Star camera is a kind of sensitive attitude sensors used for navigation of space vehicles. In order to use it on aircrafts in
daytime, the conceptual design and the principle of airborne daytime infrared star cameras are introduced in this paper, as
there is enough number of stars in near infrared band to be used as reference of a star camera for calculating attitude.
Through analyzing the atmospheric scattering background light intensity for different altitudes, observing angles, and
solar angles with Modtran software, and considering IR FPA (infrared focal plane array) performance, shot noise and the
required star magnitude for daytime star trackers and sensors, the optical system parameters, i.e. FOV (field of view),
clear aperture diameter and effective focal length, are determined according to the required SNR (signal to noise ratio).