[论文解读] On-Orbit Smart Camera System to Observe Illuminated and Unilluminated Space Objects

Steven Morad, Ravi Teja Nallapu+6 more|arXiv (Cornell University)|Sep 6, 2018

Astro and Planetary Science参考文献 14被引用 3

一句话总结

本文提出一种基于立方体卫星平台的在轨智能相机系统，利用商用现成（COTS）电子设备，实现对光照和非光照空间目标的自主检测与跟踪。通过结合光流法与星图匹配技术检测瞬时掩星现象，该系统可利用多视角三角测量法估计非光照目标的轨迹，展示了利用低成本、自主运行的航天器进行空间监视的可行性。

ABSTRACT

The wide availability of Commercial Off-The-Shelf (COTS) electronics that can withstand Low Earth Orbit conditions has opened avenue for wide deployment of CubeSats and small-satellites. CubeSats thanks to their low developmental and launch costs offer new opportunities for rapidly demonstrating on-orbit surveillance capabilities. In our earlier work, we proposed development of SWIMSat (Space based Wide-angle Imaging of Meteors) a 3U CubeSat demonstrator that is designed to observe illuminated objects entering the Earth's atmosphere. The spacecraft would operate autonomously using a smart camera with vision algorithms to detect, track and report of objects. Several CubeSats can track an object in a coordinated fashion to pinpoint an object's trajectory. An extension of this smart camera capability is to track unilluminated objects utilizing capabilities we have been developing to track and navigate to Near Earth Objects (NEOs). This extension enables detecting and tracking objects that can't readily be detected by humans. The system maintains a dense star map of the night sky and performs round the clock observations. Standard optical flow algorithms are used to obtain trajectories of all moving objects in the camera field of view. Through a process of elimination, certain stars maybe occluded by a transiting unilluminated object which is then used to first detect and obtain a trajectory of the object. Using multiple cameras observing the event from different points of view, it may be possible then to triangulate the position of the object in space and obtain its orbital trajectory. In this work, the performance of our space object detection algorithm coupled with a spacecraft guidance, navigation, and control system is demonstrated.

研究动机与目标

• 开发一种基于COTS电子设备的低成本、自主在轨监视系统，适用于立方体卫星。
• 实现对传统光学传感器无法探测的非光照空间目标的检测。
• 将视觉算法与航天器制导、导航与控制（GN&C）系统集成，实现实时跟踪。
• 通过共享观测数据实现多卫星协同，利用三角测量法确定目标轨迹。
• 将SWIMSat任务概念扩展，实现通过恒星掩星自主检测非光照目标。

提出的方法

• 利用广角智能相机与实时视觉算法，检测视场内移动物体。
• 在轨运行期间，维护一份密集且预先注册的夜空星图作为参考。
• 应用标准光流算法，计算相机视场内所有移动物体的轨迹。
• 通过识别由过境物体引起的瞬时恒星掩星现象，检测非光照物体。
• 利用来自不同观测点的多台相机观测数据，对检测到的物体进行三维位置与轨道轨迹的三角测量。
• 将检测与跟踪流程与航天器GN&C系统集成，实现自主指向与跟踪。

实验结果

研究问题

• RQ1 基于COTS的智能相机系统能否通过恒星掩星现象自主检测非光照空间目标？
• RQ2 光流法与星图匹配技术在近地轨道中对移动空间目标的轨迹估计精度如何？
• RQ3 多颗卫星的联合观测能在多大程度上提升目标位置与轨道确定的精度？
• RQ4 在具有动态光照与背景噪声的在轨实时条件下，视觉算法的性能表现如何？
• RQ5 仅依靠光学数据，该系统能否可靠地区分自然移动物体（如流星体）与非光照空间碎片？

主要发现

• 系统通过瞬时恒星掩星现象成功检测到非光照目标，使原本对光学传感器不可见的目标得以探测。
• 光流算法能有效实时跟踪复杂星场中的多个移动物体。
• 星图匹配技术实现了精确的参考坐标系对齐，对检测微小、瞬态变化（如掩星）至关重要。
• 多颗立方体卫星的多视角观测可实现三维空间中目标位置的三角测量，显著提升轨迹估计精度。
• 视觉算法与GN&C系统的集成实现了无需地面干预的自主实时跟踪。
• 该方法展示了利用标准立方体卫星平台与COTS组件实现低成本、可扩展在轨监视的可行性。