Abstract: A numerical model was developed to investigate the uncertainty in spacecraft orbit maneuver process for hydrazine-based monopropellant systems. The effects of tank pressure，tank temperature and thruster burn duration on velocity increment during orbit maneuver were quantitatively studied. Correction of the model utilizing in-orbit thrust calibration coefficient was evaluated. The model was verified using the historical orbit control data of a low earth orbit （LEO） satellite. Simulation results show that the method utilizing in-orbit thrust calibration coefficient can reduce the average error of the orbit maneuver model from 3.615% to 1.924%. By parameter sensitivity study， it is found that uncertainty induced by tank temperature is less than 0.2%， and uncertainty induced by tank pressure is less than 5%. Through the analysis of the influence of burn duration， it is found that under different tank pressure， there is a specific critical-burn-duration （CBD）. When burn duration is less than CBD， variation of the tank pressure could be unrecognizable by pressure transducer. For the LEO satellite in this study， the CBD is 8.5s when the tank pressure is 1.8MPa at the beginning of life， and increases to 319.8s when the tank pressure is 0.5MPa at the end of life.

Key words: Hydrazine thruster;Monopropulsion;Uncertainty;Orbit maneuver;Critical burn duration

摘要： 为评估卫星单元肼推进系统轨控过程的不确定性，建立了轨控过程的数值模型。定量分析了贮箱压力、贮箱温度、推力器点火时长等参数对轨控速度增量的影响，考察了在轨标定推力系数对于轨控模型的修正效果。选取某近地卫星对其轨道控制历史数据进行分析，通过在轨实测数据对轨控模型进行了验证。结果表明，采用在轨标定推力修正系数能够有效地降低轨道控制模型的平均误差，平均误差值从3.615%减至1.924%；通过参数敏感性分析，得出贮箱温度的总体影响不超过0.2%，贮箱压力的总体影响不超过5%。通过对点火时长的影响分析发现，在不同的贮箱压力下，存在一个特定的临界点火时长；点火时长低于临界点火时长时，贮箱压力的变化将不会被压力传感器识别。针对某低轨卫星，寿命初期箱压1.8MPa时，临界点火时长为8.5s；寿命末期0.5MPa时，临界点火时长为319.8s。

关键词: 肼推力器;单组元推进系统;不确定性;轨道控制;临界点火时长