Instead, a female bioengineer will conduct scientific experiments on a Russian voyage to the International Space Station next month, the South Korean Ministry of Education, Science and Technology said.
Russia's Federal Space Agency asked for the change last month, saying Ko San - the original choice - repeatedly violated regulations at the training center near Moscow, Lee Sang-mok, a senior ministry official, told a news conference.
He was replaced by Yi So-yeon, a 29-year-old with a doctorate in bioengineering who had been South Korea's second choice for the mission.
Russian authorities said Ko took his training manual out of the center without permission and sent it to his home in South Korea in September, Lee said. Ko later returned the manual, explaining he accidentally sent it home together with other personal belongings, Lee added.
In February, Ko again broke the rules by getting what was believed to be a manual used by space pilots from the center through a Russian colleague - material he was not supposed to read, Lee said. Ko had signed the center's instructions on the rules.
"The Russian space agency has stressed that a minor mistake and disobedience can cause serious consequences," Lee told reporters.
Lee said he believed the materials in question were not classified.
The state-run Korea Aerospace Research Institute - which employs Ko - has rebuked him, both verbally and in writing, Lee said.
The institute offered an apology to Russia both times, he said. The institute has no plan to take further disciplinary measures.
Anatoly Perminov, chief of the space agency, said in a statement on its Web site Monday that the change was because Ko "violated the code of conduct for cosmonauts," adding that the substitution scientific groundwork for space exploration in coming decades.
Since 1992, South Korea has had 11 satellites launched, mostly for space and ocean observation and communications.
