Presented at the 2015 Aquarius/SAC-D Science Team MeetingDuring the almost 4 years of Aquarius operational life, we have focused our efforts towards the development of an alternative soil moisture product for the mission. In this context, an Observing System Simulation Experiment for Aquarius was developed to assess the impact of sources of errors in the soil moisture retrieval. Using Aquarius observations, different soil moisture retrieval algorithms were developed. A novel retrieval algorithm was developed, which uses bayesian inference to retrieve soil moisture and optical depth using horizontal and vertical polarization brightness temperature. Advantages of bayesian inference include: i) errors on the retrieved variables can be estimated in an univocal way, ii) it gives the possibility to use prior information about the retrieved variables, iii) it can handle uncertainties on the ancillary parameters. Moreover, a radar-only retrieval algorithm for soil moisture mapping was applied to Aquarius scatterometer measurements. The algorithm is based on a nonlinear relation between L-band backscatter and volumetric soil moisture and does not require ancillary information on the surface. Currently, we are working on an algorithm that also considers the improvement of the radiometer soil moisture spatial scale and on a combined active-passive soil moisture retrieval that benefits from all the work done so far.