AI 中文总结
本研究提出一种自动形状模型天体测量流水线，将其应用于火星快车SRC图像的火卫一测量，测试显示其性能与控制点方法相当，可扩展至大型数据集，残差精度良好，适用于火卫一及其他已分辨天体的天体测量归算。
AI 中文摘要
高分辨率航天器图像为轨道精化提供了重要的天体测量约束，但对已分辨天体的测量常受限于耗时的控制点选择，以及在大型图像档案中实现一致归算的困难。我们提出一种用于火卫一的自动形状模型天体测量流水线，并将其应用于火星快车（Mars Express）超分辨率通道（Super Resolution Channel, SRC）图像。对于每幅曝光图像，在标称航天器-目标-太阳几何条件下，从高分辨率三维形状模型渲染合成图像；采用SuperPoint与SuperGlue建立观测图像与合成图像间的特征对应关系，随后进行RANSAC过滤。匹配的合成图像关键点通过射线-形状相交与表面点关联。几何平差固定采用的天体取向、航天器状态及校正后的相机指向，仅使用精确透视投影模型估计两个有效天球平面位置偏移，这些偏移用于推导火卫一的图形中心位置。我们首先在一组先前采用控制点方法分析的图像集上测试该方法，获得了可比的天体测量性能；随后将分析扩展至2007-2025年的更大SRC数据集，共获得1113次成功测量。相对于JPL MAR099星历，所得观测减计算残差在α×cos(δ)方向的平均值为0.186 km，标准偏差为0.609 km；在δ方向的平均值为0.053 km，标准偏差为0.583 km。这些结果表明，所提出的流水线为火卫一档案航天器图像的大规模、均匀天体测量归算提供了实用方法，且有望应用于其他已分辨天体。
英文摘要
High-resolution spacecraft images provide important astrometric constraints for orbit refinement, but measurements of resolved bodies are often limited by labor-intensive control-point selection and the difficulty of achieving consistent reductions over large image archives. We present an automated shape-model-based astrometric pipeline for Phobos and apply it to Mars Express Super Resolution Channel (SRC) images. For each exposure, a synthetic image is rendered from a high-resolution 3D shape model under the nominal spacecraft-target-Sun geometry. Feature correspondences between the observed and synthetic images are established using SuperPoint and SuperGlue, followed by RANSAC filtering. The matched synthetic-image keypoints are then associated with surface points through ray-shape intersection. The geometric adjustment fixes the adopted body orientation, spacecraft state, and corrected camera pointing and estimates only two effective plane-of-sky position offsets using the exact perspective-projection model. These offsets are used to derive the center-of-figure position of Phobos. We first test the method on an image set previously analysed with a control-point approach and obtain comparable astrometric performance. We then extend the analysis to a larger SRC dataset spanning 2007-2025 and obtain 1113 successful measurements. Relative to the JPL MAR099 ephemeris, the resulting observed-minus-computed residuals have mean values of 0.186 km in $α\times cos(δ)$ and 0.053 km in $δ$, with corresponding standard deviations of 0.609 km and 0.583 km. These results demonstrate that the proposed pipeline provides a practical approach to large-scale, homogeneous astrometric reduction of archival spacecraft images of Phobos, with potential application to other resolved bodies.
Comments13 pages, 6 figures, journal article
