Observing system simulation experiments AQUARIUS 8 Aquarius 8 Soil moisture 8 soil moisture 8 Computer simulation 6 Experiments 6 Remote sensing 6 Soil moisture retrievals 6 radiative transfer 6 Error analysis 4 Microwave emission models 4 OSSE 4 Quantitative error analysis 4 Radiative transfer model 4 Soil moisture estimation 4 Volumetric soil moistures 4 accuracy assessment 4 data assimilation 4 error analysis 4 numerical model 4 Arkansas Basin 2 Atmospheric general circulation models 2 Backscatter model 2 Backscattering 2 Bias 2 Canopy structure 2 Data assimilation 2 Dense vegetation 2 Direct inversion 2