(CNN) -- The prison sentence for the highest-ranking CIA officer ever convicted of espionage should grow significantly Tuesday when a federal judge penalizes him for continuing his covert activities while incarcerated.
According to the U.S. District Court of Oregon website, Harold James "Jim" Nicholson will be sentenced -- again -- at 1:30 p.m. (4:30 p.m. ET) in Portland after admitting to working through his son to secretly pass information to and get payments from Russia.
The elder Nicholson received a 23-year sentence in 1997 after pleading guilty to spying for Russia, one year after he was arrested at Dulles International Airport outside Washington while attempting to board a flight to Switzerland.
Federal prosecutors said that at the time of his arrest, Nicholson was carrying 10 rolls of film of classified documents as well as coded messages on a computer disk. They said he planned to meet his Russian handlers, who would pay him more than $180,000.
But his covert, and profitable, relationship with the Russians did not end while he was imprisoned at the Federal Correctional Institution in Sheridan, Oregon.
Nicholson admitted as much in November, when -- 21 months after being indicted again -- he pleaded guilty to conspiracy to act as an agent of a foreign government and conspiracy to commit international money laundering as part of an agreement with federal prosecutors.
At that hearing, the 16-year former CIA station chief confessed to working with his son, Nathan, to funnel information to and get money from the Russian government between 2006 and December 2008.
Nicholson could have faced 25 years in prison and $750,000 in fines for both crimes. But instead, he will have eight years tacked onto his existing sentence per the plea deal, a statement from the U.S. Attorney's office in Oregon said.
According to court documents, Nathan Nicholson, 26, cooperated with prosecutors in their case against his father after FBI agents confronted him about frequent international travel.
The younger Nicholson, a former U.S. Army paratrooper, admitted to authorities during the FBI questioning that he had not gone overseas to visit "a battle buddy" as he had claimed previously. FBI agents then informed Nicholson that lying to them was a federal crime and offered him a chance to change his story, according to one agent's testimony.
At that point, FBI Special Agent John Cooney testified, Nicholson became more "forthcoming."
Nathan Nicholson told the agents that at his father's behest, he made trips to California, Mexico, Peru and Cyprus, where he met with Russian government representatives who gave him payments totaling more than $35,000 in cash.
During Nathan Nicholson's prison visits to his father, according to court records, "Harold Nicholson spent a significant amount of time advising (the) defendant on how to conduct himself in a clandestine manner as he traveled to and from various international meeting locations. Harold Nicholson tried to impart his CIA training to (the) defendant."
Prosecutors alleged the Russians gave the elder Nicholson back-pay for his prior espionage activities and for details on how he was caught.
"The Russian Federation was specifically interested in how Harold Nicholson got caught by the FBI," according to a government sentencing memo filed with the court. It added that the information concerned "who interrogated him after his arrest and the timing of his transfers as a CIA Officer prior to his arrest."
According to court records, the elder Nicholson and his son put the plot into motion after Nathan Nicholson complained to his father about the family's precarious finances.
The sentencing memo said that Nathan Nicholson provided crucial help in the prosecution of his father. The elder Nicholson pleaded guilty on the day that his trial was set to have begun last month and who now faces an additional 20 years in prison.
In an October psychological report entered into the court record by prosecutors, Nathan Nicholson took aim at his ex-spy father.
"I wasn't aware of his selfish side," Nathan Nicholson said, according to the records. "I allowed myself to be blindsided. I was like a lobster in a pot, heated slowly until it was too late."
CNN's Patrick Oppman contributed to this report.