[eng] Following several earlier feasibility studies, in 1998 ESA began the MIRAS Demonstrator Pilot Project within the Agency's Technology Research Programme (TRP) and General Support Technology Programme (GSTP) in an attempt to provide a technology solution to the inherent challenges of L-band radiometry. The objective was to build a representative element of the MIRAS instrument, which has subsequently been selected as the main payload for the Soil Moisture and Ocean Salinity (SMOS) mission. A second phase was initiated in April 2001 to demonstrate key end-to-end instrument performances, including antenna deployment and image validation, following approval of the SMOS mission Phase-A at the end of 1999.