Issue |
A&A
Volume 637, May 2020
|
|
---|---|---|
Article Number | A90 | |
Number of page(s) | 9 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202037609 | |
Published online | 21 May 2020 |
Effect of the 3D distribution on water observations made with the SWI
I. Ganymede
1
Department of Space, Earth, and Environment, Chalmers University of Technology, Onsala Space Observatory,
439 92
Onsala,
Sweden
e-mail: eva.wirstrom@chalmers.se
2
Max-Planck-Institut für Sonnensystemforschung,
Justus-von-Liebig-Weg 3,
37077
Göttingen,
Germany
3
Research Group for Genomic Epidemiology, National Food Institute, Technical University of Denmark,
Kgs. Lyngby
2800,
Denmark
Received:
24
January
2020
Accepted:
3
April
2020
Context. Characterising and understanding the atmospheres of Jovian icy moons is one of the key exploration goals of the Submillimetre Wave Instrument (SWI), which is to be flown on ESA’s Jupiter Icy Moons Explorer (JUICE) mission.
Aims. The aim of this paper is to investigate how and under which conditions a 3D asymmetric distribution of the atmosphere may affect the SWI observations. In this work we target the role of phase angle for both nadir and limb geometries for unresolved and partially resolved disc observations from large distances.
Methods. We adapted the LIME software package, a 3D non-local thermodynamical equilibrium radiative transfer model, to evaluate ortho-H2O populations and synthesise the simulated SWI beam spectra for different study cases of Ganymede’s atmosphere. The temperature and density vertical distributions were adopted from a previous work. The study cases presented here were selected according to the distance and operational scenarios of moon monitoring anticipated for SWI during the Jupiter phase of the JUICE mission.
Results. We demonstrate that nadir and limb observations at different phase angles will modify the line amplitude and width. Unresolved observations where both absorption against surface continuum and limb emission contributes within the beam will lead to characteristic line wing emission, which may also appear in pure nadir geometry for specific phase angles. We also find that for Ganymede, the 3D non-local thermodynamical equilibrium populations are more highly excited in the upper atmosphere near the sub-solar region than they are in 1D spherically symmetric models. Finally, the 3D radiative transfer is better suited to properly simulate spectral lines for cases where density or population gradients exist along the line of sight.
Key words: planets and satellites: atmospheres / planets and satellites: individual: Ganymede / submillimeter: planetary systems / radiative transfer / space vehicles: instruments
© ESO 2020
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.