In June 1975, O'Neill led a ten-week study of permanent space habitats at NASA Ames. During the study he was called away to testify on July 23 to the House Subcommittee on Space Science and Applications. On January 19, 1976, he also appeared before the Senate Subcommittee on Aerospace Technology and National Needs. In a presentation titled "Solar Power from Satellites", he laid out his case for an Apollo-style program for building power plants in space. He returned to Ames in June 1976 and 1977 to lead studies on space manufacturing. In these studies, NASA developed detailed plans to establish bases on the Moon where space-suited workers would mine the mineral resources needed to build space colonies and solar power satellites.