The planned encounter of the Giotto spacecraft with comet Grigg-Skjellerup on 10th July 1992 promises to extend our knowledge of the solar wind interaction with comets substantially. While there have been spacecraft missions to comets before now, this mission is exploratory in the sense that the target comet is much older and therefore it has a much lower gas production rate than comets Halley (by a factor ~200) or Giacobini-Zinner (factor ~10). Here we present theoretical predictions for the location of the bow shock and contact surface features, and compare similar predictions with the observed features at the previous encounters. We discuss the applicability of fluid-type theory which these models employ, in the case of strong and weak comets in the solar wind. ¿ American Geophyscial Union 1992