While adopting an elevation-over-azimuth architecture by an inter-satellite linkage antenna of a user satellite, a zenith pass prob- lem always occurs when the antenna is tracing the tracking and data relay satellite (TDRS).

Moreover,the models of zenith blind zone for polar coordinates stabilized platform were presented and the reason of this type of zenith blind zone was analyzed.

Practice of getting across the roof leakage area during the end session of mining in mechanized coal face;