Affiliation: | School of Mathematics and Statistics, University of St Andrews, St Andrews KY16 9SS;School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS;Laboratoire d'Astrophysique, Observatoire Midi-Pyrénées, 14 Av. E. Belin, F-31400 Toulouse, France;ESTEC, European Space Agency, PO Box 299, 2200 AG Noordwijk, the Netherlands |