shematovich, V.I. et al

Conference (2017, January)

We present recent modeling results based on observations performed with the UV spectrographs on board the Mars Express and MAVEN missions.Two types of aurora are discussed: the localized and transient ... [more ▼]

We present recent modeling results based on observations performed with the UV spectrographs on board the Mars Express and MAVEN missions.Two types of aurora are discussed: the localized and transient discrete aurora and the more stable diffuse aurora observed during periods of active solar periods. [less ▲]

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See detailInfluence of the crustal magnetic field on the Mars aurora electron flux and UV brightness
Bisikalo, D. V.; Shematovich, V. I.; Gérard, Jean-Claude ULg et al

in Icarus (2017), 282

Observations with the SPICAM instrument on board Mars Express have shown the occasional presence of localized ultraviolet nightside emissions associated with enhanced energetic electron fluxes. These ... [more ▼]

Observations with the SPICAM instrument on board Mars Express have shown the occasional presence of localized ultraviolet nightside emissions associated with enhanced energetic electron fluxes. These features generally occur in regions with significant radial crustal magnetic field. We use a Monte-Carlo electron transport model to investigate the role of the magnetic field on the downward and upward electron fluxes, the brightness and the emitted power of auroral emissions. Simulations based on an ASPERA-3 measured auroral electron precipitation indicate that magnetic mirroring leads to an intensification of the energy flux carried by upward moving electrons- from about 20% in the absence of crustal magnetic field up to 33-78% when magnetic field is included depending on magnetic field topology. Conservation of the particle flux in a flux tube implies that the presence of the B-field does not appreciably modify the emission rate profiles for an initially isotropic pitch angle distribution. However, we find that crustal magnetic field results in increase of the upward electron flux, and, consequently, in reduction of the total auroral brightness for given energy flux of precipitating electrons. [less ▲]

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See detailSimilarity of the Jovian satellite footprints: spots multiplicity and dynamics
Bonfond, Bertrand ULg; Grodent, Denis ULg; Badman, S. V. et al

in Icarus (2017)

In the magnetospheres of Jupiter and Saturn, the intense interaction of the satellites Io, Europa, Ganymede and Enceladus with their surrounding plasma environment leaves a signature in the aurora of the ... [more ▼]

In the magnetospheres of Jupiter and Saturn, the intense interaction of the satellites Io, Europa, Ganymede and Enceladus with their surrounding plasma environment leaves a signature in the aurora of the planet. Called satellite footprints, these auroral features appear either as a single spot (Europa and Enceladus) or as multiple spots (Io and Ganymede). Moreover, they can be followed by extended trailing tails in the case of Io and Europa, while no tail has been reported for Ganymede and Enceladus, yet. Here we show that all Jovian footprints can be made of several spots. Furthermore, the footprints all experience brightness variations on timescale of 2-3 minutes. We also demonstrate that the satellite location relative to the plasma sheet is not the only driver for the footprint brightness, but that the plasma environment and the magnetic field strength also play a role. These new findings demonstrate that the Europa and Ganymede footprints are very similar to the Io footprint. As a consequence, the processes expected to take place at Io, such as the bi-directional electron acceleration by Alfvén waves or the partial reflection of these waves on plasma density gradients, can most likely be extended to the other footprints, suggesting that they are indeed universal processes. [less ▲]

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See detailThe complex behavior of the satellite footprints at Jupiter: the result of universal processes?
Bonfond, Bertrand ULg; Grodent, Denis ULg; Badman, Sarah V. et al

Poster (2016, December 14)

At Jupiter, some auroral emissions are directly related to the electromagnetic interaction between the moons Io, Europa and Ganymede on one hand and the rapidly rotating magnetospheric plasma on the other ... [more ▼]

