Absolute Positioning Based on the Sun for Mars Rover

Absolute positioning plays an important role in Mars rover's attitude determination and safe driving. This paper dedicates to improve the absolute positioning accuracy based on the sun observations. Firstly, calibration and alignment model for sun sensor and inclinometer are put forward. Then Sobel operator and Zernike moment operator are combined together to detect the sub-pixel edge of the sun image, and general ellipse fitting algorithm is adopted to extract the centroid of the sun image. A novel celestial positioning algorithm without initial value and iteration (NIYI) is derived by introducing anti-symmetric matrix. At last, two field tests on the earth are introduced, and three positioning algorithms including NIYI are compared. Results of the tests prove early success of the paper, and 30-minute observation time produces mean positioning error of 1.6km. When the observation time is extended to 90 minutes, positioning error drops to 0.82km~1.15km.