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PRIME is a proposed space mission for a deep survey of 25% to 100% of the sky in four near-IR bands (0.9-3.5 μm), to M AB 24 (K 22). The PRIME survey should be ~ 600 times deeper than 2MASS. Deeper surveys in selected regions are planned. Its main goal is to find the first massive objects formed: quasars up to z = 15-25 if any, galaxies up to z ~20, clusters of galaxies up to z ~ 3-5. PRIME should also be a major step in the study of brown dwarfs and nearby free floating warm planets, and serve many other goals, in particular as a pilot mission for NGST. It should be a central piece of The Virtual Observatory, complementary to other surveys.