Impact of Remote Sensing Satellite Attitude Parameters on Image Quality

The image quality of very high-resolution optical satellites (VHROS) is affected by several factors, including optics, detector, pointing accuracy errors, attitude stability errors, and altitude variations. Though providing low noise and improved light sensitivity, the time delay and integration (TDI) charge-coupled devices (CCDs) employed in VHROS play an important role along with the satellite attitude parameters in characterizing the image quality. Failure of the satellite control system to maintain the required pointing accuracy and attitude stability during the imaging process leads to a serious degradation in the quality of the acquired images. Hence, it is required to investigate their impacts carefully during the satellite preliminary design phase. In this paper, the combined effect of the TDI steps, satellite attitude parameters, and orbital altitude variations on the image quality are investigated in detail. The results show that cross-track image quality is affected severely by yaw angle and roll angular velocity bias, whereas the along-track image quality is affected merely by pitch angular velocity bias. Furthermore, the proposed mathematical model in this paper reveals that total modulation transfer function (MTF), as a measure of image quality, is affected severely by the satellite altitude variation, especially when employing a high number of TDI steps. For example, for a given scenario, when employing TDI steps of 64 the effect of a satellite altitude variation of 10 Km will result in a 65% reduction in total system MTF.