Explanipedia

The Lyα Sky as Observed by New Horizons at 57 au Open

G. R. Gladstone, J. Michael Shull, W. R. Pryor, Jonathan D. Slavin, Joshua A. Kammer , et al. · 2025

During 2023 September the Alice ultraviolet spectrograph on the New Horizons (NH) spacecraft was used to map diffuse Lyα emission over most of the sky, at a range of ∼56.9 au from the Sun. At that distance, models predict that the interpla…

Uranus’ hydrogen upper atmosphere: Insights from pre- and post-equinox HST Lyman-α images Open

Sushen Joshi, Lorenz Roth, G. R. Gladstone, Nickolay Ivchenko, W. R. Pryor , et al. · 2024

We present the first spatially resolved images of Lyman- α (Ly α ) emissions from Uranus taken by the Hubble Space Telescope (HST). The observations were carried out using HST’s Space Telescope Imaging Spectrograph instrument as part of tw…

SOHO SWAN Lyα Models Supporting LRO LAMP: 2008–2023 Open

W. R. Pryor, W. Kent Tobiska, K. D. Retherford, C. Grava, A. F. Egan , et al. · 2024

The Lunar Reconnaissance Orbiter Lyman-Alpha Mapping Project (LAMP) has been mapping the Moon since its launch in 2009. Faint ultraviolet illumination of the lunar dark side includes light from stars and from hydrogen Ly α emissions, mostl…

Cassini UVIS Observations of the Enceladus Auroral Footprint on Saturn in 2017 Open

W. R. Pryor, F. P. Magalhães, Laurent Lamy, R. Prangé, L. W. Esposito , et al. · 2024

Ultraviolet Imaging Spectrograph (UVIS) observations show the Enceladus auroral footprint on Saturn on 2017 September 14, near the end of the Cassini mission. A series of Saturn north polar auroral images were obtained by slowly slewing th…

Modeling Cassini UVIS Interplanetary Hydrogen Lyα Observations from 1999 to 2017 Open

W. R. Pryor, G. R. Gladstone, Kurt D. Retherford, W. Kent Tobiska, G. M. Holsclaw , et al. · 2024

The Cassini Orbiter Ultraviolet Imaging Spectrograph (UVIS) obtained interplanetary hydrogen Ly α observations from 1999 to 2017, with mid-2004 to 2017 observations obtained from Saturn orbit. During its Saturn orbital phase, the spacecraf…

LRO‐LAMP Lunar South Pole Cold Traps: Assessment of H2O and Potential CO2 and NH3 Reserves Open

L. O. Magaña, K. D. Retherford, Benjamin Byron, Amanda Hendrix, C. Grava , et al. · 2023

Nighttime Lyman Alpha Mapping Project (LAMP) observations are used to investigate condensed volatiles at the south polar region of the Moon. This study incorporates LAMP data from the first ∼7 years of the mission and Diviner annual maximu…

Supporting Evidence for a Galactic Lyα Background from Cassini UVIS Data Open

W. R. Pryor, G. R. Gladstone, Kurt D. Retherford, W. Kent Tobiska · 2022

Cassini UVIS interplanetary hydrogen Ly α measurements from 2003 to 2004, obtained from a heliospheric downwind to sidewind location on approach to Saturn and during the first Saturn orbit, are presented and fit by a heliospheric hot densi…

New Horizons Detection of the Local Galactic Lyman-α Background Open

G. R. Gladstone, W. R. Pryor, D. T. Hall, Joshua A. Kammer, D. F. Strobel , et al. · 2021

Since 2007 the Alice spectrograph on the New Horizons (NH) spacecraft has been used to periodically observe the Lyman- α (Ly α ) emissions of the interplanetary medium (IPM), which mostly result from resonant scattering of solar Ly α emiss…

Ultraviolet-Based Science in the Solar System: Advances and Next Steps Open

Amanda Hendrix, Tracy M. Becker, Dennis Bodewits, E. T. Bradley, S. M. Brooks , et al. · 2021

We review the importance of recent UV observations of solar system targets and discuss the need for further measurements, instrumentation and laboratory work in the coming decade. In the past decade, numerous important advances have been m…

Saturn's Nightside Dynamics During Cassini's F Ring and Proximal Orbits: Response to Solar Wind and Planetary Period Oscillation Modulations Open

