火星车测日天文导航关键理论及技术研究

American mars rover Opportunity has driven for more than 40 km since it landed on the mars in 2004, and the dead reckoning technology based on the sun sensor and IMU plays an important role in safe exploration. Azimuth determination by observing the sun is used to correct the accumulated azimuth error of IMU when the rover is stationary. However, the azimuth determination precision is only 3°, which caused the error of dead reckoning up to 10%. This program puts forward the multiplexing conception for sun sensor and star sensor for the first time, and thousands of stars will be utilized as control points to calibrate the sun senor and determine the rotation relationship between the sun sensor frame and inclinometer frame, which can solve the on-line and high-precision calibration problem caused by the long travel of the rover and complex environment. Sub-pixel edge detection and efficient edge points fitting methods will be considered to extract the centroid of the non-regular sun image precisely and intelligently in dust and fog weather. Celestial positioning using the sun will be considered as ill-posed problem, and the new positioning model will be built to improve the precision, and the mechanism of the biased estimation and bias correction theories will be studied. Through the research of this program, precisions of azimuth and position determination will hopefully reach 15″ ( 1σ ) and 300m ( 1σ ) under static conditions. Using the Sun/Inclinometer/SINS integrated navigation method, the positioning error of the rover will be controlled at about 1% of the mileage under the low dynamic and long-static condition in a Mars day.

美国机遇号火星车自2004年登陆火星以来，已在火星表面行驶40余公里，基于太阳敏感器和惯性导航系统的航迹推算技术发挥了重要作用。火星车静止时通过测日定向改正惯导的航向累积误差，精度仅为3º，使最终的航迹推算误差达到里程的10%。本项目首次提出太阳敏感器与恒星敏感器复用的概念，拟在夜晚火星车静止时，采用天然的恒星作为检校场，实现长时间、复杂环境下太阳敏感器与水平仪的永久在线检校和标定。考虑亚像素边缘检测+有效边缘点拟合的方法，解决尘雾天气条件下不规则太阳图像的质心提取问题。拟从病态角度看待和分析测日定位问题，构建新的定位模型，并探索有偏估计及偏改正理论作用于测日定位的机理，改善定位精度。本项目有望将静态下的测日定向精度从0.1º提高到15″（1σ），定位精度从3km提高到300m（1σ），并通过太阳/水平仪/惯性组合导航，将低动态、多停留条件下火星车一个火星日的定位误差控制在里程的1%左右。

美国机遇号火星车自2004年登陆火星以来，在火星表面行驶了40余公里，基于太阳敏感器和惯性导航系统的航迹推算技术发挥了重要作用。本项目首次提出太阳敏感器与恒星敏感器复用的概念，在夜晚火星车静止时，采用天然的恒星作为检校场，实现了长时间、复杂环境下太阳敏感器与水平仪的永久在线检校和标定，检校精度达到±0.4像素。考虑亚像素边缘检测+有效边缘点拟合的方法，解决了超大视场太阳图像质心提取问题，精度达到±0.05像素。构建了基于矢量观测的天文定位模型，显著改善了测日定位精度。在地表实验结果表明，测日定向精度优于±1´（3σ），有望将火星车太阳/惯性组合导航误差降低到里程的1%以下；白天测日定位精度达到±300m（1σ），夜间测星定位精度达到±15m（1σ）。项目的研究成果对于我国正在开展的火星探测任务具有重要的参考价值。