And the paper gives a simple formula which can make the ground tracks of the orbit repeat and recover the whole globe.

并且提出了使得地面轨迹形成覆盖循环所需要满足的简要公式。

youdao

The ground tracks of satellites required for mission should be maintained close to those of reference orbits over the lifetime of satellites.

轨道维持的任务是将卫星的星下点轨迹保持在设计的参考轨迹附近。

youdao

He said the machine moved slowly at walking pace along the tracks putting the new equipment in the ground.

BBC: Electrification of Swansea to London trains 'by 2018'