In-situ measurement of the deformation of the off-axis parabolic mirror with large aperture

For the radiometric calibration of remote sensors, it is required to in-situ measure the variation of the surface shape of the large aperture off-axis parabolic mirror under simulated space condition. A digital knife-edge test method was proposed to overcome the difficulty of the interferometer for the in-situ measurement of deformation of the off-axis parabolic mirror with larger aperture. Key components of the system were selected and test system was built up. An off-axis parabolic mirror with aperture of 120 mm and focus length of 1000 mm was tested. Results show that our method is feasible. This method offers great potential in various applications pertaining to the need of in-situ measuring wave-front errors on aspheric surface in the special test condition such as space environment where interferometry are difficult to use.