WASHINGTON — A former senior government scientist who held the highest security clearances pleaded guilty to espionage on Wednesday and agreed to a 13-year prison term for selling top-secret information on military satellites and other technology to an F.B.I. agent posing as an Israeli spy.

The scientist, Stewart D. Nozette, 54, who worked at the White House in 1989-90 and helped lead the search for water on the moon, was not charged with spying for Israel.

But Dr. Nozette consulted for a state-owned Israeli company, identified in the Israeli news media as Israel Aerospace Industries, from 1998 to 2008. The company paid him a total of $225,000 for answering technical questions it posed monthly, according to court documents.

Dr. Nozette, who holds a Ph.D. in planetary sciences from the Massachusetts Institute of Technology, told the undercover agent that he had believed the company was a front for Israeli intelligence.