By the year 2020 US intents to build a permanent human base on the Moon. To do so, space agency NASA will send four astronauts and, as the base extends, will progressively send more. The best place to establish the outpost is at one of Moon's poles -- most likely Shackleton crater, South pole -- but this will be chosen after Lunar Reconnaissance Orbiter will be launched in late 2008 and completes a detailed map of the Moon.