STEREO-WAVES antennas - Reception properties in the quasi-static frequency range

The STEREO mission will be launched in April 2006. Its target is to investigate the plasma environment of the Sun with its complex, sometimes even hazardous consequences for the Earth.

On each spacecraft three monopoles are mounted to receive electromagnetic waves. For the purpose of accurate data evaluation, especially geometric triangulation, an accurate knowledge of the antenna reception properties, represented by the so-called effective length vector, is essential.

The objective of this project is the determination of these vectors and of the antenna impedances by means of two different techniques: First, rheometry is based on electrolytic tank measurements of a 1:20 scale model of the spacecraft and the antennas yielding the effective length vectors in the quasi-static frequency range where the wave length is much greater than the dimension of the antenna system.

Rheometry facilitates modelling of the antennas-spacecraft system in great detail, and the measurement set-up is rather disturbance-free in contrast to high-frequency measurements. Second, numerical computer simulations are used in order to study the antenna properties over a wide frequency range. The main advantage of the numerical method is flexibility with regard to the representation of spacecraft parts, which can easily be altered to test their influence on antenna properties.

Furthermore, computer simulations enable us to estimate an upper frequency limit below which the quasi-static results are valid. The data evaluation of the WAVES experiment will be improved substantially by our analysis, in particular the direction finding and source localization for the observed radio signals are only possible with the results of this project.

Coordinator

Department of Extraterrestrial Physics Space Research Institute Austrian Academy of Sciences - Helmut O. Rucker

Partners

• Prototypenbau Meister
• Observatoire de Paris-Meudon
• France NASA Goddard Space Flight Center
• USA University of Minnesota
• USA University of California, Berkeley, USA

Department of Extraterrestrial PhysicsSpace Research InstituteAustrian Academy of Sciences
Institute Austrian Academy of Sciences
Schmiedlstr. 6
A-8042 Graz
Helmut O. Rucker
E-mail: helmut.rucker@oeaw.ac.at
Wolfgang Macher
E-mail: wolfgang.macher@oeaw.ac.at
Web: www.iwf.oeaw.ac.at