Search Publications
The Uranus system from occultation observations (1977-2006): Rings, pole direction, gravity field, and masses of Cressida, Cordelia, and Ophelia
Nicholson, Philip D.; French, Richard G.; Hedman, Matthew M. +2 more
From an analysis of 31 Earth-based stellar occultations and three Voyager 2 occultations spanning 1977-2006 (French et al. 2023a), we determine the keplerian orbital elements of the centerlines of the nine main Uranian rings to high accuracy, with typical RMS residuals of 0.2-0.4 km and 1- σ formal errors in a , ae , and a sin i of order 0.1 km, r…
A study of Jupiter's UV Great Dark Spot and tropopause to stratosphere winds in the high northern latitudes as seen by Cassini imaging
West, R. A.; Sinclair, J. A.; Del Genio, A. D. +1 more
Images of Jupiter taken during the year 2000 Cassini flyby revealed the early stages and evolution of a high northern-latitude UV Great Dark Spot over a three-month period. They also provided a window on the circulation of Jupiter's polar stratosphere. Jupiter's rarely-detected UV Great Dark Spot (UVGDS) is unusual in several respects. It is an ep…
Ultraviolet spectrum reveals the presence of ozone on Jupiter's moon Callisto
Janardhan, P.; Bhardwaj, Anil; Ramachandran, R. +11 more
Sulphur dioxide (SO2) is known to be present on Callisto. In this paper, we studied the chemical evolution of SO2 astrochemical ice induced by irradiation using 9 eV (137.7 nm) vacuum ultraviolet light produced from the high-flux beamline of the storage ring at the National Synchrotron Radiation Research Centre in Taiwan. Ult…
The puzzling north polar region of Uranus: Continued zero-shear winds and increasing brightness from 2015 through 2022 according to 7 years of Keck AO imaging
de Pater, Imke; Sromovsky, Lawrence A.; Fry, Patrick M. +1 more
There may be a permanent north–south asymmetry in the zonal wind profile of Uranus. According to high signal-to-noise near-IR observations with the Keck telescope NIRC2 camera, through 2014 the winds north of 60∘N had a constant (zero shear) longitudinal drift rate of 4.1∘/h westward (Sromovsky et al., 2015). Yet the south polar winds in 1986 had …
Overview of a large observing campaign of Jupiter's aurora with the Hubble Space Telescope combined with Juno-UVS data
Bonfond, B.; Nichols, J. D.; Gérard, J. -C. +8 more
Between February and September 2019, Jupiter's ultraviolet aurorae were frequently observed during a large campaign of the Hubble Space Telescope (HST GO-15638). The campaign included approximately 10 visits around each of the perijoves of the Juno spacecraft orbits 18 to 22 around Jupiter. During this time, the solar activity was minimal, giving …
Update on SO2, detection of OCS, CS, CS2, and SO3, and upper limits of H2S and HOCl in the Venus mesosphere using SOIR on board Venus Express
Aoki, S.; Vandaele, A. C.; Trompet, L. +6 more
We report on the update of SO2 and first detections of SO3, CS, and CS2, and detection of OCS above the cloud deck using the SOIR instrument on-board Venus Express, and upper limit profiles of H2S and HOCl. Based on the solar occultation spectra measured by SOIR covering all latitudes over the 2006-2014 …
Ganymede's atmosphere as constrained by HST/STIS observations
Leblanc, F.; Galand, M.; Roth, L. +7 more
A new analysis of aurora observations of Ganymede's atmosphere on the orbital leading and trailing hemispheres has been recently published by Roth et al. (2021), suggesting that water is its main constituent near noon. Here, we present two additional aurora observations of Ganymede's sub-Jovian and anti-Jovian hemispheres, which suggest a modulati…
Evolution of Neptune at near-infrared wavelengths from 1994 through 2022
de Pater, Imke; Wong, Michael H.; Hueso, Ricardo +16 more
Using archival near-infrared observations from the Keck and Lick Observatories and the Hubble Space Telescope, we document the evolution of Neptune's cloud activity from 1994 to 2022. We calculate the fraction of Neptune's disk that contained clouds, as well as the average brightness of both cloud features and cloud-free background over the planet…
Analysis of Charon's spectrum at 2.21- µm from New Horizons/LEISA and Earth-based observations
Singer, Kelsi N.; Stern, S. Alan; Weaver, Harold A. +9 more
We examine the 2.21- µm band from 19 disk-integrated Charon spectra measured by New Horizons/LEISA in the week leading up to its closest encounter with the Pluto system. These observations cover one Charon rotation period. Additionally, we analyze Charon's 2.21- µm band from 22 Earth-based spectra obtained over the last two decades. We…
Uranus ring occultation observations: 1977-2006
Nicholson, Philip D.; French, Richard G.; Sicardy, Bruno +25 more
The Uranian rings were discovered serendipitously on 10 March 1977 during a stellar occultation (Elliot et al., 1977a; Millis et al., 1977), and a rich set of subsequent Earth-based occultations revealed that these narrow and sharp-edged rings were eccentric and inclined, precessing under the gravitational influence of the oblate central planet. C…