1. Institut Charles Gerhardt Montpellier, Univ. Montpellier, CNRS, ENSCM, Montpellier F-34293, France
2. Centre National d’Etudes Spatiales, DTN/QE/LE, 18 Avenue Edouard Belin, Toulouse 31401 Cedex 09, France
3. Department of Chemical Engineering, Yeditepe University, Istanbul 34755, Turkey
4. Surface Measurement Systems, Unit 5, Wharfside, Rosemont Road, London HA0 4PE, U.K.