Washington (CNN) -- A former NASA scientist accused of trying to sell classified information to Israel about American military satellites pleaded guilty Wednesday to a felony count of attempted espionage.

Stewart David Nozette, an MIT-trained scientist, admitted guilt in exchange for a proposed sentence of 13 years. He faced from 30-years to life had he been convicted at trial on a four-count indictment.

"I think it's a fair sentence," his lawyer, John Kiyonaga, told CNN after a plea agreement hearing at U.S. District Court.

Nozette signed a statement of facts in which he admitted meeting with undercover FBI agents intending to trade secrets for money. Reading from that statement Wednesday, prosecutor Anthony Asuncion quoted Nozette as telling an agent, "So, I guess I gave you some of the most classified information that there is."

The undercover case developed out of a tax fraud case involving a contracting company Nozette led, and unsubstantiated invoices he sent to the government for work performed. Authorities in 2002 had found classified documents at his Chevy Chase, Maryland home while executing a search warrant.

In 2009, the FBI conducted a sting and found Nozette willing to sell secrets to undercover operatives portraying themselves as agents of the Israeli government.

Prosecutors Tuesday said Nozette apparently thought he was selling the information too cheaply, and he tried to negotiate upward his initial demand for $50,000.

Asuncion told the court Nozette told agents about the overall development cost of the secret program designed to detect and intercept a large-scale attack, and told the operative, "I should charge you at least 1 percent," of that cost, which would have been in the millions of dollars.

"The defendant was arrested soon afterward," Asuncion said, during a meeting in October 2009 at the Mayflower Hotel in Washington.

During his arraignment two years ago, prosecutors played video of that covert meeting. Nozette was heard demanding a falsified Israeli passport, transport out of the United States, and a "kitty" for his expenses.

His wife, who was at that arraignment, did not return to pre-trial hearings after the government said Nozette intended to leave without her. She was not at Wednesday's plea hearing.

Nozette, who received a doctorate in planetary sciences from Massachusetts Institute of Technology, held sensitive positions involving U.S. aerospace research.

He had a "top secret" clearance, and served at the White House on the National Space Council for President George H.W. Bush, according to court documents.

An FBI affidavit filed with the October 21, 2009 indictment says Nozette, for about six years until 2006, did research and development for the Defense Advanced Research Projects Agency, the Naval Research Laboratory, and NASA's Goddard Space Flight Center.

The document says Nozette also acted as a technical consultant from 1998 until early 2008 "for an aerospace company that was wholly owned by the government of the state of Israel."

Prosecutors, in setting up their case, never directly linked Israel to the allegations against Nozette of attempted espionage.

Nozette, has looked disheveled in court appearances from the time of his initial arrest to Wednesday. But in those two years he also has lost a substantial amount of weight, and his attorneys have cited medical problems requiring treatment and detention closer to his Maryland home.

Because of his threat to intelligence, he remains confined under conditions known as special administrative measures, that were not further defined.

He earlier entered a guilty plea in the tax fraud case and sentencing will be concurrent according to U.S. District Judge Paul Friedman, presiding over the combined case against Nozette.

CNN's Carol Cratty contributed to this story