The problem of a space vehicles (SV) navigation while processing the moments of signals from several space sources of Roentgen illumination incoming taking into consideration random error of measurements is discussed in the paper. The device of processing realizes Kalman filter quasi-optimal sigma-point algorithm and forms at the output estimates of SV current coordinates and velocity. It is done estimates error analysis when a-priory input and measured date about the SV position and velocity differ. There is also analyzed intensity of measurement of incoming moments errors due to the observation properties compared with the initial values. Method of statistical tests allowed to estimate the influence of a-prioryinaccuracy on the root-mean-square error of the SV coordinate and velocity estimation.