T. J. Bradley, S. W. H. Cowley, E. J. Bunce, Henrik Melin, G. Provan , et al. · 2020

We examine the final 44 orbits of the Cassini spacecraft traversing the midnight sector of Saturn's magnetosphere to distances of ~21 Saturn radii, to investigate responses to heliospheric conditions inferred from model solar wind and Cass…

Constraints on Pluto’s H and CH profiles from New Horizons Alice Ly observations Open

G. R. Gladstone, Joshua A. Kammer, Danica Adams, Yuk L. Yung, W. R. Pryor , et al. · 2020

The Alice spectrograph on New Horizons performed several far-ultraviolet (FUV) airglow observations during the July 2015 flyby of Pluto. One of these observations, named PColor2, was a short (226 s) scan across the dayside disk of Pluto fr…

The Morphology of Saturn's Aurorae Observed During the Cassini Grand Finale Open

Alexander Bader, S. W. H. Cowley, S. V. Badman, L. C. Ray, J. Kinrade , et al. · 2019

Cassini's mission exploring the Saturn system ended with the Grand Finale, a series of orbits bringing the spacecraft closer to the planet than ever before and providing unique opportunities for observations of the ultraviolet aurorae. Thi…

Energetic Particle Signatures Above Saturn's Aurorae Open

Alexander Bader, S. V. Badman, L. C. Ray, C. Paranicas, C. T. S. Lorch , et al. · 2019

Near the end of its mission, NASA's Cassini spacecraft performed several low‐altitude passes across Saturn's auroral region. We present ultraviolet auroral imagery and various coincident particle and field measurements of two such passes, …

Two-dimensional model for the martian exosphere: Applications to hydrogen and deuterium Lyman α observations Open

Dolon Bhattacharyya, Jean‐Yves Chaufray, Majd Mayyasi, J. T. Clarke, Shane W. Stone , et al. · 2019

Auroral Beads at Saturn and the Driving Mechanism: Cassini Proximal Orbits Open

Aikaterini Radioti, Zhonghua Yao, Denis Grodent, Benjamin Palmaerts, E. Roussos , et al. · 2019

During the Grand Finale Phase of Cassini , the Ultraviolet Imaging Spectrograph on board the spacecraft detected repeated detached small-scale auroral structures. We describe these structures as auroral beads, a term introduced in the terr…

The Dynamics of Saturn's Main Aurorae Open

Alexander Bader, S. V. Badman, S. W. H. Cowley, Zhonghua Yao, L. C. Ray , et al. · 2019

Saturn's main aurorae are thought to be generated by plasma flow shears associated with a gradient in angular plasma velocity in the outer magnetosphere. Dungey cycle convection across the polar cap, in combination with rotational flow, ma…

Cassini UVIS Detection of Saturn's North Polar Hexagon in the Grand Finale Orbits Open

W. R. Pryor, L. W. Esposito, A. Jouchoux, Robert A. West, Denis Grodent , et al. · 2019

Cassini's final orbits in 2016 and 2017 provided unprecedented spatial resolution of Saturn's polar regions from near‐polar spacecraft viewing geometries. Long‐wavelength channels of Cassini's Ultraviolet Imaging Spectrograph instrument de…

Observations of Continuous Quasiperiodic Auroral Pulsations on Saturn in High Time‐Resolution UV Auroral Imagery Open

Alexander Bader, S. V. Badman, Zhonghua Yao, J. Kinrade, W. R. Pryor · 2019

Saturn's aurora represents the ionospheric response to plasma processes occurring in the planet's entire magnetosphere. Short‐lived ∼1‐hr quasiperiodic high‐energy electron injections, frequently observed in in situ particle and radio meas…

Modulations of Saturn's UV Auroral Oval Location by Planetary Period Oscillations Open

Alexander Bader, S. V. Badman, J. Kinrade, S. W. H. Cowley, G. Provan , et al. · 2019

It is well known that Saturn's magnetospheric dynamics are greatly influenced by the so‐called planetary period oscillations (PPOs). Based on Cassini Ultraviolet Imaging Spectrograph (UVIS) imagery, it has been shown previously that the UV…

Statistical Planetary Period Oscillation Signatures in Saturn's UV Auroral Intensity Open

Alexander Bader, S. V. Badman, J. Kinrade, S. W. H. Cowley, G. Provan , et al. · 2018

