The Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) instrument is a passive microwave 2-D interferometric radiometer (L-Band, 1.4 GHz, 21 cm) onboard the SMOS satellite. It picks up faint microwave emissions from Earth's surface to map levels of soil moisture, sea surface salinity, sea ice thickness and others geophysical variable such as wind speed over ocean and freeze / thaw soil state.

MIRAS consists of a central structure and three deployable arms. The 69 LICEF (Lightweight Cost-Effective Front-end) receivers are equally distributed over the three arms and the central structure. Each LICEF is an antenna-received integrated unit that measures the radiation emitted from Earth at L-band. The acquired signal is transmitted to a central correlator unit, which performs interferometry cross-correlations of the signals.