Analysis of Attitude Errors Effect on the Measurement of Interferometric Radar Altimeter Based on the Imaging Principle

Systematic attitude errors (the roll, pitch, and yaw errors) are important sources of altimetric error in interferometric radar altimeters (IRAs). So far, the effect of systematic attitude errors on the measurement of IRA has been investigated based on the interferometric geometry, in which the impact of the attitude errors on the IRA image quality and the coupling between each attitude error are not considered. In this work, the influence of attitude errors on the measurement accuracy of IRA is reanalyzed according to the IRA imaging principle and the interferometry theory. The theoretical formulas derived in this article demonstrate that the roll is the most important factor affecting the measurement accuracy of IRA. Although the altimetric error directly introduced by yaw and pitch is smaller, the yaw and pitch would cause the altimetric error to be offset along the azimuth direction, and the offset grows approximately linearly across the range direction in the IRA images. Meanwhile, the attitude jitter would also introduce additional high-frequency altimetric errors, although these high-frequency altimetric errors can be removed through a Gaussian low-pass filter with the cut-off frequency determined by wavelet analysis. To verify the validity of the theoretical formulas and exhibit the impact of diverse attitude errors, a full-link simulation method is proposed, which encompasses the entire process from IRA observation to imaging and interference processing; furthermore, the theoretical results are compared with the results of the full-link simulation and the experimental data acquired by an airborne IRA.