Detecting performance of airborne daytime star sensor for navigation is analyzed and its experiment is researched in this paper. Mathematical models of SNR (Signal-Noise-Ratio) and contrast of photoelectric imaging system in daytime under noise are established

and calculated results by different focal lengths and different apertures are compared to conclude the influence of system parameters and requirements of optical system

and conclusion is get that the proper relative aperture of optical system is 1/15. Overall design of daytime star sensor prototype for tracking stars of magnitude 3 or brighter is put forward. Tracking images of polestar from sunrise to noon are acquired by ground experiment using a F/15 objective

and brightness and contrast of star images at different time are compared. The contrast of star image descends from 1.55 at 5:00 a.m. to 1.2 at 12:00 a.m. The minimal degree of modulation is always more than 0.03 by calculating with the prototype’s parameters

which shows the Φ70mm

F/15 optical system can satisfy the detecting requirements. Processing result by frames cumulating and filtering is showed in this paper. The theoretic analysis and design is proved to be available

and the research in this paper can be a reference to developing of miniaturized and precise airborne daytime navigation star sensors.