Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

P (Space and Planetary Sciences ) » P-PS Planetary Sciences

[P-PS01] Outer Solar System Exploration Today, and Tomorrow

Tue. May 28, 2019 9:00 AM - 10:30 AM A03 (TOKYO BAY MAKUHARI HALL)

convener:Jun Kimura(Osaka University), Yasumasa Kasaba(Planetary Plasma and Atmospheric Research Center, Tohoku University), Kunio M. Sayanagi(Hampton University), Chairperson:Kunio Sayanagi(Hampton University), Takeshi Kuroda

9:00 AM - 9:15 AM

[PPS01-06] Radiative transfer simulation including a non-LTE model for terahertz observations of Ganymede's atmosphere

*Takayoshi Yamada1, Ladislav Rezac2, Richard Larsson2, Paul Hartogh2, Naohiro Yoshida3, Yasuko Kasai1,3 (1.National Institute of Information and Communications Technology, 2.Max Planck Institute for Solar System Research, 3.Tokyo Institute of Technology)

Keywords:THz, Radiative trasfer

We are developing a teraherz radiative transfer code, named Atmospheric Teraherz Radiation Simulator (ATRASU), for simulations of sub-millimeter observations of planetary atmospheres.
Because of the tenuous Ganymede atmosphere we need to include non-local thermodynamic equilibrium (non-LTE) conditions of H2O rotational levels to simulate observations by the Submillimeter Wave Instrument (SWI) on the JUpiter ICy moon Explorer (JUICE). The frequency windows of the JUICE/SWI are 530 to 625 GHz and 1080 to 1275 GHz with 100 kHz spectral resolution.
We developed a deterministic non-LTE solution based on the multilevel Gauss–Seidel method. The simulated energy level populations of H2O for SWI observations start to deviate from LTE at 100 to 200 km altitude around sub-solar latitudes of 10 degrees. At sub-solar latitudes around 60 degrees the populations are in non-LTE over the entire range, starting from the surface. The difference of the simulated spectra between LTE and non-LTE conditions, and their sensitivity to various parameters, such as collisional rates for H2O, will be presented.