Abstract:  A method of improving the accuracy of the attitude angle of a satellite obtained by a digital sun sensor was studied.Due to large systematic errors in directly computing the attitude angle by the sun sensor，the equations of nonlinear angle computation to modify refraction effects were given by the light propagation principle.Two computational methods of solving the nonlinear equations by control system software were proposed，including the specific implementation of spaceborne programming and computation.Finally，actual validation was performed by measured data.Compared with the previous uncorrected angle，the accuracy is improved by approximately 3.94°.It is improved from 0.04° to 0.02° compared with the multivariate function fitting method of other system error correction.The feasibility of spaceborne programming computation and the effectiveness of improving system accuracy were verified.

Key words: digital sun sensor, attitude accuracy improvement, actual validation, modified refraction, spaceborne programming and computation