The fluxes and phase space densities for a fixed 1st adiabatic invariant for high energy electrons and protons provide important inputs for various scientific studies for determining the physics of particle diffusion and energization. This study provides estimates of the 1st adiabatic invariant and phase space density based on the complete and large data base available from the Energetic Particle Detector (EPD) on Galileo for the jovian environment. To be specific, 10 minute averages of the high energy electron and proton data are used to compute differential flux spectra versus energy for L=~8 - 25 over the Galileo mission. These spectra provide estimates of the differential fluxes and phase space density for constant 1st adiabatic invariants between 102 to 105 MeV/G. As would be expected, the electron and proton fluxes and phase space densities generally trend lower as the planet is approached. The results indicate that, whereas the overall trends for each orbit are consistent, detailed orbit to orbit variations can be observed. Galileo orbit C22 is presented as a specific example of deviations from the mean downward trend. To validate the Galileo results and extend the findings into L=3, the GIRE3 model was also used to compute the fluxes and phase space densities for constant 1st adiabatic invariant versus L-shell. Comparison between GIRE3 and EPD demonstrates that the model adequately reproduces the EPD data trends and they consistently show additional variations near Io. This provides proof that the GIRE3 is a useful starting point for diffusion analyses and similar studies.

We review the mechanisms that shape the spatial distributions of energetic electrons trapped in the magnetospheres of Jupiter, Saturn, Uranus and Neptune. To determine what controls the energy and spatial distributions throughout the different magnetospheres, we compute the time evolution of particle distributions with the help of a diffusion theory particle transport code that solves the governing 3-D Fokker-Planck equation. We discuss the processes already accounted for in our physics-based models of the outer planet electron radiation belts but also those suspected to be missing to improve our model results. Our theoretical modeling is guided by the analysis of particle, field and wave data collected by Pioneer 10&11 and Galileo at Jupiter, Cassini at Saturn, and during Voyager 2’s flyby of Uranus in January 1986 and at Neptune in August 1989.

Neutron spectroscopy has become a standard technique for remotely measuring planetary surface compositions from orbital spacecraft around various planets. Measurements have successfully been carried out at the Moon, Mars, Mercury, and the asteroids Vesta and Ceres. The NASA Psyche mission is planning to make neutron measurements to characterize the composition of the M-class asteroid (16) Psyche. Earth-based remote sensing measurements allow for a wide range of Fe concentrations, ranging from ~25 wt.% to 90 wt.%, and geochemically plausible Ni concentrations range from 0 wt.% to 10 wt.% or higher. To prepare for the analysis of Psyche neutron data, we have developed a new principal component analysis framework using four neutron energy ranges of thermal, low-energy epithermal, high-energy epithermal, and fast neutrons. With this analysis framework, we have demonstrated that the neutron measurements can uniquely distinguish variations of metal-to-silicate fraction, Ni, and hydrogen compositions. The strongest principal component is that of metal-to-silicate; the second strongest is Ni variations; the third is hydrogen variations. The validity of this framework can be first tested during a Mars gravity assist prior to arrival at Psyche.