Abstract Achieving a soft landing over the surface of small celestial bodies is an essential maneuver in space to advance the status of space exploration, sample collecting and in-situ resource utilization, among other on-orbit tasks. Landing on these bodies is challenging due to the reduced-gravity and airless environment. The correct planning of execution of the trajectory to land on the surface of the body is of cumbersome importance to prevent the vehicle from bouncing up and eventually reach escape velocity. In this paper, a bio-inspired trajectory planning method to land on the surface of a Near-Earth Asteroid (NEA) with zero relative velocity is proposed. The method is based on Tau theory, which has been demonstrated to explain the way that humans and some other animals’ approach to different target spots to perform tasks such as perching, landing, and grasping. We have selected the NEA Apophis asteroid as our case study due to its accessibility, and small rotational velocity and orbit condition code. Two landing scenarios are studied; one considers the case where the satellite is hovering at a low altitude; the other corresponds to a landing maneuver right after a deorbiting or breaking phase, which may cause residual initial velocity in the vehicle prior to the landing maneuver. Once the descending trajectory is obtained, a closed-loop controller is in charge of achieving trajectory tracking and calculating the continuous and on/off thrust control signals. The simulation results show that the introduced approach can achieve zero final relative velocity in both cases for different initial condition, which is a requirement for a soft landing. Besides, different kinematic behaviors can be obtained by modifying the single variable named the Tau constant. The particular advantages of the method with respect to a commonly used approach are devised and analyzed as well.

中文翻译：

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近地小行星软着陆仿生制导方法

摘要 实现小天体表面软着陆，是推进空间探索、样本采集、原位资源利用等在轨任务中的一项重要太空举措。由于低重力和无空气环境，在这些物体上着陆具有挑战性。正确规划执行轨迹以降落在身体表面上对于防止车辆弹起并最终达到逃逸速度非常重要。本文提出了一种仿生轨迹规划方法，以零相对速度降落在近地小行星（NEA）表面。该方法基于 Tau 理论，该理论已被证明可以解释人类和其他一些动物接近不同目标点以执行诸如栖息、落地，抓握。我们选择 NEA Apophis 小行星作为我们的案例研究，因为它的可达性，以及小的旋转速度和轨道条件代码。研究了两种着陆场景；一是考虑卫星低空盘旋的情况；另一个对应于刚离轨或中断阶段之后的着陆操纵，这可能会在着陆操纵之前导致飞行器中的残余初始速度。一旦获得下降轨迹，闭环控制器负责实现轨迹跟踪并计算连续和开/关推力控制信号。仿真结果表明，对于不同的初始条件，引入的方法在两种情况下都可以实现零最终相对速度，这是软着陆的要求。除了，通过修改名为 Tau 常数的单个变量可以获得不同的运动学行为。还设计和分析了该方法相对于常用方法的特殊优势。