Deriving the rotational state of comet 103P/hartley 2 to interpret epoxi data we will determine the rotational state of the nucleus of comet 103P/hartley 2 and its evolution in the months…

This is a $390,912.39 grant award from the National Aeronautics and Space Administration (NASA) to the Planetary Science Institute (PSI), a non-profit research organization headquartered in Tucson, Arizona. The award is for a project titled "Deriving the Rotational State of Comet 103P/Hartley 2 to Interpret EPOXI Data". The objective is to determine the rotational state of the nucleus of Comet 103P/Hartley 2 and its evolution, in order to accurately interpret observations made by the NASA EPOXI mission. The work involves using multiple data sets and modeling techniques to analyze the comet's coma morphology and lightcurve. This research is relevant to NASA's Discovery Data Analysis Program, as it will provide critical information for interpreting EPOXI mission data. The award does not have a set-aside designation, reflecting PSI's competitive capabilities in planetary science research. PSI frequently collaborates with university partners on NASA-funded projects through sub-awards.

Deriving the rotational state of comet 103P/hartley 2 to interpret epoxi data we will determine the rotational state of the nucleus of comet 103P/hartley 2 and its evolution in the months surrounding the 2010 encounter by the NASA epoxi mission in order to interpret key observations made by the epoxi mission. The nucleus of comet 103P/hartley 2 is in a non-principal-axis (complex) rotational state and the knowledge of the definite rotational state of the nucleus is essential for accurately interpreting a multitude of observations of the comet made by epoxi. We will use multiple observational data sets and extensive modeling to derive the rotational state of the nucleus and its temporal evolution. Solutions for the rotational state will be tested against a vast array of observational data and theoretical predictions and the results will be validated using a number of numerical models. For this investigation, our existing and proven coma simulation routines will be used to model the morphology of the gas and dust in the coma. We will also introduce two new numerical modeling efforts aimed at (a) accurately interpreting the periodicity signatures in the lightcurves of active nuclei and (b) simulating the coma morphology due to cumulative dust outflow from multiple active facets on a shape model in the sunward side of the nucleus. These two numerical efforts, together with the modeling of coma features with the existing coma simulation software, will be an integral part of critically evaluating the candidate rotational states. Once the rotational state is determined, we will use that to interpret (a) coma morphology seen by epoxi, and (b) the lightcurve of the active nucleus observed by epoxi. In addition, we will determine the nuclear orientation as a function of time thus facilitating the interpretation not only of additional epoxi data but also of groundbased observations. The proposed investigation is relevant to NASA's discovery data analysis program (ddap) since IT provides critical information necessary to interpret a multitude of epoxi data.