Speaker
Dr
Ghislain Franssens
(BISA)
Description
The Altius Radiative Transfer In-flight Simulator (ARTIS) is a software tool, developed at BISA, to simulate the light observed by the ALTIUS instrument on its orbit around the Earth.
Current key functionalities of this program are: (i) simulation of the movements of relevant planets in the solar system (including Earth), (ii) vectorial radiative transfer calculation in an oblate spheroid atmosphere, (iii) including refraction, single Rayleigh scattering, absorption by gases (1D), single scattering and absorption by aerosols (1D), (iv) calculation of Jacobians, (v) satellite orbit simulation based on osculating Kepler parameters and (vi) realistic time and space awareness.
Over the last year, another (parallel) effort was started to develop a standalone software library of core RT and related algorithms, called the Altius RTLib, in order to extend the functionality of ARTIS and to support the design of retrieval algorithms. The goal is to let RTLib evolve into a central algorithm repository and to move core algorithms currently in ARTIS to RTLib, so that then ARTIS, retrieval modules and possibly other software components can call on the functionality in RTLib.
Current features of RTLib are: (i) vectorial multiple Rayleigh scattering, (ii) efficient production of lookup tables and (iii) the calculation of Jacobians for gases. To be included later this year: (i) a general albedo treatment, (ii) refraction (taken from ARTIS), (iii) vectorial multiple scattering by aerosols and (iv) support for line-absorbers in the IR (contribution by Nina Mateshvili).
Special care went into the design of the multiple Rayleigh scattering algorithm, trying to make it both accurate and fast, while respecting the spherical geometry of the atmosphere. The development of a broadband model for IR line-absorbers, based on the correlated-k method, is also nearing completion. A brief overview of both these algorithms will be given in the talk.
Primary author
Dr
Ghislain Franssens
(BISA)