At Jupiter, some auroral emissions are directly related to the electromagnetic interaction between the moons Io, Europa and Ganymede on one hand and the rapidly rotating magnetospheric plasma on the other hand. Out of the three, the Io footprint is the brightest and the most studied. Present in each hemisphere, it is made of at least three different spots and an extended trailing tail. The variability of the brightness of the spots as well as their relative location has been tentatively explained with a combination of Alfvén waves’ partial reflections on density gradients and bi-directional electron acceleration at high latitude. Should this scenario be correct, then the other footprints should also show the same behavior. Here we show that all footprints are, at least occasionally, made of several spots and they all display a tail. We also show that these spots share many characteristics with those of the Io footprint (i.e. some significant variability on timescales of 2-3 minutes). Additionally, we present some Monte-Carlo simulations indicating that the tails are also due to Alfvén waves electron acceleration rather than quasi-static electron acceleration. Even if some details still need clarification, these observations strengthen the scenario proposed for the Io footprint and thus indicate that these processes are universal. In addition, we will present some early results from Juno-UVS concerning the location and morphology of the footprints during the first low-altitude observations of the polar aurorae. These observations, carried out in previously unexplored longitude ranges, should either confirm or contradict our understanding of the footprints. [less ▲]

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See detailJupiter’s auroras during the Juno approach phase as observed by the Hubble Space Telescope
Nichols, Jonathan D; Clarke, John T; Orton, Glennn S et al

Conference (2016, December 13)

We present movies of the Hubble Space Telescope (HST) observations of Jupiter’s FUV auroras observed during the Juno approach phase and first capture orbit, and compare with Juno observations of the ... [more ▼]

We present movies of the Hubble Space Telescope (HST) observations of Jupiter’s FUV auroras observed during the Juno approach phase and first capture orbit, and compare with Juno observations of the interplanetary medium near Jupiter and inside the magnetosphere. Jupiter’s FUV auroras indicate the nature of the dynamic processes occurring in Jupiter’s magnetosphere, and the approach phase provided a unique opportunity to obtain a full set of interplanetary data near to Jupiter at the time of a program of HST observations, along with the first simultaneous with Juno observations inside the magnetosphere. The overall goal was to determine the nature of the solar wind effect on Jupiter’s magnetosphere. HST observations were obtained with typically 1 orbit per day over three intervals: 16 May – 7 June, 22-30 June and 11-18 July, i.e. while Juno was in the solar wind, around the bow shock and magnetosphere crossings, and in the mid-latitude middle-outer magnetospheres. We show that these intervals are characterised by particularly dynamic polar auroras, and significant variations in the auroral power output caused by e.g. dawn storms, intense main emission and poleward forms. We compare the variation of these features with Juno observations of interplanetary compression regions and the magnetospheric environment during the intervals of these observations. [less ▲]

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See detailInitial observations of Jupiter’s aurora from Juno’s Ultraviolet Spectrograph (Juno-UVS)
Gladstone, Randy; Versteeg; Greathouse, Thomas et al

Conference (2016, December 13)

Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 nm. This wavelength range includes important far-ultraviolet (FUV) emissions from the H2 bands and the H Lyman series which are produced in ... [more ▼]

Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 nm. This wavelength range includes important far-ultraviolet (FUV) emissions from the H2 bands and the H Lyman series which are produced in Jupiter’s auroras, and also the absorption signatures of aurorally-produced hydrocarbons. The Juno-UVS instrument telescope has a 4x4 cm2 input aperture and uses an off-axis parabolic primary mirror. A flat scan mirror situated near the entrance of the telescope is used to observe at up to ±30° perpendicular to the Juno spin plane. The light is focused onto the spectrograph entrance slit, which has a “dog-bone” shape, with three sections of 2.55°x0.2°, 2.0°x0.025°, and 2.55°x0.2° (as projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses FUV light onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV-sensitive CsI photocathode. The two mirrors and the grating are coated with MgF2 to improve FUV reflectivity. Tantalum surrounds the spectrograph assembly to shield the detector and its electronics from high-energy electrons. All other electronics are located in Juno’s spacecraft vault, including redundant low-voltage and high-voltage power supplies, command and data handling electronics, heater/actuator electronics, scan mirror electronics, and event processing electronics. The purpose of Juno-UVS is to remotely sense Jupiter’s auroral morphology and brightness to provide context for in situ measurements by Juno’s particle instruments. Here we present the first near-Jupiter results from the UVS instrument following measurements made during PJ1, Juno’s first perijove pass with its instruments powered on and taking data. [less ▲]

