大视场空间相机在轨成像期间, 由于地球自转、卫星姿态机动和颤振等因素导致焦面像速场呈非线性各向异性分布。为此提出了一种新的基于刚体运动学的像移速度场建模方法, 考虑离轴角参数, 推导了离轴三反大视场空间相机的像速场解析式。以某大视场空间相机为例, 分析了侧摆成像时同速与异速像移速度匹配模式对相机成像质量的影响。分析结果表明: 以传函下降5%为约束, 侧摆15°成像时, 当积分级数大于10级时应采用异速匹配模式, 积分级数为32级时, 异速匹配相比于同速匹配使焦面动态MTF从0.340 8提高到0.970 2。当积分级数确定为16级时, 侧摆角在12.3°以内时可采用同速匹配模式。在轨成像结果证明了像移速度场模型的准确性, 可为大视场空间相机像移补偿提供可靠依据。

During the onboard imaging process of space camera with large field of view, due to the effects of earth rotation, satellite attitude maneuverings, jittering and other factors, image motion velocity field of the focal plane has a non-linear anisotropic distribution. To overcome this problem, a novel image motion velocity field modeling method which is based on kinematics of rigid body was proposed. In this model, off-axis angle parameter was introduced and formulas of image motion velocity field in the large view off-axis three-mirror system were derived. Taking a certain large field space camera as an example, influences of synchronous and asynchronous velocity matching models on the camera image qualities were analyzed. Results show that, under a constraint of 5% drop and with scroll angle of 15°, if integral stages are larger than 10, asynchronous velocity matching models should be adopted. Especially when integral stages are fixed to 32, its dynamic MTF on focal plane can be improved to 0.970 2 while it is 0.340 8 in the synchronous model case. However, synchronous velocity matching model outperforms in the condition of 16 integral stages and 12.3° scroll angle. Onboard imaging experiments proved the accuracy of the models which will provide a reliable basis for large field space camera image motion compensation.