摘要
为实现天问一号着陆点快速精确定位,规划火星车行驶路径,并将火星车后续数据纳入统一的地理坐标系,本研究利用着陆初期有限数据(天问一号环绕器获取的遥感影像、一幅悬停避障缓速下降阶段的GNC(guidance,navigation and control)避障敏感器拍摄的降落影像和导航相机在着陆平台的环拍立体像对)完成定位任务.首先,通过导航相机的环拍影像生成着陆点周围陨石坑、沙丘、火山口、山梁之间的拓扑关系.然后,以根据环绕器的遥感影像生成的数字正射影像图(digital orthophoto map,DOM)为底图,将导航相机生成的陨石坑、沙丘、火山口、山梁之间的拓扑关系与底图预着陆区的陨石坑、沙丘、火山口、山梁之间的拓扑关系进行模糊匹配,以确定疑似着陆点,并结合降落影像在疑似着陆点中确定着陆点的粗略位置.最后,根据导航相机影像多像空间后方交会解算着陆点的精确位置为109.925°E,25.066°N.
At 7:18 on May 15, 2021, Beijing time, more than 9 months after the launch of China’s first Mars exploration mission Tianwen-1, the lander successfully landed in the pre-selected landing area in the southern Utopia Plain of Mars. The overall terrain in this area is relatively flat, making it easier for the Tianwen-1 lander to land safely, but there are still scattered obstacles such as craters, sand dunes, and ridges. Therefore, the Tianwen-1 lander still needs to be accurately located, in order to plan the path of the rover, preventing the rover from overturning due to obstructive terrain. Besides, incorporating the follow-up data of the rover into the unified Martian geographic coordinate system also needs the accurate landing site.The location of the landing site can be estimated according to the lander’s landing orbit data, however, due to the parachute landing method, the error of the estimated location is large, so the image obtained after the landing of the Tianwen-1 lander should be used to accurately locate the landing site.Mars is far away from the Earth, and data transmission channel is limited. After the Tianwen-1 landed, the relevant image data received until May 22, 2021 only had the following three types of data: Remote sensing images obtained by the orbiter,a descent image during hovering obstacle avoidance and slow descent phase, and the ring-shot stereo image pairs of the Mars rover’s navigation camera on the landing platform after landing. In order to locate the landing site of the Mars rover as soon as possible, this article proposes a precise positioning method based on the above limited data. At first, using the digital orthophoto map(DOM) generated by the orbiter remote sensing image as the base map, extract the craters, sand dunes, craters and ridges in the pre-selected landing area, and calculate the topological relationship between them. In addition, the topological relationship between the crater, sand dune, crater and ridge around the landing site is also calculated based on the ring-shot stereo image pair of the navigation camera. The second step is to perform fuzzy matching between the topological relationship of the feature geomorphology calculated by the navigation camera’s ring-shooting stereo pair and the topological relationship of the feature geomorphology extracted from the DOM of the orbiter remote sensing image to obtain several suspected landing sites, and then to determine one of them as the initial position of the landing site based on the descent image during the hovering obstacle avoidance and slow descent phase obtained near the landing site. Finally, through the multi-image space resection of the navigation camera images, the precise position of the landing site is calculated as(109.925°E, 25.066°N). This method makes full use of the limited data at the initial stage of the landing, and realizes the first-time positioning of the Tianwen-1 lander’s landing site. It has strong timeliness and ensures the safe movement of the rover.On June 6, 2021, U.S. time, the Hi RISE camera on the Mars reconnaissance orbiter(MRO) captured high-resolution remote sensing images of the Tianwen-1 lander and the Mars rover. The position of the Tianwen-1 lander on the image is the same as that in this article, which further verifies the accuracy of the positioning method.
作者
鄢咏折
张建利
亓晨
温博
吴运佳
彭松
马友青
金晟毅
张烁
张天翼
田鹤
贾阳
刘少创
Yongzhe Yan;Jianli Zhang;Chen Qi;Bo Wen;Yunjia Wu;Song Peng;Youqing Ma;Shengyi Jin;Shuo Zhang;Tianyi Zhang;He Tian;Yang Jia;Shaochuang Liu(Aerospace Information Research Institute,Chinese Academy of Sciences,Beijing 100101,China;University of Chinese Academy of Sciences,Beijing 100049,China;Beijing Institute of Spacecraft System Engineering,Beijing 100094,China;School of Geodesy and Geomatics,Wuhan University,Wuhan 430072,China;School of Mechanical and Aerospace Engineering,Jilin University,Changchun 130025,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2022年第2期204-211,共8页
Chinese Science Bulletin
基金
国家自然科学基金(42071447)资助。
关键词
天问一号火星探测器
着陆点快速定位
拓扑关系的模糊匹配
多像空间后方交会
Tianwen-1 Mars rover
fast localization of landing point
fuzzy match based on topological relationship
resection based on multiple images
