Summary of my Ph.D. thesis


        My Ph.D. thesis consists of the results from observations of comets 73P-C/Schwassmann-Wachmann 3, 17P/Holmes, and 8P/Tuttle, which I observed at millimeter wavelengths between May 2006 and March 2008, using the Submillimeter and the Kitt Peak telescopes of the Arizona Radio Observatory. I also investigated prospects for in-situ observations of comet 67P/Churyumov-Gerasimenko with the Microwave Instrument for the Rosetta Orbiter (MIRO).
        Observations of the first comet, analyzed with a simple model, revealed the nucleus rotation period to be unusually short. This tentatively suggests a rotational break-up of the parent body, and sets a meaningful upper limit on the bulk tensile strength of the nucleus.
        Observations of the second comet provided a detailed evolution of the molecular environment during its spectacular outburst. I concluded that the gas cloud was anisotropic, and presumably resulted from activities of several competing sources. The explosion itself appears as a sudden impulsive event, and only 1.5 months later the nucleus was back to – or at least close to – its regular non-explosive activity.
        The last comet exhibited periodic changes in the HCN line profile, which I interpreted as being caused by jets emanating from a rotating nucleus. Therefore, I also developed a new model of molecular line emission in microwaves, which is the first of that kind that accounts for these effects. Applied to the data of comet Tuttle, it provided the spin axis orientation, and the distribution of activity over the nucleus.
        The simulations of the MIRO observations of comet 67P/Churyumov-Gerasimenko were based on the most advanced models of the comet's coma available to date, and the radiative-transfer code that had been developed in house. They show that water vapor can already be detected at the arrival of Rosetta, and that the most favorable observing direction will be nadir, whereas zenith should be avoided. I also demonstrate that the lines will be optically thick, thus the full radiative transfer treatment is the only plausible approach.
        Overall, my Ph.D. research provides characterization of three objects, supports the preparation for science with Rosetta, and contributes to the methodology of observational astrophysics of comets. It is also a baseline for future studies, an example of which is also presented in the thesis.
        Full thesis is available for download. Enjoy!