Temperature has a significant impact on measurement accuracy of star sensors. In order to improve the accuracy of star sensors in different temperature conditions, the temperature errors of star sensors are analyzed and modeled systematically, and a high-accuracy online temperature error compensation scheme is proposed in this paper. Firstly, by analyzing the temperature influences on the optical system of star sensors, the relationships between focal length drifts, optical distortion and temperature are obtained respectively, and then a systematic temperature error model of star sensors is established. Secondly, by analyzing the charge coupling device(CCD) noise characteristics, the fluctuation relationship between star positions and temperature is given, and a random temperature error model of star sensors is established. Then, according to the characteristics of systematic and random temperature errors of star sensors, a high-accuracy online temperature error compensation scheme is proposed. In the end, by the simulated CCD star sensor, it is indicated that the proposed temperature error compensation scheme can effectively restrain the shifts and fluctuation of star positions, and then can improve the measurement accuracy of star sensors in different temperature conditions.
Temperature variations can greatly reduce the measurement accuracy of star sensors. In this paper, by analyzing the temperature error characteristics of star sensors, a comprehensive temperature error model is established, and a high-accuracy online temperature error compensation scheme is proposed. The following conclusions are obtained.
For the optical system of star sensors, temperature variations can change the refractive index, the radius of curvature and other parameters of the lenses, which generates focal length drifts and radial distortion. Temperature variations can also change the coaxiality of the lenses and can bring about thermal expansion of the lens barrel, which causes decentering distortion. These factors result in the star position shifts jointly, namely systematic errors. For CCD chips, CCD noises increase significantly with temperature increment. It causes variations of star map noises, resulting in star position fluctuation, namely random errors.
The established temperature models of star sensors in this paper contain the effects of focal length drifts, optical distortion and CCD noises. The proposed online temperature error compensation scheme is simple to be implemented and suitable for online compensation. It can guarantee the measurement accuracy of star sensors at different temperatures. In future studies, performance of the proposed online temperature error compensation scheme for star sensors should be further verified by combining the measured data obtained by the star sensor in engineering applications.
Send us a message,we will answer your email shortly!
TY-Space Technology (Beijing) Ltd. is professional focusing on advanced attitude optical sensors, especially Star Trackers for space industry.
