The Design And Optimization Of Earth Sensor Used In Micro-satellites

Earth sensor, as an important attitude determination sensor in the attitude control system (ADCS) of satellites, has been widely used in all kinds of satellites and aircrafts. Along with the trend of the minimization of satellites, traditional earth sensors are no longer suitable for micro-satellites, due to the weakness of great bulk, high power consumption and low precision. In order to solve this problem, a novel earth sensor for micro-satellites has been designed in this paper.The whole system of earth sensor includes the visible light earth sensor and the infrared earth sensor. The optical system of the visible light earth sensor is composed of panoramic annular lens, which is developed by Zhejiang University. So the visible light earth sensor has a large field of60°×360°. Besides, the visible earth sensor uses the CMOS image sensor as the light detector and the power consumption of the system is greatly reduced. The infrared earth sensor utilizes the infrared detector of M100, which possesses very low power consumption, about0.58W. The visible light earth sensor and the infrared earth sensor can use the same signal processing circuit, which is based on CPLD and DSP. CPLD is mainly used to capture images and DSP is mainly used to conduct image processing. A digital image processing algorithm to track the center of the earth, including border detection and Hough transform, has been designed in this paper. In order to obtain the attitude determination precision of the earth sensor, a test platform for the visible earth sensor and the infrared earth sensor has been built. The experiment results reveal that both earth sensors can reach a measurement precision of0.1°, which meets the requirement of the attitude control system of micro-satellites.