This submission is an unsolicited proposal to support my research duties as a seti principal investigator in collaboration with the NASA ames research center for the period beginning april 15, 2017,…

This is a $189,300.00 cooperative agreement awarded by the National Aeronautics and Space Administration (NASA) Shared Services Center to the non-profit SETI Institute. The agreement supports the SETI Institute's research duties as a principal investigator in collaboration with the NASA Ames Research Center from April 15, 2017 to May 14, 2019. The work will focus on data analysis and radiative transfer modeling to improve understanding of the evolution of Saturn's rings due to micrometeoroid bombardment and ballistic transport of impact ejecta. This will involve using existing Cassini mission data, including infrared, imaging, ultraviolet, and radar observations, along with the Institute's modeling capabilities. There is no set-aside designation for this award.

This submission is an unsolicited proposal to support my research duties as a seti principal investigator in collaboration with the NASA ames research center for the period beginning april 15, 2017, to may 14, 2019. The data analysis and radiative transfer modeling proposed for this work constitutes a significant undertaking, so that the PI will be hiring a postdoc to collaborate with him in doing this work and other projects that the PI is involved in. The bulk of the allocated funds will be used to partially fund this postdoctoral candidate. The objective of this aspect of the PI s work is to improve our understanding of how the rings composition and structure evolve over time due to the effects of micrometeoroid bombardment and ballistic transport of their impact ejecta. The rings huge surface-areato mass ratio ensures that micrometeoroid impacts are an important compositional and dynamical process, and by unraveling the effects of bombardment over the rings lifetime, we may gain a better understanding of their compositional diversity, origin and age. The PI s and collaborator s ballistic transport code estrada ET AL., 2015 is fully capable of modeling the structural evolution and bulk compositional redistribution of material due to this process over the radial extent of the rings, and over a wide range of parameter space that has seen steady refinement through cassini observations. Of particular interest has been the revelation from the cassini cosmic dust analyzer experiment (CDA) that the micrometeoroid flux at saturn is comparable to previous estimates, or could even be as much as an order of magnitude higher s. Kempf, priv. Comm. Furthermore, the flux is characterized by an entirely different population altogether which has its dynamical origins in the kuiper belt altobelli ET AL., 2015. This means that the flux is much more gravitationally focused than the previously assumed cometary flux e.g., cuzzi and estrada, 1998 with the result being that the impact flux, the actual amount of material hitting the rings, is over an order of magnitude higher for a given flux at infinity. This will have a significant impact on ring age and evolution estrada ET AL., 2017. For this proposal, our tasks will focus on the determination of specific candidates for the rings non-ICY compositional constituents through a combination of data analysis of existing cassini data, and radiative transfer modeling employing a suite of codes we have already developed for this purpose including a recently completed monte carlo RAY tracing code beam. We will make use of publicly available cassini data that include vims-IR, as well as 8- and 15-color filter ISS data, which allow for a multiple wavelength reflectance study, as well as uvis occultation and even radar radiometer data. The available data in the PDS includes many ISS and vims radial scans, and over 100 stellar occultations covering all ring regions with a wide range of geometries. Analysis of uvis and vims occultation data continues to refine our knowledge of ring surface density and opacity which we use in our dynamical simulations. Determining the non-ICY compositional constituents of the rings will involve ring layer radiative transfer modeling to obtain the best-fit combination of phase function, packing density, and particle albedo from the observations, and ring particle radiative transfer to infer particle composition from the albedo. The former will involve the use of our monte carlo RAY-tracing code which can handle locally inhomogeneous ring structure such as clumpy and azimuthally asymmetric self-gravity wakes which we will constrain using uvis stellar occultation data. The latter will involve the use of a particle regolith radiative transfer code to infer particle composition. Our proposed work thus combines data analysis and modeling. Our first goal is to extract the particle phase function and apparent particle albedo from the ensemble scattering properties of the layer