Characteristics of Titan's haze derived from solar occultation observations in the infrared
Abstract
The Visual and Infrared Mapping Spectrometer (VIMS) has acquired 14 solar occultation observations between January 2006 and April 2016. The observations span a large range of latitude and seasons, allowing us to witness atmospheric variability. We use only the infrared channel of the VIMS instrument between 884- and 5108-nm. The observations are first processed to provide light curves which are the transmission through Titan's atmosphere as a function of the impact parameter. The transmission is calculated by dividing the signal by the solar spectrum obtained when the value of the impact parameter is much larger than the thickness of Titan's atmosphere, which makes it independent of the choice of the solar spectrum. The data set is composed of 14 3D arrays (transmission, wavelength, impact parameter). Errors are calculated using the SNR derived from the acquisition of the solar spectra and the value of transmission. The observations use a solar port which is aligned with the UVIS boresight in order to simultaneously record the atmospheric transmission in both UV and IR. For this purpose, VIMS has a solar port. However, one difficulty is to remove the additional light that often comes from the boresight. The technic will be described. In the seven infrared wavelengths where Titan's surface can be observed, the transmission is a direct measurement of the scattering by the aerosols. An inversion process has been set up to provide the density distribution of the aerosols as a function of altitude for each of these observations. The model is simple model with only one population of aerosols with a cross section that is wavelength-dependent. The model allows us to provide extinction curves at those wavelengths. The three observations obtained at the equator, close to where the Huygens probe landed, are compared with the DISR observations which have been recently revised (Doose et al., Icarus, 2016).This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #48
- Pub Date:
- October 2016
- Bibcode:
- 2016DPS....4851508S