The space industry has recently seen rising research interest in satellites developed to operate for extended periods at lower altitudes than ever before. The combination of lower launch costs, reduced radiation effects, and ease of deorbit, among other benefits, outlines very low Earth orbit (VLEO) missions as a key prospect of the space sector in the near future.

Neutral atomic oxygen (ATOX), the dominant gas species in lower orbital altitudes, is a major consideration for VLEO missions. The oxidising nature of ATOX with relative speeds at least 7.8 km/s can easily cause an early end to a satellite mission through generation of drag forces, as well as degradation of solar array surfaces and optical instruments. During a mission, accurate quantification of this erosion damage aboard the spacecraft may be gained though gathering data regarding ATOX gas flux impinging on susceptible surfaces at a given point in time.

Additionally, increased aerodynamic loading, caused by greater gas densities at lower altitudes, plays a substantial role in satellite station keeping and attitude control; an aerodynamically unstable spacecraft may experience undesirable rotational forces or even enter a tumbling state if left unchecked. Real-time measurement of ATOX flux allows a mission to determine short-term variations in ATOX flux and therefore estimate fluctuations of satellite lift and drag, enabling a satellite to react appropriately. Long-term recording of these fluctuations may also hold influence over future satellite aerodynamic design.

Atomic oxygen sensing methods are a crucial aspect of future VLEO satellite design as we begin to tackle the obstacles of reduced altitude orbits. These sensors are able to measure the quantity of atomic oxygen atoms impinging on a satellite per unit area. In the interest of reacting to, and designing for the erosive environment and aerodynamic forces presented by ATOX and gas species in VLEO, we review available ATOX sensing methods and their respective applications.

Each ATOX sensing method has its own benefits and drawbacks. The most appropriate method for a given mission depends on factors such as altitude, mission lifetime, and mass budget. A review of the most common methods will clarify design options, and outline suitable areas for future research.

This paper builds upon a review of ATOX measurement methods performed by Osborne, et al. in 2001, updating with technologies from the past two decades as well as providing further examples of each method’s real-world applications.

It also conducts a semiquantitative analysis of spacecraft-based atomic oxygen sensing methods, describing the relative merits of each and their relevant applications. Generalised recommendations are made with regards to the most appropriate sensing method for a range of satellite mission scenarios.

This review finds that proven methods, such as mass spectroscopy, remain the most appropriate sensing methods for many missions. However, the progress seen within technologies of lower heritage, such as renewable actinometers, suggests that we may see missions exhibiting more recent ATOX sensing methods in the near future.

航天工业最近发现，人们对开发能够在比以往任何时候都低的高度运行更长时间的卫星的研究兴趣日益浓厚。较低的发射成本、减少的辐射效应和易于脱轨等优势相结合，将极低地球轨道 (VLEO) 任务概述为不久的将来航天部门的一个主要前景。

中性原子氧 (ATOX) 是较低轨道高度的主要气体种类，是 VLEO 任务的主要考虑因素。相对速度至少为 7.8 公里/秒的 ATOX 的氧化性质很容易通过产生阻力以及太阳能电池阵列表面和光学仪器的退化导致卫星任务提前结束。在执行任务期间，通过收集有关在给定时间点撞击敏感表面的 ATOX 气体通量的数据，可以获得航天器上这种侵蚀损坏的准确量化。

此外，由于较低高度的气体密度增加而导致的空气动力载荷增加，在卫星站保持和姿态控制中起着重要作用；空气动力学不稳定的航天器可能会遇到不希望的旋转力，如果不加以控制，甚至会进入翻滚状态。ATOX 通量的实时测量允许任务确定 ATOX 通量的短期变化，从而估计卫星升力和阻力的波动，使卫星能够做出适当的反应。对这些波动的长期记录也可能对未来的卫星空气动力学设计产生影响。

随着我们开始解决降低高度轨道的障碍，原子氧传感方法是未来 VLEO 卫星设计的一个重要方面。这些传感器能够测量每单位面积撞击卫星的原子氧原子的数量。为了对 ATOX 和 VLEO 中的气体种类所呈现的侵蚀环境和空气动力做出反应并进行设计，我们回顾了可用的 ATOX 传感方法及其各自的应用。

每种 ATOX 传感方法都有其自身的优点和缺点。对于给定的任务，最合适的方法取决于高度、任务寿命和质量预算等因素。对最常用方法的回顾将阐明设计选项，并概述未来研究的合适领域。

本文以 Osborne 等人对 ATOX 测量方法的回顾为基础。2001 年，更新了过去二十年的技术，并提供了每种方法在实际应用中的更多示例。

它还对基于航天器的原子氧传感方法进行了半定量分析，描述了每种方法的相对优点及其相关应用。就一系列卫星任务场景的最合适的传感方法提出了一般性建议。

这篇综述发现，经过验证的方法，如质谱，仍然是许多任务最合适的传感方法。然而，可再生光度计等传统技术取得的进步表明，我们可能会在不久的将来看到展示更多最新 ATOX 传感方法的任务。