The Microwave Imagine Radiometer with Aperture Synthesis (MIRAS) aboard the SMOS satellite measures the Earth's surface brightness temperature at L-Band at a frequency of 1.4 GHz. These measurements are full polarimetric and are carried out at nadir incidence angles of between 0 and 65°. Both polar hemispheres are covered completely every day.
Here we offer mean daily brightness temperature intensities gridded onto a polar-stereographic grid with 12.5 km grid resolution. In order to do so, first all brightness temperature (TB) measurements carried out during one day at both polarizations (horizontal and vertical, h and v) and nadir incidence angles of between 0 and 40° are collected on the special SMOS ISEA grid (The special viewing geometry of SMOS required a special native grid.). TBh and TBv have to acquired within 2.5 s to form a data pair to be used. For each SMOS ISEA grid cell all TB values are averaged over the given incidence angle range to compute the brightness temperature intensity (TBh + TBv)/2. Subsequently, the data are interpolated onto the mentioned polar-stereographic grid.
Attention! Since Dec 2, 2016 version 3 is available. The data are reprocessed consistently using v620 L1C data. An improved data filtering method regarding to RFI and geophysical noises is applied in the processing chain from L1C to L3B, which improved the L3B data quality and availability.
The documentation reveals more details of the processing.