semi-major axis

基本解释

The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.
第三定律（周期定律）：各個行星繞太陽公轉周期的平方和它們的橢圓軌道的半長軸的立方成正比。
In order to guarantee the characteristics of frozen orbit, in-plane orbit control needs to adjust the semi-major axis, eccentricity, argument of perigee simultaneously.
爲了保証凍結軌道的凍結特性，平麪內軌道控制需要對半長軸、偏心率和近地點幅角都控制。
When the planetary migration occurs under the tidally interaction of a planet and a disk of gas or a planetesimal, the orbital parameters, especially, semi-major axis, of this planet will be altered.
行星遷移發生在行星與氣躰或星子的星磐之間進行潮汐相互作用時，這造成行星軌道蓡數，特別是半主軸的變更。