Mark D Hofstadter
1,
Paul Von Allmen2, Gerard Beaudin
3, Nicolas Biver
4, Dominique Bockelée-Morvan
5, Mathieu Choukroun
6, Jacques Crovisier
4, Pierre Encrenaz
3, Therese Encrenaz
7, Margaret A. Frerking
8, Samuel Gulkis
9, Paul Hartogh
10, Wing-Huen Ip
11, Michael A Janssen
2, Christopher Jarchow
12, Stephen Joseph Keihm
13, Seungwon Lee
8, Emmanuel Lellouch
14, Cedric Leyrat
15, Ladislav Rezac
16, F. Peter Schloerb
17 and Thomas R Spilker
18, (1)Jet Propulsion Laboratory/California Institute of Technology, Pasadena, CA, United States, (2)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (3)Observatoire de Paris, LERMA, Paris, France, (4)LESIA Observatoire de Paris, Meudon, France, (5)Paris Observatory, Paris, France, (6)Jet Propulsion Laboratory, Pasadena, United States, (7)Paris Observatory-PSL, LIRA, Meudon, France, (8)Jet Propulsion Laboratory, Pasadena, CA, United States, (9)California Institute of Technology, Pasadena, CA, United States, (10)Max Planck Institute for Solar System Research, Göttingen, Germany, (11)NCU National Central University of Taiwan, Jhongli, Taiwan, (12)Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, (13)JPL/NASA/Caltech, Pasadena, CA, United States, (14)LESIA, Observatoire de Paris, Paris, France, (15)Paris Observatory Meudon, Meudon, France, (16)Max Planck Institute for Solar System Research, Gottingen, Germany, (17)University of Massachusetts Amherst, Amherst, MA, United States, (18)Independent Consultant, Pasadena, CA, United States
Contact First Author: Mark D Hofstadter; george.ellery.hale@gmail.com
English Abstract:
The Microwave Instrument for the Rosetta Orbiter (MIRO) makes millimeter and submillimeter observations of the nucleus and coma of Rosetta's target comet. This presentation summarizes the instrument, its observations, and our team's scientific analyses to date. MIRO makes continuum measurements at 190 and 563 GHz (1.6 and 0.5 mm) to study the thermal and electrical properties of the nucleus near-surface (depths from ~1 millimeter to 10 centimeters). MIRO also makes spectroscopic measurements of 8 lines near 560 GHz (H
2O, H
217O, H
218O, CO, NH
3, and three CH
3OH transitions). The abundance, gas velocity, and temperature of those species are measured as functions of time and location. To interpret its data, the MIRO team has developed sophisticated nucleus and coma models. Our goal is to understand the dominant physical processes that create the coupled nucleus-coma system.
MIRO began measuring water in the coma on 6 June 2014, at a heliocentric distance of 3.9 AU. By October (3.3 AU from the Sun), the total production rate had increased a factor of 6. Water production varies both with location on the nucleus and time-of-day. At the time of this writing, H2O and H218O have been clearly measured, with detections of H217O and CH3OH. We will report on our composition measurements and on the time and spatial variability of nucleus outgassing. Our analysis of spectral data uses a non-LTE coma model, accounting for the boundary layer at the nucleus, regions dominated by gas collisions, electron collisions, and radiative processes.
MIRO's continuum channels have detected the nucleus since 19 July 2014, and the nucleus has been spatially resolved since early August. All surface regions appear to have a very low thermal inertia, as expected for a porous, dusty layer. We see variability in properties horizontally and with depth, and will present our latest results. MIRO has developed a 3-D nucleus thermal/radiative model to assist in observation planning and interpretation.