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See detailSearch for low-latitude atmospheric hydrocarbon variations on Jupiter from Juno-UVS measurements
Hue, Vincent; Gladstone, Randy; Greathouse, Thomas et al

Conference (2016, December 13)

The Juno mission offers the opportunity to study Jupiter, from its inner structure, up to its magnetospheric environment. Juno was launched on August 2011 and its Jupiter orbit insertion (JOI) occurred on ... [more ▼]

The Juno mission offers the opportunity to study Jupiter, from its inner structure, up to its magnetospheric environment. Juno was launched on August 2011 and its Jupiter orbit insertion (JOI) occurred on July 4th 2016. The nominal Juno mission involves 35 science polar-orbits of 14-days period, with perijove and apojove distances located at 0.06 Rj and 45 Rj, respectively. Juno-UVS is a UV spectrograph with a bandpass of 70<λ<205 nm, designed to characterize Jupiter UV emissions. One of the main additions of UVS compared to its predecessors (New Horizons- and Rosetta- Alice, LRO-LAMP) is a 2.54 mm tantalum shielding, to protect it from the harsh radiation environment at Jupiter, and a scan mirror, to allow for targeting specific auroral and atmospheric features at +/- 30˚ perpendicular to the Juno spin plane. It will provide new constraints on Jupiter’s auroral morphology, spectral features, and vertical structure, while providing remote-sensing constraints for the onboard waves and particle instruments. It will also be used to probe upper-atmospheric composition through absorption features found in the UV spectra using reflected solar UV radiation. For example, stratospheric hydrocarbons such as C2H2 and C2H6 are known to absorb significantly in the 150-180 nm regions, and these absorption features can be used to determine their abundances. We will present our search for the spectroscopic features seen in Jupiter’s reflected sunlight during the first perijove. [less ▲]

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See detailDynamics of the flares in the active polar region of Jupiter
Bonfond, Bertrand ULg; Grodent, Denis ULg; Badman, S. V. et al

in Geophysical Research Letters (2016)

The dusk-side of the polar region of Jupiter's UV aurorae, called the active region, sometimes exhibits quasi-periodic (QP) flares on time-scales of 2-3 minutes. Based on Hubble Space Telescope Far-UV ... [more ▼]

The dusk-side of the polar region of Jupiter's UV aurorae, called the active region, sometimes exhibits quasi-periodic (QP) flares on time-scales of 2-3 minutes. Based on Hubble Space Telescope Far-UV time-tag images, we show for the first time that the northern hemisphere also displays QP-flares. The area covered by these flares can reach up to 2.4 × 108 km2 (i.e. the whole active region), but often only involves an area an order of magnitude smaller. Using a magnetic field mapping model, we deduced that these areas correspond to the dayside outer magnetosphere. In our dataset, quasi-periodic features are only seen on half of the cases and even on a given observation, a region can be quiet for one half and blinking on the other half. Consecutive observations in the two hemispheres show that the brightening can occur in phase. Combined with the size and location of the flares, this behaviour suggests that the QP-flares most likely take place on closed magnetic field lines. [less ▲]

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See detailLimb observations with NOMAD (UV,visible, IR)
Gérard, Jean-Claude ULg; Soret, Lauriane ULg

Scientific conference (2016, December)

We examine the possibilities and conditions to observe the Mars airglow and aurora (dayside and nightside) at the limb with the NOMAD instrument on board the TGO/EXOMARS orbiter.

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See detailFirst Hubble Space Telescope Movies of Jupiter’s Ultraviolet Aurora During the NASA Juno Prime Mission
Grodent, Denis ULg; Gladstone, G. Randall; Clarke, John T. et al

Poster (2016, December)

The primary goal of this HST campaign is to complement Juno-UVS (Ultraviolet Spectrograph) observations. This complementarity is four-fold as HST observes Jupiter’s aurora when: 1) Juno-UVS is turned off ... [more ▼]

