The models we use are based on line-by-line methods. The molecular absorption is calculated by summing the contributions of many individual spectral line profiles. The line databases used contain more than a billion spectral lines of many different molecules. The molecular absorption is then combined with the effects of scattering of light by clouds and dust particles, and a solution of the radiative transfer equation is then performed for each spectral point.

We are using two such models. The VSTAR (Versatile Software for Transfer of Atmospheric Radiation) model developed at UNSW.

VSTAR Paper at Granada Mars Atmosphere Workshop

Expample of VSTAR model results. Top panel - radiance emitted at the top of the Martian atmosphere for Mars atmosphere models with no methane (green), 10ppb of methane (red) and 50ppb of methane (yellow), Middle panel - Transmission of the earth atmosphere for the Mauna Kea site. Lower panel - Radiance as seen from the ground at the Mauna Kea site with Mars at a recession veocity of 16kms^-1 with the same colour code as the top panel. The Martian methane lines are just visible on the edge of the broad telluric absorption at about 3.2706 microns.

The other model we use is SMART (Spectral Mapping Atmospheric Radiative Transfer) developed over many years at NASA's Jet Propulsion Laboratory in California by our collaborator Dr. David Crisp.
 

The plots above show SMART models of the infrared spectrum of the night-side of Venus. We use these two models for a range of studies:

• Analysing observations of Venus to study the structure and composition of its lower atmospheres.
• Modelling the transmission of the Earth's atmosphere in the infrared to improve the quality of astronomical observations from ground-based telescopes.
• Analysing spectra of Mars to obtain basic meteorogical parameters such as atmospheric pressure.
• Predicting the spectra of extrasolar planets.