Someone who travels into little known regions (especially for some scientific purpose); SYN. adventurer.
Series of US scientific satellites. Explorer 1, launched Jan 1958, was the first US satellite in orbit and discovered the Van Allen radiation belts around the Earth.

ETYM Latin: cf. French investigateur.
Someone who investigates.

ETYM French, from voyager to travel. Related to Voyage.
A traveler; -- applied in Canada in the nineteenth-century to a man employed by the fur companies in transporting goods by the rivers and across the land, to and from the remote stations in the Northwest.