Prospectors are volunteers who visit Gateway and ride the Heechee ships by using the predefined destination coordinates of the memory databanks. They hope to discover other worlds and discover Heechee remnants and alien machines, tools and other technologies that they can bring back for exploitation by human science..
The guidance systems of the starships remained a mystery and destinations were in fact random. The missions carry an extraordinary degree of risk, however Prospectors who returned with artifacts were rewarded by the Gateway Enterprises.
80% missions return with little or nothing, 5% produce substantial return, and 15% don't ever come back