[论文解读] MinXSS-1 CubeSat On-Orbit Pointing and Power Performance: The First Flight of the Blue Canyon Technologies XACT 3-axis Attitude Determination and Control System

James Mason, Matt Baumgart+11 more|arXiv (Cornell University)|Jun 21, 2017

Spacecraft Design and Technology被引用 25

一句话总结

本文评估了蓝山技术公司XACT三轴姿态确定与控制系统（ADCS）在MinXSS-1立方星上的在轨性能，展示了0.0042°–0.0117°（15″–42″，3σ）的指向精度以及通过伪峰值功率追踪器实现的65%功率余量，确保了电源系统的稳定性。该系统性能超出规格要求，并在脱轨前保持了可靠运行，验证了小型卫星任务中ADCS与EPS设计的有效性。

ABSTRACT

The Miniature X-ray Solar Spectrometer (MinXSS) is a 3 Unit (3U) CubeSat designed for a 3-month mission to study solar soft X-ray spectral irradiance. The first of the two flight models was deployed from the International Space Station in 2016 May and operated for one year before its natural deorbiting. This was the first flight of the Blue Canyon Technologies XACT 3-axis attitude determination and control system -- a commercially available, high-precision pointing system. We characterized the performance of the pointing system on orbit including performance at low altitudes where drag torque builds up. We found that the pointing accuracy was 0.0042\\degree\\ - 0.0117\\degree\\ (15$''$ - 42$''$, 3$\\sigma$, axis dependent) consistently from 190 km - 410 km, slightly better than the specification sheet states. Peak-to-peak jitter was estimated to be 0.0073\\degree\\ (10 s$^{-1}$) - 0.0183\\degree\\ (10 s$^{-1}$) (26$''$ (10 s$^{-1}$) - 66$''$ (10 s$^{-1}$), 3$\\sigma$). The system was capable of dumping momentum until an altitude of 185 km. We found small amounts of sensor degradation in the star tracker and coarse sun sensor. Our mission profile did not require high-agility maneuvers so we are unable to characterize this metric. Without a GPS receiver, it was necessary to periodically upload ephemeris information to update the orbit propagation model and maintain pointing. At 400 km, these uploads were required once every other week. At $\\sim$270 km, they were required every day. We also characterized the power performance of our electric power system, which includes a novel pseudo-peak power tracker -- a resistor that limited the current draw from the battery on the solar panels. With 19 30\\% efficient solar cells and an 8 W system load, the power balance had 65\\% of margin on orbit. We present several recommendations to other CubeSat programs throughout.

研究动机与目标

• 评估蓝山技术公司XACT三轴ADCS在3U立方星上的在轨性能。
• 在不同高度下表征XACT系统的指向精度、抖动及动量释放能力。
• 评估新型伪峰值功率追踪（PPPT）电源系统（EPS）在轨条件下的性能。
• 识别在轨运行中的挑战，如星历更新频率及近地轨道中传感器性能退化问题。
• 基于在轨经验，为未来立方星任务提供可操作的改进建议。

提出的方法

• XACT ADCS在MinXSS-1上运行，该3U立方星从国际空间站部署于411 km的轨道高度。
• 通过星跟踪器和粗略太阳传感器的数据表征在轨指向性能，精度与抖动通过3σ测量值计算得出。
• 电源系统采用固定阻值电流限制电阻作为伪峰值功率追踪器（PPPT），替代传统PPT，以防止功率振荡。
• 通过Maxim MAX17049电量计芯片监控电池荷电状态与电压，数据用于评估功率平衡。
• 定期上传星历更新以维持轨道预报精度，随着轨道衰减加剧，更新频率逐步提高。
• 根据三块太阳电池板上19块太阳能电池的电压与电流测量值计算功率生成量。

实验结果

研究问题

• RQ1 在190–410 km的轨道高度范围内，XACT三轴ADCS的在轨指向精度与抖动性能如何？
• RQ2 伪峰值功率追踪（PPPT）设计在未采用完整PPT或分流器的情况下，维持功率正向系统的有效性如何？
• RQ3 当航天器从400 km衰减至185 km时，为实现准确的轨道预报，星历更新的频率需求是多少？
• RQ4 传感器性能退化（如星跟踪器与太阳传感器）对近地轨道中长期运行的立方星任务有何影响？
• RQ5 基于MinXSS-1任务经验，可为未来小型卫星任务提出哪些可操作的运行与设计建议？

主要发现

• XACT ADCS实现了0.0042°–0.0117°（15″–42″，3σ）的指向精度，优于规格书要求，且在190 km至410 km范围内保持一致。
• 在10 s⁻¹频率下，峰峰值抖动测量值为0.0073°–0.0183°（26″–66″，3σ），表明指向性能稳定。
• XACT系统成功在185 km高度实现动量释放，证明其在高阻力环境下的能力。
• 基于PPPT的电源系统在轨维持了65%的功率余量，平均功率生成量为10.81 W，峰值功耗达20 W。
• 在400 km高度时，星历更新频率为每两周一次；在约270 km高度时，因轨道衰减与预报误差加剧，需每日更新。
• 由于采用固定电阻PPPT，电池荷电状态在40%至80%之间振荡，虽限制了SoC范围，但有效防止了功率振荡，并确保了系统功率正向。