References of "Esposito, Larry"
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See detailCassini Ultraviolet Images of Saturn's Aurorae
Pryor, Wayne; Jouchoux, Alain; Esposito, Larry et al

Scientific conference (2014, August 04)

Cassini has been obtaining auroral images and spectra of Saturn with the Ultraviolet Imaging Spectrograph (UVIS). We will present highlights of the auroral images, showing a variety of morphologies ... [more ▼]

Cassini has been obtaining auroral images and spectra of Saturn with the Ultraviolet Imaging Spectrograph (UVIS). We will present highlights of the auroral images, showing a variety of morphologies, including multiple arcs, spiral forms, polar cusp activity, and rotating emission features, some of them pulsating with a roughly 1-hour period. A satellite footprint of Enceladus is occasionally visible. [less ▲]

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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 detailCharacteristics of Saturn’s FUV airglow from limb-viewing spectra obtained with Cassini-UVIS
Gustin, Jacques ULg; Stewart, Ian; Gérard, Jean-Claude ULg et al

in Icarus: International Journal of Solar System Studies (2010), 210

This study reports the analysis of far ultraviolet (FUV) limb spectra of the airglow of Saturn in the 1150–1850 Å spectral window, obtained with the Ultraviolet Imaging Spectrograph (UVIS) onboard Cassini ... [more ▼]

This study reports the analysis of far ultraviolet (FUV) limb spectra of the airglow of Saturn in the 1150–1850 Å spectral window, obtained with the Ultraviolet Imaging Spectrograph (UVIS) onboard Cassini, spanning altitudes from 1200 to 4000 km. The FUV limb emission consists of three main contributions: (1) H Ly-a peaking at 1100 km with a brightness of 0.8 kilo-Rayleighs (kR), (2) reflected sunlight longward of 1550 Å which maximizes at 950 km with 16.5 kR and (3) H2 bands in the 1150–1650 Å bandwidth, peaking at 1050 km reaching a maximum of 3.9 kR. A vertical profile of the local H2 volume emission rate has been derived using the hydrocarbon density profiles from a model of the Saturn equatorial atmosphere. It is well matched by a Chapman function, characterized by a maximum value of 3.5 photons cm-3 s-1 in the 800–1650 Å UV bandwidth, peaking at 1020 km. Comparisons between the observed spectra and a first-order synthetic airglow H2 model in the 1150–1650 Å bandwidth show that the spectral shape of the H2 bands is accounted for by solar fluorescence and photoelectron excitation. The best fits are obtained with a combination of H2 fluorescence lines and 20 eV electron impact spectra, the latter contributing 68% of the total H2 airglow emission. [less ▲]

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See detailTitan airglow spectra from the Cassini Ultraviolet Imaging Spectrograph: FUV disk analysis
Ajello, Joseph M.; Gustin, Jacques ULg; Stewart, Ian et al

in Geophysical Research Letters (2008)

We present a spectral analysis of the far ultraviolet (FUV: 1150–1900 A ° ) disk airglow observations of Titan’s atmosphere by the Cassini Ultraviolet Imaging Spectrograph (UVIS). The FUV spectrum ... [more ▼]

We present a spectral analysis of the far ultraviolet (FUV: 1150–1900 A ° ) disk airglow observations of Titan’s atmosphere by the Cassini Ultraviolet Imaging Spectrograph (UVIS). The FUV spectrum consists of emissions from the Lyman-Birge-Hopfield (LBH) band system of N2 excited by photoelectrons (a 1Pg ! X 1Sg+), N I multiplets from solar photodissociative excitation of N2, resonantly scattered solar H Ly-a and sunlight reflected by N2 in the mesosphere-stratosphere and modified by aerosols (e.g.,tholins) and hydrocarbon absorption. Below 1450 A, the strongest emissions arise from H Ly-a with an intensity of 208 Rayleighs (R), LBH bands with an intensity of 43 R, and the N I multiplets with a combined intensity of 16 R. Above 1450 A , most of the UVIS signal is due to reflected sunlight. Mixing ratios of tholins, C2H2, C2H4 and C4H2 have been derived from the reflected sunlight using a Rayleigh scattering model. The derived mixing ratios are in good agreement with Voyager infrared observations and with FUV photochemical models, assuming solar energy deposition above 1450 A occurs near 250 km (Wilson and Atreya, 2004). We also present the first geometric albedo measurement of Titan from 1500–1900 A [less ▲]

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See detailTitan airglow spectra from Cassini Ultraviolet Imaging Spectrograph (UVIS): EUV analysis
Ajello, Joseph M.; Stevens, Michael H.; Stewart, Ian et al

in Geophysical Research Letters (2007), 34

We present the first UV airglow observations of Titan's atmosphere by the Ultraviolet Imaging Spectrograph (UVIS) on Cassini. Using one spectral channel in the EUV from 561-1182 Å and one in the FUV from ... [more ▼]

