Increase of accuracy as the minimization proceeds, at various temporal sampling frequencies, for a fixed assimilation window of width 1.5 solar cycle and a fixed number of observation points in latitude (﹩{N}_{\theta }^{o}=63﹩). The effect of the sampling frequency on the convergence is less significant than that of the temporal window width, except for the most complex asymmetric case with the sparsest temporal sampling.