Slanted-edge MTF Focus Test Verification with PRF Testing to Establish Best Focus Position of Infinite Conjugate Space Optical Systems

For earth-viewing, fixed-focus space optical systems, carefully finding the best focus position of the instrument is critical to achieving the best possible image performance and mission success. For such space optical systems, modulation transfer function (MTF) test data is directly applicable to system optical resolution. Furthermore, MTF test products can be combined to predict overall imaging performance. The infinite conjugate slanted edge MTF test can be used in ground testing to identify best focus of the optical system while taking into account the entire imaging system, operational parameters, and simulated operational environment. The point-response function (PRF) test can be used to verify the results of the slanted edge MTF test to ensure that the optimum best focus position is determined. This paper discusses the slanted edge MTF test for establishing best focus and the PRF test for verifying the best focus. Actual MTF and PRF test results are presented.