We present the first UV airglow observations of Titan's atmosphere by the Ultraviolet Imaging Spectrograph (UVIS) on Cassini. Using one spectral channel in the EUV from 561-1182 Å and one in the FUV from 1115-1913 Å, UVIS observed the disk on 13 December, 2004 at low solar activity. The EUV spectrum consists of three band systems of N[SUB]2[/SUB] (b [SUP]1[/SUP]∏[SUB]u[/SUB], b' [SUP]1[/SUP]∑[SUB]u[/SUB] [SUP]+[/SUP], c[SUB]4[/SUB]' [SUP]1[/SUP]∑[SUB]u[/SUB] [SUP]+[/SUP] -> X [SUP]1[/SUP]∑[SUB]g[/SUB] [SUP]+[/SUP]), while the FUV spectrum consists of one (a [SUP]1[/SUP]∏[SUB]g[/SUB] -> X [SUP]1[/SUP]∑[SUB]g[/SUB] [SUP]+[/SUP]). Both the EUV and FUV spectra contain many N I and N II multiplets that are produced primarily by photodissociative ionization. Spectral intensities of the N[SUB]2[/SUB] c[SUB]4[/SUB]' [SUP]1[/SUP]∑[SUB]u[/SUB] [SUP]+[/SUP](v' = 0) -> X [SUP]1[/SUP]∑[SUB]g[/SUB] [SUP]+[/SUP](v'' = 0-2) progression from 950-1010 Å are resolved for the first time. The UVIS observations reveal that the c[SUB]4[/SUB]' [SUP]1[/SUP]∑[SUB]u[/SUB] [SUP]+[/SUP](0) -> X [SUP]1[/SUP]∑[SUB]g[/SUB] [SUP]+[/SUP] (0) vibrational band near 958 Å is weak and undetectable, and that N I multiplets near 953.2 and 964.5 Å are present instead. Magnetospheric particle excitation may be weak or sporadic, since the nightside EUV spectrum on this orbit shows no observable nitrogen emission features and only H Ly-β. [less ▲]

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See detailThe Cassini Campaign observations of the Jupiter aurora by the Ultraviolet Imaging Spectrograph and the Space Telescope Imaging Spectrograph
Ajello, Joseph M.; Pryor, Wayne; Esposito, Larry et al

in Icarus (2005), 178(2), 327-345

We have analyzed the Cassini Ultraviolet Imaging, Spectrometer (UVIS) observations of the Jupiter aurora with an auroral atmosphere two-stream electron transport code. The observations Of Jupiter by UVIS ... [more ▼]

We have analyzed the Cassini Ultraviolet Imaging, Spectrometer (UVIS) observations of the Jupiter aurora with an auroral atmosphere two-stream electron transport code. The observations Of Jupiter by UVIS took place during the Cassini Campaign. The Cassini Campaign included Support spectral and imaging observations by the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS). A major result for the UVIS observations was the identification of a large color variation between the far ultraviolet (FUV: 1100-1700 angstrom) and extreme ultraviolet (EUV: 800-1100 angstrom) spectral regions. This change probably occurs because of a large variation in the ratio of the soft electron flux (10-3000 eV) responsible for the EUV aurora to the hard electron flux (similar to 15-22 keV) responsible for the FUV aurora. On the basis of this result a new color ratio for integrated intensities for EUV and FUV was defined (4 pi I1550-1620 angstrom/4 pi I (1030-1150 angstrom)) which varied by approximately a factor of 6. The FUV color ratio (4 pi I (1550-1620) angstrom/4 pi (1230-1300) (angstrom)) was note stable with a variation of less than 50% for the observations studied. The medium resolution (0.9 angstrom FWHM, G140M grating) FUV observations (1295-1345 angstrom and 1495-1540 angstrom) by STIS on 13 January 2001, on the other hand, were analyzed by a spectral modeling technique using a recently developed high-spectral resolution model for the electron-excited H-2 rotational lines. The STIS FUV data were analyzed with a model that considered the Lyman band spectrum (B (1) Sigma(u)(+) -> X-1 Sigma(g)(+)) as composed of an allowed direct excitation component (X-1 Sigma(g)(+) B-1 (+)(Sigma u)) and an optically forbidden component (X-1 Sigma(g)(+) -> EF, GK, H (H) over bar,.... (1)Sigma(u)(+) followed by the cascade transition (1)Sigma -> B-1 Sigma(u)(+)). The medium-resolution spectral regions for the Jupiter aurora were carefully chosen to emphasize the cascade component. The ratio of the two components is a direct measurement of the mean secondary electron energy of the aurora. The mean secondary electron energy of the aurora varies between 50 and 200 eV for the polar cap, limb and auroral oval observations. We examine a long time base of Galileo Ultraviolet Spectrometer color ratios from the standard mission (1996-1998) and compare them to Cassini UVIS, HST, and International Ultraviolet Explorer (IUE) observations. (c) 2005 Elsevier Inc. All rights reserved. [less ▲]

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