Stewart D. Nozette of Chevy Chase was a gifted scientist privy to America’s top secrets.

On Wednesday, he admitted trying to sell those secrets to a foreign government. With his guilty plea to attempted espionage, the astrophysicist was rebranded a would-be traitor.

Nozette, 54, stood in an orange prison jumpsuit in the District’s federal court as he conceded that he had accepted $11,000 in cash in 2009 in exchange for passing classified materials about U.S. satellite defense systems to what he believed was an Israeli intelligence officer.

Nozette answered “Yes” when U.S. District Judge Paul L. Friedman asked whether he understood that he faced 13 years in federal prison.

The purported Israeli was actually an FBI employee in an undercover espionage investigation launched after Nozette drew law enforcement’s attention for fraud he had committed through his aerospace consulting company.

During a 2007 search of his home on the contracting case, officers discovered classified materials and an e-mail in which Nozette threatened to take a program he was working on to a foreign country “or Israel,” court records show. The court files do not say to whom that e-mail was sent, and prosecutors declined to provide more details Wednesday.

Nozette’s intertwined cases are complicated, but court records make this clear: Just months after he’d acknowledged ripping off the government as a consultant, Nozette was ready to do business selling state secrets to a man who had called him claiming to be part of Israel’s Mossad.

U.S. Attorney Ronald C. Machen Jr. said that Nozette had gone from a “once-trusted scientist” with high-level clearances to “a disgraced criminal who was caught red-handed attempting to trade American secrets for personal profit.”

Nozette had admitted overbilling the government $265,000 between 2000 and 2006 through his company and using the money to pay credit-card bills, maintain his swimming pool and cover the cost of sedan service. He pleaded guilty, but his admission was sealed in court in January 2009 and sentencing was held off as Nozette agreed to help investigators expose other government corruption, prosecutors said.

Yet by September 2009, Nozette was passing classified information to the undercover agent and discussing how he could get more cash as well as help with a passport and a new identity to travel overseas.

Singapore appealed to him because “it’s clean, it’s nondescript, they speak English there,” according to a video of Nozette talking to the undercover agent Oct. 19, 2009, at the Mayflower Hotel on Connecticut Avenue. But at a minimum, Nozette wanted a place with no extradition, he confirms to the agent.

Nozette was arrested that day and has been jailed since.

Nozette held a variety of sensitive military and civilian jobs, including service on the National Space Council at the White House in 1989 and 1990 and work at the Energy Department’s Lawrence Livermore National Laboratory from 1990 through 1999, prosecutors have said. He held top-secret clearance and had regular access to classified information until 2006. Many of his friends described him as brilliant and ambitious.

The indictment against Nozette did not allege that the Israeli government committed any offense. Nozette was originally indicted on two counts of attempted espionage shortly after his arrest. Two more counts of attempted espionage were added in a November 2010 indictment, and Nozette pleaded guilty to one of those charges Wednesday.  Nozette's attorneys — Robert L. Tucker and John C. Kiyonaga — declined to comment after the hearing.

Attempted espionage is a felony that carries the death penalty, but federal prosecutors took that off the table in late 2010. The 13-year sentence covers the attempted espionage conviction and the prior fraud and tax-evasion convictions.

On the day of his arrest, court files show, Nozette told the undercover agent “I've crossed the Rubicon . . . I've made a career choice,” and laughed.

Staff writer Jeremy Borden contributed to this report.