Brightness temperature measurements in L-Band (1.0 - 2.0 GHz) acquired by the MIRAS sensor aboard the Soil Moisture and Ocean Salinity (SMOS) sensor are used to retrieve a global data set of the near surface (0 - 5 cm) soil moisture.
For the soil moisture retrieval an iterative minimization of a cost function is carried out. That cost function is constructed from the quadratic differences of observed and modeled brightness temperatures and from the quadratic differences of retrieved and a-priori geophysical parameters such as the soil moisture, the soil dielectric constant and the vegetation optical depth - all scaled with their uncertainty.
This Level-3 product retrieval uses multi-angular, multi-orbit brightness temperature measurements of the same location collected for the day of soil moisture retrieval and from days up to three days in the past and three days ahead of the respective day, i.e. a 7-day period. More details about the soil moisture retrieval is given in the ATBD.
We note that this Level-3 product does not follow the common procedure and is not retrieved from the level-2 soil moisture products but for ease of usage is retrieved directly from the Level 1B data.
This data set was included in the ICDC data base on May 4, 2017.