1. Universität Stuttgart, D-70569 Stuttgart, Germany
2. Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
3. European Space Agency/European Space Research and Technology Centre, NL-2200 AG Noordwijk, The Netherlands
4. Astrium SAS, F-33160 Saint-Médard-en-Jalles, France