Application of conformal optical design in star sensor

Abstract

Star sensor is a special high accuracy photoelectric instrument. It is often used in navigation of aircraft, cruise missiles, and ballistic missiles, so the imaging quality of the optical system in a star senor is very important. The spherical windows with a small impact to imaging performance are usually used in traditional star sensors. However, the spherical surfaces are not ideal aerodynamic surfaces and would cause problems such as high drag. In this paper the conformal window whose outer shape is neither spherical nor flat is used in a star sensor. Unfortunately, the conformal shape introduces amounts of aberration which may lead to low imaging resolution. The various correctors can be used to eliminate the aberrations, for example, the fixed corrector, the arch, Zernike wedges, and the deformable mirror. The fixed corrector method is selected to decrease aberrations from the conformal window in this paper. The surface of the conformal window in the star senor is described as the Von Karman equation. The field of view is 17.6°×13.5°, and the size of the CCD pixel is 6.45 um×6.45um. The optical design program ZEMAX is used to design this system. After the optimization, under the max frequency of 77.52lp/mm, the MFT can almost achieve 30%. The design results show that the aerodynamic requirements can be satisfied by the application of the conformal window in the star sensor, and the aberrations can be corrected by proper ways.