Image motion velocity field of off-axis TMA space camera with large field of view

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.