The Lunar Reconnaissance Orbiter (LRO) has been orbiting the Moon since 2009, obtaining unique and foundational datasets important to understanding the evolution of the Moon and the Solar System. The high-resolution data acquired by LRO benefit from precise orbit determination (OD), limiting the need for geolocation and co-registration tasks. The initial position knowledge requirement (50 meters) was met with radio tracking from ground stations, after combination with LOLA altimetric crossovers. LRO-specific gravity field solutions were determined and allowed radio-only OD to perform at the level of 20 meters, although secular inclination changes required frequent updates. The high-accuracy gravity fields from GRAIL, with <10 km spatial resolution, further improved the radio-only orbit reconstruction quality (<10 meters). However, orbit reconstruction is in part limited by the 0.3-0.5 mm/s measurement noise level in S-band tracking. One-way tracking through Laser Ranging can supplement the tracking available for OD with 28-Hz ranges with 20-cm single-shot precision, but is available only on the nearside (the lunar hemisphere facing the Earth due to tidal locking). Here, we report on the status of the OD effort since the beginning of the mission, a period spanning more than seven years. We describe modeling improvements and the use of new measurements. In particular, the LOLA altimetric data give accurate, uniform, and independent information about LRO's orbit, with a different sensitivity and geometry which includes coverage over the lunar farside and is not tied to ground-based assets. With SLDEM2015 (a combination of the LOLA topographic profiles and the Kaguya Terrain Camera stereo images), another use of altimetry is possible for OD. We extend the 'direct altimetry' technique developed for the ICESat mission to perform OD and adjust spacecraft position to minimize discrepancies between LOLA tracks and SLDEM2015. Comparisons with the radio-only orbits are used to evaluate this new tracking type, of interest for the OD of future lunar orbiters carrying a laser altimeter. LROC NAC images also provide independent accuracy estimation, through the repeated views taken of anthropogenic features for instance.

中文翻译：

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月球勘测轨道器的轨道确定：七年后的状态

Lunar Reconnaissance Orbiter (LRO) 自 2009 年以来一直围绕月球运行，获得了对了解月球和太阳系演化非常重要的独特基础数据集。LRO 获得的高分辨率数据受益于精确的轨道确定 (OD)，限制了对地理定位和联合注册任务的需求。在与 LOLA 高度交叉结合后，地面站的无线电跟踪满足了初始位置知识要求（50 米）。确定了 LRO 特定重力场解决方案，并允许仅无线电 OD 在 20 米的水平上执行，尽管长期的倾斜度变化需要频繁更新。来自GRAIL的高精度重力场，空间分辨率<10公里，进一步提高了纯无线电轨道重建质量（<10米）。然而，轨道重建部分受到 S 波段跟踪中 0.3-0.5 mm/s 测量噪声水平的限制。通过激光测距的单向跟踪可以补充可用于 OD 的跟踪，其范围为 28 赫兹，单发精度为 20 厘米，但仅在近侧可用（由于潮汐锁定，月球半球面向地球）。在这里，我们报告了自任务开始以来 OD 工作的状态，这段时间跨越了七年多。我们描述了建模改进和新测量的使用。特别是，LOLA 高度数据提供了关于 LRO 轨道的准确、统一和独立的信息，具有不同的灵敏度和几何形状，包括对月球背面的覆盖，并且与地面资产无关。借助 SLDEM2015（LOLA 地形剖面和 Kaguya Terrain Camera 立体图像的组合），OD 可以使用另一种高度测量。我们扩展了为 ICESat 任务开发的“直接测高”技术，以执行 OD 并调整航天器位置，以最大限度地减少 LOLA 轨道和 SLDEM2015 之间的差异。与纯无线电轨道的比较被用来评估这种新的跟踪类型，对未来携带激光高度计的月球轨道飞行器的 OD 感兴趣。LROC NAC 图像还提供独立的精度估计，例如通过对人为特征的重复视图。为 ICESat 任务开发的技术，用于执行 OD 和调整航天器位置，以尽量减少 LOLA 轨道和 SLDEM2015 之间的差异。与纯无线电轨道的比较被用来评估这种新的跟踪类型，对未来携带激光高度计的月球轨道飞行器的 OD 感兴趣。LROC NAC 图像还提供独立的精度估计，例如通过对人为特征的重复视图。为 ICESat 任务开发的技术，用于执行 OD 和调整航天器位置，以最大限度地减少 LOLA 轨道和 SLDEM2015 之间的差异。与纯无线电轨道的比较被用来评估这种新的跟踪类型，对未来携带激光高度计的月球轨道飞行器的 OD 感兴趣。LROC NAC 图像还提供独立的精度估计，例如通过对人为特征的重复视图。