Search Publications
Cassini's CDA observes a variety of dust populations just outside Saturn's main rings
Postberg, Frank; Hillier, Jon K.; Srama, Ralf +5 more
Before the end of its mission, the Cassini spacecraft orbited Saturn in a series of highly inclined elliptical 'Ring-Grazing' orbits (RGO). During the RGO, the spacecraft passed repeatedly through the ring plane outside the F ring, near the orbits of Janus and Epimetheus, at an average relative speed of ~20 km s-1. For the first time, C…
Estimating the optical depth of Saturn's main rings using the Cassini Langmuir Probe
Arridge, Christopher S.; Wahlund, Jan-Erik; Xystouris, Georgios +1 more
A Langmuir Probe (LP) measures currents from incident charged particles as a function of the applied bias voltage. While onboard a spacecraft the particles are either originated from the surrounding plasma, or emitted (e.g. through photoemission) from the spacecraft itself. The obtained current-voltage curve reflects the properties of the plasma i…
Implications from secondary emission from neutral impact on Cassini plasma and dust measurements
Edberg, N. J. T.; Vigren, E.; Eriksson, A. I. +4 more
We investigate the role of secondary electron and ion emission from impact of gas molecules on the Cassini Langmuir probe (RPWS-LP or LP) measurements in the ionosphere of Saturn. We add a model of the emission currents, based on laboratory measurements and data from comet 1P/Halley, to the equations used to derive plasma parameters from LP bias v…
Impacts of zonal winds on planetary oscillations and Saturn ring seismology
Fuller, Jim; Dewberry, Janosz W.; Mankovich, Christopher R.
The excitation of density and bending waves in Saturn's C ring by planetary oscillation modes presents a unique opportunity to learn about gas giant interiors and rotation. However, theoretical complications related to Saturn's rapid and differential rotation pose a barrier to the full utilization of ring wave detections. We calculate oscillation …
Particle-in-cell simulations of the Cassini spacecraft's interaction with Saturn's ionosphere during the Grand Finale
Shebanits, Oleg; Zhang, Zeqi; Desai, Ravindra T. +2 more
A surprising and unexpected phenomenon observed during Cassini's Grand Finale was the spacecraft charging to positive potentials in Saturn's ionosphere. Here, the ionospheric plasma was depleted of free electrons with negatively charged ions and dust accumulating up to over 95 per cent of the negative charge density. To further understand the spac…
Photometric modelling and VIS-IR albedo maps of Rhea from Cassini-VIMS
Buratti, B. J.; Clark, R. N.; Stephan, K. +6 more
Photometric correction based on the Shkuratov method is applied to derive visible and infrared albedo maps of Rhea from disc-resolved Cassini VIMS data. Differently from I/F images, albedo maps offer an optimal disentanglement of composition and physical properties of the surface from illumination-viewing effects and to study spectral variations o…
Kinetic Alfvén solitary waves in a plasma with two-temperature superthermal electron populations: the case of Saturn's magnetosphere
Singh, Manpreet; Saini, N. S.; Kourakis, I.
Thanks to the evidence provided by the Cassini spacecraft mission, it is now established that Saturn's magnetospheric plasma consists of various types of positive ions, as well as two distinct populations of electrons, at different temperatures. The electron population energy distributions are characterized by long suprathermal tails and have been…
Heavy negative ion growth in Titan's polar winter
Coates, A. J.; Jones, G. H.; Wellbrock, A. +4 more
A significant but unexpected result of the Cassini mission was the discovery of heavy organic negative ions in Titan's ionosphere at altitudes between about 950 and 1400 km by the CAPS Electron Spectrometer (ELS). The heaviest ions were observed during the T16 fly-by with masses over 13 000 u/q. This is significantly higher than the maximum masses…
Depth of the dynamo region and zonal circulation of the molecular layer in Saturn inferred from its equatorially symmetric gravitational field
Schubert, Gerald; Kong, Dali; Zhang, Keke
The high-precision equatorially symmetric gravitational field of Saturn (the even gravitational coefficients J2, J4, …, J12) measured by the Cassini Grand Finale reflects its internal structure, its non-spherical shape caused by rotation and its strong zonal circulation whose location is controlled by the depth of …
Axisymmetric density waves in Saturn's rings
Nicholson, P. D.; Hedman, M. M.
Density waves in Saturn's rings are usually tightly wrapped spiral patterns generated by resonances with either Saturn's moons or structures inside the planet. However, between the Barnard and Bessel Gaps in the Cassini Division (i.e. between 120 240 and 120 300 km from Saturn's spin axis), there are density variations that appear to form an axisy…