1. S. Besse, M. A’Hearn and the DIXI team
IR detailled results
S. Besse, M. A’Hearn and the DIXI team
Osiris team meeting
June , 2011

2. Instrument Spectrometer from 1 to 5μm Slit of 10μm
Two channels, one for the visible, one for the near infra red.
Observations can be made simultaneously

3. Emission features CO2 (gas) H2O (gas) Organics CO?? Coma at CA
Spectra of the coma, average of several pixels
Co emission is relatively weak. We are still fixing the calibration, We have not worked that much with CO so far.
Coma at CA

4. Emission features 1H before CA
Spectra of the coma, average of several pixels
Asymetry for water and carbon dioxide.
Grains map correlate more with the water map

5. Spatial distribution CO2 and Organics are roughly in the same area
H2O is coming from a different location of the nucleus, coming from the “shaved” area
We suggested that this region is a re-deposition of ice grains in the coma that sublimate later (thus producing water emission)
Species are correlated with the sunward direction

6. Water  +8h and -8h from CA
Dust = grains (ice +solid particles)
Organics correlated to CO2

7. Jet and waist Average of few pixels (10x10)
This is the same thing as previous map
CO2 correlated to organics and ice (we will see that in few minutes)
Water vapor is not absent from the CO2 region. We have in the case of the waist an optically thick region

8. Temporal variation
CO2, H2O and “grains” can be observed approximately 7 days before CA and 10 days after CA
We can produce light curves of these species
CO2, H2O and “grains” are in phase
We have a factor of 2 in absolute brightness between CO2 and H2O
However, this factor varies, can be equal to 0 also.

9. Variability
Preliminary analysis show possible offset in the peak of brightness in some case before CA. This could be errors in the measurements (flux is weak), preliminary calibration or related to complex rotation.
Extention of CO2 is larger, brighness is 2 times higher during the big peak.
For the grains, we have found that different aperture can tell us about the velocity of the grains.
The idea is to try the same for CO2 and H2O.

10. Absorption features H2O (ICE) CO2 (ICE)? Pyroxenes? Olivine? ICE
Nucleus is largely saturated, we focused our work on the coma.
ICE
CO2 ice is very close to CO2 emission so very difficult to find.
Pyroxenes and Olivine are associated to the nucleus and the nucleus is largely saturated

11. Ice modelling Hapke model of grains, 1, 10, 100 μm
Optical constants from Warren & Brandt
Requires grains <10 μm
Lifetimes imply pure ice
Fluffy aggregates

12. Spectra are um particles
Image are cm particules
(discussion of Paris and response from Silvia and Jess)

13. Ice is correlated to CO2 and Organics.
Ice also in “cold trap”, in shadows. But still, this ice is correlated to jets activity.

14. Impact for OSIRIS observations
We have important heterogeneity of the nucleus and thus the coma environment at a given time
We have variation with time (correlated with the rotation period and sun direction)
Separation of H2O and CO2
Photo-dissociation of H2O and CO2
Refer to mike