火星探路者
The first two Discovery missions were Near Earth Asteroid Rendezvous (NEAR) (later called Shoemaker NEAR) and "Mars Pathfinder". These initial missions did not follow the same selection process that started once the program was under-way. "Mars Pathfinder" was salvaged from the idea for a technology and EDL demonstrator from the Mars Environmental Survey program. One of the goals of "Pathfinder" was to support the Mars Surveyor program. Later missions would be selected by a more sequential process involving Announcements of Opportunity.