Star in the sky. The SMOS payload: MIRAS

Abstract

MIRAS is more than just the payload of SMOS. It is a radio telescope pointed towards Earth, an instrument that has challenged the fundamental theories of radio astronomy, and made a major contribution to science even before being launched.

Built by a consortium of over 20 European companies led by EADS-CASA Espacio (E), MIRAS is the single instrument carried on board ESA’s Soil Moisture and Ocean Salinity (SMOS) mission. MIRAS stands for the Microwave Imaging Radiometer with Aperture Synthesis.

The theory behind microwave remote sensing of soil moisture and ocean salinity is based on the significant contrast between the electromagnetic properties of pure liquid water and dry soil, and pure water and saline water respectively. As the proportion of water in the soilwater mixture (or proportion of salt in the saline mixture) increases, this change is detectable by microwave sensors in terms of the emission of microwave energy, called the ‘microwave brightness temperature’ of the surface