它们是在日出和日落这段时间内,在基准位置和当前时间上,对定位进行跟踪的机构.
这是主谓补机构,即S V P机构.
主语是they,谓语是are,补语是名词mechanisms .
of tracking locating at benchmark position and current time between sunrise and sunset是介宾结构做定语修饰mechanisms , 其中of 是介词,tracking locating是宾语,其中track是动词,在介词后面应该用ing形式,locating是名词.at benchmark position and current time是地点状语,between sunrise and sunset则是时间状语.