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C. Jarchow, P. Hartogh (MPI for Solar System Research)
The Microwave Instrument for the Rosetta Orbiter (MIRO) is one of several instruments onboard the ESA ROSETTA spacecraft headed for a rendezvous with comet 67P/Churyumov-Gerasimenko in 2014. It is a passive heterodyne receiver which measures next to the continuum emission of the nucleus especially the line emission of several key volatile species in a band centered at 562 GHz with a frequency resolution of 50 kHz. The instrument is fixed tuned to observe simultaneously eight transitions of the six molecules H2O, its isotopes H217O and H218O, CO, NH3, and CH3OH (3 transitions). The spectrally resolved lineshapes allow to retrieve molecule abundance, expansion velocity, and coma temperature as a function of the distance to the nucleus. Describing the coma by a simple Haser model and assuming local thermodynamical equilibrium for the inner 1000 km we present detailed simulations of this retrieval task using the Optimal Estimation Technique. Especially the correlation between the eight profiles obtained with a combined retrieval from all measured spectral lines has been studied. In addition the influence of the observing geometry -- nadir viewing vs. limb scanning -- on the radial resolution of the profiles is addressed.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.