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| Titel |
Monitoring greenhouse gases with astronomical observations |
| VerfasserIn |
W. Kausch, S. Noll, M. Barden, A. Smette, C. Szyszka, A. Jones, S. Kimeswenger, H. Sana, H. Horst |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066944
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| Zusammenfassung |
| Modern telescopes are equipped with high-precision multi-mode spectrographs. To obtain
proper calibration, astronomers observe the plain night sky and specific telluric standard stars
(TS stars) to estimate the influence of the Earth atmosphere on astronomical observations. TS
stars are usually white dwarfs, as their spectra are not time dependent and hardly contain any
spectral features.
Since the atmospheric emission in the thermal infrared and the absorption of stellar
radiation reflect molecular abundances in the lower atmosphere, plain night sky and TS
spectra can be used to obtain column densities of greenhouse gases. We present a method for
determining this, incorporating the radiative transfer code LBLRTM and the HITRAN
database. We fit specific molecular absorption and emission features by varying the
corresponding abundance profiles iteratively implementing a Levenberg-Marquardt Ï2
minimisation algorithm.
This method was originally developed to estimate the amount of precipitable water
vapour, which strongly influences infrared observations, above the observing site of the ESO
Very Large Telescope, Cerro Paranal. We are currently in the process of extending this
procedure to other greenhouse gases. As plain sky and TS stars are observed several times per
night these spectra can be used to monitor molecular column densities on a long term
basis. |
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