The stellar detection limit (SDL) of image sensor is a key parameter of star tracker. It plays an important role in the selection of guide stars and the star pattern identification. In order to calculate the SDL of CMOS active pixel sensor (APS), the model of star influx and the noise model of APS are presented. The main noise sources of APS are analyzed. If SNR and total noise of APS are given, the SDL of APS can be calculated based on the typical response of 0 magnitude visual star per second per mm^2. As an example, a specific SDL of APS is provided with given optical parameters and exposure time.

Calculation Stellar Detection Limit for Active Pixel Sensor

Image denoising is the process of getting the location coordinates of the star point. The extent of denoising determines the measurement accuracy of star sensor attitude. As the star sensor accuracy increasing, the need for star chart-depth study of the noise reduction process, thus reducing the false rate of the target extraction. Noise sources are: Star background noise, molecular noise, electronic noise, etc. In order to reduce the noise, analyze noise source and characteristicness; compare three Laplacian noise reduction effect; and put forward the associative templates. The results show that Laplacian typically is unacceptably sensitive to noise, will produce double edges, and is unable to detect edge direction; LOG has a voluminous convolving mask so that the computation is complex; The improved mask has good edge detection and high antinoise performance.

Rui-xian Li

Papers

Research of image denoising based on high precision of star sensors