偏流角对空间相机影响研究

Study on influence of drift angle on the space camera

研究了卫星运行中偏流角对TDICCD相机像质的影响。根据卫星运动状态,推导了偏流角的具体变化形式,以及由其在穿航方向和沿航方向引起的相机像移和由此造成的像质退化调制传递函数(MTF)。并针对高度为500 km的圆形卫星轨道,定量计算了偏流角导致的像移对相机像质的影响程度。结果表明:偏流角在赤道附近最大,随着纬度的升高,偏流角呈非线性减小。并且,由它引起的像移在穿航方向对相机像质的影响远大于沿航方向。对于给定的轨道参数,偏流角最大值约为3.7°,当积分级数为32时,由其引起的像移调制传递函数接近于零,严重影响了相机的成像质量。为此,提出了使用二维摆镜和调整焦平面方向两种实时补偿偏流角影响的方法。

The influence of the drift angle on image quality of TDICCD camera was studied. The variation format of the drift angle was deduced based on orbit equation of the satellite. Then the image motion of camera along and across the course caused by the drift angle was studied, which resulted in degradation of image quality. To illustrate this effect quantitatively, the image motion and the Modulation Transfer Function （MTF） caused by the drift angle were calculate out by using a circular satellite orbit at altitude of 500 km. The results showed that the maximum drift angle was got at the equator, and the drift angle decreased nonlinearly with the increasing of the latitude. The drift-angle caused image motion across the course had far more serious effect on image quality than the image motion along course. For the given orbit parameters, the maximum drift angle was about 3.7°, and the MTF caused by it approached to zero when the integral number was equal to 32, which affected the image quality of the camera seriously. Therefore, we put forward two methods for compensating the influence of drift angle in real time： using two-dimensional swing mirror and adjusting the orientation of the focal plane.