The Hipparcos satellite generates a considerable quantity of ‘raw’ data: approximately 1Gbit per day, or some lOOOGbits over its anticipated lifetime. The Hipparcos mission follows usual practices of having elements of the observing programme selected after an invitation for proposals to the general astronomical community, as well as a strong scientific interest in the data exploitation from amongst the individuals working within the scientific consortia related to the observing programme definition and the data analysis. However, an unusual feature of this mission is the fact that the elemental observations cannot be ‘separated out’ and distributed to the proposers or the consortia ‘principal investigators’. Instead, the data analysis teams will work towards the construction of a single, agreed-upon, catalogue containing the final astrometric and photometric star parameters.