Saturn's auroral emissions are a good measure of field‐aligned current (FAC) systems in the planet's magnetospheric environment. Previous studies based on magnetic field data have identified current systems rotating with the planetary peri…

Saturn's Northern Aurorae at Solstice From HST Observations Coordinated With Cassini's Grand Finale Open

Laurent Lamy, R. Prangé, Chihiro Tao, Tae Kim, S. V. Badman , et al. · 2018

Throughout 2017, the Hubble Space Telescope (HST) observed the northern far‐ultraviolet aurorae of Saturn at northern solstice, during the Cassini Grand Finale. These conditions provided a complete viewing of the northern auroral region fr…

Auroral Storm and Polar Arcs at Saturn—Final Cassini/UVIS Auroral Observations Open

Benjamin Palmaerts, Aikaterini Radioti, Denis Grodent, Zhonghua Yao, T. J. Bradley , et al. · 2018

On 15 September 2017 the Cassini spacecraft plunged into Saturn's atmosphere after 13 years of successful exploration of the Saturnian system. The day before, the Ultraviolet Imaging Spectrograph (UVIS) on board Cassini observed Saturn's n…

LRO/LAMP study of the interstellar medium via the HeI 58.4 nm resonance line Open

C. Grava, W. R. Pryor, P. D. Feldman, K. D. Retherford, G. R. Gladstone , et al. · 2018

Context. Recent measurements by IBEX and detailed modeling have changed our understanding of the flow of the interstellar medium through the solar system. In particular, a time dependence of the direction of the interstellar medium flow ha…

Dawn Auroral Breakup at Saturn Initiated by Auroral Arcs: UVIS/Cassini Beginning of Grand Finale Phase Open

Aikaterini Radioti, Denis Grodent, Zhonghua Yao, Jean‐Claude Gérard, S. V. Badman , et al. · 2017

We present Cassini auroral observations obtained on 11 November 2016 with the Ultraviolet Imaging Spectrograph at the beginning of the F‐ring orbits and the Grand Finale phase of the mission. The spacecraft made a close approach to Saturn'…

Advances on the magnetospheric dynamics of Saturn revealed from UVIS/Cassini auroral observations during the Grand finale phase of the mission Open

Aikaterini Radioti, Denis Grodent, Zhonghua Yao, Jean‐Claude Gérard, S. V. Badman , et al. · 2017

Auroral observations are a powerful tool to study the magnetospheric processes as they provide a ‘global picture’ of the magnetosphere at once. Here we present UVIS/Cassini auroral observations during the Grand Finale phase of the mission.…

Stagnation of Saturn's auroral emission at noon Open

Aikaterini Radioti, Denis Grodent, Jean‐Claude Gérard, D. J. Southwood, E. Chané , et al. · 2017

Auroral emissions serve as a powerful tool to investigate the magnetospheric processes at Saturn. Solar wind and internally driven processes largely control Saturn's auroral morphology. The main auroral emission at Saturn is suggested to b…

An isolated, bright cusp aurora at Saturn Open

J. Kinrade, S. V. Badman, E. J. Bunce, Chihiro Tao, G. Provan , et al. · 2017

Saturn's dayside aurora displays a number of morphological features poleward of the main emission region. We present an unusual morphology captured by the Hubble Space Telescope on 14 June 2014 (day 165), where for 2 h, Saturn's FUV aurora…

Auroral evidence of flux tube blockage near noon at Saturn’s magnetosphere Open

Aikaterini Radioti, Denis Grodent, Jean‐Claude Gérard, D. J. Southwood, E. Chané , et al. · 2016

We discuss plasma circulation in Saturn’s magnetosphere on the basis of auroral observations. Auroral enhance- ments in the dawn region are suggested to be related to intense field-aligned currents generated by hot tenuous plasma carried i…

Low latitude hydrogen emission at Jupiter Open

W. Kent Tobiska, W. R. Pryor, George R. Gladstone, K. E. Simmons · 2016

Auroral spirals at Saturn Open

Aikaterini Radioti, Denis Grodent, Jean‐Claude Gérard, E. Roussos, D. G. Mitchell , et al. · 2015

We report observations of auroral spirals at Saturn propagating from midnight to noon via dawn, based on Cassini/UVIS measurements. The aurora during that sequence is observed for the first time to consist of detached features swirling as …

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