两行根数是北美防空司令部基于一般摄动理论产生的用于预报地球轨道飞行器位置和速度的一组轨道根数,其对 应模型为考虑了简化的常规、深空扰动的SGP4/SDP4模型。瞬时轨道根数和两行根数常用来描述航天器的运行情况,但 瞬时轨道根数到两行根数的转换方法鲜有介绍。文中描述了基于SGP4、SDP4模型,利用数值迭代法从瞬时轨道根数得 到两行根数的方法,经过测试验证和实际使用,该方法推导出的两行根数精度满足轨道预报的需要。

Two-line element (TLE) is the special form of satellite orbit element, which is derived on the basis of the classical general perturbation theory and can be used together with NORAD's SGP4/ SDP4 orbital model to determine the position and velocity of the associated satellite. Osculating Kepler Element (OKE) and TLE are often used to describe the orbit of spacecraft, but few conversion methods from OKE to TLE are introduced. An iterative method is described in this paper, in which TLE can be converted from OKE and which is based on SGP4/ SDP4 model. The simulation test and actual use show that the method is effective and the result TLE therewith meets the demand on orbit prediction precision.