Earth sensors are widely used in spacecraft for attitude determination. They need to have a very large field of view( FOV)( > 120°) and relatively low accuracy while being used in the aircrafts around orbit. A triple-FOV infrared earth sensor is proposed in this paper. It uses three pieces of standard infrared detectors w ith a w avelength range of 14 ~ 16μm,to sense the horizontal circle by detecting the infrared light emitted from the earth. From w hich,the geocentric vector can be obtained. A mathematic model is established and a validation model is set up to provide input parameters for the mathematic model. The simulation results of the tw o models show that the output of the mathematic model coincides w ith the know n parameters. Based on the above analysis,a prototype has been built and tested. The test results show that the angle measurement error is about 0. 002° and hence such a triple-FOV earth sensor is capable to provide high-precision position information for autonomous navigation. They need to have a very large field of view (FOV) (> 120 °) and relatively low accuracy while being used in the aircrafts around orbit. A triple-FOV infrared earth sensor is proposed in this paper. It uses three pieces of standard infrared detectors w ith aw avelength range of 14 ~ 16μm, to sense the horizontal circle by detecting the infrared light emitted from the earth. A w hich, the geocentric vector can be obtained. A The simulation results of the tw o models show that the output of the mathematic model coincides w ith the know n parameters. Based on the above analysis, a prototype has been built and tested. The test results show that the angle measurement error is about 0. 002 ° and hence such a triple-FOV earth sensor is capable to provide high-precision position information for autonomou s navigation.