在天基光学监视系统中，根据有限的导弹助推段观测信息估算目标的弹道参数是衡量系统性能的重要指标，对支持目标识别分类、判定威胁程度都有重要意义。本文针对单星观测条件下提高弹道参数估计精度的迫切需求，提出了天基条件下利用氧气 A吸收带被动测距提高估计精度的方法。利用 MODTRAN对不同大气模型、不同气象、不同信噪比条件下的天基被动测距能力进行了仿真分析，在此基础上深入分析被动测距技术对弹道参数估计精度的提升能力，并与传统经验方法进行对比。仿真表明本文方法能够有效提高单星观测下的弹道参数估计精度。

For space-based optical surveillance systems, estimated ballistic parameters are important output specifications based on limited boost-phase measures. They are useful for target classification and threat assessment. To improve estimation accuracy under a single satellite, passive ranging based on the atmospheric absorption of oxygen “A” band is introduced in this study. The performance of passive ranging under different atmosphere models, weather scenes, and signal-to-noise ratio are discussed and simulated separately in moderate resolution atmospheric transmission. Furthermore, the performance of ballistic estimation based on passive ranging is compared with an experiential method. Simulation results show that the proposed method can effectively improve the accuracy of ballistic estimation.