Determination of vision-based relative state by modified unscented Kalman filter

On the basis of the principle of a VISNAV sensor,this paper researches how to determine the vision-based relative state between two satellites with disturbances.By taking the VISNAV sensor as a relative state sensor,the problem mentioned above is solved by a modified Kalman filter algorithm.In consideration of the relative orbit dynamics equation with disturbance and the relative attitude kinematic equation,it gives modified discrete equation and a calculation method for the error covariance matrix.By which the method avoids the complicated real-time operations of large dimensional matrices in every loop and reduces computation amounts.Finally,the corresponding modified Unscented Kalman Filter(UKF)method followed by a numerical simulation experiment is performed under STK and MATLAB.Results demonstrate that the method is feasible,effective and has good convergence.Under disturbance condition,its determination accuracy in 200 m is an angle second level for the relative attitude and a millimeter level for the relative position,which meets the requirements of determining the relative state between two satellites in a shorter distance.