The primary goal of this HST campaign is to complement Juno-UVS (Ultraviolet Spectrograph) observations. This complementarity is four-fold as HST observes Jupiter’s aurora when: 1) Juno-UVS is turned off, that is about 98% of Juno’s 14-day orbit, and Juno’s in situ instruments are in operation. 2) Juno-UVS is operating, but observes the opposite hemisphere of Jupiter. 3) UVS is on in the same hemisphere, but too close to Jupiter to have a global, contextual, view of the aurora and/or UVS is affected by the noise induced by Jupiter’s radiation belts. 4) Juno is too far from Jupiter to get a detailed view of the aurora. In addition, HST will observe the auroral and airglow emissions of the Galilean moons Io, Ganymede and Europa, when UVS is measuring their auroral footprints in Jupiter’s ionosphere. During this campaign, HST is obtaining 45-min STIS time-tag images -movies- of both hemispheres of Jupiter and STIS/COS spectra of Jupiter's moons. These observations are taking place during 4 sequences of Juno's orbit (Figure: typical orbit in magnetic coordinates): 1) Perijove segment: a 6-hour sequence bracketing the time of Juno's closest approach of Jupiter. 2) Crossing segments: few hours periods during which Juno is crossing the magnetic equator of Jupiter and in situ instruments are observing the plasma sheet particles. 3) Perijove +/- 1 Jovian rotation (or more), to provide a context for the auroral activity before and after perijove. 4) Apojove segment: a 12-hour period bracketing the time when Juno is farthest from Jupiter and Juno-UVS is continuously monitoring the global auroral UV power of Jupiter. During Juno orbit PJ5, between 28 Nov. and 07 Dec. 2016, HST obtains 9 STIS movies: 3 movies of the northern aurora near perijove, 1 movie (north) one Jovian rotation before and 2 movies (south- north) one and two Jovian rotations after perijove, 2 movies (north) during two close CS crossings, and 1 movie near apojove. These movies will be commented during this presentation. [less ▲]

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See detailThe Martian diffuse aurora: Monte Carlo simulations and comparison with IUVS-MAVEN observations
Gérard, Jean-Claude ULg; Soret, Lauriane ULg; Schneider, N. et al

Conference (2016, December)

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar ... [more ▼]

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar activity on several occasions with the IUVS on board the MAVEN spacecraft. We describe the results of Monte Carlo simulations of the production of several ultraviolet and visible auroral emissions for initial electron energies from 0.1 to 200 keV. These include the CO2+ ultraviolet doublet (UVD) at 288.3 and 289.6 nm and the Fox–Duffendack–Barker (FDB) bands, CO Cameron and Fourth Positive bands, OI 130.4 and 297.2 nm and CI 156.1 nm and 165.7 nm multiplets. We calculate the nadir and limb intensities of several of these emissions for a unit precipitated energy flux. Our results indicate that electrons in the range 100-200 keV produce maximum CO2+ UVD emission near 75 km. We combine SWEA and SEP electron energy spectra measured during diffuse aurora to calculate the volume emission rates and compare with IUVS observations of the emission limb profiles. The strongest predicted emissions are the CO2+ FDB, UVD and the CO Cameron bands. The metastable a 3Π state which radiates the Cameron bands is deactivated by collisions below ~110 km. As a consequence, we show that the CO2+ UVD to the Cameron bands ratio increases at low altitude in the energetic diffuse aurora. [less ▲]

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See detailPulsations of the polar cusp aurora at Saturn
Palmaerts, Benjamin ULg; Radioti, Aikaterini ULg; Roussos, E. et al

in Journal of Geophysical Research. Space Physics (2016), 121

The magnetospheric cusp is a region connecting the interplanetary environment to the ionosphere and enabling solar wind particles to reach the ionosphere. We report the detection of several isolated high ... [more ▼]

The magnetospheric cusp is a region connecting the interplanetary environment to the ionosphere and enabling solar wind particles to reach the ionosphere. We report the detection of several isolated high-latitude auroral emissions with the Ultraviolet Imaging Spectrograph of the Cassini spacecraft. We suggest that these auroral spots, located in the dawn-to-noon sector and poleward of the main emission, are the ionospheric signatures of the magnetospheric cusp, in agreement with some previous observations with the Hubble Space Telescope. The high-latitude cusp auroral signature has been associated with high-latitude lobe reconnection in the presence of a southward interplanetary magnetic field. The occurrence rate of the polar cusp aurora suggests that lobe reconnection is frequent at Saturn. Several auroral imaging sequences reveal a quasiperiodic brightening of the polar cusp aurora with a period in the range of 60 to 70 min. Similar pulsations in the energetic electron fluxes and in the azimuthal component of the magnetic field are simultaneously observed by Cassini instruments, suggesting the presence of field-aligned currents. Pulsed dayside magnetopause reconnection is a likely common triggering process for the cusp auroral brightenings at Saturn and the quasiperiodic pulsations in the high-latitude energetic electron fluxes. [less ▲]

