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T. Hewagama, J. Goldstein (Challenger Center for Space Science Education), D. Buhl, F. Espenak (NASA/Goddard Space Flight Center), K. Fast (University of Maryland and NASA/GSFC), T. Kostiuk (NASA/Goddard Space Flight Center), T. A. Livengood (University of Maryland and NASA/GSFC)
Infrared Heterodyne Spectroscopic observations of ro-vibrational emission line spectra of CO2 on Mars and Venus and of C2H6 on Titan have been used to study molecular abundances and atmospheric dynamics to 2 ms-1 accuracy. Interpretation of these observations were limited by the lack of a beam-integrated radiative transfer algorithm.
Typically, a mean viewing angle was assumed in the analysis whereas the spectrometer FOV spans a range in velocity and mean viewing angle weighted by the spectrometer response. However, a beam-integrated spectrum is qualitatively distinct from a single viewing angle spectrum. For example, the 1" FOV on a 3-m telescope is comparable to Titan's disc and the observed beam includes dynamical contributions from all regions of the disc intercepted by the beam. Such differences affect molecular abundance and wind field retrievals.
We will discuss analysis software which model beam-integrated observations. The model is characterized by an effective beam response, molecular abundance, and a wind field. It is numerically implemented by dividing the FOV into a grid of elements, calculating the emergent spectrum of each element, and convolving the results into a beam-integrated spectrum representative of the measurements. The application of the the software to dynamical studies of the Titan and Jupiter atmospheres will be discussed. The analysis techniques are general, with potential application to other molecular astrophysical sources.
The author(s) of this abstract have provided an email address for comments about the abstract: tilak@cuzco.gsfc.nasa.gov