Abstract
We present the first published analysis of a solar occultation by Titan's atmosphere measured by the Ultraviolet Imaging Spectrograph on board Cassini. The data were measured during flyby T53 in 2009 April and correspond to latitudes between 21° and 28° south. The analysis utilizes the absorption of two solar emission lines (584 Å and 630 Å) in the ionization continuum of the N2 absorption cross section and solar emission lines around 1085 Å where absorption is due to CH4. The measured transmission at these wavelengths provides a direct estimate of the N2 and CH4 column densities along the line of sight from the spacecraft to the Sun, which we inverted to obtain the number densities. The high signal-to-noise ratio of the data allowed us to retrieve density profiles in the altitude range 1120-1400 km for nitrogen and 850-1300 km for methane. We find an N2 scale height of 76 km and a temperature of 153 K. Our results are in general agreement with those from previous work, although there are some differences. Particularly, our profiles agree, considering uncertainties, with the density profiles derived from the Voyager 1 Ultraviolet Spectrograph data, and with in situ measurements by the Ion Neutral Mass Spectrometer with revised calibration.
| Original language | English (US) |
|---|---|
| Article number | L16 |
| Journal | Astrophysical Journal Letters |
| Volume | 766 |
| Issue number | 2 |
| DOIs | |
| State | Published - Apr 1 2013 |
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Keywords
- instrumentation: spectrographs
- occultations
- planets and satellites: atmospheres
- planets and satellites: individual (Titan)
- space vehicles: instruments
- Sun: UV radiation
ASJC Scopus subject areas
- Space and Planetary Science
- Astronomy and Astrophysics
Cite this
Solar occultation by titan measured by cassini/UVIS. / Capalbo, Fernando J.; Bénilan, Yves; Yelle, Roger V.; Koskinen, Tommi T.; Sandel, Bill R.; Holsclaw, Gregory M.; McClintock, William E.
In: Astrophysical Journal Letters, Vol. 766, No. 2, L16, 01.04.2013.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Solar occultation by titan measured by cassini/UVIS
AU - Capalbo, Fernando J.
AU - Bénilan, Yves
AU - Yelle, Roger V.
AU - Koskinen, Tommi T.
AU - Sandel, Bill R.
AU - Holsclaw, Gregory M.
AU - McClintock, William E.
PY - 2013/4/1
Y1 - 2013/4/1
N2 - We present the first published analysis of a solar occultation by Titan's atmosphere measured by the Ultraviolet Imaging Spectrograph on board Cassini. The data were measured during flyby T53 in 2009 April and correspond to latitudes between 21° and 28° south. The analysis utilizes the absorption of two solar emission lines (584 Å and 630 Å) in the ionization continuum of the N2 absorption cross section and solar emission lines around 1085 Å where absorption is due to CH4. The measured transmission at these wavelengths provides a direct estimate of the N2 and CH4 column densities along the line of sight from the spacecraft to the Sun, which we inverted to obtain the number densities. The high signal-to-noise ratio of the data allowed us to retrieve density profiles in the altitude range 1120-1400 km for nitrogen and 850-1300 km for methane. We find an N2 scale height of 76 km and a temperature of 153 K. Our results are in general agreement with those from previous work, although there are some differences. Particularly, our profiles agree, considering uncertainties, with the density profiles derived from the Voyager 1 Ultraviolet Spectrograph data, and with in situ measurements by the Ion Neutral Mass Spectrometer with revised calibration.
AB - We present the first published analysis of a solar occultation by Titan's atmosphere measured by the Ultraviolet Imaging Spectrograph on board Cassini. The data were measured during flyby T53 in 2009 April and correspond to latitudes between 21° and 28° south. The analysis utilizes the absorption of two solar emission lines (584 Å and 630 Å) in the ionization continuum of the N2 absorption cross section and solar emission lines around 1085 Å where absorption is due to CH4. The measured transmission at these wavelengths provides a direct estimate of the N2 and CH4 column densities along the line of sight from the spacecraft to the Sun, which we inverted to obtain the number densities. The high signal-to-noise ratio of the data allowed us to retrieve density profiles in the altitude range 1120-1400 km for nitrogen and 850-1300 km for methane. We find an N2 scale height of 76 km and a temperature of 153 K. Our results are in general agreement with those from previous work, although there are some differences. Particularly, our profiles agree, considering uncertainties, with the density profiles derived from the Voyager 1 Ultraviolet Spectrograph data, and with in situ measurements by the Ion Neutral Mass Spectrometer with revised calibration.
KW - instrumentation: spectrographs
KW - occultations
KW - planets and satellites: atmospheres
KW - planets and satellites: individual (Titan)
KW - space vehicles: instruments
KW - Sun: UV radiation
UR - http://www.scopus.com/inward/record.url?scp=84875250409&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84875250409&partnerID=8YFLogxK
U2 - 10.1088/2041-8205/766/2/L16
DO - 10.1088/2041-8205/766/2/L16
M3 - Article
AN - SCOPUS:84875250409
VL - 766
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
SN - 2041-8205
IS - 2
M1 - L16
ER -