The Van Allen Probes Mission consists of two identical spacecraft flying in highly elliptical orbits, with perigee altitudes originally near 600 km. During the low‐altitude periods of the orbits, the spacecrafts are immersed in a region of high‐density atomic oxygen. Atomic oxygen is known to change and degrade the properties of spacecraft surfaces (Banks et al., 2004), such as those of the Van Allen Probes Electric Field and Waves (EFW) instrument. The consistency of the sensor surfaces in EFW is important because the mechanisms used to ensure the collection of high‐quality electric field measurements requires that the photoemission properties of each sensor are uniform and stable. Oxidation or erosion of the sensor surfaces could limit the instrument's ability to balance the currents produced by both the plasma electrons and the controlled bias current applied to the sensors and thus to properly operate the device. We have modeled the atomic oxygen exposure to the spacecraft to help understand the potential impact it has had on the sensors. We have calculated the fluence (time‐integrated flux) of atomic oxygen particles that have collided with the spacecrafts over the entire course of the mission. We have also looked at the distribution of atomic oxygen flux over time to further analyze malfunctions in the sensor readings at different points along the course of the mission. Additionally, we have investigated how different surfaces of the spacecraft are affected differently due to their orientation with respect to the spacecraft's motion.

中文翻译：

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Van Allen探针上的原子氧通量计算

范·艾伦探测任务由两个相同的航天器组成，它们在高度椭圆形的轨道上飞行，近地点的高度最初接近600公里。在低轨道运行期间，航天器浸没在高密度原子氧区域。众所周知，原子氧会改变和降低航天器表面的特性（Banks等，2004），例如Van Allen Probes电场和波（EFW）仪器的特性。EFW中传感器表面的一致性很重要，因为用于确保收集高质量电场测量值的机制要求每个传感器的光发射特性是均匀且稳定的。传感器表面的氧化或腐蚀可能会限制仪器的 平衡等离子体电子产生的电流和施加到传感器的受控偏置电流的能力，从而使设备正常运行。我们对航天器的原子氧暴露进行了建模，以帮助了解其对传感器的潜在影响。我们已经计算了在整个飞行过程中与航天器相撞的原子氧粒子的能量密度（时间积分通量）。我们还研究了原子氧通量随时间的分布情况，以进一步分析任务过程中不同点的传感器读数中的故障。此外，我们研究了航天器的不同表面由于其相对于航天器运动的方向而受到不同的影响。