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See detailNitric Oxide nightglow from IUVS disk images
Stiepen, Arnaud ULg; Schneider; Gonzàlez-Galindo et al

Conference (2016, November)

Detailed reference viewed: 16 (1 ULg)
See detailJuno Ultraviolet Spectrograph (Juno-UVS) Observations of Jupiter during Approach
Gladstone, G. Randall; Versteeg, Maarten; Greathouse, Thomas K. et al

Conference (2016, October)

We present the initial results from Juno Ultraviolet Spectrograph (Juno-UVS) observations of Jupiter obtained during approach in June 2016. Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 ... [more ▼]

We present the initial results from Juno Ultraviolet Spectrograph (Juno-UVS) observations of Jupiter obtained during approach in June 2016. Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 nm. This wavelength range includes all important ultraviolet (UV) emissions from the H<SUB>2</SUB> bands and the H Lyman series which are produced in Jupiter's auroras, and also the absorption signatures of aurorally-produced hydrocarbons. The Juno-UVS instrument telescope has a 4 x 4 cm<SUP>2</SUP> input aperture and uses an off-axis parabolic primary mirror. A flat scan mirror situated near the entrance of the telescope is used to observe at up to ±30° perpendicular to the Juno spin plane. The light is focused onto the spectrograph entrance slit, which has a "dog-bone" shape 7.2° long, in three sections of 0.2°, 0.025°, and 0.2° width (as projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses UV light onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV-sensitive CsI photocathode. Tantalum surrounds the spectrograph assembly to shield the detector and its electronics from high-energy electrons. All other electronics are located in Juno's spacecraft vault, including redundant low-voltage and high-voltage power supplies, command and data handling electronics, heater/actuator electronics, scan mirror electronics, and event processing electronics. The purpose of Juno-UVS is to remotely sense Jupiter's auroral morphology and brightness to provide context for in situ measurements by Juno's particle instruments. Prior to Jupiter Orbit Insertion (JOI) on July 5, Juno approach observations provide a rare opportunity to correlate local solar wind conditions with Jovian auroral emissions. Some of Jupiter's auroral emissions (e.g., polar emissions) may be controlled or at least affected by the solar wind. Here we compare synoptic Juno-UVS observations of Jupiter's auroral emissions (~40 minutes per hour, acquired during 2016 June 3-30) with in situ solar wind observations, as well as related Jupiter observations obtained from Earth. [less ▲]

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See detailCassini UVIS Auroral Observations in 2016
Pryor, Wayne R.; Jouchoux, Alain; Esposito, Larry et al

Conference (2016, October)

In June of 2016, the Cassini Saturn orbiter began a series of high inclination orbits that will continue until September 2017 when the mission ends as Cassini enters the Saturn atmosphere. These orbits ... [more ▼]

In June of 2016, the Cassini Saturn orbiter began a series of high inclination orbits that will continue until September 2017 when the mission ends as Cassini enters the Saturn atmosphere. These orbits present excellent views of Saturn's polar regions suitable for auroral imaging at the closest distances to date, with the additional prospect of simultaneous particle and fields measurements within the sources of Saturn Kilometric Radiation (SKR) associated with ultraviolet auroral emissions and/or acceleration regions likely coinciding with them. We will present new Cassini Ultraviolet Imaging Spectrograph (UVIS) auroral images, spectra and movies obtained during the summer and fall of 2016 and put them in the context of auroral data collected since Cassini orbit insertion in 2004. Included in the new data will be UVIS south polar observations obtained simultaneously with Hubble Space Telescope observations of the north polar region on June 29, 2016 and August 19, 2016. [less ▲]

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