Sentence:  Though its light-collecting mirror is modest by <WSD>terrestrial telescope</WSD> standards . . . its precision focus and perch above Earth's distorting atmosphere make Hubble's observations the benchmark by which all other observatories are measured. 
Meaning of the word marked with <WSD> tags:  An astronomical telescope which is physically located on the surface of the Earth, as distinct from a telescope located in outer space.