The seasonally frozen ground can be divided into intergradation, semi-intergradation, long-term stability and stability.
可把季节冻土分为过渡型、半过渡型、长期稳定型和稳定型等类型。
2
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.