The unreliability of communication systems may result in bit error or loss in the auxiliary data received by ground s tations from satellites. In such cases

it is impossible to obtain accurate geometric parameters by interpreting and calculating from auxiliary data

which will impede SAR imaging processing. To resolve the problem of deficient imaging parameters in spaceborne SAR imaging processing

this paper proposes a joint estimation scheme of imaging parameters based on SAR echo data. In this proposed scheme

the Doppler centroid and Doppler chirp rate are estimated using SAR data. The over-determined equations of both Doppler parameters and imaging geometrical parameters are then established

which take advantage of the Doppler properties of the spaceborne SAR. The Doppler parameter estimates are used to resolve the appropriate geometric parameter equations. Lastly

SAR imaging processing is accomplished by using the Doppler parameter estimates and geometric parameter estimates. Experimental results show that reliable estimates of both Doppler and geometric parameters are obtained using the proposed method

effectively solving the problem of deficient imaging parameters in spaceborne SAR image processing.