1. Titan tholin properties from occultation and emission observations
D. Shemansky, Xi Zhang & Y. Yung
06/26/11

2. Occultation and emission measurements are combined to extract physical properties of aerosols
The fuv occultation measurements show distinctive continuum extinction spectra have the shape of the imaginary part of the Kare et al lab measurements of solid-state tholins in the range 1500 – 1900 A. Vertical profiles extend from 300 km to 1000 km altitude.
These results are combined with emission spectra in the fuv that show the reflection of the solar flux. These observations are used to extract particle size and abundance using Mie scattering theory. There are issues with calibration and apparent deviation from isotropic scattering that need to be resolved.

5. Titan T0 encounter:
UVIS FUV spatial bin locations relative to the centre of Titan with outline of the planet and location of exobase.

6. Figure 7 Titan solar reflection at Cassini encounters T0 and TA:
See Figures 1, 3, and 5. As in Figure 6, but with T0 data plotted in true radial distance from planet centre, at lines of constant relative longitude as indicated on the plot legend ( see Figure 5).

8. Tholin properties Albedo 1826 A 4.9 x 10-3 Q(Mie) I(R/A) 1.3 Opt depth
Refr index
Tholin
(Kare) i
r(A) 76
Tholin abnd
(cm-2)
6.9 X 1011
Tholin dens
(cm-3)
3900
Tholin Mixing
ratio
1.2 x 10-6

9. Issues with observed properties
Although the revised spectral calibration reduces the brightness at 1826 A by a factor of about 4, relative to 1300 A, an isotropic l4 Mie scattering predicts measureable OI solar line reflection. If this is caused by wavelength dependent polarization, a more in-depth analysis is required.
The flatfield used in the Mos reduction at T0 needs to be reexamined with the new stellar based flatfield because of significant differences with the original 2003 LISM based flatfield.