Abstract

Using ray tracing to determine the structure of planetary atmospheres:
The Planetary Atmosphere by Occultation Numerical Analysis Program (PLATONA)

Wolfgang Beisker

Vorstellung eines Programms zur Berechnung von Planetenatmosphären durch eine strahlenoptische Analyse von Bedeckungsdaten.
Dichte- und/oder Temperaturunterschiede einer Planetenatmosphäre brechen optische Strahlen.
Atmosphärenmodelle können numerisch definiert oder aus mathematischen Modellen ( wie z.B. der Baum-Code-Beziehung ) bestimmt werden.
Während einer Bedeckung wird das Atmosphärenprofil abgetastet.
Durch Optimierungsrechnung oder Monte-Carlo-Verfahren lassen sich die atmosphärischen Parameter bestimmen.

By ray tracing the distortion of a parallel wavefront by a planetary atmosphere with arbituary structure is calculated. Using geometrical optics the refraction by the changing densities and/or temperature of the atmosphere during ray propagation is calculated and the intensity distribution in the observer plane is evaluated.

The structure of the atmosphere can be defined by numerical input or by rigorous mathematical computation, such as in the isothermal case (results in the famous Baum-Code relation).

The result of the first module of PLATONA is a FITS image, which contains the light intensities in the observer plane. In a following module, the path of the observer due to the movement of the planet and the earth is calculated and the resulting intensities are compared with the measured light curve during a real occultation. By a least square iteration process or a Monte Carlo technique as well, the parameters of the atmosphere can be changed to fit the observation data.

The program will be an attempt to provide an easy to use interface to analyze occultation data.

Dr. Wolfgang Beisker, International Occultation Timing Association - European Section
Address: Frankfurter Ring 32, 80807 München, Germany E-Mail: beisker@gsf.de
Telephone: +49 89 3507222 (private) +49 89 31872842 (office)

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